A novel widely expressed homologue of the VAV oncogene, VAV2 (53% identical residues), has been identified within the critical region for the tuberous sclerosis gene, TSC1, on human chromosome 9q34. By Southern blot analysis, analysis of allele-specific transcription, and direct sequencing of the VAV2 mRNA/cDNA from patient lymphoblastoid cell lines, we demonstrate that both alleles of this gene are expressed in TSC patients and there are no significant mutations. VAV consists of a novel array of signalling domains and is thought to play an important role in signal transduction in haematopoietic tissues where it is exclusively expressed. VAV2 is likely to serve a similar role more generally in mammalian cells, but is not the TSC1 gene.

Prenatal cytogenetic analysis of 71 fetuses conceived by intracytoplasmic sperm injection (ICSI) resulted in the detection of nine (12.7%) chromosome aberrations including two cases of 47,XXY, four cases involving a 45,X cell line and three autosomal trisomies. Molecular analysis of the parental origin of the deleted or supernumerary chromosome was performed by using polymorphic microsatellite markers. Six cases involving a sex chromosome abnormality were found to be of paternal origin while the two trisomic cases that could be analysed were of maternal origin. Two cases involved the same infertile couple who had two consecutive ICSI pregnancies terminated because of a chromosome abnormality. The replaced embryos in both cases originated from a single batch of ICSI fertilized oocytes of which part was used to initiate the first pregnancy and part was cryopreserved and used to initiate the second pregnancy.

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A cytogenetic survey and follow-up studies were performed in eight cases of full, mosaic, and pseudomosaic trisomy 9 prenatally diagnosed among 36,213 prenatal samples in our department between August 1970 and July 1996. Besides conventional chromosome analysis, interphase fluorescent in situ hybridization (FISH) was employed. FISH turned out to be a rapid and accurate method for verification of trisomy cell lines and could provide additional information to the prenatal cytogenetic results. FISH also enables the study of uncultured specimens of amniotic fluid, not accessible for traditional cytogenetic analysis. In three cases, retrospective DNA analysis showed the supernumerary chromosome 9 to be of maternal origin. The disomic cell lines in both mosaic trisomy 9 cases showed maternal uniparental disomy.