Chamaeleo calyptratus (veiled chameleon) chromosome-scale genome assembly and annotation provides insights into the evolution of reptiles and developmental mechanisms.

Abstract

The family Chamaeleonidae comprises 228 species, boasting an extensive geographic spread and an array of evolutionary novelties and adaptations, but a paucity of genetic and molecular analyses. Veiled chameleon (Chamaeleo calyptratus) has emerged as a tractable research organism for the study of squamate early development and evolution. Here we report a chromosomal-level assembly and annotation of the veiled chameleon genome. We note a remarkable chromosomal conservation across squamates, but comparisons to more distant genomes reveal GC peaks correlating with ancestral chromosome fusion events. We subsequently identified the XX/XY region on chromosome 5, confirming environmental-independent sex determination in veiled chameleons. Furthermore, our analysis of the Hox gene family indicates that veiled chameleons possess the most complete set of 41 Hox genes, retained from an amniote ancestor. Lastly, the veiled chameleon genome has retained both ancestral paralogs of the Nodal gene, but is missing Dand5 and several other genes, recently associated with the loss of motile cilia during the establishment of left-right patterning. Thus, a complete veiled chameleon genome provides opportunities for novel insights into the evolution of reptilian genomes and the molecular mechanisms driving phenotypic variation and ecological adaptation.