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Am J Hum Genet. 2013 Sep 5;93(3):471-81. doi: 10.1016/j.ajhg.2013.07.017. Epub 2013 Aug 29.

Mutations in FBXL4 cause mitochondrial encephalopathy and a disorder of mitochondrial DNA maintenance.

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Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.

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  • Am J Hum Genet. 2013 Oct 3;93(4):773.


Nuclear genetic disorders causing mitochondrial DNA (mtDNA) depletion are clinically and genetically heterogeneous, and the molecular etiology remains undiagnosed in the majority of cases. Through whole-exome sequencing, we identified recessive nonsense and splicing mutations in FBXL4 segregating in three unrelated consanguineous kindreds in which affected children present with a fatal encephalopathy, lactic acidosis, and severe mtDNA depletion in muscle. We show that FBXL4 is an F-box protein that colocalizes with mitochondria and that loss-of-function and splice mutations in this protein result in a severe respiratory chain deficiency, loss of mitochondrial membrane potential, and a disturbance of the dynamic mitochondrial network and nucleoid distribution in fibroblasts from affected individuals. Expression of the wild-type FBXL4 transcript in cell lines from two subjects fully rescued the levels of mtDNA copy number, leading to a correction of the mitochondrial biochemical deficit. Together our data demonstrate that mutations in FBXL4 are disease causing and establish FBXL4 as a mitochondrial protein with a possible role in maintaining mtDNA integrity and stability.

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