Compound heterozygous DMC1 variants cause non-obstructive azoospermia by defective replication protein A replacement

Area of Science:

• Genetics
• Reproductive Biology
• Molecular Biology

Background:

• Non-obstructive azoospermia (NOA) is a severe form of male infertility.
• Meiosis-specific recombinase DMC1 is crucial for homologous chromosome pairing and DNA repair during spermatogenesis.
• Genetic variants in DMC1 can lead to impaired meiosis and infertility.

Purpose of the Study:

• To investigate how a compound heterozygous DMC1 variant affects homologous search and strand invasion during spermatocyte meiosis in a patient with NOA.
• To elucidate the molecular mechanisms underlying DMC1-associated male infertility.

Main Methods:

• Identified a patient with compound heterozygous DMC1 variants and NOA.
• Utilized reverse transcription polymerase chain reaction and western blot to assess DMC1 expression.
• Performed histological analysis and immunofluorescence staining for spermatogenic arrest, chromosome pairing, and DNA double-strand break repair.
• Generated Dmc1 knockout mice to model the human phenotype.

Main Results:

• The patient's compound heterozygous DMC1 variants (c.494+4A>G/c.597G>C) were linked to NOA and reduced DMC1 protein levels due to nonsense-mediated mRNA decay.
• Observed spermatogenic arrest during meiosis, with significant defects in chromosome pairing and DNA double-strand break repair.
• Dmc1 knockout mice recapitulated the human phenotype, showing impaired chromosome pairing and DNA repair.
• Accumulation of replication protein A (RPA) was observed in zygotene spermatocytes, indicating a failure to replace single-stranded DNA with DMC1.

Conclusions:

• A novel compound heterozygous DMC1 variant disrupts germ cell meiosis, leading to NOA.
• This finding expands the known spectrum of DMC1 mutations associated with male infertility.
• The study highlights the critical role of DMC1 in ensuring proper homologous recombination and spermatogenesis.