MYCBPAP is a central apparatus protein essential for male fertility and spermatogenesis. Primarily localized to the central apparatus of the sperm flagellar axoneme, specifically at the base of the C2a projection 1, MYCBPAP functions as a structural component required for centrosome-nuclear envelope docking during spermiogenesis 2. This docking is critical for proper sperm tail biogenesis and flagellar elongation 2. MYCBPAP also regulates acrosome biogenesis, manchette organization, and spermatid head morphogenesis 3. Mechanistically, MYCBPAP interacts with central apparatus proteins CFAP65 and CFAP70, which form the C2a projection 12, and associates with ribosome elimination protein ARMC3 and centrosome protein CCP110 2. Homozygous deleterious variants in MYCBPAP cause asthenoteratozoospermia, characterized by abnormal sperm morphology and reduced motility due to disrupted acrosome biogenesis and flagellar defects 3. Three human cases and a Mycbpap knockout mouse model demonstrate that MYCBPAP mutations result in male infertility with significantly downregulated spermatogenesis-related proteins 3. Clinical significance includes using MYCBPAP variants as genetic diagnostic indicators for infertile men with asthenoteratozoospermia, though intracytoplasmic sperm injection can partially overcome associated infertility 3.