(2017). Double maternal effect: duplicated nucleoplasmin 2 genes, npm2a and npm2b, are shared by fish and tetrapods, and have distinct and essential roles in early embryogenesis. BioRxiv, 1-39.DOI : 10. . CC-BY-NC-ND 4.0 International license peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/104760 doi: bioRxiv preprint first posted online May. 22, 2017; Version preprint Comment citer ce document : Cheung, C., Pasquier, J., Bouleau, A., Nguyen, T. T. V., Chesnel, F., Guiguen, Y., Bobe, J. (2017). Double maternal effect: duplicated nucleoplasmin 2 genes, npm2a and npm2b, are shared by fish and tetrapods, and have distinct and essential roles in early embryogenesis. BioRxiv, 1-39. DOI : 10.1101/1047602 Abstract 1 4Nucleoplasmin 2 (npm2) is an essential maternal-effect gene that mediates early embryonic 1 5 events through its function as a histone chaperone that remodels chromatin. Here we report 1 6 the existence of two npm2 (npm2a and npm2b) genes in zebrafish. We examined the 1 7evolution of npm2a and npm2b in a variety of vertebrates, their potential phylogenetic 1 8relationships, and their biological functions using knockout models via the CRISPR/cas91 9system. We demonstrated that the two npm2 duplicates exist in a wide range of vertebrates, 2 0including sharks, ray-finned fish, amphibians, and sauropsids, while npm2a was lost in
1Coelacanth and mammals, as well as some specific teleost lineages. Using phylogeny and 2 2 synteny analyses, we traced their origins to the early stages of vertebrate evolution. Our 2 3findings suggested that npm2a and npm2b resulted from an ancient local gene duplication,
4and their functions diverged although key protein domains were conserved. We then 2 5investigated their functions by examining their tissue distribution in a wide variety of species 2 6and found that they shared ovarian-specific expression, a key feature of maternal-effect 2 7genes. We also showed that both npm2a and npm2b are maternally-inherited transcripts in 2 8vertebrates. Moreover, we used zebrafish knockouts to demonstrate that npm2a and npm2b 2 9play essential, but distinct, roles in early embryogenesis. npm2a functions very early during 3 0 embryogenesis, at or immediately after fertilization, while npm2b is involved in processes 3 1 leading up to or during zygotic genome activation. These novel findings will broaden our 3 2 knowledge on the evolutionary diversity of maternal-effect genes and underlying mechanisms 3 3 that contribute to vertebrate reproductive success. . CC-BY-NC-ND 4.0 International license peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/104760 doi: bioRxiv preprint first posted online May. 22, 2017; Version preprint Comment citer ce document : Cheung, C., Pasquier, J., Bouleau, A., Nguyen, T. T. V., Chesnel, F., Guiguen, Y., Bobe, J. (2017). Double maternal effect: duplicated nucleop...