Characterization of the Expression Profile and Genetic Polymorphism of the Cellular Retinol-Binding Protein (CRBP IV) Gene in Erlang Mountainous Chickens

In this study, we cloned the coding sequence of chicken CRBP IV, quantified the mRNA expression in Erlang Mountainous Chickens, and investigated a polymorphism in this gene and its association with egg production traits among 349 individuals. The cloned fragment contained a 384 bp open reading frame, which encoded a predicted protein of 127 amino acids and was highly conserved among species. Expression of CRBP IV mRNA was detected in all eight tissues (small intestine, heart, liver, kidney, oviduct, ovary, pituitary, and hypothalamus) at different ages (12, 24, 32 and 45 w). High expression was found in small intestine, pituitary, kidney and liver, whereas it was low in the heart (p < 0.05). The CRBP IV mRNA levels changed with age in the various tissues, and were highly expressed in all tissues at 32 w, except for the heart. We identified one nucleotide substitution (c. 826T>C) in the second exon, which caused an amino acid change (p. S49L). Genotypes (TT, TC and CC) had significant effects on the age at first egg (AFE), total eggs for 300 days (TE300) and highest continuous laying days (HCLD). The CC genotype would be genetically advantageous to improve egg production traits due to earlier AFE, more TE300, and longer HCLD.