Introduction: Despite advances in molecular diagnostics, the etiology of most male infertility remains unknown or undiagnosed. Multiple morphological abnormalities of the sperm flagella (MMAF) is a major cause of asthenoteratozoospermia. We identified the protease, PRSS50, with a crucial role in sperm development since Prss50-null mice present with impaired fertility and sperm tail abnormalities. PRSS50 could play a role in centrosome and tail formation since Prss50-null mice present with a 3-fold increase in acephalic sperm (head-tail junction defect), sperm with multiple heads (spermatid division defect), and sperm with multiple tails including the novel two-sperm-conjoined (complete or partial parts of several flagellum on the same plasma membrane). Proteases have multiple paralogues likely from duplicated genes that cluster together. PRSS50 is part of a cluster in human chromosome 3 that includes PRSS-42, -43, -44, -45, -46. Since copy number variants (CNVs) and single nucleotide variants (SNV) have emerged as one cause of male fertility, our objective is to determine if CNVs and SNV in PRSS50 contribute to human infertility as they do in mice. The objective of this study is to understand how the role of PRSS50 in male fertility.
Methods: : A cohort of 444 men including 203 men with non-obstructive azoospermia (NOA) (normal karyotypes with no Y-chromosome microdeletions) and 241 controls were evaluated by 3p21.31-PRSS CNV-taqman qPCR assay and Sanger sequencing of the exons of PRSS50.
Results: : We identified a 58Kb microdeletion at chromosome 3p21.31 in the PRSS cluster in 4 of 20 NOA men absent in 20 controls. Validation and analysis by qPCR of a total of 241 NOA men identified 32 NOA men with microdeletion (9 of them have 0 copy of the gene) and 7 with microduplication (3 copies). From the 241 controls, 21 of them have microdeletions lacking only 1 copy. The absence of both copies or extra copy of the gene was significant difference when compared to control (p=0.01). All patients with microduplication have a diagnosis of maturation arrest (MA). From the patients with no copy of the genes, only 2 have biopsy results that indicate MA and hypospermatogenesis. We are currently performing Sanger sequencing in the exons of PRSS50 in infertile men with asthenoteratozoospermia.
Conclusions: Gene-dosage changes of 3p21.31 in the PRSS cluster represent a previously unrecognized cause of infertility. PRSS50 plays an essential role in sperm development and, consequentially, male ferility.
Source of Funding: This is supported by 5R01HD00985 awarded to Dr. Abhishek Seth by the NICHD.
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