The acrocentric part of der(Y)t(Y;acro)(q12;p1?2) contains D15Z1 sequences in the majority of cases

Chromosomal heteromorphisms (CHMs) are currently largely disregarded in human genetic diagnostics. One exception is der(Y)t(Y;acro)(q12;p1?2), which has at least been mentioned in karyotypes and discussed in reports. This derivative is frequently observed in healthy males with idiopathic infertility, which is not uncommon for CHMs. Here, we present the first systematic fluorescence in situ hybridization (FISH)-based study of 7 carriers of der(Y)t(Y;acro)(q12;p1?2). Specific probes for 15p11.2 (D15Z1) and 22p11.2 (D22Z4) were applied to answer the question of whether either of the short arms may be involved in the formation of the derivative Y-chromosome. In 6 out of 7 cases, specific staining was achieved using the D15Z1 probe, while the derivative acrocentric chromosomal region was not positive for D22Z4 in any of the 7 cases. In conclusion, this study implies that the acrocentric chromosomal region is derived from chromosome 15 in the majority of cases with der(Y)t(Y;acro)(q12;p1?2).