Calcium ions play a primary role in the regulation of sperm motility. This gene belongs to a family of putative cation channels that are specific to spermatozoa and localize to the flagellum. The protein family features a single repeat with six membrane-spanning segments and a predicted calcium-selective pore region. This gene is part of a tandem repeat on chromosome 15q15; the second copy of this gene is thought to be a pseudogene. Additional splice variants have been described but their full-length nature has not been determined. [provided by RefSeq, Aug 2008].