Embryology History - Robert Winston
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- 1 Introduction
- 2 Engineering Reproduction: Will We Still Be Human At The End of the 21st Century
- 2.1 Introduction
- 2.2 Implantation
- 2.3 Ovary
- 2.4 Early Egg
- 2.5 Mitochondria
- 2.6 Blastomere Removal
- 2.7 Adrenoleukodystrophy
- 2.8 Cell Death
- 2.9 Aneuploidy
- 2.10 Dolly the Sheep
- 2.11 Making Transgenics
- 2.12 Testis
- 2.13 Gene Transfer
- 2.14 Showing Gene Transfer Technique
- 2.15 Transgenic Animals
- 2.16 Beta Thalassemia
- 2.17 Beta Thalassemia 2
- 2.18 Historic Reflection
- 3 References
- 4 External Links
- 5 Glossary Links
Below is the transcript from a speech given as part of the Alfred Deakin Lecture series in 2001 by Professor Lord Robert Winston. Robert Winston is a researcher, clinician, academic and educator in human development. The speech was also broadcast on ABC (Australia) Radio National Monday 14/05/01.
| I have included this transcript by Prof Robert Winston due to his exceptional contribution to Embryology both in its research and presentation to the public. Each part of his talk was associated with a new slide (slides were not available) and is presented in a new subheading (these subheading titles were not part of the original transcript). I have also added links and images to relevant topics that were also not part of the original speech.
- Links: Stem Cells
|Embryologists: William Hunter | Wilhelm Roux | Caspar Wolff | Wilhelm His | Oscar Hertwig | Julius Kollmann | Hans Spemann | Francis Balfour | Charles Minot | Ambrosius Hubrecht | Charles Bardeen | Franz Keibel | Franklin Mall | Florence Sabin | George Streeter | George Corner | James Hill | Jan Florian | Thomas Bryce | Thomas Morgan | Ernest Frazer | Francisco Orts-Llorca | José Doménech Mateu | Frederic Lewis | Arthur Meyer | Robert Meyer | Erich Blechschmidt | Klaus Hinrichsen | Hideo Nishimura | Arthur Hertig | John Rock | Viktor Hamburger | Mary Lyon | Nicole Le Douarin | Robert Winston | Fabiola Müller | Ronan O'Rahilly | Robert Edwards | John Gurdon | Shinya Yamanaka | Embryology History | Category:People|
Engineering Reproduction: Will We Still Be Human At The End of the 21st Century
Alfred Deakin Lecture by Professor Lord Robert Winston (Capitol Theatre, Australia, Sunday, May 13, 2001, 6pm)
Well, it's a real honour for me to be here on this podium and a great privilege to follow two such distinguished speakers such as Lee Hood and Alan Trounsen. Lee Hood has done so much for the study and understanding of molecular genetics. Alan Trounsen has a very special place in my heart, because I think it is fair to say that he has been the signally most influential figure in reproductive technology translated into the human anywhere in the world. His remarkable science has been combined with an extraordinary generosity which has meant that its always impossible to get the information from him which has lead so many other groups to continue and improve the technology of this extraordinary subject of reproduction.
I'm going to try to combine some of the themes that have been discussed this morning and see perhaps where we may be leading ourselves because the combination I suppose, of a greater understanding of genetics and the access to the human embryo and early human development, I think raises some very important things for society, and I believe can act in many ways as a whole paradigm for a whole range of philosophical, social and ethical questions which society needs to be addressing in a rather more defined and educated way I think than perhaps we have been doing so to date, and that is probably which is my theme, but I will try to keep throughout the question of our humanity as defined by genetics.
And the first thing I want to draw your attention to is this extraordinary thing - the human embryo. If you take one hundred human embryos in an in-vitro fertilisation program for example, only about eighteen of them will end up actually as a baby, as a foetus. The rest perish and perish naturally for all sorts of different reasons. It is probable that it isn't actually very different in nature. The average couple having unprotected intercourse at least in Britain, have only about an eighteen percent chance of conception from the menstrual cycle. It is true that in Australia it is about twenty-two percent, but I think it is because you have sex rather more often.
But this extraordinary fragility of the human embryo is actually a key aspect of the background I think of the ethical questions that have been raised to a very great extent already this morning. Certainly, of course, some of the reasons why the embryo seems to be expendable are due to the lining of the uterus, the endometrium. We know very little about implantation, but about three weeks ago my group published at least one gene polymorphism which is associated with failure of implantation and we have another gene which we are following at the moment which also seems to cause unexplained infertility.
What I have built up here is an image of the endometrium using scanning electron microscopy. I've collapsed into about a minute and a quarter, sixteen days of development in the lining of the uterus. There is a window of opportunity very briefly when implantation of that delicate embryo is possible as these structures start to develop, these so called pinnapods (spelling?), which lasts for some twenty four to forty eight hours. You'll see them on your screen in just a second and here they are.
And certainly for implantation to take place, various adhesion events need to take place and these are genetically determined. It is very probable that there are all sorts of genes which are related and important in human implantation, whether a message is going between embryo and the uterine cavity. But fundamentally, I don't think that this is a particularly important mechanism. I don't think that the genetics of what is actually happening in the endometrium are nearly as important as to what is happening in the embryo itself. And in order to understand the human embryo, we need to go back to the human egg. Certainly, it is very clear that there are a large number of defects in the human embryo, as I am going to show you in just a minute or two, and that these do date way back in human development.
- Links: Ovary Development
What we have here are two photographs. This is an ovary from a sixteen weekly person. As you can see it is absolutely packed with oocytes, each of these is a germ cell, genetically unique. And already by twenty-one weeks development in-utero, the germ cells have started to get fewer. And what is remarkable is that this aging process starts when we are still inside our mother's uterus.
By the time we get to reproductive age, there are relatively few follicles in the human ovary. We probably start with about 7 million before birth, 2 million at birth, 300,000 by the time we reach puberty and although a woman ovulates averagely once a month, by the time thirty years of reproductive life have concluded in the late 40's, there are only a handful of these follicles left. This particular lady is 38 and in this slice of ovary there are only four follicles. That is a peculiarly female situation. It is perhaps worth bearing in mind whilst you have been listening to these three male speakers, if you are a woman of reproductive age, by the process of cell death, apoptosis, averagely by sitting in this audience you will have lost two or three eggs from your ovary. And in the same amount of time, Dr Hood and Dr Trounsen and I will have made between us some 500,000 sperm. (Audience laugh). I suspect that in Dr Trounsen's case it might be even more, he seems to look younger each time I see him.
Now there are various ways that eggs and embryos can be manipulated, and I want to look now specifically at this question of engineering reproduction, because one of the problems quite clearly is, because we are such an infertile mammal, because we lose so many embryos for whatever reason. In reproductive medicine, great attempts have been made to improve IVF technology. And one of the things that seems to happen with aging is that as women get older, not only do they have fewer eggs but it is probable that the eggs are of less good quality. That is, they are more likely fertilise abnormally and when they do fertilise, more likely to produce miscarriage.
One of the focuses of attention has been on these little structures inside the cell, the so-called mitochondria. So far this morning we have been discussing exclusively the DNA in the nucleus which is where virtually all our DNA is packed. But actually in these little organelles there are some 16,000, 16,500 base pairs which do an important job in the cell, largely regulating energy. And it is true that sometimes, when the genes, very few genes, but when they do go wrong in these cells there are catastrophic effects for the human being, particularly metabolic disorders, usually affecting muscle, sometimes blindness, often brain function and liver function. Usually, children with mitochondrial disease die very soon, within a few years of birth.
It has been postulated, I mean there are many reasons for aging and Alan [Trounson] just touched on one, the immortalisation of cells, the so-called production of enzymes which maintain immortality of the cell. It also has been postulated that mitochondria also age in the cell and may actually affect the eggs of older women.
As you will be aware one thing that has recently been done and has actually just attracted attention in the Australian press and in the British Press is the notion of taking the eggs from women who are having reproductive failure in most cases older women that is to say in their late 30's or 40's and then transferring into the egg the cytoplasm containing the mitochondria that is the jelly like substance surrounding the nucleus, not the nucleus itself, into the egg cell to make a hybrid egg with some donor DNA from the younger woman in the hope that this royal jelly will kick start the egg into action.
This has been done by amongst other people, Jacques Cohen in New Jersey and here is some film clip of them actually taking mitochondria through a glass pipette from a donor egg and then as you will see in just a second injecting it into a recipient egg. Here is in fact a probe going into outer shell, the zona pellucida, of the egg to be renewed, and then some cytoplasm may be injected in this sort of way and then that egg may be fertilised. And here you see this particular human embryo developing into the two-cell stage, the first stages of cell division in the human. Now, I have to say that I have great problems with this kind of experimenting.
It is interesting to consider that today is Mother's Day. One might ask for example how many parents might now be possible using this kind of reproductive technology. You could use donor sperm with a donor egg, with donor cytoplasm, that's three parents, two mothers and one father, a surrogate mother to make a third mother and two further parents, an adopting couple who take the child after birth. And does all that matter? I don't think it does. It's a piece of fun really. But of course it has actually raised a kind of frisson about reproductive technology, and I think that we have to be aware that many members of the public not unreasonably, including I think we ourselves have problems with what this might be doing to the way society is developing.
- Links: Jacques Cohen
I've actually, rather sadly lost a slide here, but I was going to show you some of the newspaper coverage of this particular event. Certainly the criticism of this technology, in the British media, and I think to some extent in the Australian media, has been very considerable. It seems to me to have been very wrongly focused. The issue for most of the journalists that I have spoken to and read their pieces has been the notion of the mixing the DNA in this sort of way. My view is that is actually is probably trivial even though it changes the germ line because of those mitochondria, we now know or we seem to think, from a recent publication are persisting in the babies. What I really think is at issue here is something which hasn't been discussed probably and that is that it seems to me that there has been a jump too fast into technology which is of no real proven benefit.
One of the concerns that I have is that this particular experimental approach, which has been quite hyped in the press not necessarily by people who did themselves, but by other people who have been commenting on it, really has not been proved to be any benefit. There is no real evidence that you make an older woman's egg more fertile by mixing the DNA in this way. And it seems to me that unless we have done extensive animal work first to see what is exactly happening in the relationship, the complicated relationship between mitochondria and nuclear DNA, this is not a step that should not be taken.
In my view, I think one of the things that I want to make is a plea for animal work. Sadly, of course, in some societies, particularly in Britain, that animal work is under huge threat at the present time and I think it constitutes one of the greatest threats to science because I believe that without properly conducted, ethically done animal experimentation, many of the important advances that we have been talking about today will actually be impossible, in fact would have been impossible so far and will be impossible in the future.
Let me come now to a different kind of genetic manipulation. This is the removal of a single blastomere, one cell from an embryo three or so days after fertilisation. This is an old photograph where what we did was to take the nuclear material and then analyse this to see whether or not this was a male or female embryo and looking at specific DNA sequences only found on the Y chromosome, and this was used by my group initially and other groups subsequently to sex the embryo. That is permitted in Britain providing that there is a very good medical reason for sexing. And that has been limited in Britain to the use of this technology for sex-linked disorders.
There are about 200 - 300 single gene defects which are carried on the X chromosome and which affect males, largely only affect males, sometimes they do affect females as well. The female is the more deadly of the species in this extent at least. This has been used now to prevent disease in the handful of families around the world.
In this particular case it was used to prevent adrenoleukodystrophy. We now in fact don't use DNA analysis so much for this particular approach. We rather stay in parts of particular chromosomes and this is one cell nucleus taken from a human embryo and this is part of the Y chromosome, and that's the centre part of the X chromosome and here are two copies of the chromosome 1 or just a part of chromosome 1 using a technique of tagging the DNA with a fluorescent dye and then looking under a laser con-focal microscope. This is a highly reliable technique for looking at chromosomes in a whole range of tissues and in particular in embryos and it can be done pretty quickly so that you can make a diagnosis on the third day after fertilisation and it is possible therefore for women to start a pregnancy knowing that their pregnancy is free of a defect without having to consider the possibility of a termination of a pregnancy once they have developed a foetus which is implanted.
And indeed nearly all women who have come to us, and I suspect to other groups who are doing pre-implantation diagnosis, have come for the strongest moral reasons. Not because they want to go through in-vitro fertilisation and this very complicated technology because they fundamentally believe they want to avoid an abortion but because they now know they have a gene defect because they already have an affected child. They feel that this is an alternative for them. That seems to me for them to be a highly ethical position for them to take and therefore I think it's a matter of very grave disquiet for many of us that there are people in our society who attitudinise about this sort of approach and really say the most violent things in opposition to it. It seems to me that in pluralistic societies like yours and mine that this is matter really for the individuals concerned.
This technology has been important for a whole range of reasons. I want to show one or two photographs of one of the issues to come back to this fragility of the human embryo.
- Links: OMIM- adrenoleukodystrophy
One of the things that we have consistently seen in human embryos - these are cells of a blastocyst at day five - and what we have done here is a process called tunnel labelling and you here you see nuclei from human embryos. These are cells which are undergoing cell death, programmed cell death. And it turns out that human embryos have a very large number of cells, a variably large number of cells, perhaps 5%, 8% may be even 10% which undergo cell death in this sort of way. What we don't know is whether this is a regulatory phenomenon, an attempt to avoid having abnormal cells which have got abnormal chromosomes in them or whether this is just something that happens.
Later on of course in development, cell death is very important in modelling. For example if you take a pentadactyl limb, the human hand. During development we have webbing, which is lost by cell death as development occurs. Cell death actually helps modelling. It is interesting that it happens this early in the development of the embryo. One of the questions of course which remains unanswered, is just how reliable pre-implantation genetic diagnosis really is. It is true of course that it has been grasped with great enthusiasm by a number of people, but I think it's a very great concern that if you take the wrong cell that you may end up with an erroneous result.
- Links: Blastocyst
Here for example, is a cell from a patient who is failing in-vitro fertilisation where she has an extraordinarily chaotic distribution of chromosomes on this fluorescent technique. There is the Y chromosome, here are three copies of the X and she has four copies of chromosome 1 using the same staining procedure using just 3 dyes that I mentioned before. And now when we look with five or seven different chromosomes we can see these defects occurring with startling regularity. Moreover, human embryos are often extremely mosaic.
And I want to show you interesting work which was published a month or two ago by Dr Delhanty and Dagem Wells using a technique called comparative genomic hybridisation where they have taken a number of human embryos and looked at the entire genome and stained it and in fact where there is too much red or too much green there is actually an exchange of DNA of material between chromosomes in different cells of the same embryo. Here we are looking at chromosome two and chromosome seven, from Joy Del Hanty's paper.
Very interestingly in that particular publication - what I think is quite horrifying is that of the 12 embryos they examined and they were able to get a signal from nearly all the cells, but not quite all the cells, 6 out of 6, 3 out of 4, 4 out of 4, 6 out of 7, 7 out of 8, and so on. Only 3 human embryos out of 12 that looked outwardly normal down the microscope actually have a normal complement of chromosomes. This one was a normal female, that was normal female in all 6 cells. This one was a normal male in five out of seven cells that gave a signal. But quite remarkably a huge number of embryos have chaotic distribution of chromosomes or deletions of chromosomes, or other abnormalities, so called aneuplody. And this may account for why so many human embryos are lost.
I think that I am allowed to say this, that this technique has now been used remarkably in Melbourne to actually screen embryos for chromosomal defects and chromosomal diagnosis to actually get live children. There are problems with the complicated technology at the moment because it takes quite a few days to do the staining and so one needs to store the embryo by freezing. There is no doubt that this type of technology may be used to help reduce certain defects which are prevalent in different patients. But the problem still remains that when you are looking at only one or two cells you may not see something which is necessarily representative of the rest of the embryo and I think that this is a very significant problem indeed for pre-implantation diagnosis.
It has been said of pre-implantation diagnosis that it will help eradicate genetic disorders. It will do no such thing. It might reduce them in specific families, but we mustn't ever forget that gene disorders occur de novo all the time. Some gene disorders for example muscular dystrophy occur as spontaneous mutations about 30% of the time, so some are occurring very commonly.
One of the issues for us both in terms of scientists and members of the public is to try and understand the ethics of all this about whether or not such embryos are truly human beings because of course there are strong voices heard particularly in the United Kingdom and the United States and in Australia which regard the human embryo as sacrosanct no matter how early. But it seems to me that it might be better to look at it really as a potential.
I am drawn by this wonderful woodcut drawn of a man called Hartsoeker, which was published in about 1740 - 1750. Some of you may have seen this before because it is quite a familiar drawing. It shows a little sperm, a human sperm with of course a little a man, the homunculus in the head of the sperm. When they were looking down the van Leeuwenhoek microscope with its imperfect optics they thought they could see in the nucleus a little person. And this gave rise to this rather fanciful drawing because of the imperfect optics. It might interest you to know that apparently in Paris, Brussels and parts of London it was quite fashionable that after a good alcoholic dinner party to get out the microscope and examine drops of the seminal fluid of the assembled guests as a kind of sport after dinner.
Interestingly because it is relevant to the question of ethics I came across this passage which I have translated rather imperfectly from the original classical Hebrew by a man called Rabbi Pinchas Elijah Ben Meir, quite an obscure writer, but he writes this and I think it is a very interesting observation.
- "It is been seen through the viewing instrument that magnifies called a microscope that a drop of a man's sperm whilst yet in its original environment contains small creatures in man's image. They live and move within the sperm. And now we can see how right the sages were in their notion that if we destroy the sperm, we are destroying the little man inside the sperm, so that this is actually murder."
He says how strange that the talmudic idea of "hash-hattat zera" hash-hattat means destruction and zera means seed - destruction of the seed - the destruction of the seed is like murder. And they were saying this from the basis of intuition before the microscope was invented. Now the microscope is invented and we can see how right they were. [Judaism - Sefer ha B'rit (Book of the Covenant), published in 1797. Referred to by David Feldmas, Birth Control in Jewish Law, published in 1968 by Loftus Wattlegrow, p121.]
Judiasm has always tried to follow scientific observation, it respects scientific observation very greatly. Now of course, there's no question Ben Meir's philosophy is admirable. He is absolutely right. If indeed there is a little man inside the sperm then to masturbate is totally wrong, it is indeed like murder. But of course the microscopy was imperfect, the scientific observation was imperfect. And what we have to understand is that we have to look at the human embryo I think for what it biologically truly is. It isn't actually a perfect human being either. It is a step on the way to becoming a human being in some cases, actually probably in less than one in five cases. It seems to me that our ethics must be driven by the scientific understanding of the natural world.
Alan has already talked about the scope for tissue engineering, but I want to merely observe that if you take the UK situation alone, does it seem right that whilst we are wasting embryos at each menstrual period, whilst we are wasting embryos with each IVF cycle, whilst we are using methods of contraception that destroy human embryos, surely there is a moral imperative to be using this tissue if it will help to save human life because this actually is the guiding force behind our whole ethic as Jews, Christians and Moslems this is certainly true.
Therefore, I am very grateful that the houses of parliament have allowed this kind of process in Britain to go forward at least on a tentative basis. In the House of Commons, which is an elected body, 68% voted in favour of human embryonic stem cell work. And it seemed to me to be really quite surprising that they did so given the huge public outcry, which was driven by a tiny pressure group which is the point. Very often our laws both in your country and in mine are driven to some extent and our politicians are driven to some extent, by people who protest the most vigorously. And I think that it is interesting that in the House of Lords which is not an elected body that there for rather strange reasons, some people say that they are experts, and others say because they need stem cell transplants in the brain, but whatever, 70% of the House of Lords voted in favour of maintaining this work! It moves forward in a cautious way in Britain and it seems to me that the overwhelming imperative in that debate was the notion that dealing with something which only has potential for life, but we will be dealing with people who will die if they are not effectively treated, and that pragmatic approach which is not uncommon in British law, and I think it is a very good example of how it works.
Dolly the Sheep
This is Dolly the Sheep and that is Dr Kate Hardy of whose slides I just rather disgracefully showed the work on apoptosis in the human embryo. One of the issues I think for us is that the whole approach of the press to issues like cloning has really had a hugely negative effect on how we perceive things like stem cell biology. Indeed in Britain we were being told consistently before the votes that it was shocking that what the scientists wanted was to clone little human beings. And of course as Alan [Trounsen] has pointed out, that actually isn't true.
Indeed the stem cell biology can proceed probably pretty well without nuclear transfer, and indeed it is rather likely that nuclear transfer may only have a very limited value in growing stem cells for self transplantation, not least because the sick person requiring stem cells will have to wait for their development in the petrie dish. And that actually is a real problem if you've had for example a brain injury. Because if the brain injury is left too long, I suspect it will be too late to try and regenerate brain. I imagine, I think that it is because of the development of scar tissue we will need to work quite fast if are going help people like stroke victims for example. I think that's quite a long way in the future.
But there is no doubt one of the things that is really troublesome is that we have got this view that human cloning is just around the corner and irresponsible people will do this. The truth is when you look at cloning, whether you look at mice or sheep or pig experiments whatever they might be, there are a huge number of animals or embryos which do not survive the process. I think in the case of Dolly there were something like 300 - 400 embryos needed to get one live sheep. Many of these animals have been born with abnormalities like being too large, and many of them have died shortly after birth or have had other body abnormalities, phenotypic abnormalities.
It is very likely that this process of nuclear transfer actually changes the way that genes express and may also affect a process called genomic imprinting and therefore it seems to me to be unthinkable that this will be done in the human. Indeed if a doctor tried to transfer a human embryo that give rise to one of these defects the very nature of his existence would be finished, at least economically because he would be wiped out by the lawsuits that followed. Indeed given that something like that 2% to 3% of human embryos are abnormal in some way or another, courts would find that when the abnormal baby was born even if it wasn't due to the cloning process that he had actually caused this. I find that we are a lot safer by that very basic fact than perhaps we give credibility for.
Like Alan I am an optimist, I believe that these things can also be used for good and therefore I would say that really the main message for people like Dr Antonori and his colleagues, that what you are doing with your bombastic comment is to fundamentally damage the standing of science in all undeveloped societies. And that seems to me to be a terrible injury because it affects how we will live in the future. It affects the way how our countries run, and I think we should be absolutely strong of our condemnation that sort of self promotion.
Let me now finally deal with the issue of transgenic technology.
Oddly, and I think that this shows very clearly why we are not about to clone human embryos, is that for the last 20 years we have been making animals, mostly mice that carry genes or parts of genes which are marked, that are not fundamentally originally in the mouse itself. Indeed making a transgenic animal, which carries a foreign gene or part of a foreign gene or knocking out part of a gene, has been one of the biggest advances in understanding of that genome, that we are now able to study, is working.
Because of course transgenics give us working practical models of how genes actually work in real whole animals. We can do much of this work in cells, but much of this needs to go on in animals. And although in Britain it has been suggested that we should be reducing the number of animal transgenics, I feel that probably there will be a pressure to increase the number of mouse models. We can look at single genes, we can remove genes to see what happens then, we can look at animal models of human disease, we can look at the relationship between the genes and the appearance, for example if we alter a gene we can see what happens to the abnormalities. And a whole range of diseases can be looked at in this way. For example in my own unit we have recently found (not my group but one of my colleague's parallel groups) a very important gene using transgenic technology which causes a very severe, quite common neural abnormality, ‚Äòfailure of fusion abnormality' in human embryos using a mouse model. So there are many reasons why transgenics should continue.
The problem is that making transgenics is very inefficient. I think that is one of the reasons at least why nobody has mentioned about making a transgenic human carrying foreign genes. This is rather an old publication but it is still quite an important summary of our knowledge and transgenics have not improved much since then. You can see that in transgenic mice ‚Äì only a few percent ‚Äì probably rather more than 2% now actually, of the ones where you inject DNA end up expressing and performing using the gene normally and it's less efficient than that in other big animals and it's also very expensive because access to embryos which isthe way this is normally is done is very difficult. I think therefore there's been a limit to this kind of technology because when we modify the germ line in animals we inject DNA into an egg just before cell division, or we try and introduce a gene during its early cleavage stages in the first couple of days, or once it reaches a blastocyst as Alan showed you which in the human is round about five days, you could then transfer stem cells which have been modified into that animal's embryo.
One of the things that I want to explore with you is some work that I have been doing with a good colleague from California Institute of Technology ‚Äì Caltech, a university that formerly Lee Hood was associated with. And Carol and I were in a rather drunken burgundy enriched mood in my house one day and we said why don't we actually try rather than going to embryos which are very complicated, try to transfect a much more common germ cell. As I mentioned to you I would be making quite a few germ cells during this talk. If one could get your genes into the testes and modify some of the cells ‚Äì the spermatagonia ‚Äì the cells in the testes which make the sperm, you might be able to incorporate your gene, and then actually have transgenics not by complicated IVF techniques but actually using simply natural mating.
And so we did, Carol and I, a number of experiments. One of the things we have done is to isolate the vas deferens which is a series of ducts, the vasa deferentia which go from the testis up there in the mouse into the epididymis down there. Here is a single strand, which measures perhaps 150 microns across. This pipette is just a millimetre in diameter so it's a very fine structure, but it is possible using a handheld glass injector without a micro manipulator to actually get into this and to direct cells and indeed DNA into this tubing. Once you do that of course, you can get into the whole of the testes because of the nature of the way tubules in the testis are formed.
Links: Spermatozoa Development
You can see in this photograph here, the testis is filled with a single injection very rapidly, in a matter of about a second and a half, filled with a blue dye to demonstrate that I've got in and distributed my fluid fairly evenly throughout the testis.
One of things that we have been doing is to denude the testis, to take away as many of the spermatagonia as we could already (these are individual tubules with very few stem cells left inside them, primal cells), by either radiation in some of the animals we have looked at, but more recently using drugs, a particular a drug call busulfan which given in the right dose will kill off most of the spermatagonia, the progenitor sperm cells.
One of the experiments we did sometime ago was this one. This in fact is the father mouse which has a dominant gene for black-coatedness. This is his wife who has a brown coat and these are the three children who all have a brown coat, which actually is physically impossible because they were produced by mating this mouse and this mouse and they should actually inherit the dominant gene. They don't because we filled this mouse's testicles with sperm from a donor.
And Brinster in the United States has also managed to even transfer sperm in this way between species, so it is possible to have sperm from a rat transferred to a mouse.
This raises extraordinary possibilities but there are important reasons why this kind of experiment can add to our understanding of what we might do. What we've now been able to do in the laboratory at least, though we haven't managed to transfer them, is to transduce, to change spermatagonia taken from young animals, modify them genetically. And the hope is that we might be able to transfer them in a simple injection and get transgenic animals, but so far we have not managed to do that.
Showing Gene Transfer Technique
What we have been able to do is to inject a gene sequence with an appropriate virus, which acts as a carrier directly into the testis, and here I have just injected a tiny amount of air to show that I am really in the right place, and we have got transgenic animals.
Here you can see several weeks after injection 14, 15 19, 20 and up to 38 weeks afterwards, the production of a small number of transgenic animals but really quite efficiently. Up to 70% of the offspring are actually with the transgene in them. A potentially a very, very potent technology, because this means we can have animals which are simply produced by natural mating. Interestingly at leastone out of 40 here and one out of 23 animals here are transgenic a long time after injection, suggesting we may have got in a few cases to founder stem cells in the testis. Quite clearly we need to do a lot more experimental work but I think this encourages us to believe that that this might be a much more effective way to make transgenic animals of large size, possibly for the transplantation for example, xenograph transplantation, for human organs in the pig. I think that there a lot of possibilities for this kind of technology. But it does raise important issues because if transgenesis becomes easy which it isn't at the moment, it raises the possibility we might want to try and to enhance human beings.
Let me just show you Manuelli. Manuelli, look at his forehead by the way in particular. This photograph was taken in Sardinia so some of you will realise what's wrong with him. He's, apart from the fact that he's using my camera and trying to destroy it and not taking very good photographs with it either, Manuelli has this very bowed forehead. He has actually got beta thalassemia. This is a blood disorder, a gene a single gene defect which is carried in a very large proportion of the population. When there's only one copy of the gene these children are not badly ill but with two copies they have a very serious blood disorder, a very serious anaemia which requires very repeated blood transfusion.
Links: OMIM- beta thalassemia
Beta Thalassemia 2
This is his younger brother who is actually free of the defect. Now these children are very common in Sardinia even with screening of the population. Indeed it is such a serious problem now that it affects something like 60% of the total health care budget for the whole island. It saps up all the resources and the only future for Manuelli is probably a bone marrow transplant - incredibly expensive. That would be the only cure and without that just the repeated transfusions carry all sorts of risks particularly endocrine risks, the risk for example of diabetes later on in life and iron overload. Interestingly I looked at some skulls from the island, which date some 3,000 years ago and were dated by carbon dating and they show the same deformity. It seems that beta thalassemia has been on that island for a very long time, at least three or possibly four thousand years and one has to ask oneself how it is that people have survived with such a prevalent gene in 1 in 7 of the population. Interestingly one of the things it does is that it protects against malaria and of course malaria was common in some Mediterranean countries. So there's a very interesting conundrum here. If we enhance this population or at least remove this gene by genetic engineering which might seem an absolutely reasonable thing to do given the severe cost of the disease and the problems that it causes, we might actually make them much more susceptible to other disorders which at the moment they have a healthy robustness against. This I think is one of the really difficult problems about meddling with genetics. It's been suggested by Robertson (spelling?) in the United States that there should be no reason why we shouldn't try and improve the human condition. After all we use fluoride toothpaste in our children to improve their beauty, as we give them orthodontic treatment. We will try to give them the very best education that we can. We send people to the Sydney Olympic Games in the best possible physical condition so that they actually have the best musculature, which requires training. We use hormone replacement therapy for example increasingly as we age and we use military discipline to make sure that we have a healthy aggression when we are attacked. So why not actually simply do it genetically? Well of course the arguments are really very considerable against. First of all there are the issues of inequality in our society: the risk of increasing racial prejudice and class distinction; the risk of having have-nots and haves, having a genetic inferior race and the fact that our children may not reach the expectation. But I think that it is inevitable that this is something first of all that we should be discussing in our society and thinking about because I think it is very possible given the technology that eventually we might actually want to try and use it. At the moment there are two reasons why I think it is out of the question as Doctor Hood pointed out. First of all mistakes are likely and if they occurred they would be irreversible and they would be imprinted on every generation to come thereafter. And secondly of course at the present time until we understand integration of the DNA much more and until we have much better computation and a whole range of other things, the results of this kind of meddling with the genome are likely to be entirely unpredictable as it is at the moment with transgenic technology. And that's why I think at least we are safe. I believe that we are as humans reasonable to be optimistic but it does raise one very interesting, for me, philosophical notion. Our reason for really wanting to protect human life, the greatest single moral imperative is because we argue that we are made in God's image and you could argue that if you consistently change the genome although I think what Lee Hood pointed out is that you'd have to change it an awful lot given the minor difference between us and the chimpanzee, if we really changed the genome the question is whether we would redefine what is human or whether we would make something which is superhuman. And if we did that would human life still therefore be sacred and would it still be in our new notion of the image of God. I think it's a very interesting question for our society still. One of the things I want to just finally say is this. There is at least many members of the public, though I think not amongst the geneticists and the biologists, a very strong deterministic view which I believe is fundamentally wrong. There is this notion for example when we talk about pre-implantation diagnosis, these are the first two babies born as a result of pre-implementation diagnosis, their elder brother has died. They're now aged 12. This is by the way not a gene defect. This is an acquired defect. It was environmental. She fell over two hours before the photograph. The perfect baby is not made by its genetics, actually, but it's made by the environment into which it finds itself, by its education, by its economic potential, by how it relates to society and how we care for it and by I think human love. And that seems to me to be something which has gone on in our genes for 40,000 years and will continue at least for the next century. So I believe essentially we are safe.
Can I just conclude by something I showed on Friday? It's such a favourite of mine. I hope those of you that were at the lecture on Friday don't mind seeing this again.
This woodcut by Peter Bruegel the Elder was done in 1553 and it shows the alchemist in his laboratory here reading from his tome 'Al ge mist' (Flemish for alchemist). There is one of his PhD students trying to transmute base metals into gold. This one is looking for the elixir of life and unfortunately there is no more NRH funding, his wife has run out of money. But Peter Bruegel is saying something very, very important to us. If you look in the background you can see his family, the three children left neglected in this shambolic laboratory, one with a coal scuttle on his head and the key to what Bruegel is on about is actually the reason why he's definitely talking about technology is because here in the window you see this classic medieval device. In the window we see the future and in the future these three children are being led, one with the coal scuttle still on his head into 'lospital', the hospital. Not the hospital of course. In medieval times ‚Äòlospital' means the poor house where they would be ultimately neglected. 'Al ge mist' means alchemist but it also means "all has miscarried". How interesting for a reproductive biologist. What the alchemist has forgotten of course is that he's pursued his technology forgetting the welfare of the next generation and perhaps that's the most important message for us too in this field of genetics. Thank you very much.
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- London University Professor of Fertility Studies at Imperial College
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- BBC science programmes Series include "Your Life in Their Hands" (five series), "Making Babies, "The Human Body" (three BAFTAs and a Peabody award), "Secret Life of Twins", "Superhuman" (October 2000 - Wellcome Award for Medicine and Biology), "Child of our Time", "Walking with Cavemen" and "The Human Mind".
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Cite this page: Hill, M.A. (2020, November 27) Embryology Embryology History - Robert Winston. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Embryology_History_-_Robert_Winston
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