UNSW Embryology

Prenatal Diagnosis - Comparative Genomic Hybridization

© Dr Mark Hill (2009)

Acknowledgements

Introduction

This new test under development is based upon microarray-based comparative genomic hybridization (array CGH).

All fetal cells should have complete copies of maternal and paternal genomes. The test compares regions of fetal DNA that deviate from this "pattern" due to either too much or too little DNA, alterations reflect regions of the genome that are either copied or deleted. These genetic changes may therefore cause disease. (More? see recent article Nature 438, 733-734 (8 December 2005) Fetal genetic testing: Screen test)

Some Recent Findings

Preimplantation genetic diagnosis: State of the art. Basille C, Frydman R, Aly AE, Hesters L, Fanchin R, Tachdjian G, Steffann J, Lelorc'h M, Achour-Frydman N. Eur J Obstet Gynecol Reprod Biol. 2009 May 1. [Epub ahead of print] PMID: 19411132

"Preimplantation genetic diagnosis (PGD) is used to analyze embryos genetically before their transfer into the uterus. It was developed first in England in 1990, as part of progress in reproductive medicine, genetic and molecular biology. PGD offers couples at risk the chance to have an unaffected child, without facing termination of pregnancy. Embryos are obtained by in vitro fertilization with intracytoplasmic sperm injection (ICSI), and are biopsied mostly on day 3; blastocyst biopsy is mentioned as a possible alternative. The genetic analysis is performed on one or two blastomeres, by fluorescent in situ hybridization (FISH) for cytogenetic diagnosis, or polymerase chain reaction (PCR) for molecular diagnosis. Genetic analysis of the first or second polar body can be used to study maternal genetic contribution. Only unaffected embryos are transferred into the uterus. To improve the accuracy of the diagnosis, new technologies are emerging, with comparative genomic hybridization (CGH) and microarrays."

Microarray

Microarrays are a new technique that allows a large number of different genetic sequences to be arrayed on a slide which can then be used to identify specific sequences in an unknown mix of either DNA or RNA. This technique required the development of DNA synthetic techniques and microprocessor controlled robotics for array design and has been used extensively in cell biology.

What is an array? "to place in an orderly arrangement" Think of a hairbrush with each "hair" dipped in individual coloured inks and applied to paper. Each "hair" would makes an individual coloured "spot". Now consider instead of ink, if each hair had a different piece of DNA then a specific pattern is generated.

(More? UNSW Cell Biology Microarray)

References

Reviews

• Shen Y, Wu BL. Microarray-based genomic DNA profiling technologies in clinical molecular diagnostics. Clin Chem. 2009 Apr;55(4):659-69. Epub 2009 Feb 20. Review. PMID: 19233918
• Kennett JY, Watson SK, Saprunoff H, Heryet C, Lam WL. Technical demonstration of whole genome array comparative genomic hybridization. J Vis Exp. 2008 Aug 5;(18). pii: 870. doi: 10.3791/870. PMID: 19066503
• Check E. Fetal genetic testing: Screen test. Nature. 2005 Dec 8;438(7069):733-4.
• Tempest HG, Griffin DK. The cytogenetics of preimplantation human development: insights provided by traditional and novel techniques. Chromosoma. 2005 Sep;114(4):295-9. Epub 2005 Oct 15. Review.

Articles

• Preimplantation genetic diagnosis: State of the art. Basille C, Frydman R, Aly AE, Hesters L, Fanchin R, Tachdjian G, Steffann J, Lelorc'h M, Achour-Frydman N. Eur J Obstet Gynecol Reprod Biol. 2009 May 1. [Epub ahead of print] PMID: 19411132
• Vissers LE, Veltman JA, van Kessel AG, Brunner HG. Identification of disease genes by whole genome CGH arrays. Hum Mol Genet. 2005 Oct 15;14 Spec No. 2:R215-23.
• Rickman L, Fiegler H, Carter NP, Bobrow M. Prenatal diagnosis by array-CGH. Eur J Med Genet. 2005 Jul-Sep;48(3):232-40.
• Barrett MT, Scheffer A, Ben-Dor A, Sampas N, Lipson D, Kincaid R, Tsang P, Curry B, Baird K, Meltzer PS, Yakhini Z, Bruhn L, Laderman S. Comparative genomic hybridization using oligonucleotide microarrays and total genomic DNA. Proc Natl Acad Sci U S A. 2004 Dec 21;101(51):17765-70. Epub 2004 Dec 10. PNAS

Search PubMed: term = comparative genomic hybridization | preimplantation cytogenetics |

The Australian NHMRC

1988 recommendations for neonates be assessed for follow-up care under the following conditions.

(see the NHMRC WWW Page)

• Birthweight less than 1500g or gestational age less than 32 weeks
• Small-for-gestational-age neonates
• Perinatal asphyxia
• Apgar score less than 3 at 5 minutes
• clinical evidence of neurological dysfunction
• delay in onset of spontaneous respiration for more than 5 minutes and requiring mechanical ventilation
• Clinical evidence of central nervous system abnormalities ie., seizures, hypotonia
• Hyperbilirubinaemia of greater than 350umol/l in full term neonates
• Genetic, dysmorphic or metabolic disorders or a family history of serious genetic disorder
• Perinatal or serious neonatal infection including children of mothers who are HIV positive
• Psychosocial problems eg., infants of drug-addicted or alcoholic mothers.

Finally

Each section of the notes covering early development and specific systems contain references to specific abnormalities (on Page 2 of each notes section). The best source for Australian statistical data is the Australian Institute of Health and Welfare National Perinatal Statistics Unit, UNSW which publishes "Congenital Malformations Australia" every 2 years. Be aware that some congenital abnormalities, by their nature, affect multiple systems. In the USA, the Center for Disease Control (CDC) keeps and publishes relevant statistical information. A very difficult issue in abnormal development are the many different Ethical implications.

This current page is a link to Normal and Abnormal Development and Population Data.

Where to Next?

Look at types of Abnormal Development that can occur during development.

Alternatively, look at normal development. Development Notes

Quick Links

Finally

For those wanting to see dynamic processes of development (and have a reasonably quick connection) then the Movies pages are good for watching changes occur.

Other Embryos

The study of human development has relied extensively on studying the process in other model animals. For those wanting to see the process of development in other species then the other embryos pages are a good start.

UNSW Embryology ISBN: 978 0 7334 2609 4

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