Exploring evolution in Ceboidea (Platyrrhini, primates) by Williams-Beuren probe (HSA 7q11.23) chromosome mapping.

The ancestral platyrrhine karyotype was characterised by a syntenic association of human 5 and a small segment of human 7 orthologues. This large syntenic association has undergone numerous rearrangements in various phylogenetic lines. We used a locus-specific molecular cytogenetic approach to study the chromosomal evolution of the human 7q11.23 orthologous sequences (William-Beuren syndrome, WS) in various Ceboidea (Platyrrhini) species. The fluorescent in situ hybridisation of the WS probe revealed a two-way pattern of chromosomal organisation that suggests various evolutionary scenarios. The first pattern (seen in Callimico and Saimiri) includes a fairly simple disruption of the 7/5 syntenic association by a chromosome fission. The second pattern (seen in Atelinae, Alouattinae and in Callicebus) is characterised by an increasing complexity in the 7/5 association as a consequence of a series of inversions and translocations resulting in different syntenic associations. These data support recent proposals for phylogenomic groupings of New World monkeys. The study also illustrates how single-locus probe hybridisations can reveal intrachromosomal rearrangements.

Prenatal diagnosis of del(9)(p24): a sex reverse case.

BACKGROUND: We report on a fetus with sex reversal and del(9)(p24) consequent to a malsegregation of a maternal balanced complex translocation involving chromosomes 7, 9 and 11. METHODS: Fluorescence in situ hybridization (FISH) was performed in order to verify the presence of the SRY gene and the absence of DMRT1 and DMRT2 genes located in 9p24.3 region and frequently associated with sex reversal. RESULTS AND CONCLUSIONS: The prenatal karyotype revealed an unbalanced male fetus. The postmortem examination showed a malformed fetus with female external genitalia. Lack of DMRT1-2 genes established by FISH.