Sexual Dimorphism in the Early Embryogenesis in Zebra Finches

Sex-specific gene expression before the onset of gonadogensis has been documented in embryos of mammals and chickens. In several mammalian species, differences in gene expression are accompanied by faster growth of pre-implantation male embryos. Here we asked whether avian embryos before gonadal dif...

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Main Authors:	Tagirov, Makhsud, Rutkowska, Joanna
Format:	Online
Language:	English
Published:	Public Library of Science 2014
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262425/

id	pubmed-4262425
recordtype	oai_dc
spelling	pubmed-42624252014-12-15 Sexual Dimorphism in the Early Embryogenesis in Zebra Finches Tagirov, Makhsud Rutkowska, Joanna Research Article Sex-specific gene expression before the onset of gonadogensis has been documented in embryos of mammals and chickens. In several mammalian species, differences in gene expression are accompanied by faster growth of pre-implantation male embryos. Here we asked whether avian embryos before gonadal differentiation are also sex-dimorphic in size and what genes regulate their growth. We used captive zebra finches (Taeniopygia guttata) whose freshly laid eggs were artificially incubated for 36–40 hours. Analyses controlling for the exact time of incubation of 81 embryos revealed that males were larger than females in terms of Hamburger and Hamilton stage and number of somites. Expression of 15 genes involved in cell cycle regulation, growth, metabolic activity, steroidogenic pathway and stress modulation were measured using RT-PCR in 5 male and 5 female embryos incubated for exactly 36 h. We found that in the presence of equal levels of the growth hormone itself, the faster growth of male embryos is most likely achieved by the overexpression of the growth hormone receptor gene and three other genes responsible for cell cycle regulation and metabolism, all of them located on the Z chromosome. Autosomal genes did not show sex-specific expression, except for the steroidogenic factor 1 which was expressed only in female embryos. To our knowledge this is the first report of sexual size dimorphism before gonadogenesis in birds. The finding suggests that faster growth of early male embryos is conserved through the mammalian and bird phyla, irrespective of their differential sex chromosome systems. Public Library of Science 2014-12-10 /pmc/articles/PMC4262425/ /pubmed/25493645 http://dx.doi.org/10.1371/journal.pone.0114625 Text en © 2014 Tagirov, Rutkowska http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Tagirov, Makhsud Rutkowska, Joanna
spellingShingle	Tagirov, Makhsud Rutkowska, Joanna Sexual Dimorphism in the Early Embryogenesis in Zebra Finches
author_facet	Tagirov, Makhsud Rutkowska, Joanna
author_sort	Tagirov, Makhsud
title	Sexual Dimorphism in the Early Embryogenesis in Zebra Finches
title_short	Sexual Dimorphism in the Early Embryogenesis in Zebra Finches
title_full	Sexual Dimorphism in the Early Embryogenesis in Zebra Finches
title_fullStr	Sexual Dimorphism in the Early Embryogenesis in Zebra Finches
title_full_unstemmed	Sexual Dimorphism in the Early Embryogenesis in Zebra Finches
title_sort	sexual dimorphism in the early embryogenesis in zebra finches
description	Sex-specific gene expression before the onset of gonadogensis has been documented in embryos of mammals and chickens. In several mammalian species, differences in gene expression are accompanied by faster growth of pre-implantation male embryos. Here we asked whether avian embryos before gonadal differentiation are also sex-dimorphic in size and what genes regulate their growth. We used captive zebra finches (Taeniopygia guttata) whose freshly laid eggs were artificially incubated for 36–40 hours. Analyses controlling for the exact time of incubation of 81 embryos revealed that males were larger than females in terms of Hamburger and Hamilton stage and number of somites. Expression of 15 genes involved in cell cycle regulation, growth, metabolic activity, steroidogenic pathway and stress modulation were measured using RT-PCR in 5 male and 5 female embryos incubated for exactly 36 h. We found that in the presence of equal levels of the growth hormone itself, the faster growth of male embryos is most likely achieved by the overexpression of the growth hormone receptor gene and three other genes responsible for cell cycle regulation and metabolism, all of them located on the Z chromosome. Autosomal genes did not show sex-specific expression, except for the steroidogenic factor 1 which was expressed only in female embryos. To our knowledge this is the first report of sexual size dimorphism before gonadogenesis in birds. The finding suggests that faster growth of early male embryos is conserved through the mammalian and bird phyla, irrespective of their differential sex chromosome systems.
publisher	Public Library of Science
publishDate	2014
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262425/
_version_	1613166227225575424

Sexual Dimorphism in the Early Embryogenesis in Zebra Finches

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