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Recessive germline SDHA and SDHB mutations causing leukodystrophy and isolated mitochondrial complex II deficiency

Lookup NU author(s): Dr Charlotte Alston, Dr Hue Hornig - Do, Professor Bobby McFarland, Professor Robert Taylor

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Abstract

Background Isolated complex II deficiency is a rare form of mitochondrial disease, accounting for approximately 2% of all respiratory chain deficiency diagnoses. The succinate dehydrogenase (SDH) genes (SDHA, SDHB, SDHC and SDHD) are autosomally-encoded and transcribe the conjugated heterotetramers of complex II via the action of two known assembly factors (SDHAF1 and SDHAF2). Only a handful of reports describe inherited SDH gene defects as a cause of paediatric mitochondrial disease, involving either SDHA (Leigh syndrome, cardiomyopathy) or SDHAF1 (infantile leukoencephalopathy). However, all four SDH genes, together with SDHAF2, have known tumour suppressor functions, with numerous germline and somatic mutations reported in association with hereditary cancer syndromes, including paraganglioma and pheochromocytoma. Methods and results Here, we report the clinical and molecular investigations of two patients with histochemical and biochemical evidence of a severe, isolated complex II deficiency due to novel SDH gene mutations; the first patient presented with cardiomyopathy and leukodystrophy due to compound heterozygous p. Thr508Ile and p.Ser509Leu SDHA mutations, while the second patient presented with hypotonia and leukodystrophy with elevated brain succinate demonstrated by MR spectroscopy due to a novel, homozygous p.Asp48Val SDHB mutation. Western blotting and BN-PAGE studies confirmed decreased steady-state levels of the relevant SDH subunits and impairment of complex II assembly. Evidence from yeast complementation studies provided additional support for pathogenicity of the SDHB mutation. Conclusions Our report represents the first example of SDHB mutation as a cause of inherited mitochondrial respiratory chain disease and extends the SDHA mutation spectrum in patients with isolated complex II deficiency.


Publication metadata

Author(s): Alston CL, Davison JE, Meloni F, van der Westhuizen FH, He LP, Hornig-Do HT, Peet AC, Gissen P, Goffrini P, Ferrero I, Wassmer E, McFarland R, Taylor RW

Publication type: Article

Publication status: Published

Journal: Journal of Medical Genetics

Year: 2012

Volume: 49

Issue: 9

Pages: 569-577

Print publication date: 01/09/2012

Date deposited: 23/11/2012

ISSN (print): 0022-2593

ISSN (electronic):

Publisher: BMJ Group

URL: http://dx.doi.org/10.1136/jmedgenet-2012-101146

DOI: 10.1136/jmedgenet-2012-101146


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