Molecular cloning and characterization of the endothelin 3 gene in black bone sheep.

Background: Black bone sheep was first discovered in Yunnan province of China in 1970, with unique black pigmentation on the body and internal organs. Endothelin 3 () has been known as a key gene causing hyperpigmentation in black bone chicken, the Silky fowl.

Methods: In this study, was employed as a candidate gene for regulating black color pigmentation. First, was cloned from sheep to obtain the full-length cDNA by using the rapid amplification of cDNA ends (RACE). Genomic was screened and a total of thirty predicted single nucleotide polymorphisms (SNPs) were genotyped for allele and genotype frequency analysis in a case-control study involving two black bone sheep populations. Genomic copy number analysis of in sheep was conducted to measure the variation in copy number. expression levels were observed among the groups in adult liver, lymph node, and kidney tissues, as well as embryo kidney samples. Also, among the tissues of black bone and non-black bone sheep.

Results: The size of the full-length cDNA was 1,578 bp, which included 426 bp of 5'-untranslated region (5'-UTR), an open reading frame (ORF) of 639 bp encoding a protein of 212 amino acids, and a 3'-UTR of 513 bp. Genotype and allele frequencies of all the discovered SNPs were found insignificantly different in black bone and non-black bone sheep ( > 0.05). Genomic copy number analysis of in sheep revealed no significant difference between the two sheep groups. No significant variations were found in the adult liver and kidney embryo samples. However, the expression in lymph node and kidney tissue was significantly higher in black bone sheep than that in non-black bone sheep ( < 0.05). Significant variations in the expression levels were observed among the tissues of non-black bone sheep.

Conclusions: The findings of the present study indicate that unlike in Silky chickens, is not responsible for hyperpigmentation but may play a key functional role in immune and excretory systems of black bone sheep.