TY - JOUR
T1 - A Recurrent Gain-of-Function Mutation in CLCN6, Encoding the ClC-6 Cl−/H+-Exchanger, Causes Early-Onset Neurodegeneration
AU - Polovitskaya, Maya M.
AU - Barbini, Carlo
AU - Martinelli, Diego
AU - Harms, Frederike L.
AU - Cole, F. Sessions
AU - Calligari, Paolo
AU - Bocchinfuso, Gianfranco
AU - Stella, Lorenzo
AU - Ciolfi, Andrea
AU - Niceta, Marcello
AU - Rizza, Teresa
AU - Shinawi, Marwan
AU - Sisco, Kathleen
AU - Johannsen, Jessika
AU - Denecke, Jonas
AU - Carrozzo, Rosalba
AU - Wegner, Daniel J.
AU - Kutsche, Kerstin
AU - Tartaglia, Marco
AU - Jentsch, Thomas J.
N1 - Publisher Copyright:
© 2020 American Society of Human Genetics
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/12/3
Y1 - 2020/12/3
N2 - Dysfunction of the endolysosomal system is often associated with neurodegenerative disease because postmitotic neurons are particularly reliant on the elimination of intracellular aggregates. Adequate function of endosomes and lysosomes requires finely tuned luminal ion homeostasis and transmembrane ion fluxes. Endolysosomal CLC Cl−/H+ exchangers function as electric shunts for proton pumping and in luminal Cl− accumulation. We now report three unrelated children with severe neurodegenerative disease, who carry the same de novo c.1658A>G (p.Tyr553Cys) mutation in CLCN6, encoding the late endosomal Cl−/H+-exchanger ClC-6. Whereas Clcn6−/− mice have only mild neuronal lysosomal storage abnormalities, the affected individuals displayed severe developmental delay with pronounced generalized hypotonia, respiratory insufficiency, and variable neurodegeneration and diffusion restriction in cerebral peduncles, midbrain, and/or brainstem in MRI scans. The p.Tyr553Cys amino acid substitution strongly slowed ClC-6 gating and increased current amplitudes, particularly at the acidic pH of late endosomes. Transfection of ClC-6Tyr553Cys, but not ClC-6WT, generated giant LAMP1-positive vacuoles that were poorly acidified. Their generation strictly required ClC-6 ion transport, as shown by transport-deficient double mutants, and depended on Cl−/H+ exchange, as revealed by combination with the uncoupling p.Glu200Ala substitution. Transfection of either ClC-6Tyr553Cys/Glu200Ala or ClC-6Glu200Ala generated slightly enlarged vesicles, suggesting that p.Glu200Ala, previously associated with infantile spasms and microcephaly, is also pathogenic. Bafilomycin treatment abrogated vacuole generation, indicating that H+-driven Cl− accumulation osmotically drives vesicle enlargement. Our work establishes mutations in CLCN6 associated with neurological diseases, whose spectrum of clinical features depends on the differential impact of the allele on ClC-6 function.
AB - Dysfunction of the endolysosomal system is often associated with neurodegenerative disease because postmitotic neurons are particularly reliant on the elimination of intracellular aggregates. Adequate function of endosomes and lysosomes requires finely tuned luminal ion homeostasis and transmembrane ion fluxes. Endolysosomal CLC Cl−/H+ exchangers function as electric shunts for proton pumping and in luminal Cl− accumulation. We now report three unrelated children with severe neurodegenerative disease, who carry the same de novo c.1658A>G (p.Tyr553Cys) mutation in CLCN6, encoding the late endosomal Cl−/H+-exchanger ClC-6. Whereas Clcn6−/− mice have only mild neuronal lysosomal storage abnormalities, the affected individuals displayed severe developmental delay with pronounced generalized hypotonia, respiratory insufficiency, and variable neurodegeneration and diffusion restriction in cerebral peduncles, midbrain, and/or brainstem in MRI scans. The p.Tyr553Cys amino acid substitution strongly slowed ClC-6 gating and increased current amplitudes, particularly at the acidic pH of late endosomes. Transfection of ClC-6Tyr553Cys, but not ClC-6WT, generated giant LAMP1-positive vacuoles that were poorly acidified. Their generation strictly required ClC-6 ion transport, as shown by transport-deficient double mutants, and depended on Cl−/H+ exchange, as revealed by combination with the uncoupling p.Glu200Ala substitution. Transfection of either ClC-6Tyr553Cys/Glu200Ala or ClC-6Glu200Ala generated slightly enlarged vesicles, suggesting that p.Glu200Ala, previously associated with infantile spasms and microcephaly, is also pathogenic. Bafilomycin treatment abrogated vacuole generation, indicating that H+-driven Cl− accumulation osmotically drives vesicle enlargement. Our work establishes mutations in CLCN6 associated with neurological diseases, whose spectrum of clinical features depends on the differential impact of the allele on ClC-6 function.
KW - anion/proton antiport
KW - channelopathy
KW - chloride channel
KW - chloride/proton exchange
KW - copper metabolism
KW - gain of function
KW - gating glutamate
KW - luminal pH
KW - neurogenic bladder
KW - vacuole fusion
UR - http://www.scopus.com/inward/record.url?scp=85097420738&partnerID=8YFLogxK
U2 - 10.1016/j.ajhg.2020.11.004
DO - 10.1016/j.ajhg.2020.11.004
M3 - Article
C2 - 33217309
AN - SCOPUS:85097420738
VL - 107
SP - 1062
EP - 1077
JO - American Journal of Human Genetics
JF - American Journal of Human Genetics
SN - 0002-9297
IS - 6
ER -