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Original article
SEC31A mutation affects ER homeostasis, causing neurological syndrome
  1. Daniel Halperin1,
  2. Rotem Kadir1,
  3. Yonatan Perez1,
  4. Max Drabkin1,
  5. Yuval Yogev1,
  6. Ohad Wormser1,
  7. Erez M Berman1,
  8. Ekaterina Eremenko2,
  9. Barak Rotblat3,
  10. Zamir Shorer4,
  11. Libe Gradstein5,
  12. Ilan Shelef6,
  13. Ruth Birk7,
  14. Uri Abdu3,
  15. Hagit Flusser8,
  16. Ohad S Birk1,9
  1. 1The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
  2. 2The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences, Zlotowski Center for Neuroscience, The National Institute of Biotechnology in the Negev; Ben-Gurion University of the Negev, Beer Sheva, Israel
  3. 3Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
  4. 4Pediatric Neurology Unit, Division of Pediatrics, Soroka University Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
  5. 5Department of Ophthalmology, Clalit Health Services, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
  6. 6Department of Imaging, Soroka University Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
  7. 7Department of Nutrition, Faculty of Health Sciences, Ariel University, Ariel, Israel
  8. 8Zussman Child Development Center, Division of Pediatrics, Soroka University Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
  9. 9Genetics Institute, Soroka University Medical Center, Ben-Gurion University of the Negev, Beer Sheva, Israel
  1. Correspondence to Prof. Ohad S Birk, Genetics Institute, Soroka Medical Center, Beer Sheva 84101, Israel; obirk{at}bgu.ac.il

Abstract

Background Consanguineous kindred presented with an autosomal recessive syndrome of intrauterine growth retardation, marked developmental delay, spastic quadriplegia with profound contractures, pseudobulbar palsy with recurrent aspirations, epilepsy, dysmorphism, neurosensory deafness and optic nerve atrophy with no eye fixation. Affected individuals died by the age of 4. Brain MRI demonstrated microcephaly, semilobar holoprosencephaly and agenesis of corpus callosum. We aimed at elucidating the molecular basis of this disease.

Methods Genome-wide linkage analysis combined with whole exome sequencing were performed to identify disease-causing variants. Functional consequences were investigated in fruit flies null mutant for the Drosophila SEC31A orthologue. SEC31A knockout SH-SY5Y and HEK293T cell-lines were generated using CRISPR/Cas9 and studied through qRT-PCR, immunoblotting and viability assays.

Results Through genetic studies, we identified a disease-associated homozygous nonsense mutation in SEC31A. We demonstrate that SEC31A is ubiquitously expressed, and that the mutation triggers nonsense-mediated decay of its transcript, comprising a practical null mutation. Similar to the human disease phenotype, knockdown SEC31A flies had defective brains and early lethality. Moreover, in line with SEC31A encoding one of the two coating layers comprising the Coat protein complex II (COP-II) complex, trafficking newly synthesised proteins from the endoplasmic reticulum (ER) to the Golgi, CRISPR/Cas9-mediated SEC31A null mutant cells demonstrated reduced viability through upregulation of ER-stress pathways.

Conclusion We demonstrate through human and Drosophila genetic and in vitro molecular studies, that a severe neurological syndrome is caused by a null mutation in SEC31A, reducing cell viability through enhanced ER-stress response, in line with SEC31A’s role in the COP-II complex.

  • COP-II complex
  • Sec31A
  • neurological syndrome
  • genetic mutation

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Footnotes

  • HF and OSB contributed equally.

  • Contributors DH, RK, YP, BR, UA, RB, HF and OSB contributed to the conception and design of the study. DH, ZS, LG, IS, MD, YY, OW, EE and EB contributed to the acquisition and analysis of data. DH, RK, YP and BR contributed to preparing the figures. DH and OSB drafted the text.

  • Funding Funding for this research was provided by the Legacy Heritage Bio-Medical Program of the Israel Science Foundation (grants no. 1814/13 and 1798/16) awarded to Professor Ohad Birk and the National Knowledge Center for Rare/Orphan Diseases sponsored by the Israel Ministry of Science, Technology and Space.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval Soroka Medical Center IRB.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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