Reduced gene expression and missense mutations in the transporter protein SLC45A2 in a hypopigmented Egyptian...

Oculocutaneous albinism-characterized by absent or decreased melanin in the skin, eyes and hair-often co-occurs with sensory, skin and immunity disorders. The genetic basis of albinism in humans is complex, with many loci implicated in multiple forms of the disorder. Less is known about the underlying genetic causes of albinism and leucism in other species, and cross-species studies of the molecular correlates of hypopigmentation could highlight common and conserved pathways underlying mammalian pigmentation disorders. We characterize the putative causal loci of reduced pigmentation in an Egyptian fruit bat (Rousettus aegyptiacus) that displayed features indicative of albinism. Despite albino or leucistic individuals having been reported in >100 bat species, the associated genetic backgrounds have not previously been studied. We used a digital gene expression panel to quantify mRNA levels in wing membrane samples of four candidate pigmentation genes in the focal albino fruit bat and control individuals. Significantly reduced SLC45A2 mRNA expression was found in the albino compared to five bats with typical coloration. Additionally, intraspecific sequence analyses of the albino bat SLC45A2 coding sequence identified two missense mutations, E18A and Q298R, the former of which was private to the albino bat. Position 18 of SLC45A2 was otherwise found to be highly conserved across 60 bat species and has not been previously linked to human albinism. By identifying SLC45A2 as the likely contributing locus, our results also indicate further support for the necessity of genetic testing for the reliable categorization of hypopigmented animals as either albino or leucistic.