Project description:Commercial production of tilapia relies on monosex cultures of males, which so far proved difficult to maintain in large scale production facilities. Thus, a better understanding of the genetic architecture of the complex trait of sex determination in tilapia is needed.We aimed to detect genes that were differentially expressed by gender at early embryonic development. Artificial fertilization of O. niloticus females with either sex-reversed males (ΔXX) or genetically-modified YY 'supermales' resulted in all-female and all-male embryos, respectively. Pools of all-female and all-male embryos at 2, 5 and 9 days post fertilization were used for custom Agilent eArray. 56 pool samples of Nile tilapia full siblings groups (female or male) at day 2, 5 or 9 post fertilization were subjected to total RNA extraction from whole embryo tissues and hybridized to the custom Agilent array. Each sample was yielded from different cross of artificial fertilization: six dams X five sires. The resulting gender were known based on the sire, sex-reversed males (ΔXX) or genetically-modified YY 'supermales' resulted in all-female and all-male embryos, respectively.
Project description:Elongation of very long-chain fatty acids protein 6 (Elovl6) is a crucial enzyme in the synthesis of endogenous fatty acids, which participates in the energy balance and metabolic diseases. The main objective of this study was to explore the molecular characterization of elovl6 and study regulatory mechanism of elovl6 on male Nile tilapia, Oreochromis niloticus. In the present study, the full-length cDNA of Nile tilapia elovl6 was 2255 bp, comprising a 5'-UTR of 193 bp, an ORF of 810 bp, and a 3'-UTR of 1252 bp, encoding 269 amino acids that possesses the characteristic features of Elovl proteins. The transcription expression of elovl6 transcripts showed differential expression in different tissues and fed with different lipid sources diet. Antisense RNA technology was used to knock-down elovl6 in Nile tilapia. Compared with the control treatments (transfected with ultrapure water (control) or the blank expression vector (negative control)), knockdown elovl6 altered hepatic morphology, Long chain fatty acid synthesis, fatty acid oxidation, lead to excess fat deposition in the liver, ultimately cause abnormal glucose/lipid metabolism in male Nile tilapia. Transcriptome analyses (AGPAT2 knock-down vs. negative control) revealed a total of 5877 differentially expressed genes (DEGs). Transcriptome analyses revealed DEGs were greatly involved in some signaling pathways, such as PPAR signaling pathway, fatty acid degradation, glycolysis/gluconeogenesis, and insulin signaling pathway, which were related to lipid and glucose metabolism. We used qRT-PCR to verify the mRNA expression changes of 13 DEGs in related signaling pathways. Our results demonstrate that knock-down of elovl6 in tilapia blocks the synthesis of oleic acid and leads to abnormal glucose/lipid metabolism.
Project description:Cichlids fishes exhibit extensive phenotypic diversification and speciation. In this study we integrate transcriptomic and proteomic signatures from two cichlids species, identify novel open reading frames (nORFs) and perform evolutionary analysis on these nORF regions. We embark comparative transrcriptomics and proteogenomic analysis of two metabolically active tissues, the testes and liver, of two cichlid species Oreochromis niloticus (Nile tilapia, ON) and Pundamilia nyererei (Makobe Island, PN). Our results suggest that the time scale of speciation of the two species can be better explained by the evolutionary divergence of these nORF genomic regions.