Mammalian colour patterns are among the most recognizable characteristics found in nature and can have a profound impact on fitness. However, little is known about the mechanisms underlying the formation and subsequent evolution of these patterns. Here we show that, in the African striped mouse (Rhabdomys pumilio), periodic dorsal stripes result from underlying differences in melanocyte maturation, which give rise to spatial variation in hair colour. We identify the transcription factor ALX3 as a regulator of this process. In embryonic dorsal skin, patterned expression of Alx3 precedes pigment stripes and acts to directly repress Mitf, a master regulator of melanocyte differentiation, thereby giving rise to light-coloured hair. Moreover, Alx3 is upregulated in the light stripes of chipmunks, which have independently evolved a similar dorsal pattern. Our results show a previously undescribed mechanism for modulating spatial variation in hair colour and provide insights into how phenotypic novelty evolves.

De novo assembly of Rhabdomys pumilio transcriptome and detailed differential gene expression results This dataset contains a fasta file, including the de novo assembly of Rhabdomys pumilio transcriptome (built from RNA-Seq data using the Trinity suite of de novo transcriptome assembly tools - https://github.com/trinityrnaseq/trinityrnaseq/wiki), as well as a tab separated text file indicating the gene annotations corresponding to each assembly contig, obtained by mapping the de novo assembly to the human reference transcriptome, as described in the manuscript. A third Excel file contains the detailed results of RNA-Seq differential gene expression study in skin obtained from three dorsal regions, as described in the manuscript. Rhabdomys_pumilio.zip

Peer reviewed