A novel homozygous loss-of-function mutation in RAD51AP2 induces male infertility with nonobstructive azoospermia

Dear Editor,The most severe type of male infertility,nonobstructive azoospermia(NOA),is characterized by clinical heterogeneity,implying the involvement of different acquired and genetic factors.However,the cause of NOA is unidentified in a substantial number of patients after the exclusion of all-known acquired factors and routine genetic testing,such as karyotype and Y chromosome microdeletion analysis.1 With the recent rapid development of whole-exome sequencing(WES),an increasing number of novel monogenic causes have been identified.Recently,RAD51-associated protein 2(RAD51AP2)was reported to be a novel causative gene of NOA in a monogenic recessive manner in two sporadic patients.2 Here,we studied the WES data for a family with two NOA patients and found that both carried a novel homozygous loss-of-function(LoF)mutation in RAD51AP2.