Atp7a determines a hierarchy of copper metabolism essential for notochord development

Abstract

The critical developmental and genetic requirements of copper metabolism during embryogenesis are unknown. Utilizing a chemical genetic screen in zebrafish, we identified small molecules that perturb copper homeostasis. Our findings reveal a role for copper in notochord formation and demonstrate a hierarchy of copper metabolism within the embryo. To elucidate these observations, we interrogated a genetic screen for embryos phenocopied by copper deficiency, identifying calamity, a mutant defective in the zebrafish ortholog of the Menkes disease gene (atp7a). Copper metabolism in calamity is restored by human ATP7A, and transplantation experiments reveal that atp7a functions cell autonomously, findings with important therapeutic implications. The gene dosage of atp7a determines the sensitivity to copper deprivation, revealing that the observed developmental hierarchy of copper metabolism is informed by specific genetic factors. Our data provide insight into the developmental pathophysiology of copper metabolism and suggest that suboptimal copper metabolism may contribute to birth defects.

Drosophila Ctr1A Functions as a Copper Transporter Essential for Development

“…Indeed experiments in Zebrafish suggest that a hierarchy of copper metabolism exists such that when copper is limiting, copper-dependent cellular processes most essential for viability are prioritized over less essential processes. Specifically within the Zebrafish model, pigmentation mediated by tyrosinase activity was typically one of the first copper-dependent processes to be affected by copper limitation, whereas notochord development, potentially mediated by lysyl oxidase activity and perhaps other copper-dependent processes, was one of the last processes to be affected (56). Thus tyrosinase activity and pigmentation in flies might also be lower on the copper metabolism hierarchy and more dispensable under conditions of copper deprivation such that enzymes and processes higher up within the hierarchy can be metallated with limited amounts of copper available.…”

Analysis of the Zebrafish Proteome during Embryonic Development

“…The zebrafish has emerged as a tractable model organism for high throughput screening in vertebrate biology and genetics (6) due to its large clutch size, external development, transparency during development, and ease of husbandry. More recently, small chemical compound screens targeting organ systems, such as the cardiovascular system (44), central nervous system (45), and the blood-forming organs (46), have illustrated the utility of zebrafish in drug development. Its genome has been sequenced, and about 40% of its genes have been comprehensively annotated (Vertebrate Genome Annotation (VEGA) 49).…”

Menkes disease

“…53,54 Very recently the phenotypic alterations of two calamity mutant alleles have been corrected by antisense therapy. 55 …”