Translocation breakpoints of chromosome 4 in male carriers: clinical features and implications for genetic counseling.

Cytogenetic analysis remains a powerful and cost-effective technology, and has wide applicability in genetic counseling for infertile males. Chromosomal rearrangements are thought to be one of the major genetic factors that influence male infertility. Some carriers with balanced reciprocal translocation have been identified as having oligozoospermia or azoospermia, and there is an association between balanced translocation and recurrent abortion. Researchers have reported the involvement of chromosome 4 translocations in male factor infertility and recurrent miscarriages. A translocation breakpoint might interrupt the structure of an important gene, and it is associated with reproductive failure. However, the clinical characteristics of the breakpoints in chromosome 4 translocations have not been studied. Here, we report the breakpoints in chromosome 4 translocation and the clinical features presented in carriers to enable informed genetic counseling of these patients. Of 82 patients with balanced reciprocal translocations, 14 were carriers of the chromosome 4 translocation: four presented with pregestational infertility (clinical manifestations: oligozoospermia, severe oligozoospermia, or azoospermia), whereas 10 presented with gestational infertility (able to conceive but with a tendency to miscarry). The breakpoint at 4q12 was associated with pregestational infertility, whereas the breakpoints at 4q13, 4q21, 4q25, and 4q32 were associated with gestational infertility. However, the breakpoint at 4q35 was associated with both pregestational and gestational infertility. Chromosome 4 translocation carriers with pregestational or gestational infertility should be counseled on chromosomal breakpoints and the different technologies available to assist reproduction.

Chromosome 7 translocation breakpoints in male carriers: clinical features and implications for genetic counseling.

Balanced reciprocal translocations are associated with reproductive failure. Some reciprocal translocation carriers exhibit azoospermia or oligozoospermia, and an association exists between these chromosomal abnormalities and recurrent abortion. Previous reports have indicated the involvement of chromosome 7 translocations in male infertility and recurrent miscarriage. A translocation breakpoint can occur within an important gene, interrupting its structure and leading to male infertility. However, clinical characteristics resulting from chromosome 7 translocation breakpoints have not been studied. Here, we report such breakpoints and their associated clinical features, to enable informed genetic counseling of carriers. Balanced reciprocal translocations were found in 1.57% of the tested patients. Among these 82 individuals, 14 (17.07%) carried a chromosome 7 translocation, of which, five presented with pregestational infertility and clinical manifestations of oligozoospermia or necrospermia, while nine presented with gestational infertility (i.e., were able to conceive, but often resulting in miscarriage). Breakpoints at 7q31 and 7q36 were associated with pregestational infertility, whereas those at 7p10, 7q21.2, 7q22, and 7q32 were connected to gestational infertility. However, the breakpoint at 7p15 was associated with both. Chromosome 7 translocation carriers with pregestational or gestational infertility should be counseled on chromosomal breakpoints and the various molecular technologies available for assisted reproduction.