Clinical, genetic, and functional characterization of the glycine receptor β-subunit A455P variant in a family affected by hyperekplexia syndrome
AuthorsAboheimed, Ghada I
AlRasheed, Maha M
Peña-Guerra, Karla A
Cardona-Londoño, Kelly J
Salih, Mustafa A
Seidahmed, Mohammed Z
Arold, Stefan T
Ruiz, Arnaud J
KAUST DepartmentComputational Bioscience Research Center (CBRC)
Permanent link to this recordhttp://hdl.handle.net/10754/676715
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AbstractHyperekplexia is a rare neurological disorder characterized by exaggerated startle response affecting newborns with the hallmark characteristics of hypertonia, apnea, and noise or touch-induced non-epileptic seizures. The genetic causes of the disease can vary and several associated genes and mutations have been reported to affect glycine receptors (GlyRs); however, the mechanistic links between GlyRs and hyperekplexia are not yet understood. Here, we describe a patient with hyperekplexia from a consanguineous family. Extensive genetic screening using exome sequencing coupled with autozygome analysis and iterative filtering supplemented by in silico prediction identified that the patient carries the homozygous missense mutation A455P in GLRB, which encodes the GlyR β-subunit. To unravel the physiological and molecular effects of A455P on GlyRs, we used electrophysiology in a heterologous system as well as immunocytochemistry, confocal microscopy, and cellular biochemistry. We found a reduction in glycine-evoked currents in N2A cells expressing the mutation compared to wild type cells. Western blot analysis also revealed a reduced amount of GlyR β protein both in cell lysates and isolated membrane fractions. In line with the above observations, co-immunoprecipitation assays suggested that the GlyR α1-subunit retained co-assembly with βA455P to form membrane-bound heteromeric receptors. Finally, structural modelling showed that the A455P mutation affected the interaction between the GlyR β-subunit transmembrane domain 4 and the other helices of the subunit. Taken together, our study identifies and validates a novel loss-of-function mutation in GlyRs whose pathogenicity is likely to cause hyperekplexia in affected individuals.
CitationAboheimed, G. I., AlRasheed, M. M., Almudimeegh, S., Peña-Guerra, K. A., Cardona-Londoño, K. J., Salih, M. A., Seidahmed, M. Z., Al-Mohanna, F., Colak, D., Harvey, K., Arold, S. T., Kaya, N., & Ruiz, A. J. (2022). Clinical, genetic, and functional characterization of the glycine receptor β-subunit A455P variant in a family affected by hyperekplexia syndrome. Journal of Biological Chemistry, 102018. https://doi.org/10.1016/j.jbc.2022.102018
SponsorsWe are very grateful to the family for their participation in this study. We thank colleagues at King Faisal Specialist Hospital and Research Center (KFSHRC) and staff at Genotyping and Sequencing Core Facilities of the Genetics Department, Research Advisory Council Committees and Saudi Human Genome Program. We thank the National Plan for Science, Technology and Innovation program under King Abdulaziz City for Science and Technology, and the King Salman Center for Disability Research, for supporting Dr Namik Kaya and Dr Dilek Colak. We are grateful to Prof Robert Harvey for early mentorship of Ghada Aboheimed at UCL School of Pharmacy and for his role in liaising with Dr Mustafa Salih. We also thank Prof Dimitri Kullmann for the providence of Labview routines.
This research was conducted through intramural funds (RAC# 2060035, 2120022, 2110006) provided by KFSHRC. GA was sponsored by a PhD studentship provided by the External Joint Supervision Program, King Saud University. STA, KPG and KCL were supported by the King Abdullah University of Science and Technology through the baseline fund and the Office of Sponsored Research under awards numbers FCC/1/1976-25 and REI/1/4446-01. MS was supported by Researchers Supporting Project grant (RSP 2020/38), King Saud University.
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