Noninvasive fetal RHD genotyping from maternal plasma. Use of a new developed Free DNA Fetal Kit RhD

Fetal RHD genotyping from maternal plasma was performed by real-time PCR amplification of exons 7 and 10 of the RHD gene and the amplified products were detected either with SYBR Green I dye according to our previously published method [Mol Diagn 8 (2004) 23-31] or with hydrolysis probes in a new Free DNA Fetal Kit RhD((R)). Plasma specimen from 300 RhD-negative pregnant women (between 10 to 34 weeks of gestation) were analysed and validation of the results was ascertained either by RHD genotyping on amniotic cells or by blood typing of the neonate at birth. We found 100% concordant results when comparing the two methods. Two false-positive but no false-negative results were found. Thus, the sensitivity of the assay was 100% and the specificity superior than 99%. These data confirm the accuracy of fetal RHD genotyping on maternal plasma using the Free DNA Fetal Kit RhD, thus allowing to propose non invasive PCR-based fetal RHD genotyping for all RhD-negative pregnant women and to restrict the use of anti-D immunoglobulins only to those bearing an RhD-positive fetus.

Paternité tardive : aspects spermatiques et génétiques

The effect of maternal age on the risk of meiotic abnormality is well documented. In contrast little is known about the effect of the paternal age. The question of the risk related to paternal age is raised because of the increased demand of Assisted Reproduction Techniques for older men. This review focuses on the alterations of male semen parameters, testis histology and genetic risks related to age. The motility, vitality and morphology of spermatozoa and semen volume are found decreasing with age. Histomorphometric studies reveal various alterations including a thickening of the basal membrane when spermatogenesis is arrested. The number of germinal and Sertoli cells decreases with increased age. Up to 95 years old, we could find subjects with complete spermatogenesis. Chromosomal analyses in different studies have provided controversial results. Our investigation on subjects aged from 29 to 102 showed that the rate of aneuploidy in the group of aged subjects with preserved spermatogenesis was not statistically different from the young control group. However the incidence of postmeiotic aneuploidy was increased when spermiogenesis had stopped. On the other hand from epidemiological studies, autosomal dominant diseases are known to be associated with paternal age. However, in the case of achondroplasia and Apert syndrome, direct DNA sperm analysis did not reveal significant increase in the mutation frequency with paternal age.