Preimplantation genetic haplotyping
Preimplantation genetic haplotyping (PGH) is a clinical method of preimplantation genetic diagnosis (PGD). It identifies a haplotype of genetic markers that have statistical associations to a target disease rather than identifying the mutation causing the disease.
Once a panel of associated genetic markers have been established for a particular disease it can be used for all carriers of that disease. In contrast, since even a monogenic disease can be caused by many different mutations within the affected gene, conventional PGD methods based on finding a specific mutation would require mutation-speciﬁc tests. Thus, PGH widens the availability of PGD to cases where mutation-specific tests are unavailable.
PGH also has an advantage over fluorescence in situ hybridization (FISH) in that FISH is not usually able to make the differentiation between embryos that possess the balanced form of a chromosomal translocation and those carrying the homologous normal chromosomes. This inability can be seriously harmful to the diagnosis made. PGH can make the distinction that FISH often cannot. PGH does this by using polymorphic markers that are better suited at recognizing translocations. These polymorphic markers are able to distinguish between embryos that carried normal, balanced, and unbalanced translocations. FISH also requires more cell fixation for analysis whereas PGH requires only transfer of cells into polymerase chain reaction tubes. The cell transfer is a simpler method and leaves less room for analysis failure.
PGH has been used to screen for:
- cystic fibrosis
- Duchenne muscular dystrophy
- Huntington's disease
- Spinal Muscular Atrophy
- Alport's syndrome
- Von Hippel-Lindau disease
- Sickle-cell disease
- and recurrent Hydatidiform mole
- Renwick PJ, Trussler J, Ostad-Saffari E et al. (2006-07-13). "Proof of principle and first cases using preimplantation genetic haplotyping--a paradigm shift for embryo diagnosis" (subscription required). Reprod Biomed Online 13 (1): 110–9. doi:10.1016/S1472-6483(10)62024-X. PMID 16820122.
- Shamash, J. et al. (2011). Preimplantation genetic haplotyping a new application for diagnosis of translocation carrier’s embryos – preliminary observations of two robertsonian trans-location carrier families. Journal of Assisted Reproduction and Genetics, 28(1), 77-83.
- "Revolutionary new technology will allow more couples to benefit from preimplantation genetic diagnosis". PGH Press Release. 2006 Guy's and St Thomas' NHS Foundation Trust. 2006-09-12. Archived from the original on 2006-09-30. Retrieved 2006-09-26.
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