Visceral Peritoneum Hyperpigmentation in Chickens Is Associated with DCT Expression.

Hyperpigmentation of the visceral peritoneum (HVP) is a pigmentation abnormality in chickens that adversely affects carcass appearance, consumer acceptance, and poultry production. However, the genetic basis of HVP remains unclear. To investigate the causes and regulatory mechanisms of HVP, we employed high-performance liquid chromatography (HPLC), bulk RNA sequencing (RNA-seq), qRT-PCR, Western blotting, and siRNA interference. Additionally, single-cell RNA sequencing (scRNA-seq) was used to examine gene expression at the cellular level. Anatomical examination and hematoxylin and eosin (HE) staining revealed melanin deposition in the peritoneum of HVP-affected chickens. Spectrophotometric analysis at 500 nm showed significantly higher absorbance in the HVP group (p < 0.05), which correlated with the degree of pigmentation. HPLC confirmed the pigmentation as eumelanin, based on the pyrrole-2,3,5-tricarboxylic acid (PTCA) peak. RNA-seq identified 61 differentially expressed genes. Functional studies showed that dopachrome tautomerase (DCT) overexpression, combined with L-tyrosine (L-Tyr) supplementation, significantly increased melanin content (p < 0.05) and promoted melanocyte proliferation. In contrast, DCT silencing reduced melanin secretion and inhibited cell growth. ScRNA-seq analysis of over 9700 high-quality cells identified distinct melanocyte clusters, with DCT expression approximately 2.5-fold higher in melanocytes from the HVP group compared to the normal group. Furthermore, a DCT polymorphism (g.147917398 C > T) was identified as a potential marker for genetic selection (p-values = 0.033). These findings demonstrate that HVP is driven by DCT overexpression and excessive eumelanin deposition. DCT could serve as a molecular marker for genomic selection to improve poultry carcass quality and reduce economic losses in the poultry industry.