Mutations in FBXL4, encoding a mitochondrial protein, cause early-onset mitochondrial encephalomyopathy.

Abstract

Whole-exome sequencing and autozygosity mapping studies, independently performed in subjects with defective combined mitochondrial OXPHOS-enzyme deficiencies, identified a total of nine disease-segregating FBXL4 mutations in seven unrelated mitochondrial disease families, composed of six singletons and three siblings. All subjects manifested early-onset lactic acidemia, hypotonia, and developmental delay caused by severe encephalomyopathy consistently associated with progressive cerebral atrophy and variable involvement of the white matter, deep gray nuclei, and brainstem structures. A wide range of other multisystem features were variably seen, including dysmorphism, skeletal abnormalities, poor growth, gastrointestinal dysmotility, renal tubular acidosis, seizures, and episodic metabolic failure. Mitochondrial respiratory chain deficiency was present in muscle or fibroblasts of all tested individuals, together with markedly reduced oxygen consumption rate and hyperfragmentation of the mitochondrial network in cultured cells. In muscle and fibroblasts from several subjects, substantially decreased mtDNA content was observed. FBXL4 is a member of the F-box family of proteins, some of which are involved in phosphorylation-dependent ubiquitination and/or G protein receptor coupling. We also demonstrate that FBXL4 is targeted to mitochondria and localizes in the intermembrane space, where it participates in an approximately 400 kDa protein complex. These data strongly support a role for FBXL4 in controlling bioenergetic homeostasis and mtDNA maintenance. FBXL4 mutations are a recurrent cause of mitochondrial encephalomyopathy onset in early infancy.

• Authors: Xiaowu Gai, Daniele Ghezzi, Mark A Johnson, Caroline A Biagosch, Hanan E Shamseldin, Tobias B Haack, Aurelio Reyes, Mai Tsukikawa, Claire A Sheldon, Satish Srinivasan, Matteo Gorza, Laura S Kremer, Thomas Wieland, Tim M Strom, Erzsebet Polyak, Emily Place, Mark Consugar, Julian Ostrovsky, Sara Vidoni, Alan J Robinson, Lee-Jun Wong, Neal Sondheimer, Mustafa A Salih, Emtethal Al-Jishi, Christopher P Raab, Charles Bean, Francesca Furlan, Rossella Parini, Costanza Lamperti, Johannes A Mayr, Vassiliki Konstantopoulou, Martina Huemer, Eric A Pierce, Thomas Meitinger, Peter Freisinger, Wolfgang Sperl, Holger Prokisch, Fowzan S Alkuraya, Marni J Falk, Massimo Zeviani
• Journal: American journal of human genetics (Am J Hum Genet) Vol. 93 Issue 3 Pg. 482-95 (Sep 05 2013) ISSN: 1537-6605 [Electronic] United States
• PMID: 23993194 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2013 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

Chemical References

• DNA, Complementary
• F-Box Proteins
• Mitochondrial Proteins
• Mutant Proteins
• Ubiquitin-Protein Ligases
• FbxL4 protein, human

Topics

• Age of Onset
• Child
• Child, Preschool
• Chromosomes, Human, Pair 6 (genetics)
• DNA, Complementary (genetics)
• F-Box Proteins (chemistry, genetics)
• Female
• Fibroblasts (metabolism, pathology)
• Genes, Recessive (genetics)
• Genetic Predisposition to Disease
• HEK293 Cells
• Humans
• Infant
• Infant, Newborn
• Male
• Mitochondria (metabolism)
• Mitochondrial Encephalomyopathies (epidemiology, genetics)
• Mitochondrial Proteins (genetics)
• Muscle, Skeletal (pathology)
• Mutant Proteins (metabolism)
• Mutation (genetics)
• Oxidative Phosphorylation
• Pedigree
• Protein Transport
• Subcellular Fractions (metabolism)
• Syndrome
• Ubiquitin-Protein Ligases (chemistry, genetics)