2.1 Study participants and sample collection
The two infertile patients and their parents were enrolled at the West China Second University Hospital of Sichuan University, and these patients all had normal chromosomal karyotypes (46, XY). No large-scale deletions were found in the Y chromosome. This study was conducted following the tenets of the Declaration of Helsinki, and ethical approval was obtained from the Ethical Review Board of West China Second University Hospital, Sichuan University. Written informed consent was obtained from each study participant prior to sample collection.