Research Letter A dicentric Y chromosome resulting from pericentric inversion between the centromere and Yq heterochromatin

A 34-year-old Taiwanese woman, gravida 2, para 1, underwent amniocentesis at the 18th week of gestation. A chromosomal analysis of the amniocytes showed abnormal Y chromosomes in all of the cells analyzed. The cells were in the metaphase stage at the time of analysis. The chromosomal anomaly was tentatively designated as 46,X,var(Y) (Fig. 1A). The woman conceived spontaneously and had not experienced any miscarriage. Three years previously, she delivered a female baby who developed normally. Karyotyping of the couple showed that the abnormal Y chromosome in all cells analyzed was inherited from the 34-year-old husband (Fig. 1A). The semen parameters and hormone profile of the husband were within normal ranges. The pregnancy was uneventful, and the woman delivered a grossly normal male baby with a body weight of 3250 g and body length of 52 cm. C banding showed that the Y chromosome contained two centromeres and two segments of heterochromatin blocks (Fig. 1B). Array-based comparative genomic hybridization (aCGH) using high-density CytoScan v3 (Agilent Technologies) was applied to detect genomic aberrations. The CytoScan v3 chip (Agilent Technologies) encompassed 60,000 DNA probes with a resolution of approximately 50 kb. Fluorescence in situ hybridization (FISH) was performed using the DYZ1 probe corresponding to the Yq heterochromatin and the DYZ3 probe corresponding to the centromere. The DYZ1 probe was labeled with an indigo fluorophore (Vysis, Inc.) and the DYZ3 probe was labeled with a green fluorophore (Vysis, Inc.). The FISH results revealed two centromeres and two blocks of heterochromatin in the Y chromosome. Multicolor chromosome banding (mBAND) was performed to characterize the abnormal Y chromosome further using the