New Disorder of Copper Metabolism Identified, Caused by Variants in CTR1 Gene

New Disorder of Copper Metabolism Identified, Caused by Variants in CTR1 Gene 1024 575 Abbie Roth

A novel missense mutation in identical twins leads to discovery and definition of new inherited disorder of brain copper metabolism.

Copper is essential for many cellular functions, including cellular respiration, antioxidant defense, neurotransmitter biosynthesis and neuropeptide amidation, among others. Until recently, only two inborn errors of copper metabolism were well established. Both are rare. Wilson’s disease and Menkes disease result from mutations in the copper-transporting P-type ATPases; ATP7B and ATP7A, respectively.

CTR1 is a high-affinity copper uptake protein essential for mammalian development and copper homeostasis, as well as progression of certain cancers. Until recently, no cases of human CTR1 deficiency were reported.

Now, in a study published in Human Molecular Genetics, Stephen Kaler, MD, MPH, and his colleagues report the first description of CTR1 deficiency due to a homozygous missense mutation of the CTR1 gene in two children. They also present the associated clinical, biochemical and molecular phenotypes of this deficiency.

Identical twin boys with the same missense mutation in the CTR1 gene both presented with hypotonia, global developmental delay, seizures and rapid brain atrophy after appearing well for the first two months of life. Brain imaging indicated more atrophy than in children with untreated Menkes disease.

The team used clinical phenotyping, brain imaging, assays for copper, cytochrome c oxidation and mitochondrial respiration, western blotting, cell transfection experiments, confocal and electron microscopy, protein structure modeling and fetal brain and cerebral organoid transcriptome analyses.

“This paper represents the culmination of an extraordinary international collaboration spanning contributions from five countries and eight different institutions, all focused on efforts to diagnose, understand, and treat two infants with a previously unrecognized inborn error of human copper metabolism,” says Dr. Kaler, senior author of the publication and principal investigator in the Center for Gene Therapy at the Abigail Wexner Research Institute.

The team also evaluated the effects of copper histidinate in the patients’ cultured cells and, under a formal research protocol, in the patients themselves.

“In the cell cultures, the copper histidinate treatment normalized cytochrome c oxidase activity and enhanced mitochondrial respiration,” says Dr. Kaler. “In the patients, we saw modest clinical improvements. Growth improved and serum copper levels increased, but overall clinical improvements were limited, possibly because of pathology sustained before the treatment was initiated.”

In combination with present and prior studies, these infants’ clinical, biochemical and molecular phenotypes establish the impact of this novel variant on copper metabolism and cellular homeostasis and illuminate a crucial role for CTR1 in human brain development. CTR1 deficiency represents a newly defined inherited order of brain copper metabolism.

“The research findings are highly relevant to our further understanding of copper transport into and within the brain and may lead to advances in developing remedies for this disorder and other human illnesses, including cancer,” Dr. Kaler says. “We are indebted to these children and their devoted parents for participating in this study.”

 

 

Reference:

Batzios S, Tal G, DiStasio AT, Peng Y, Charalambous C, Nicolaides P, Kamsteeg E-J, Korman SH, Mandel H, Steinbach PJ, Yi L, Fair SR, Hester ME, Drousiotou A, Kaler SG. Newly identified disorder of copper metabolism caused by variants in CTR1, a high-affinity copper transporter. Human Molecular Genetics. 2022 Aug 1. [Online ahead of print]

 

About the author

Abbie Roth, MWC, is a passionate communicator of science. As the managing editor for science communication at Nationwide Children’s Hospital, she shares stories about innovative research and discovery with audiences ranging from parents to preeminent researchers and leaders. Before coming to Nationwide Children’s, Abbie used her communication skills to engage audiences with a wide variety of science topics. As a subject-matter expert, she developed content for science education materials for McGraw-Hill Education, bringing science concepts to life for middle and high school aged students. She also provided technical editing for manuscripts spanning the American Chemical Society journal portfolio, in addition to serving as production lead for ACS Synthetic Biology. Abbie earned her BS in Life Sciences at Otterbein University while working at the Tan & Cardinal newspaper and minoring in Public Relations. She is a Medical Writer Certified®, credentialed by the American Medical Writers Association.