Required for formation of the sperm connecting piece during spermiogenesis. Sperm connecting piece is essential for linking the developing flagellum to the head during late spermiogenesis (PubMed:12771232, PubMed:25605924). May be involved in myosin-based microfilament transport through interaction with myosin subunits (PubMed:25605924). Interacts with MYL6. Specifically localizes to the segmented columns and the capitulum of the sperm connecting piece. Specifically expressed in developing spermatids and mature spermatozoa (at protein level) (PubMed:25605924). Isoform 1 is weakly expressed in testis, ovary, thymus and placenta. Isoform 2 and isoform 3 are testis-specific. Expression isw higher in spermatids than in spermatocytes and spermatogonia (PubMed:12771232). Weak expression of isoform 1 is seen throughout testicular development. Isoform 2 and isoform 3 could not be detected until postnatal day 15. Expressed from postnatal day 20, and thereafter increased. Expressed in blastocysts and in embryos from 8.5 dpc-12.5 dpc. After 13.5 dpc, the level of expression decreases. Expressed at 9.5-10.5 dpc in the neural tube, in somites and limb buds. Male are sterile due to disruption of sperm connecting piece formation, leading to acephalic spermatozoa in the epididymis and ejaculates. Belongs to the SPATA6 family. Knockout experiments to inactivate Spata6 were first attempted but were unsuccessful, because chimeras did not transmit the targeted allele to their progeny, generating high-percentage of lethality for chimeric embryos (PubMed:12771232). This suggests that genes other than Spata6 may have been targeted or affected in this study (PubMed:25605924). Truncated N-terminus.