SUPERNUMERARY MARKER CHROMOSOMES (SMCS) IN TURNER-SYNDROME ARE MOSTLYDERIVED FROM THE Y-CHROMOSOME

DNA and FISH (fluorescence in situ hybridization) analysis were carrie d out in 12 patients with stigmata of Turner syndrome to determine whe ther the Supernumerary Marker Chromosome (SMC) found cytogenetically i n each of these patients was derived from the Y chromosome. The presen ce of a Y chromosome in these patients may predispose them to develop gonadoblastoma. PCR-Southern blot analysis, followed by FISH, was used to detect the presence of Y chromosome material. The Sex determining Region Y (SRY), Testis Specific Protein Y-encoded (TSPY) and Y-chromos ome RNA Recognition Motif (YRRM) genes, which map at Yp11.31, Yp11.1-1 1.2 and Yp11.2/Yq11.21-11.23, respectively, were selected as markers, because they span the whole Y chromosome, and more importantly, they a re considered to be involved in the development of gonadoblastoma. It was shown that in 12 patients, all of whom had an SMC, the SMC of 11 w as derived from the Y chromosome. Furthermore, the presence of the SRY , TSPY and YRRM gene sequences was determined and FISH analysis confir med the Y origin of the SMCs. The methodology described in this report is a rapid, reliable and sensitive approach which may be easily appli ed to determine the Y origin of an SMC carried in Turner syndrome. The identification of an SMC is important for the clinical management and prognostic counseling of these patients with Turner syndrome.