A missense mutation (A5346G) in the endogenous avian leukosis virus subgroup E <i>ev3</i> locus is associated with body weight in Langshan chickens

This study investigated the influence of the endogenous avian leukosis virus ev3 (ALV-E ev3) locus on production traits in Langshan chickens, expanding on established evidence of ALV-E’s role in growth regulation. Two single nucleotide polymorphisms (SNPs; T3689C and A5346G) within the ALV-E ev3 locus were identified using PCR-SSCP and sequencing in a population of 300 hens. Association analysis revealed that the synonymous T3689C mutation showed no significant correlation with cumulative egg production to 300 days of age (300-day egg production) and body weight at 16 weeks of age (16-week body weight). In contrast, the non-synonymous A5346G mutation (resulting in a Thr597Ala substitution) was significantly associated (P < 0.01) with increased 16-week body weight, where GG genotype chickens exhibited higher weight (1.65 ± 0.28 kg) compared to AA/AG genotypes (1.53 ± 0.10 kg/1.54 ± 0.14 kg). Quantitative RT-PCR analysis demonstrated significantly elevated expression of the ALV-E ev3 locus in digestive tract tissues compared to muscle tissues, suggesting its potential role in modulating nutrient metabolism to influence growth. These findings establish the A5346G SNP within the ALV-E ev3 locus as a promising genetic marker for body weight in Langshan chickens, providing valuable insights for marker-assisted selection strategies to enhance growth performance in poultry breeding programs.