VASA as a specific marker for germ cells lineage: In light of evolution

The DEAD-box RNA helicases belong to a family of proteins known to participate in various aspects of RNA metabolism, including transcription, splicing, RNA trafficking, translational regulation of specific mRNAs and degradation. Additionally, RNA helicases are implicated in regulation of specific gene expression and participate in central pathways like innate immunity and proliferation. One of the prominent members of this family is Vasa, repeatedly reported as a specific marker for cells of the germ line lineages in vertebrates and invertebrates. Recent in vivo and in vitro studies on model organisms have revealed a wide range of cases of Vasa expression in soma cells and stress-related situations, refuting the prevailing dogma of its exclusive specificity for germ cells lineage. Most of the cases where Vasa was found to be expressed in the soma were confined to invertebrates specialized in asexual reproduction, also characterized by the mode of somatic embryogenesis. We found that in multicellular animals with high regenerative power and with pluripotent stem cell populations produced gametes, Vasa was expressed in various somatic constituents, exerting housekeeping functions, like cell cycle checkpoint regulation, responses to damages of UV radiation or responses to directional signals during cell migration. With the advent of exclusively dedicated germ cells in metazoans that lost the power for major regeneration schemes, Vasa has become specialized as a germ line marker trait and hence a germ line specific marker.