PSVIII-36 Polymorphisms at the 5’ region flanking the ovine IGF-1 gene affect mRNA levels in dorper lambs

Abstract

Abstract The insulin-like growth factor-1 (IGF-1) plays a key role in muscle development and has been described in several studies as a candidate marker gene for growth traits in farm animals. The aim of the study was to investigate IGF-1 single nucleotide polymorphisms (SNPs) at the 5’ flanking region and their association with gene expression levels and phenotypic characteristics in lambs. The experiment was executed in two phases. First, a 265 bp-long region of gDNA localized up-stream of the IGF-1 gene was scanned for SNPs by sequencing. Sequence analysis revealed that animals with low IGF-1 plasm concentration had nucleotide changes from Guanine (G) to Cytosine (C) at position 85 (85G >C), and from G to Adenine (A) at position 87 (87G >A). A PCR-RFLP protocol was set up to accomplish allelic discrimination in 22 lambs sired by Dorper rams. The frequency of the variant-carrier lambs was 50 %. The statistical analysis showed differences (P < 0.05) between carrier and non-carrier female lambs for IGF-1 concentration at 13 d (168.76 ± 15.01 vs 229.95 ± 16.78), 41 d (191.02 ± 38.28 vs 324.50 ± 42.80) and 69 d (209.18 ± 30.63 vs 375.87 ± 34.2) of the feeding trial. Statistical differences (P < 0.05) were also found for total weight gain (22.16 ± 1.07 vs 26.75 ± 1.2). In a second phase, 55 Dorper females were genotyped, then 2 homozygotes, 5 heterozygotes and 5 wild-type for the variant were randomly selected for IGF-1 qPCR gene expression analysis. Gene expression was higher (fold-change 2.6) in non-carrier animals (P < 0.05). Nevertheless, daily weight gain and weight at 150 d were not statistically significant. The variant for the IGF-1 gene here reported has lower levels of gene expression. However, additional experiments are needed to measure phenotypic characteristics such as carcass traits, diameter and density of muscle fibers.