Sex chromosome mosaicism in males carrying Y chromosome long arm deletions

Microdeletions of the long arm of the Y chromosome (Yq) are a common cause of male infertility, Since large structural rearrangements of the Y chromos ome are commonly associated with a 45,XO/46,XY chromosomal mosaicism, we st udied whether submicroscopic Yq deletions could also be associated with the development of 45,XO cell lines. We studied blood samples from 14 infertil e men carrying a Yq microdeletion as revealed by polymerase chain reaction (PCR), Patients were divided into two groups: group 1 (n = 6), in which kar yotype analysis demonstrated a 45,X/46,XY mosaicism, and group 2 (n = 8) wi th apparently a normal 46,XY karyotype, 45,XO cells were identified by fluo rescence in-situ hybridization (FISH) using X and Y centromeric probes, Lym phocytes from 11 fertile men were studied as controls. In addition, sperm c ells were studied in three oligozoospermic patients in group 2, Our results showed that large and submicroscopic Yq deletions were associated with sig nificantly increased percentages of 45,XO cells in lymphocytes and of sperm cells nullisomic for gonosomes, especially for the Y chromosome. Moreover, two isodicentric Y chromosomes, classified as normal by cytogenetic method s, were detected. Therefore, Yq microdeletions may be associated with Y chr omosomal instability leading to the formation of 45,XO cell lines.