An Integrated Investigation of <scp>SOX10</scp> in Feather Color in Domestic Rock Pigeon ( <scp> <i>Columba livia</i> </scp> )

The transcription factor SOX10 plays an important role in promoting determination and differentiation of melanocytes, and mutations affecting SOX10 expression or function often result in dramatic pigment phenotypes. In domestic rock pigeon, homozygosity for either of two regulatory mutations upstream of Sox10 known as recessive red causes birds to display bright red pheomelanic plumage instead of wild-type blue/black eumelanic plumage. In this study, we identify a common set of differentially expressed melanogenic genes in feathers from recessive red birds homozygous for either mutant allele, most notably a downregulation of Tyrp1, Slc24a5, Pmel, Mlana, and Hpgds and upregulation of Slc7a11. Collectively, these changes may promote pheomelanin synthesis and inhibit eumelanin synthesis. We also identify other altered pathways including genes involved in galactolipid synthesis and stem cell biology. We further examined the chromatin occupancy of SOX10 in pigeon melanocytes by ChIPseq to identify the subset of differentially expressed genes that are most likely to be direct targets of SOX10 function, and uncover evidence that SOX10 promotes its own expression by binding to the mcs7 melanocyte enhancer. Together, these data provide a more comprehensive picture of the role that SOX10 plays in melanocyte biology.