Aquaculture and Fisheries (Sep 2022)
Germ cell markers in fishes - A review
Abstract
Identification of germ cell markers in fishes is crucial to track the germ cell differentiation and migration for manipulation of the cells to study sexual differentiation as well as to carry out transgenic transplantation techniques. Several germ cell-specific markers such as vasa, cnbp, dnd, nanos3, cbx2, amh, dmrt1, Ly75/CD205 have been characterized so far in fishes using localization and expression analysis, which have highlighted the spatio-temporal pattern of expression in early gonadal development. Incidentally, seasonal breeders show dramatic changes during gonadal recrudescence, which might also influence germ cell differentiation and growth to entrain the reproductive cycle. Hence, an in-depth analysis of the gonadal cycle is required to delineate germ cell progress, differentiation, and maturation explicitly. In this context, fishes undergoing gonadal recrudescence for the seasonal cycle show germ cell proliferation differentially. Most of these germ cell markers belong to the DEAD-box protein family of ATP-dependent RNA helicases sharing consensus motifs and clustering in phylogenetic analysis. These markers were found to be well-conserved throughout evolution. In situ hybridization approaches confirmed the germ cell specific distribution of these molecular markers. In addition, several genes such as fgf and gsdf seem to facilitate germ cell development and differentiation. Hence, more detailed studies on these factors will facilitate a better understanding of germ cell development. This review highlights various germ cell markers in fishes and their immense potential to use these cells for germ cell transplantation. The extensive knowledge of the germ cell markers can also be exploited to carry out other biotechnological experiments aiming at the preservation of genetic information of endangered species or the analytical study of gonadogenesis.
