Identification a rare chromosomal translocation 45,X, der(Y;15)(q11.2;q11.2) in an azoospermic patient using C-MoKa

The 45,X karyotype (X monosomy) is prevalent in females with Turner syndrome. However, in rare cases, it can also manifest in males. It typically results from an unbalanced translocation between the Y chromosome and an autosome, leading to the presence of the short arm of the Y chromosome (Yp) harboring the sex-determining region Y gene (SRY) and the concurrent deletion of the long arm of the Y chromosome (Yq) containing the azoospermia factor (AZF). This study aimed to identify the translocation of the SRY gene using chromosome conformation-based karyotyping (C-MoKa) and validate the results using FISH.

A 32-year-old male, 155 cm in height, presented with normal sexual function but was unable to achieve clinical pregnancy after two years of unprotected intercourse. Three separate seminal fluid analyses indicated azoospermia. Chromosomal G-banding analysis suggested a 45,X karyotype, and CNV-seq identified a 15.16 Mb deletion in Yq11.21.

Structural chromosomal variations were investigated using C-MoKa, a molecular karyotyping technique. According to the results, targeted probes were selected for validation via FISH.

C-MoKa identified a rare chromosomal translocation 45,X, der(Y;15)(q11.2;q11.2), whilst FISH analysis revealed that the patient harbored an abnormal derivative chromosome with positive signals for the CEPY/CEP15, XYpter and 15qter probes.

In this study, the C-MoKa technique was used to identify a rare case of Y chromosome translocation involving chromosome 15 in a male with Turner syndrome, which was challenging to detect using conventional chromosomal G-banding and CNV-seq. C-MoKa is a rapid and accurate cytogenetic detection method that offers high-resolution detection of structural variations and improved breakpoint characterization, thereby overcoming the limitations of traditional karyotyping approaches.