Inhibits signal transduction by increasing the GTPase activity of G protein alpha subunits thereby driving them into their inactive GDP-bound form. Interacts with GNA11, GNA12 AND GNA13. Expressed in the cytoplasm of spermatogonia and spermatocytes. In spermatids, also expressed in the nucleus. Testis-specific. Expressed in Leydig cells and spermatogenic cells from the spermatogonia to spermatid stages (at protein level). May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. May be due to competing donor splice site.