Coat color patterning in mammals is a fascinating developmental process whose molecular underpinnings are largely unexplored.

Recently, mutations in Transmembrane aminopeptidase Q (Taqpep) were found in domestic cats (Felis catus) that change the regularly spaced dark stripes observed in Mackerel tabby cats to the whorled pattern observed in Blotched cats. With the knowledge that Taqpep acts during embryogenesis to shape the pigmentation pattern, we examined the temporal and spatial distribution of Taqpep expression in 18-25 day-post-conception (dpc) domestic cat embryos (Stage 12-15) using Advanced Cell Diagnostics’ (ACD) RNAScope® technology and Taqpep-specific probes. Although we had originally hypothesized Taqpep expression to be concentrated in epidermal cells or in dermal cells that were close to the epidermis with pattern establishment believed to be happening in the epidermis, we found that Taqpep is to be first expressed at day 19 dpc (Stage 13) in deep dermal cells, a distance from the pattern-expressing cells in the epidermis that are marked by Dickkopf 4 (Dkk4). Unpatterned Taqpep expression is maintained in the deep dermis at all embryonic stages examined. This study is the first of its kind to visualize Taqpep expression in cat embryos, expands our understanding of the cell populations that contribute to mammalian patterning and highlights that communication among cell populations is essential in shaping the pattern.

Photo: Courtesy of iStock by Getty Images