1. De novo missense variants in exon 9 of SEPHS1 cause a neurodevelopmental condition with developmental delay, poor growth, hypotonia, and dysmorphic features.
- Author
-
Mullegama SV, Kiernan KA, Torti E, Pavlovsky E, Tilton N, Sekula A, Gao H, Alaimo JT, Engleman K, Rush ET, Blocker K, Dipple KM, Fettig VM, Hare H, Glass I, Grange DK, Griffin M, Phornphutkul C, Massingham L, Mehta L, Miller DE, Thies J, Merritt JL 2nd, Muller E 2nd, Osmond M, Sawyer SL, Slaugh R, Hickey RE, Wolf B, Choudhary S, Simonović M, Zhang Y, Palculict TB, Telegrafi A, Carere DA, Wentzensen IM, Morrow MM, Monaghan KG, Yang J, and Juusola J
- Subjects
- Animals, Child, Humans, Developmental Disabilities genetics, Exons, Mammals genetics, Muscle Hypotonia genetics, Neuroblastoma genetics, Reactive Oxygen Species, Intellectual Disability genetics, Musculoskeletal Abnormalities genetics, Neurodevelopmental Disorders genetics
- Abstract
Selenophosphate synthetase (SEPHS) plays an essential role in selenium metabolism. Two mammalian SEPHS paralogues, SEPHS1 and SEPHS2, share high sequence identity and structural homology with SEPHS. Here, we report nine individuals from eight families with developmental delay, growth and feeding problems, hypotonia, and dysmorphic features, all with heterozygous missense variants in SEPHS1. Eight of these individuals had a recurrent variant at amino acid position 371 of SEPHS1 (p.Arg371Trp, p.Arg371Gln, and p.Arg371Gly); seven of these variants were known to be de novo. Structural modeling and biochemical assays were used to understand the effect of these variants on SEPHS1 function. We found that a variant at residue Trp352 results in local structural changes of the C-terminal region of SEPHS1 that decrease the overall thermal stability of the enzyme. In contrast, variants of a solvent-exposed residue Arg371 do not impact enzyme stability and folding but could modulate direct protein-protein interactions of SEPSH1 with cellular factors in promoting cell proliferation and development. In neuronal SH-SY5Y cells, we assessed the impact of SEPHS1 variants on cell proliferation and ROS production and investigated the mRNA expression levels of genes encoding stress-related selenoproteins. Our findings provided evidence that the identified SEPHS1 variants enhance cell proliferation by modulating ROS homeostasis. Our study supports the hypothesis that SEPHS1 plays a critical role during human development and provides a basis for further investigation into the molecular mechanisms employed by SEPHS1. Furthermore, our data suggest that variants in SEPHS1 are associated with a neurodevelopmental disorder., Competing Interests: Declaration of interests S.V.M., E.T., H.G., T.B.P., A.T., D.A.C., M.M.M., I.M.W., K.G.M., and J.J. are employees of GeneDx., LLC. This article was prepared while M.S. was employed at the University of Illinois at Chicago. The opinions expressed in this article are the author’s own and do not reflect the view of the National Institutes of Health, the Department of Health and Human Services, or the United States government., (Copyright © 2024 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)
- Published
- 2024
- Full Text
- View/download PDF