Important for spermatogenesis where it may have a role in sperm individualization. Highly expressed in testis. RNAi-mediated knockdown severely impairs male fertility. Morphology of the sperm individualization complex is highly abnormal. Seminal vesicles contain very few mature spermatozoa, which are often bundled together. Female fertility is not affected. Gudu is Chinese for 'alone without progeny' and refers to the male infertility phenotype.