Peptidyl Arginine Deiminase 2 (PADI2) is Expressed in Post-Meiotic Germ Cells in the Mouse Testis and is Localized Heavily on the Acrosomal Region of Spermatozoa

Peptidyl Arginine Deiminase 2 (PADI2) is a widely expressed Ca 2+ ion-dependent enzyme in rodents and humans belonging to Peptidyl Arginine Deiminases (PAD) family. It regulates various cellular processes like proliferation, differentiation, apoptosis, migration, epithelial-mesenchymal transition and chromatin organization. Altered expression of PADI2 was associated with various autoimmune diseases, neurological disorders and different types of cancers. Based on our previously published miRNA-mRNA network during the first wave of spermatogenesis in the mouse, Padi2 appeared to be a common potential target of miR-34c and miR-449a in the mouse testes. In the present study, the expression of Padi2 in the mouse testes during the first wave of spermatogenesis was evaluated using real-time PCR, western blot analysis and immunohistochemistry. Transcript levels of Padi2 showed progressive down-regulation during the first wave of spermatogenesis. However, we detected a progressive increase in the levels of PADI2 as the first wave of spermatogenesis progressed, with heavy expression of this protein in post-meiotic germ cells. Additionally, a prominent localization of PADI2 in the acrosomal region of late spermatids and spermatozoa was identified through immunohistochemical analysis. Padi2 expression was identified in germ cell-derived cell lines, C18-4 and GC-1 spg as well. Thus, the present study illustrates for the first time the expression of PADI2 in germ cells in the testis and its predominant localization on the acrosome region of spermatozoa, suggesting its potential role in fertilization.