Meiotic studies in an azoospermic human translocation (Y;1) carrier.

A reciprocal translocation between the long arm of the Y chromosome and the long arm of chromosome 1 was observed in an infertile man with non-obstructive azoospermia. The study was performed using a combination of techniques: immunocytogenetic analysis, which allows the detection of synaptonemal complexes (SCs) and recombination sites (MLH1) simultaneously, and fluorescence in-situ hybridization analysis. Meiotic pairing analysis on 100 pachytene spreads showed the presence of a quadrivalent containing chromosomes 1 and Y. There were many abnormalities in chromosome pairing and recombination. These abnormalities included a great reduction of recombination events (as many as one fifth of the SCs had no MLH1 foci), and high proportions of unpaired regions and discontinuities in the SCs. We discuss the possibility that infertility in this patient may be due to transcriptional repression of part of chromosome 1 involved in the translocation, silencing some genes necessary for the progression of meiosis and causing defective meiotic pairing and recombination.