Pre-implantation genetic diagnosis-should we use ICSI for all?

OBJECTIVE: Intracytoplasmic sperm injection (ICSI) is commonly used during pre-implantation genetic diagnosis (PGD) in vitro fertilization (IVF), aiming to eliminate the risk of contamination from extraneous sperm DNA. Recently, ICSI "overuse" in non-male infertility has been doubted, since it does not offer an advantage over IVF. Prompted by the aforementioned observations, we sought to assess the accuracy of IVF vs ICSI in PGD cases, as might be reflected by a difference in the prevalence of discarded embryos as a consequent of parental contamination. METHODS: Cohort-historical study of all consecutive patients admitted to the IVF-PGD program in a large tertiary center. The percentages of complete, incomplete diagnosis, PCR failure, abnormal embryos, and the contamination rate with paternal DNA in the IVF-only and the ICSI-only groups. We reviewed the computerized files of all consecutive women admitted to our IVF for a PGD-PCR cycle. Patients were divided accordingly into three groups: an IVF group-where all the oocytes underwent IVF only, an ICSI group-where all oocytes underwent ICSI, and a mixed group-where sibling oocytes underwent both IVF and ICSI. The laboratory data and the genetic diagnostic results were collected and compared between the different insemination groups. RESULTS: Nine-hundred and twenty-seven patients underwent IVF-PGD cycles in our program, 315 in the IVF group, 565 in the ICSI group, and 47 in the mixed group. No differences were observed in fertilization rates, the percentage of embryos available for biopsy, and the percentages of complete, incomplete diagnosis, PCR failure, or abnormal embryos, between the IVF-only and the ICSI-only groups and between the IVF and the ICSI of sibling oocytes in the mixed group. Moreover, contamination with paternal DNA, through contamination with sperm cells, was negligible. Not one single case of misdiagnosis was encountered during the study period. CONCLUSION: It might be therefore concluded that IVF should be the preferred insemination methods in PGD cycles, and ICSI should be indicated only in cases of male-factor infertility.

The single cell as a tool for genetic testing: credibility, precision, implication.

PURPOSE: To investigate the influence of amplicons size and cell type on allele dropout and amplification failures in single-cell based molecular diagnosis. METHODS: 730 single lymphocytes and amniotic cells were collected from known heterozygotes individuals to one of the common Ashkenazi Jewish mutations: 1278+TATC and IVS12+1G>C which cause Tay Sachs Disease, IVS20+6T and 854A>C which underlie Familial Dysautonomia and Canavan Disease. DNA was extracted and analyzed by our routine methods. RESULTS: Reduced rates of allele dropout and amplification failure were found when smaller amplification product were designed and in amniotic cultured cells compared to peripheral lymphocytes. Cultured lymphocytes, induced to divide, demonstrated significantly less allele dropout than non induced lymphocytes suggesting the role of division potential on amplification efficiency. CONCLUSION: Single cell based diagnosis should be designed for each mutation. Minimal sized amplicons and cell having division potential should be preferred, as well as sensitive techniques to detect preferential amplification.

Bloom syndrome and Fanconi's anemia: rate and ethnic origin of mutation carriers in Israel.

BACKGROUND: The Bloom syndrome gene, BLM, was mapped to 15q26.1 and its product was found to encode a RecQ DNA helicase. The Fanconi's anemia complementation group C gene was mapped to chromosome 9q22.3, but its product function is not sufficiently clear. Both are recessive disorders associated with an elevated predisposition to cancer due to genomic instability. A single predominant mutation of each disorder was reported in Ashkenazi Jews: 2281delATCTGAinsTAGATTC for Bloom syndrome (BLM-ASH) and IVS4 + 4AT for Fanconi's anemia complementation group C. OBJECTIVES: To provide additional verification of the mutation rate of BLM and FACC in unselected Ashkenazi and non-Ashkenazi populations analyzed at the Sheba Medical Center, and to trace the origin of each mutation. METHODS: We used polymerase chain reaction to identify mutations of the relevant genomic fragments, restriction analysis and gel electrophoresis. We then applied the Pronto kit to verify the results in 244 samples and there was an excellent match. RESULTS: A heterozygote frequency of 1:111 for BLM-ASH and 1:92 for FACC was detected in more than 4,000 participants, none of whom reported a family history of the disorders. The Pronto kit confirmed all heterozygotes. Neither of the mutations was detected in 950 anonymous non-Ashkenazi Jews. The distribution pattern of parental origin differed significantly between the two carrier groups, as well as between each one and the general population. CONCLUSIONS: These findings as well as the absence of the mutations in non-Ashkenazi Jews suggest that: a) the mutations originated in the Israelite population that was exiled from Palestine by the Roman Empire in 70 AD and settled in Europe (Ashkenazi), in contrast to those who remained; and b) the difference in origin distribution of the BS and FACC mutations can be explained by either a secondary migration of a subgroup with a subsequent genetic drift, or a separate geographic region of introduction for each mutation.