Project description:The highly conserved members of the zic family of zinc-finger transcription factors are primarily known for their roles in embryonic signaling pathways and regulation of cellular proliferation and differentiation. This study describes sexual phenotype differences in abundances of zic2 mRNA in the preoptic area of the hypothalamus, a region strongly implicated in sexual behavior and function, in an adult teleost, Thalassoma bifasciatum. The bluehead wrasse (Thalassoma bifasciatum) is a valuable model for studying neuroendocrine processes because it displays two discrete male phenotypes, initial phase (IP) males and territorial, terminal phase (TP) males, and undergoes socially-controlled protogynous sex change. Previously generated microarray-based comparisons suggested that zic2 was upregulated in the brains of terminal phase males relative to initial phase males. To further explore this difference, we cloned a 727 bp sequence for neural zic2 from field-collected animals. Riboprobe-based in situ hybridization was employed to localize zic2 signal in adult bluehead brains and assess the relative abundance of brain zic2 mRNA across sexual phenotypes. We found zic2 mRNA expression was extremely abundant in the granular cells of the cerebellum and widespread in other brain regions including in the thalamus, hypothalamus, habenula, torus semicircularis, torus longitudinalis, medial longitudinal fascicle and telencephalic areas. Quantitative autoradiography and phosphorimaging showed zic2 mRNA hybridization signal in the preoptic area of the hypothalamus was significantly higher in terminal phase males relative to both initial phase males and females, and silver grain analysis confirmed this relationship between phenotypes. No significant difference in abundance was found in zic2 signal across phenotypes in the habenula, a brain region not implicated in the control of sexual behavior, or cerebellum.
Project description:Stomach-less fishes comprise a diverse phylogenetic group within the teleosts indicating that the organ has been lost several times during evolution. In the present project we have combined Illumina short read platform with the PacBio long read platform to sequence the ballan wrasse (Labrus bergylta) genome and its intestinal transcriptome. The genome was applied to investigate the elimination and conservation of genes related to stomach function and appetite regulation in wrasse in relation to the loss of stomach in this species. We have sequenced the transcriptome of four intestinal segments from six ballan wrasse (Labrus bergylta) for the purpose of identifying possible functional organization along the wrasse intestine. The transcriptomic reads were mapped against the newly assembled genome. The analysis revealed a transcriptional gradient showing genes involved in nutrient digestion and uptake being highly expressed in the anterior intestine and declining towards the end of the intestine. The last segment, hind-gut, had the most distinct expression between the four segments with increased expression of genes coding for proteins involved in lysosomal activity, antigen presenting and vitamin b12 uptake. Overall, our results suggests that the wrasse entire digestive system is comparable to the small intestine of mammals with regards to gene expression missing both a stomach and colon. Gene expression related to colon in humans such as MS4A12 were found in the last segment. The genome analysis also confirmed the lack of genes coding for gastric proteins such as gastric lipase, pepsin, gastrin and ghrelin. Although ghrelin is not only related to stomach, ghrelin was missing in all stomach-less fish species with the exception of cyprinid. Ghrelin is currently the only known orexigenic hormone.