Using transmission electron microscopy, we show that the leucistic morph of the Texas rat snake (Pantherophis obsoletus lindheimeri) lacks both melanophores and xanthophores in its skin and exhibits a uniform ivory white color generated by iridophores and collagen fibers. In addition, we sequenced the full genome of the species and identified potential causal mutations for the leucistic phenotype.
Albinism and leucism are phenotypes resulting from impaired melanin pigmentation in the skin and skin appendages. Here, Athanasia Tzika and her PhD student Asier Ullate-Agote (i) characterise the ivory-white phenotype of the leucistic Texas Rat Snake Pantherophis obsoletus with transmission electron microscopy, (ii) generate a highly-contiguous near-chromosome quality assembly of its genome, (iii) show that leucistic individuals exhibit a significantly decreased expression of the 'melanocyte inducing transcription factor gene' (MITF) and (iv) identify a single-nucleotide deletion that generates a frameshift and a premature termination codon in the same gene of some leucistic individuals. Tzika and Ullate-Agote thus suggest that mutations affecting the regulation of MITF is associated with the leucistic phenotype in Texas rat snake and predated the coding sequence mutation of the same gene.
Dorsal view of normal (left) and Leucistic (right) Texas rat snake.