Endogenous Retrovirus EAV-HP Linked to Blue Egg Phenotype in Mapuche Fowl

Oocyan or blue/green eggshell colour is an autosomal dominant trait found in native chickens (Mapuche fowl) of Chile and in some of their descendants in European and North American modern breeds. We report here the identification of an endogenous avian retroviral (EAV-HP) insertion in oocyan Mapuche fowl and European breeds. Sequencing data reveals 100% retroviral identity between the Mapuche and European insertions. Quantitative real-time PCR analysis of European oocyan chicken indicates over-expression of the SLCO1B3 gene (PAhR/Ar, a modulator of oestrogen, as a possible promoter/enhancer leading to reproductive tissue-specific over-expression of the SLCO1B3 gene. Analysis of all jungle fowl species Gallus sp. supports the retroviral insertion to be a post-domestication event, while identical LTR sequences within domestic chickens are in agreement with a recent de novo mutation.

卵蓝壳（Oocyan）性状属于常染色体显性遗传性状，存在于智利本土的马普切鸡（Mapuche fowl）以及欧洲、北美部分现代培育的其衍生品种中。本研究首次报道了在马普切鸡与欧洲卵蓝壳鸡群体中鉴定到内源性禽逆转录病毒（endogenous avian retroviral, EAV-HP）的插入序列。测序数据显示，马普切鸡与欧洲鸡群中的该逆转录病毒插入序列具有100%的同源一致性。对欧洲卵蓝壳鸡的实时荧光定量PCR（quantitative real-time PCR）分析表明，SLCO1B3基因存在过表达现象；作为雌激素调节因子的PAhR/Ar，可作为潜在的启动子/增强子，介导生殖组织中SLCO1B3基因的特异性过表达。对所有原鸡属（Gallus sp.）物种的分析支持该逆转录病毒插入事件发生于家鸡驯化之后，而家鸡体内高度一致的长末端重复序列（long terminal repeat, LTR）则与近期发生的从头突变（de novo mutation）现象相符。