Steroid responsive regulation of IFNγ2 alternative splicing and its possible role in germ cell proliferation in medaka

Interferon gamma (IFN gamma) is an active player in estrogen dependent immuno-regulation of fish. The present work was aimed to characterize the alternatively spliced isoforms of IFN gamma 2 in the gonadal sex development in medaka. Phylogenetic analysis demonstrated that IFN gamma 2a and 2b were clustered with fish specific interferon gamma. Our in vitro promoter and mini-genome analysis data confirmed that alternative splicing of IFN gamma 2 is regulated by estrogens and androgens. Tissue distribution, quantitative PCR and ISH data demonstrated ubiquitous expression of IFN gamma 2a, while IFN gamma 2b was only expressed predominantly in female germ cells than males. This was further confirmed by germ cell specific GFP signals in the IFN gamma 2b-GFP over-expressed embryos and specific induction of IFN gamma 2b expression in the BrdU positive cells. All together our data suggest that steroid responsive alternatively spliced IFN gamma 2b isoforms might have some indirect roles in germ cell proliferation and thus can be an important candidate for immuno-reproductive interaction studies. (C) 2014 Elsevier Ireland Ltd. All rights reserved.