May operate as a co-chaperone of the male germ cell- and haploid stage-specific Hsp70 proteins. Testis specific. Expression is confined to the germline without any contribution of the somatic components. Its expression occurs in the postmeiotic phase of male germ cell development. First detected in 30 days old mice and thereafter into adulthood. Barely detectable in 20 days old mice and absent before this period.