UNSW Banner

UNSW Embryology

Week 1 - Abnormalities

© Dr Mark Hill (2008)

Acknowledgements

Introduction

Week 1 abnormalities relate to germ cell formation, fertilization and abnormal implantation.

Down Syndrome

Aneuploidy - male trisomy 21

Below are shown some examples of week 1 abnormalities with links to specific internal and external resources. Some of these abnormalities are also covered in other sections of notes.

Abnormal germ cell formation (gametogenesis) of both egg and sperm, can result from gonad (ovary or testes) abnormalities. In the ovary these including abnormal oogenesis, ovulation, hormonal abnormalities that can impact upon the normal menstrual cycle. In the testes abnormal spermatogenesis can result in either low spermatozoa numbers or motility.

Fertilization is a process requiring egg and sperm interaction, finally resulting in a diploid zygote. These include development of the blastocyst without an embryo, a hydatiform mole.

Abnormal implantation (Note: implantaion is a week 2 topic) or ectopic pregnancy is the result of premature or inappropriate implantation of the developing blastocyst. (More? Week 2 Abnormalities)

Please note that in order to best understand abnormal development issues, you must first understand normal development.

Page Links: Introduction | Some Recent Findings | Germ Cell Formation | Fertilization | Tubal Factor Infertility | Hydatidiform Mole | Parthenogenesis | Mitochondria | Capacitation in vitro | References | Glossary

Related Pages:

Some Recent Findings

"Bone morphogenetic protein 15 (BMP-15) gene cause female infertility in the monoovulatory human and sheep; however, in the polyovulatory mouse, loss-of-function of BMP-15 results only in reduced ovulation rate. ...The species-specific differences in the phenotypes caused by BMP-15 mutations may thus be attributed to the temporal variations in the production of the mature form of BMP-15." Yoshino O, McMahon HE, Sharma S, Shimasaki S. A unique preovulatory expression pattern plays a key role in the physiological functions of BMP-15 in the mouse. Proc Natl Acad Sci U S A. 2006 Jul 3

Self Assessment Questions

Germ Cell Formation

Abnormal germ cell formation (gametogenesis) of both egg and sperm, can result from gonad (ovary or testes) abnormalities. (More? Gonadal Dysfunction)

In the ovary, these including abnormal oogenesis, ovulation, hormonal abnormalities that can impact upon the normal menstrual cycle. (More? Oogenesis | Human Menstrual Cycle)

In the testes, abnormal spermatogenesis can result in, low spermatozoa numbers or motility: obstructive azoospermia, non-obstructive azoospermia (NOA). In addition to defects in spermatozoa production genital abnormalites can affect delivery and this is common in male infertility. (More? Spermatogenesis)

Fertilization

Fertilization is a process requiring egg and sperm interaction, finally resulting in a diploid zygote. These include development of the blastocyst without an embryo, a hydatidiform mole.

Hydatidiform Mole

Tumour with "grape-like" placental appearance without enclosed embryo formation, arises mainly from a haploid sperm fertilizing an egg without a female pronucleus. (More? Week 2 Abnormalities - Hydatidiform Mole)

Hydatidiform Mole

WWW Links: International Society for the Study of Trophoblastic Diseases | Sydney Gynaecological Oncology Group Gestational Trophoblastic Disease | ACT Pathology Uterus benign fibromyoma hydatidiform mole | The Journal of Reproductive Medicine Gestational Trophoblastic Disease (1998)

Parthenogenesis

Other than mammals, many different species (plants, insects, reptiles) can develop from unfertilized eggs. An embryo so formed without sperm contribution is called parthenogenesis (Greek parthenos = virgin, genesis = birth). Blocking of parthenogenesis in mammals appears to be related to genomic imprinting. Abnormal parthenogenic processes can occur in mammals, and more recently a parthenogenic mouse has been made in the laboratory.

Kono T. Genomic imprinting is a barrier to parthenogenesis in mammals. Cytogenet Genome Res. 2006;113(1-4):31-5.

Coullin P. [From human andro- and parthenogenesis (hydatidiform moles and benign ovarian teratomas) to cancer] Gynecol Obstet Fertil. 2005 Jul-Aug;33(7-8):469-82. Review. French.

Kono T, Obata Y, Wu Q, Niwa K, Ono Y, Yamamoto Y, Park ES, Seo JS, Ogawa H. Birth of parthenogenetic mice that can develop to adulthood. Nature. 2004 Apr 22;428(6985):860-4. "Mouse parthenogenetic embryos die by day 10 of gestation. Bi-parental reproduction is necessary because of parent-specific epigenetic modification of the genome during gametogenesis..... Here we show the development of a viable parthenogenetic mouse individual from a reconstructed oocyte containing two haploid sets of maternal genome, derived from non-growing and fully grown oocytes."

Tateno H, Kamiguchi Y. How long do parthenogenetically activated mouse oocytes maintain the ability to accept sperm nuclei as a genetic partner? J Assist Reprod Genet. 2005 Feb;22(2):89-93. "Intracytoplasmic sperm injection (ICSI) into oocytes within 1 h after parthenogenetic activation produces cytogenetically competent embryos in the mouse."

Wrzeska M, Rejduch B. Genomic imprinting in mammals. J Appl Genet. 2004;45(4):427-33. Review.

Tubal Factor Infertility

Tubal factor infertility (TFI) is described as a structural or functional damage to one or both Fallopian (uterine) tubes that reduces fertility. Genital tract infections can lead to "scarring" of the lining epithelilim or the cilia associated with the epithelium.

Mycoplasma genitalium (M. genitalium), a genital tract parasitic bacterium that can populate this tubal epithelial layer can cause epithelial cilia damage and therefore contribute to this process. A study has also shown that M. genitalium can bind to human spermatozoa, which could then be carried by motile sperm, and contribute to this process of female genital disease and infertility.

Implantation

Abnormal implantation is covered in detail in week 2 abnormalities, as one major form is premature implantation it is included in these week 1 abnormalities. Ectopic pregnancies are the result of implantation occurring at sites other than the within the uterus, including the uterine horns and outside the uterus on the external uterine surface or other structures in the peritoneal cavity (ovary, peritoneal wall, gastrointestinal tract, mesentry, blood vessels). (More? Week 2- Tubal Pregnancy)

OMIM Database

Online Mendelian Inheritence in Man Database OMIM is an external database with a OMIM Database Search option. (Note: For computers without internet access, earlier search results below will work).

List Results (1999)

Individual Entries (1999)

PubMed

PubMed provided by National Library of Medicine (US) search service to access the 9 million citations in MEDLINE and Pre-MEDLINE (with links to participating on-line journals), and other related databases.

Selected lists of references (from PubMed March 1999 search) are available for users without internet access.

Computers with internet access can search from either Below or PubMed Internet Access

Fertilization

Development journal search results "blasocyst" (1999)

Glossary of Terms

A |B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Quick Links

Week 1 Pages:

Introduction | Abnormalities | Gamete formation | Cell division | Fertilization | Zygote | Blastocyst | Male sex determination| X inactivation | References | Text only page | WWW Links |

UNSW Embryology ISBN: 978 0 7334 2609 4

UNSW CRICOS Provider Code No. 00098G