Novel SNPs in the leptin gene: implications for growth performance in cultured European sea bass (Dicentrarchus labrax)

Introduction Leptin, a class I helical cytokine, regulates growth, appetite, energy homeostasis and reproductive functions in fish. The leptin gene ( lep ) is a candidate gene for growth trait influence in both farm animals and teleost fish. Material and Methods This study investigated variations in the lep gene and their associations with growth-related traits in European sea bass ( Dicentrarchus labrax ) using DNA sequencing. Results Twelve novel single-nucleotide polymorphisms (SNPs) were identified in the first and second introns and the third exon of the gene, including a non-synonymous third exon variant (g.11004767C>T) causing an arginine-to-tryptophan substitution. This locus was significantly associated with multiple growth traits, including total and fillet weights and standard, body and post-anal lengths (P-value < 0.05). Analysis revealed two haploblocks; block 1 having four haplotypes (GCG, GTG, ACA and GTA), with GTA associated with the highest total and fillet weights and body length measurements (P-value < 0.01). Block 2 comprised three haplotypes (AG, GG and AA), where AG carriers exhibited superior growth to GG and AA carriers (P-value < 0.01). In silico analysis of the non-synonymous third exon variant (g.11004767C>T) suggested its potential effects on local protein conformation and receptor binding. Conclusion These findings indicate that lep gene polymorphisms, particularly the g.11004714G>A locus and specific haplotypes, are associated with growth variability in European sea bass. The identified SNPs and haplotypes may facilitate molecular marker–assisted selection in growth performance breeding programmes in economically important aquaculture species.