Incomplete masculinisation of XX subjects carrying the SRY gene on an inactive X chromosome
- Kamila Kusza,
- Maciej Koteckia,
- Alina Wojdaa,
- Maria Szarras-Czapnikb,
- Anna Latos-Bielenskac,
- Alina Warenik-Szymankiewiczd,
- Anna Ruszczynska-Wolskab,
- Jadwiga Jaruzelskaa
- aInstitute of Human Genetics, Polish Academy of Sciences, Strzeszynska 32, 60-479 Poznan, Poland, bThe Children’s Memorial Health Institute, 04-736 Warszawa-Miedzylesie, Aleja Dzieci Polskich 20, Poland, cInstitute of Medical Genetics, University School of Medicine, Szpitalna 27/33, 60-572 Poznan, Poland, dInstitute of Obstetrics and Gynaecology, Clinics of Endocrinology, Polna 33, 60-535 Poznan, Poland
- Dr Jaruzelska.
- Received 13 January 1998
- Revised 27 January 1999
Abstract
46,XX subjects carrying the testis determining SRY gene usually have a completely male phenotype. In this study, five very rare cases of SRY carrying subjects (two XX males and three XX true hermaphrodites) with various degrees of incomplete masculinisation were analysed in order to elucidate the cause of sexual ambiguity despite the presence of the SRY gene. PCR amplification of 20 Y chromosome specific sequences showed the Yp fragment to be much longer in XX males than in true hermaphrodites. FISH analysis combined with RBG banding of metaphase chromosomes of four patients showed that in all three true hermaphrodites and in one XX male the Yp fragment was translocated onto a late replicating inactive X chromosome in over 90% of their blood lymphocytes. However, in a control classical XX male with no ambiguous features, the Yp fragment (significantly shorter than in the XX male with sexual ambiguity and only slightly longer than in XX hermaphrodites) was translocated onto the active X chromosome in over 90% of cells.
These studies strongly indicate that inactivation on the X chromosome spreading into a translocated Yp fragment could be the major mechanism causing a sexually ambiguous phenotype in XX (SRY+) subjects.
