Family with sequence similarity 209 member B (FAM209B)

Family with sequence similarity 209 member B (FAM209B) is a small transmembrane protein predominately expressed in the testis, where it plays a critical role in acrosome biogenesis and proper sperm formation[1][2]. In mammalian studies, loss of FAM209 leads to male infertility due to severely impaired sperm motility and abnormal sperm morphology. The protein associates with DPY19L2—a known acrosomal protein—and is located at the inner nuclear membrane, underneath the developing acrosome. There are two paralogs in humans: FAM209A and FAM209B, both predominantly expressed in testis. The FAM209B domain is evolutionarily conserved across all mammalian branches, but its precise molecular function is not fully annotated and it does not resemble any characterized enzyme, receptor, or transporter. No clinical drugs are targeted to FAM209B, and it is not established as a biomarker or safety concern for current therapies[1][2].

Other names

Protein FAM209BFAM209BC20orf107dJ1153D9.4uncharacterized protein C20orf107