ATP-dependent RNA helicase TDRD9
nucleus
Mutation in TDRD9 causes non-obstructive azoospermia in infertile men.
<h4>Background</h4>Azoospermia is diagnosed when sperm cells are completely absent in the ejaculate even after centrifugation. It is identified in approximately 1% of all men and in 10%-20% of infertile males. Non-obstructive azoospermia (NOA) is characterised by the absence of sperm due to either a Sertoli cell-only pattern, maturation arrest, hypospermatogenesis or mixed patterns. NOA is a severe form of male infertility, with limited treatment options and low fertility success rates. In the majority of patients, the cause for NOA is not known and mutations in only a few genes were shown to be causative.<h4>Aim</h4>We investigated the cause of maturation arrest in five azoospermic infertile men of a large consanguineous Bedouin family.<h4>Methods and results</h4>Using whole genome genotyping and exome sequencing we identified a 4 bp deletion frameshift mutation in <i>TDRD9</i> as the causative mutation with a Lod Score of 3.42. We demonstrate that the mutation results in a frameshift as well as exon skipping. Immunofluorescent staining with anti-TDRD9 antibody directed towards the N terminus demonstrated the presence of the protein in testicular biopsies of patients with an intracellular distribution comparable to a control biopsy. The mutation does not cause female infertility.<h4>Conclusion</h4>This is the first report of a recessive deleterious mutation in <i>TDRD9</i> in humans. The clinical phenotype recapitulates that observed in the <i>Tdrd9</i> knockout mice where this gene was demonstrated to participate in long interspersed element-1 retrotransposon silencing. If this function is preserved in human, our data underscore the importance of maintaining DNA stability in the human male germ line.