Silvana Guioli

The expression pattern of a mouse doublesex-related gene is consistent with a role in gonadal differentiation

The signal for somatic sex determination in mammals, Caenorhabditis elegans and Drosophila melanogaster is chromosomal, but the overall mechanisms do not appear to be conserved between the phyla. However it has been found quite recently that the C. elegans sex-determining gene Mab-3 contains a domain highly homologous to the Drosophila sex-determining gene doublesex (dsx) and shares a similar role. These data suggest that at least some aspects of the regulation of sex determination might be conserved. In humans, a doublesex-related gene (DMRT1) was identified at less than 30 kb from the critical region for sex reversal on chromosome 9p24 (TD9). In order to get insights into the role of DMRT1 in sex determination/differentiation, we have isolated DMRT1 mouse homologue (Dmrt1) and analysed its expression pattern. The gene is expressed in the genital ridges of both sexes during the sex-determining switch and it shows male/female dimorphism at late stages of sex differentiation.

Two families of low-copy-number repeats are interspersed on Xp22.3: Implications for the high frequency of deletions in this region

The locations of two families of low-copy-number repeats (CRI-S232 and G1.3) in the physical and genetic maps of the distal short arm of the human X chromosome (Xp22.3) have been determined. Single-copy fragments flanking several repeat elements from each family have been cloned and assigned to specific intervals on a deletion map of Xp22.3. Physical distances between these loci and previously isolated Xp22.3 markers have been determined by pulsed-field gel electrophoresis (PFGE). The positions of some of these markers on the genetic map of the region have been established by segregation analysis in CEPH families. Four members of the CRI-S232 family have been localized within 3 Mb on Xp22.3, interspersed with two members of the G1.3 family. Both deletion and PFGE mapping data suggest that a CpG island localized in a specific position on the map might be associated with the Kallmann syndrome gene. Unlike the previously reported data on hyperpolymorphic minisatellite sequences, no increase in the recombination rate was detected around the CRI-S233 repeats. The presence of several repeat elements in a region with a very high frequency of deletions, such as Xp22.3, is highly suggestive of the occurrence of unequal crossovers between the various elements, leading to deletion events.

Molecular analysis of 9p deletions associated with XY sex reversal: refining the localization of a sex-determining gene to the tip of the chromosome.

We thank Dr. C. P. Bennet, R. Hawkins, and Dr. O. Zuffardi, for providing us with some of the patient material; Giuliana Peverali, for technical support in the microsatellite typing; M. Davies, for technical support in tissue culture; and Drs. C. Farr and E.A. Oakenfull, for critical reading of the manuscript. This work was supported by Welcome grant 035201/Z/92 (to P.N.G and S.G.), EU grant Biomed2-CT960790 (to P.N.G.), a Telethon research fellowship (to S.G.), and an EMBO long-term fellowship (to K.S.).

22-P015 Chicken oocytes and meiotic silencing

maximise lifetime reproduction. The aim of the current study is to determine the patterns of gene expression associated with longevity and reproduction in fruit fly. The Drosophila are fed varying ratios of a protein/carbohydrate diet, whole fly RNA is extracted and gene expression is assayed via Affymetrix microarrays, and differentially expressed genes are verified with qRT-PCR. Once candidate genes have been identified, mutation studies will be used to further validate the results and identify pathways that control the trade-offs between reproduction and longevity.