Oligonucleotide correction of an intronic TIMMDC1 variant in cells of patients with severe neurodegenerative disorder

Raman Kumar; Mark A Corbett; Nicholas J C Smith; Daniella H Hock; Zoya Kikhtyak; Liana N Semcesen; Atsushi Morimoto; Sangmoon Lee; David A Stroud; Joseph G Gleeson; Eric A Haan; Jozef Gecz

doi:10.1038/s41525-021-00277-7

Oligonucleotide correction of an intronic TIMMDC1 variant in cells of patients with severe neurodegenerative disorder

NPJ Genom Med. 2022 Jan 28;7(1):9. doi: 10.1038/s41525-021-00277-7.

Authors

Raman Kumar¹, Mark A Corbett¹, Nicholas J C Smith^{1

2}, Daniella H Hock³, Zoya Kikhtyak⁴, Liana N Semcesen³, Atsushi Morimoto¹, Sangmoon Lee⁵, David A Stroud^{3

6}, Joseph G Gleeson⁵, Eric A Haan⁷, Jozef Gecz⁸

Affiliations

¹ Adelaide Medical School and the Robinson Research Institute, University of Adelaide, Adelaide, 5000, SA, Australia.
² Department of Neurology, Women's and Children's Health Network, Adelaide, 5006, SA, Australia.
³ Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, 3052, VIC, Australia.
⁴ Dame Roma Mitchell Cancer Research Laboratories, Adelaide Medical School, University of Adelaide, Adelaide, 5000, SA, Australia.
⁵ Neurogenetics Laboratory, Institute for Genomic Medicine and Departments of Neurosciences and Paediatrics, University of California, San Diego, 92093, CA, USA.
⁶ Murdoch Children's Research Institute, The Royal Children's Hospital, Parkville, 3052, VIC, Australia.
⁷ Adult Genetics Unit, Royal Adelaide Hospital and Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, 5000, SA, Australia.
⁸ Adelaide Medical School and the Robinson Research Institute, University of Adelaide, Adelaide, 5000, SA, Australia. jozef.gecz@adelaide.edu.au.

Abstract

TIMMDC1 encodes the Translocase of Inner Mitochondrial Membrane Domain-Containing protein 1 (TIMMDC1) subunit of complex I of the electron transport chain responsible for ATP production. We studied a consanguineous family with two affected children, now deceased, who presented with failure to thrive in the early postnatal period, poor feeding, hypotonia, peripheral neuropathy and drug-resistant epilepsy. Genome sequencing data revealed a known, deep intronic pathogenic variant TIMMDC1 c.597-1340A>G, also present in gnomAD (~1/5000 frequency), that enhances aberrant splicing. Using RNA and protein analysis we show almost complete loss of TIMMDC1 protein and compromised mitochondrial complex I function. We have designed and applied two different splice-switching antisense oligonucleotides (SSO) to restore normal TIMMDC1 mRNA processing and protein levels in patients' cells. Quantitative proteomics and real-time metabolic analysis of mitochondrial function on patient fibroblasts treated with SSOs showed restoration of complex I subunit abundance and function. SSO-mediated therapy of this inevitably fatal TIMMDC1 neurologic disorder is an attractive possibility.