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Sexual Dimorphism in the Early Embryogenesis in Zebra Finches.

Tagirov M, Rutkowska J - PLoS ONE (2014)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Poultry Research Institute, Ukrainian Academy of Agrarian Sciences, Borky, Ukraine.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Agarose gel electrophoresis of the PCR amplification products of the GH1 and NR5A1 genes.A – expression of the GH1 gene in the 6 h zebra finch embryos. B – amplification of the reaction product in the nested PCR. Lanes: 1, 2, 3–6 h embryo samples, PC- positive control, reverse transcribed RNA from adult zebra finch pituitary gland. The negative control was RNA treated in the absence of reverse transcriptase. The negative control is not shown, but in all repeats it showed no products. C – expression of the steroidogenic factor 1 gene (NR5A1) in female (Lanes: F1, F2 and F3) and lack of the product in male (Lanes: M1, M2 and M3) zebra finch embryos incubated for 36 h. On all photos M is a DNA marker (100–1000 b.p.).
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pone-0114625-g003: Agarose gel electrophoresis of the PCR amplification products of the GH1 and NR5A1 genes.A – expression of the GH1 gene in the 6 h zebra finch embryos. B – amplification of the reaction product in the nested PCR. Lanes: 1, 2, 3–6 h embryo samples, PC- positive control, reverse transcribed RNA from adult zebra finch pituitary gland. The negative control was RNA treated in the absence of reverse transcriptase. The negative control is not shown, but in all repeats it showed no products. C – expression of the steroidogenic factor 1 gene (NR5A1) in female (Lanes: F1, F2 and F3) and lack of the product in male (Lanes: M1, M2 and M3) zebra finch embryos incubated for 36 h. On all photos M is a DNA marker (100–1000 b.p.).

Mentions: Growth hormone gene (GH1) showed similar expression in male and female embryos. Because of the size differences between male and female embryos observed at 36 h of incubation, it was reasonable to expect that expression of the GH1 gene occurs earlier in the embryonic development. Thus, we analyzed amplification of the GH1 gene in 3 embryos incubated for 6 h. Expression of the GH1 gene was detected in all the samples and the size of the amplified fragment was 98 b.p. (Fig. 3A, B).


Sexual Dimorphism in the Early Embryogenesis in Zebra Finches.

Tagirov M, Rutkowska J - PLoS ONE (2014)

Agarose gel electrophoresis of the PCR amplification products of the GH1 and NR5A1 genes.A – expression of the GH1 gene in the 6 h zebra finch embryos. B – amplification of the reaction product in the nested PCR. Lanes: 1, 2, 3–6 h embryo samples, PC- positive control, reverse transcribed RNA from adult zebra finch pituitary gland. The negative control was RNA treated in the absence of reverse transcriptase. The negative control is not shown, but in all repeats it showed no products. C – expression of the steroidogenic factor 1 gene (NR5A1) in female (Lanes: F1, F2 and F3) and lack of the product in male (Lanes: M1, M2 and M3) zebra finch embryos incubated for 36 h. On all photos M is a DNA marker (100–1000 b.p.).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4262425&req=5

pone-0114625-g003: Agarose gel electrophoresis of the PCR amplification products of the GH1 and NR5A1 genes.A – expression of the GH1 gene in the 6 h zebra finch embryos. B – amplification of the reaction product in the nested PCR. Lanes: 1, 2, 3–6 h embryo samples, PC- positive control, reverse transcribed RNA from adult zebra finch pituitary gland. The negative control was RNA treated in the absence of reverse transcriptase. The negative control is not shown, but in all repeats it showed no products. C – expression of the steroidogenic factor 1 gene (NR5A1) in female (Lanes: F1, F2 and F3) and lack of the product in male (Lanes: M1, M2 and M3) zebra finch embryos incubated for 36 h. On all photos M is a DNA marker (100–1000 b.p.).
Mentions: Growth hormone gene (GH1) showed similar expression in male and female embryos. Because of the size differences between male and female embryos observed at 36 h of incubation, it was reasonable to expect that expression of the GH1 gene occurs earlier in the embryonic development. Thus, we analyzed amplification of the GH1 gene in 3 embryos incubated for 6 h. Expression of the GH1 gene was detected in all the samples and the size of the amplified fragment was 98 b.p. (Fig. 3A, B).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Poultry Research Institute, Ukrainian Academy of Agrarian Sciences, Borky, Ukraine.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus