HCFC1 loss-of-function mutations disrupt neuronal and neural progenitor cells of the developing brain.
Both gain- and loss-of-function mutations have recently implicated HCFC1 in neurodevelopmental disorders. Here, we extend our previous HCFC1 over-expression studies by employing short hairpin RNA to reduce the expression of Hcfc1 in embryonic neural cells. We show that in contrast to over-expression, loss of Hcfc1 favoured proliferation of neural progenitor cells at the expense of differentiation and promoted axonal growth of post-mitotic neurons. To further support the involvement of HCFC1 in neurological disorders, we report two novel HCFC1 missense variants found in individuals with intellectual disability (ID). One of these variants, together with three previously reported HCFC1 missense variants of unknown pathogenicity, were functionally assessed using multiple cell-based assays. We show that three out of the four variants tested result in a partial loss of HCFC1 function. While over-expression of the wild-type HCFC1 caused reduction in HEK293T cell proliferation and axonal growth of neurons, these effects were alleviated upon over-expression of three of the four HCFC1 variants tested. One of these partial loss-of-function variants disrupted a nuclear localization sequence and the resulting protein displayed reduced ability to localize to the cell nucleus. The other two variants displayed negative effects on the expression of the HCFC1 target gene MMACHC, which is responsible for the metabolism of cobalamin, suggesting that these individuals may also be susceptible to cobalamin deficiency. Together, our work identifies plausible cellular consequences of missense HCFC1 variants and identifies likely and relevant disease mechanisms that converge on embryonic stages of brain development.
School of Paediatrics and Reproductive Health, Robinson Research Institute and.
Lachlan A
LA
Jolly
INSERM UMR 1163, Laboratory of Molecular and Pathophysiological Bases of Cognitive Disorders, Paris Descartes-Sorbonne Paris Cité University, Imagine Institute, Necker-Enfants Malades Hospital, 75015 Paris, France.
Lam Son
LS
Nguyen
School of Molecular and Biomedical Sciences, University of Adelaide, Adelaide 5000, Australia.
Deepti
D
Domingo
School of Paediatrics and Reproductive Health, Robinson Research Institute and.
Ying
Y
Sun
School of Paediatrics and Reproductive Health.
Simon
S
Barry
Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic.
Miroslava
M
Hancarova
Department of Medical Genetics, University Hospital Ostrava, tr. 17. listopadu 1790, 708 52 Ostrava, Czech Republic.
Pavlina
P
Plevova
Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic.
Marketa
M
Vlckova
Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic.
Marketa
M
Havlovicova
Department of Human Molecular Genetics, Max Planck Institute for Molecular Genetics, Ihnestrasse 73, D-14195 Berlin, Germany and.
Vera M
VM
Kalscheuer
Unit of Medical Genetics, Department of Medical and Surgical Sciences, DIMEC, St.Orsola-Malpighi Hospital, University of Bologna, Bologna 40138, Italy.
Claudio
C
Graziano
Unit of Medical Genetics, Department of Medical and Surgical Sciences, DIMEC, St.Orsola-Malpighi Hospital, University of Bologna, Bologna 40138, Italy.
Tommaso
T
Pippucci
Unit of Medical Genetics, Department of Medical and Surgical Sciences, DIMEC, St.Orsola-Malpighi Hospital, University of Bologna, Bologna 40138, Italy.
Elena
E
Bonora
Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic.
Zdenek
Z
Sedlacek
School of Paediatrics and Reproductive Health, Robinson Research Institute and School of Molecular and Biomedical Sciences, University of Adelaide, Adelaide 5000, Australia, jozef.gecz@adelaide.edu.au.
Jozef
J
Gecz
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001921:Brain / Q000166:cytology* / Q000196:embryology; D002352:Carrier Proteins / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D049109:Cell Proliferation; D002478:Cells, Cultured; D005260:Female; D015870:Gene Expression; D057809:HEK293 Cells; D051863:Host Cell Factor C1 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics; D008297:Male; D051379:Mice; D009154:Mutation; D058953:Neural Stem Cells / Q000166:cytology / Q000378:metabolism*; D010088:Oxidoreductases; D010375:Pedigree; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D014161:Transduction, Genetic
D002352:Carrier Proteins; D051863:Host Cell Factor C1; D034741:RNA, Small Interfering; C508359:MMACHC protein, human; D010088:Oxidoreductases