Germ-cell specific protein gametogenetin protein 2 (GGN2), expression in the testis, and association with intracellular membrane

Abstract

Gametogenetin (Ggn) is a germ cell-specific gene with multiple splicing variants giving rise to three predicted protein products, gametogenetin protein 1 (GGN1), gametogenetin protein 2 (GGN2), and gametogenetin protein 3 (GGN3). GGN1 and GGN3 were reported to interact with Fanconi anemia complementation group L (FANCL) per proliferation of germ cells (POG), a ubiquitin E3 ligase involved in germ-cell-deficient (gcd) mutation. While GGN2, another protein from Ggn by alternative splicing did not interact with FANCL/POG since it lacked the domain mediating the interaction. Little is known about the expression and function of GGN2. Here through Northern blotting experiment we showed that Ggn was mainly expressed in the testis but hardly detectable in the ovary or the somatic tissues. By preparing GGN2-specific antibody we showed that GGN2 was detectable and only detectable in the testis. By comparing the expression of Ggn mRNA and GGN2 protein in developing mouse testis, we showed that there was no evident delay of the translation of Ggn mRNA after their transcription. Both the subcellular localization study and the germ cell membrane protein fractionation implied that GGN2 associated with the intracellular membrane system. Co-fractionation on Superdex and yeast two-hybrids suggested that like GGN1, GGN2 was also a potential interaction partner of gametogenetin binding protein 1 (GGNBP1). Our data suggested that gametogenetin proteins were mainly involved in male germ cell development and GGN2 was also a possible interaction partner of GGNBP1. Like GGN1, GGN2 was also possibly involved in cell trafficking. The possible involvement of GGN2 in acrosome biogenesis was proposed.