Rania Said Aboukila1, Shabaan Abd Elatif Hemeda2, Abeer Fikry El Nahas2, Walaa Slouma Hamouda Abd El Naby2*

Abstract | The objectives of the present study were to screen for nucleotide polymorphism in GHR1 gene among the large and small body weights’ Nile tilapia using DNA sequencing. Also, to compare the expression of some growth-related genes (GH, GHR1, IGF-1, MyoG, and MSTN) between variant weights in mono sex Nile tilapia using qRT-PCR. Molecular characterization of growth hormone receptor 1 (GHR1) gene revealed the presence of many SNPs among the large, and small-body weight fish, only two repeated SNPs were detected among the small body weight fish at the coding region within the gene at 2200 G>A, and the other one was at the 3`-untranslated region (2388 A>T). They can be used as a marker-assisted selection for culling of small size fish. Additionally, two SNPs at 2116 C>A and 2117 A>G reported in large body weight fish can be used as a marker for selection to increase body weight in Nile tilapia. The expression profiles of growth-related genes are variable between the small and large body weight fish. The expression of GH and MSTN genes increased in small body weight fish than large body weight. The GHR1 and MyoG gene expression significantly increased in fish of large body weight, suggesting their vital role in Nile tilapia growth. No variation in IGF-1 gene expression between the variant weights’ fish was observed. We conclude that SNPs at GHR1 and increased its expression together with the MyoG gene in large size fish proposed them as candidate genes to be more evaluated for efficient growth breeding programs in Nile tilapia.

Keywords | Nile tilapia; Growth-related genes; Expression; SNPs; Polymorphism