The genetic and epigenetic architecture of sexual dimorphism in tilapia

• Main Author: Wan, Zi Yi
• Other Authors: Valerie Lin Chun Ling
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Science::Biological sciences::Genetics
• Online Access: https://hdl.handle.net/10356/136866
• Institution: Nanyang Technological University

Tilapia is an important aquaculture species. Males outgrow females. I explored the genetic and epigenetic architecture of male and female tilapia to understand more about sexual dimorphism. Whole genome bisulfite sequencing and RNA-seq in skeletal muscle revealed sexually-dimorphic methylated regions and sex-biased gene expression. dN/dS analysis uncovered that sex-biased genes in tilapia somatic tissues were under relaxed purifying selection. Analysis of brain transcriptomes identified 124, 55 and 2706 sex-biased genes at 5, 30 and 90 days post hatch, respectively. The pro-opiomelanocortin (pomc) gene, which was female-biased in the brain, was selected for functional analysis. pomc knock-out zebrafish showed faster growth and higher sensitivity to feeding compared to wildtype. Two estrogenic response elements upstream of tilapia pomc were sensitive to estrogen induction in a luciferase reporter assay. These results suggest that pomc may be involved in sexual size dimorphism. In addition, I identified SNPs located upstream of rasgrf1, which were associated with increased growth rate and may be useful in selecting fast-growing tilapia.