In a new publication published today in Nature Communications, Athanasia Tzika and her team focus on the so-called Terrazzo morph, a single-locus spontaneous mutant of the corn snake that exhibits fuzzy longitudinal stripes instead of sharply-defined dorsal and lateral blotches in the wild type (un-mutated) snake.
Using genome mapping, Tzika’s team discovers a disruptive mutation in the coding region of the Premelanosome protein (PMEL) gene. Their transcriptomic analyses reveal that PMEL expression is significantly downregulated in Terrazzo embryonic tissues. Next, they use CRISPR-CAS9 technology to produce gene-edited corn snakes in which the PMEL gene is made inoperative. As the knockouts present a typical Terrazzo phenotype, these experiments unambiguously confirm that the mutation uncovered by genome mapping is indeed causing the abnormal skin colour pattern. In addition, using single-cell expression analyses of wild-type embryonic dorsal skin, the researchers demonstrate that all chromatophore progenitors express PMEL at varying levels.
Next, using imaging techniques, Tzika’s team shows that, in wild-type embryos, PMEL-expressing cells are initially uniformly spread before forming aggregates and eventually saddles and blotches, as seen in the adults. Conversely, in Terrazzo embryos, the aggregates fail to form.
As lead author Athanasia Tzika notes: "Our findings highlight the significance of understanding the intricate processes that shape the diversity of skin coloration in animals."
Source
PMEL is involved in snake colour pattern transition from blotches to stripes
Tzika, A.C., Ullate-Agote, A., Helleboid, PY., Kummrow, M.
Nature Communications 15, 7655 (2024). https://doi.org/10.1038/s41467-024-51927-0