OBJECTIVETo explore the possible mechanisms of spermatogenic arrest in severe oligoasthenoteratozoospermia induced by supernumerary, ring-neocentric 13q12.3 --> 13q22 chromosome and reciprocal deletion.

METHODSWe performed a genomic-wide high-density oaCGH analysis for a case of oligoasthenoteratozoospermia with abnormal chromosome 13 to characterize the breakpoints of the chromosome involved or the gene deletion caused by the rearrangement. We also conducted a fluorescence in situ hybridization analysis on the germ cells using probes of 13q14/13qter to observe the pairing condition of homologous chromosome 13.

RESULTSWe identified by oaCGH analysis a microdeletion of 4 consecutive probes (A_16_P19757882, A_16_P02744617, A_14_ P108858 and A_16_P02744687 at chr13q12.3: 27979261 --> 28039191) with 59.93 kb between the FLT1 and POMP genes, with no annotated genes in the deleted region. The signals of 13q14 and 13qter were separated from each other in 90% of all the primary spermatocytes examined, indicating the unpairing of homologous chromosome 13 or synapse failure.

CONCLUSIONChromosomal rearrangement-induced spermatogenesis failure is caused by the unpairing of the homologous chromosomes involved in the first meiotic division of germ cells.