Alternative Splicing Expands the Clinical Spectrum of NDUFS6-related Mitochondrial Disorders

Overview

Journal Genet Med

Publisher Elsevier

Specialty Genetics

Date 2024 Mar 9

PMID 38459834

Authors

Camila Armirola-Ricaurte

Noortje Zonnekein

Georgios Koutsis

Silvia Amor-Barris

Ana Lara Pelayo-Negro

Derek Atkinson

Stephanie Efthymiou

Valentina Turchetti

Argyris Dinopoulos

Antonio Garcia

Mert Karakaya

German Moris

Ayse Ipek Polat

Uluc Yis

Carmen Espinos

Liedewei Van de Vondel

Els De Vriendt

Georgia Karadima

Brunhilde Wirth

Michael Hanna

Henry Houlden

Jose Berciano

Albena Jordanova

Affiliations

Soon will be listed here.

Abstract

Purpose: We describe 3 families with Charcot-Marie-Tooth neuropathy (CMT), harboring a homozygous NDUFS6 NM_004553.6:c.309+5G>A variant previously linked to fatal Leigh syndrome. We aimed to characterize clinically and molecularly the newly identified patients and understand the mechanism underlying their milder phenotype.

Methods: The patients underwent extensive clinical examinations. Exome sequencing was done in 4 affected individuals. The functional effect of the c.309+5G>A variant was investigated in patient-derived EBV-transformed lymphoblasts at the complementary DNA, protein, and mitochondrial level. Alternative splicing was evaluated using complementary DNA long-read sequencing.

Results: All patients presented with early-onset, slowly progressive axonal CMT, and nystagmus; some exhibited additional central nervous system symptoms. The c.309+5G>A substitution caused the expression of aberrantly spliced transcripts and negligible levels of the canonical transcript. Immunoblotting showed reduced levels of mutant isoforms. No detectable defects in mitochondrial complex stability or bioenergetics were found.

Conclusion: We expand the clinical spectrum of NDUFS6-related mitochondrial disorders to include axonal CMT, emphasizing the clinical and pathophysiologic overlap between these 2 clinical entities. This work demonstrates the critical role that alternative splicing may play in modulating the severity of a genetic disorder, emphasizing the need for careful consideration when interpreting splice variants and their implications on disease prognosis.

References

Pareyson D, Piscosquito G, Moroni I, Salsano E, Zeviani M . Peripheral neuropathy in mitochondrial disorders. Lancet Neurol. 2013; 12(10):1011-24. DOI: 10.1016/S1474-4422(13)70158-3. View

Baertling F, Sanchez-Caballero L, van den Brand M, Fung C, Chan S, Wong V . NDUFA9 point mutations cause a variable mitochondrial complex I assembly defect. Clin Genet. 2017; 93(1):111-118. DOI: 10.1111/cge.13089. View

Li Y, Zhang Y, Jiang G, Wang Y, He C, Zhao X . Case report: novel mutations of NDUFS6 and NHLRC2 genes potentially cause the quick postnatal death of a Chinese Hani minority neonate with mitochondrial complex I deficiency and FINCA syndrome. Medicine (Baltimore). 2022; 101(27):e29239. PMC: 9259100. DOI: 10.1097/MD.0000000000029239. View

Koene S, Rodenburg R, van der Knaap M, Willemsen M, Sperl W, Laugel V . Natural disease course and genotype-phenotype correlations in Complex I deficiency caused by nuclear gene defects: what we learned from 130 cases. J Inherit Metab Dis. 2012; 35(5):737-47. PMC: 3432203. DOI: 10.1007/s10545-012-9492-z. View

Spiegel R, Shaag A, Mandel H, Reich D, Penyakov M, Hujeirat Y . Mutated NDUFS6 is the cause of fatal neonatal lactic acidemia in Caucasus Jews. Eur J Hum Genet. 2009; 17(9):1200-3. PMC: 2986593. DOI: 10.1038/ejhg.2009.24. View

Atkinson D, Glumac J, Asselbergh B, Ermanoska B, Blocquel D, Steiner R . Sphingosine 1-phosphate lyase deficiency causes Charcot-Marie-Tooth neuropathy. Neurology. 2017; 88(6):533-542. PMC: 5304460. DOI: 10.1212/WNL.0000000000003595. View

Montpetit V, Andermann F, Carpenter S, Fawcett J, Giberson H . Subacute necrotizing encephalomyelopathy. A review and a study of two families. Brain. 1971; 94(1):1-30. DOI: 10.1093/brain/94.1.1. View

Richards S, Aziz N, Bale S, Bick D, Das S, Gastier-Foster J . Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med. 2015; 17(5):405-24. PMC: 4544753. DOI: 10.1038/gim.2015.30. View

Mancuso M, Orsucci D, Angelini C, Bertini E, Carelli V, Comi G . "Mitochondrial neuropathies": A survey from the large cohort of the Italian Network. Neuromuscul Disord. 2016; 26(4-5):272-6. DOI: 10.1016/j.nmd.2016.02.008. View

10.

Kirby D, Salemi R, Sugiana C, Ohtake A, Parry L, Bell K . NDUFS6 mutations are a novel cause of lethal neonatal mitochondrial complex I deficiency. J Clin Invest. 2004; 114(6):837-45. PMC: 516258. DOI: 10.1172/JCI20683. View

11.

Lake N, Compton A, Rahman S, Thorburn D . Leigh syndrome: One disorder, more than 75 monogenic causes. Ann Neurol. 2015; 79(2):190-203. DOI: 10.1002/ana.24551. View

12.

Rouzier C, Chaussenot A, Fragaki K, Serre V, Ait-El-Mkadem S, Richelme C . NDUFS6 related Leigh syndrome: a case report and review of the literature. J Hum Genet. 2019; 64(7):637-645. DOI: 10.1038/s10038-019-0594-4. View

13.

Parey K, Haapanen O, Sharma V, Kofeler H, Zullig T, Prinz S . High-resolution cryo-EM structures of respiratory complex I: Mechanism, assembly, and disease. Sci Adv. 2019; 5(12):eaax9484. PMC: 6905873. DOI: 10.1126/sciadv.aax9484. View

14.

Scheffler I . Mitochondrial disease associated with complex I (NADH-CoQ oxidoreductase) deficiency. J Inherit Metab Dis. 2014; 38(3):405-15. DOI: 10.1007/s10545-014-9768-6. View

15.

Reumers J, De Rijk P, Zhao H, Liekens A, Smeets D, Cleary J . Optimized filtering reduces the error rate in detecting genomic variants by short-read sequencing. Nat Biotechnol. 2011; 30(1):61-8. DOI: 10.1038/nbt.2053. View

16.

Johnstone T, Wang J, Ross D, Balanda N, Huang Y, Godfrey R . Biallelic variants in two complex I genes cause abnormal splicing defects in probands with mild Leigh syndrome. Mol Genet Metab. 2020; 131(1-2):98-106. PMC: 7749052. DOI: 10.1016/j.ymgme.2020.09.008. View

17.

Finsterer J . Inherited mitochondrial neuropathies. J Neurol Sci. 2011; 304(1-2):9-16. DOI: 10.1016/j.jns.2011.02.012. View

18.

Kirby D, Crawford M, Cleary M, Dahl H, Dennett X, Thorburn D . Respiratory chain complex I deficiency: an underdiagnosed energy generation disorder. Neurology. 1999; 52(6):1255-64. DOI: 10.1212/wnl.52.6.1255. View

19.

Mesman R, Calleja F, de la Hoya M, Devilee P, van Asperen C, Vrieling H . Alternative mRNA splicing can attenuate the pathogenicity of presumed loss-of-function variants in BRCA2. Genet Med. 2020; 22(8):1355-1365. PMC: 7394881. DOI: 10.1038/s41436-020-0814-5. View

20.

Shapiro M, Senapathy P . RNA splice junctions of different classes of eukaryotes: sequence statistics and functional implications in gene expression. Nucleic Acids Res. 1987; 15(17):7155-74. PMC: 306199. DOI: 10.1093/nar/15.17.7155. View