Case report: birth after preimplantation genetic diagnosis of a subtle mutation in SMN1 gene.

Spinal muscular atrophy (SMA) preimplantation genetic diagnosis (PGD) has been available since 1998. Protocols are based on the detection of the homozygous deletion of exon 7, which are present in 90-98% of SMA patients. A couple where the woman was a heterozygous carrier of the usual SMN1 Del7 mutation and the man was a heterozygous carrier of pMet263Arg substitution in exon 6 of SMN1 gene was referred for PGD. The usual PGD test being unsuitable for this couple, we developed a novel duplex polymerase chain reaction (PCR)-based PGD test for the detection of the mutation pMet263Arg by allele specific amplification, combined with the amplification of D5S641 extragenic polymorphic marker. PCR conditions were established using single control lymphoblasts and lymphocytes from the pMet263Arg substitution carrier. Amplification was obtained in 100% of the 86 single cells tested, amplification refractory mutation system (ARMS) PCR was specific in 100% of single cells tested and a complete genotype (mutation plus D5S641) was achieved in 88% of them. A PGD cycle was performed successfully and a pregnancy was obtained. An unaffected girl was born and postnatal diagnosis confirmed PGD results. This is the first PGD described for SMA because of another mutation than the major homozygous exon 7 deletion of SMN1. In the future, a similar strategy could be adopted for other subtle mutations of this gene.

Fluorescence in situ hybridization sperm analysis of six translocation carriers provides evidence of an interchromosomal effect.

OBJECTIVE: To investigate the existence of an interchromosomal effect in balanced reciprocal translocation carriers and to evaluate their risk of having an affected child or repeated spontaneous abortions. DESIGN: Analysis of chromosomal sperm content by fluorescence in situ hybridization (FISH) using probes for chromosomes 1, 15, 16, 17, 18, X, and Y. SETTING: University hospital. PATIENT(S): Six male carriers of balanced chromosome rearrangements, one with normal sperm parameters and five with oligoasthenoteratozoospermia, and seven fertile controls. INTERVENTION(S): Fluorescence in situ hybridization for chromosomal enumeration on sperm samples. MAIN OUTCOME MEASURE(S): Rate of disomy for the studied chromosomes. RESULT(S): A total of 123,842 spermatozoa were scored (82,181 for controls and 41,661 for patients). For each patient, at least one chromosome studied presented a significantly increased rate of disomy. One patient showed a clear interchromosomal effect for at least three of the six chromosomes studied. Disomy rates were statistically significantly and inversely correlated with the total progressive motility of spermatozoa. CONCLUSION(S): The observed interchromosomal effect seems to be translocation, patient, and chromosome dependent. Variable effects were observed, according to the chromosome studied. When we looked at patients carrying the same translocation, the level of disomy rate was variable and affected different chromosomes.

Search for mutations involved in human globozoospermia.

BACKGROUND: Globozoospermia is a severe form of teratozoospermia characterized by round-headed sperm with an absence of acrosomes. Family cases of globozoopermia suggest that this pathology has genetic origins, but the mode of inheritance remains unknown. So far, no responsible genes have been identified. Recently, a mouse lacking the casein kinase IIalpha' (encoded by the Csnk2a2 gene) was described. This mutant mouse presents a single phenotype reminiscent of that seen in human globozoospermia. Interestingly, the fission yeast orthologue (orb5) exhibits, when mutated, a spherical phenotype. Casein kinase II is a heterotetramer, composed of two catalytic subunits alpha or alpha' and two regulatory beta subunits (encoded by the Csnk2b gene). METHODS AND RESULTS: Based on the evolution conservation, phenotypes observed in mouse and yeast mutant and the structure of casein kinase II, we analysed Csnk2a2 and Csnk2b genes in six patients with globozoospermia and 10 fertile controls. Genomic DNA was extracted from peripheral blood and PCR was performed to amplify Csnk2a2 and Csnk2b genes before sequencing. CONCLUSION: No mutation was identified among these six patients. Further work is needed, with a larger patient data set, to identify putative genes involved in this form of male infertility.

[Ontogenesis of primordial germ cells]. / Ontogenèse des cellules germinales primordiales.

In sexually reproducing animals all gametes of either sex arise from primordial germ cells (PGC). PGC represent a small cell population, appearing early during embryo development. They represent a key cell population responsible for the survival and the evolution of a species. Indeed, the production of gametes will assure fertilisation and therefore the establishment of the next generation. Until recently only few laboratories were working on PGC biology. A new interest emerged since these cells have the ability to function as pluripotent stem cells when established as cell lines. Indeed, like embryonic stem cells (ESC), embryonic germ cells (EGC) are able to differentiate in a wide variety of tissues. In vivo, EGC are able, after injection into a host blastocyst cavity to colonise the inner cell mass and to participate in embryonic development. In vitro studies in human and mouse have also shown their capacity to differentiate into a large variety of cell types allowing the study of processes involved in cardiomyocyte, haematopoietic, neuronal and myogenic differentiation pathways. We present here the last updates of PGC ontogeny focusing mainly on the murine model.

[Follow-up of children born by ICSI]. / Les enfants de l'ICSI sous la loupe.

The debate concerning the health of children conceived by artificial reproduction technology (ART) continues. Among these techniques, intracytoplasmic sperm injection (ICSI) is the subject of most attention. Indeed, several studies have concentrated on the evaluation of risks associated with ICSI. The publication of a few recent articles on the subject is providing an opportunity to reconsider the situation. Generally, women conceiving via ART are older, more often primipar and present increased rates of uterine pathologies compared to women conceiving naturally. Furthermore, ART pregnancies are sources of anxiety resulting in a significant increase rates of caesarean section. ART children present an increased risk of low birth rate often linked to multiple pregnancy, but this is also true for singleton pregnancy. Major studies have not revealed a significantly increased rate of malformations in ICSI children. However, sporadic observations of errors in genomic imprinting or of rare tumors in children conceived by ICSI point to a need for increased vigilance of ICSI practices. Finally, the mental development, the family and social life of ICSI children appears similar to children conceived naturally.