Sequence Characterization of K-gene Linked Region in Various Chicken Breeds

Abstract

The avian endogenous virus gene (ev21) and dominant sex-linked late feathering (LF) gene (K) are closely associated on the Z chromosome of LF chickens. The K gene is linked to two large repeats: ev21-unoccupied repeat region (URa) and ev21-occupied repeat region (OR). On the other hand, the recessive allele (early feathering, EF: k+) is linked to ev21-unoccupied region (URb). These three regions show high similarity but due to minor sequence differences, restriction enzyme treatment distinguishes URa and URb in White Leghorn. However, the applicability of the PCR-RFLP technique or the association between ev21 and K gene are not well investigated in the other breeds or strains. In this study, ev21 loci were detected in White Leghorn, Nagoya, Silky, Geline but not Gifujidori breeds of chickens, and the URa and URb from the various breeds were sequenced. Four types of sequence (URa-1 and URa-2 from LF or ev21 positive, URb-1 and URb-2 from EF or ev21 negative) were identified. At position 1072-1075, URa-2, URb-1 and URb-2 had “GGCC” whereas URa-1 had “AGCC”. The transition at 1072 clearly indicates that the PCR-RFLP technique used for White Leghorn is not applicable to Nagoya. Interestingly, both URa-1 and URa-2 were obtained from the ev21 positive sample of Geline. Presence of different sequence of URa in the Geline may explain that fixation of one of sequences to White Leghorn or Nagoya had occurred during breed establishment.