Analyses of Gonadoblastoma Y (GBY)-locus and of Y centromere in Turner syndrome patients.

Background: Mosaicism with cytogenetically visible Y chromosome is found in 5-6% of Turner Syndrome (TS) patients. Additionally, occult Y-chromosome derived material is increasingly found in patients with monosomy X when using more sensitive molecular techniques. These TS patients are at risk of developing gonadoblastomas when the Y genes presumed to be involved in gonadoblastoma development (Gonadoblastoma-Y-locus; GBY) are present.

Objective: To find occult Y-chromosome material in TS patients and to correlate the patient's phenotype to Y-chromosome material.

Methods: We studied 60 TS-patients for presence of the Y chromosome with focus on the Gonadoblastoma Y-locus and its extension in Yp and Yq using sensitive Y centromere and Y gene deletion PCR assays. In addition, we evaluated their individual clinical and auxological characteristics.

Results: We identified presence of the GBY-locus in 7 patients (11.7%) including 4 patients without evidence for a Y chromosome in their preceding standard karyotype analyses. Clinical and auxological characteristics were similar in GBY-positive and GBY-negative patients.

Conclusions: Presence of the GBY locus in Turner patients with no indication of the Y chromosome in standard cytogenetic chromosome analysis can be revealed by sensitive molecular PCR assays screening for presence of the Y centromere and the GBY-candidate-genes in proximal Yp11 and Yq11, respectively.