Decoding the role of naturally occurring variation in genetic and neural regulation of feeding and energy homeostasis. - Project Summary Metabolic disorders represent one of the largest burdens in our society, with an estimated 10-30% of adults affected by metabolic syndrome and over 11% of Americans diagnosed with diabetes. While genes that contribute to feeding and metabolism are well described, these phenotypes are highly polygenic, and the influence of individual alleles is shaped by genetic architecture. As such, a critical gap exists in our understanding of how naturally occurring genetic variation shapes feeding behavior and metabolism. Evolutionary medicine offers a powerful approach to explore how naturally occurring genetic variants impact feeding states, and the role genetic architecture plays in shaping these alleles. Evolution provides natural experiments that shape phenotypes in unique ways, and understanding how these phenotypes arise offers insights into how they change across taxa, including humans. We use the blind Mexican cavefish, Astyanax mexicanus, as a model to understand how naturally occurring genetic variation shapes feeding and metabolism. Astyanax exists as a single species in two forms: multiple populations of eyed, surface-dwelling fish and at least 30 populations of blind cavefish. We have shown that cavefish are hyperphagic, perpetually insulin-resistant (akin to diabetic), and exhibit slowed metabolism. We have also identified naturally occurring mutations in two well-known feeding receptors: melanocortin 3 (MC3R) and melanocortin 4 (MC4R). While the role of MC4R is well understood, much less is known about MC3R, and very little is known about how natural variations in these two receptors shape feeding. This proposal leverages innovative approaches developed in my lab over the past seven years to address this problem from a multidimensional perspective. Aim 1 will explore how MC3R and MC4R work together to regulate feeding and the impact of genomic architecture on these alleles. Aim 2 will use CRISPR-Cas9 to swap MC3R and MC4R alleles between surface fish and cavefish, allowing us to examine the impact on feeding behavior and neural activity in feeding centers. Aim 3 will assess brain-wide development in cavefish and explore the role of MC3R and MC4R in these processes. This proposal is innovative in its use of CRISPR-based allele swapping and advanced brain imaging techniques to uncover the genetic and neural mechanisms underlying these phenotypic variations. The overarching goal is to bridge the gap between laboratory-generated mutations and the complexities of natural genetic diversity, providing insights that could inform our understanding of obesity and metabolic disorders in humans.
