No Evidence of Copy Number Variation in Acidic Mammalian Chitinase Genes (CHIA) in New World and Old World Monkeys

Abstract

Copy number variation may be the most common form of structural genetic variation in the genome. Numerous studies have shown that gene copy number variation can correlate with phenotypic variation, where higher copy numbers correspond to increased expression of the protein and vice versa. Examples include some digestive enzyme genes, where variation in copy numbers and protein expression may be related to dietary differences. Increasing the expression of a digestive enzyme through higher gene copy numbers may thus be a potential mechanism for altering an organism’s digestive capabilities. I investigated copy number variation in genes coding for acidic mammalian chitinase, a chitinolytic digestive enzyme that may be used for the digestion of insect exoskeletons, in nonhuman primates with varying levels of insect consumption. I hypothesized that CHIA copy number correlates positively with level of insectivory, predicting higher copy numbers in more insectivorous primates. I assessed copy number variation with the QuantStudio 3D digital PCR platform, in a comparative sample of Old World and New World primate species (N = 10 species, one or two individuals each). Contrary to my prediction, no evidence of copy number variation was found and all species tested had two gene copies per diploid genome. These findings suggest that if acidic mammalian chitinase expression varies according to insect consumption in primates, it may be up- or downregulated through another mechanism.