Wednesday, December 9, 2020

TANGO2 mutations

Mingirulli N, Pyle A, Hathazi D, Alston CL, Kohlschmidt N, O'Grady G, Waddell L, Evesson F, Cooper SBT, Turner C, Duff J, Topf A, Yubero D, Jou C, Nascimento A, Ortez C, García-Cazorla A, Gross C, O'Callaghan M, Santra S, Preece MA, Champion M, Korenev S, Chronopoulou E, Anirban M, Pierre G, McArthur D, Thompson K, Navas P, Ribes A, Tort F, Schlüter A, Pujol A, Montero R, Sarquella G, Lochmüller H, Jiménez-Mallebrera C, Taylor RW, Artuch R, Kirschner J, Grünert SC, Roos A, Horvath R. Clinical presentation and proteomic signature of patients with TANGO2 mutations. J Inherit Metab Dis. 2020 Mar;43(2):297-308. doi: 10.1002/jimd.12156. Epub 2019 Aug 13. PMID: 31339582; PMCID: PMC7078914.


Transport And Golgi Organization protein 2 (TANGO2) deficiency has recently been identified as a rare metabolic disorder with a distinct clinical and biochemical phenotype of recurrent metabolic crises, hypoglycemia, lactic acidosis, rhabdomyolysis, arrhythmias, and encephalopathy with cognitive decline. We report nine subjects from seven independent families, and we studied muscle histology, respiratory chain enzyme activities in skeletal muscle and proteomic signature of fibroblasts. All nine subjects carried autosomal recessive TANGO2 mutations. Two carried the reported deletion of exons 3 to 9, one homozygous, one heterozygous with a 22q11.21 microdeletion inherited in trans. The other subjects carried three novel homozygous (c.262C>T/p.Arg88*; c.220A>C/p.Thr74Pro; c.380+1G>A), and two further novel heterozygous (c.6_9del/p.Phe6del); c.11-13delTCT/p.Phe5del mutations. Immunoblot analysis detected a significant decrease of TANGO2 protein. Muscle histology showed mild variation of fiber diameter, no ragged-red/cytochrome c oxidase-negative fibers and a defect of multiple respiratory chain enzymes and coenzyme Q10 (CoQ10 ) in two cases, suggesting a possible secondary defect of oxidative phosphorylation. Proteomic analysis in fibroblasts revealed significant changes in components of the mitochondrial fatty acid oxidation, plasma membrane, endoplasmic reticulum-Golgi network and secretory pathways. Clinical presentation of TANGO2 mutations is homogeneous and clinically recognizable. The hemizygous mutations in two patients suggest that some mutations leading to allele loss are difficult to detect. A combined defect of the respiratory chain enzymes and CoQ10 with altered levels of several membrane proteins provides molecular insights into the underlying pathophysiology and may guide rational new therapeutic interventions.

Bérat CM, Montealegre S, Wiedemann A, Nuzum MLC, Blondel A, Debruge H, Cano A, Chabrol B, Hoebeke C, Polak M, Stoupa A, Feillet F, Torre S, Boddaert N, Bruel H, Barth M, Damaj L, Abi-Wardé MT, Afenjar A, Benoist JF, Madrange M, Caccavelli L, Renard P, Hubas A, Nusbaum P, Pontoizeau C, Gobin S, van Endert P, Ottolenghi C, Maltret A, de Lonlay P. Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect. J Inherit Metab Dis. 2020 Sep 14. doi: 10.1002/jimd.12314. Epub ahead of print. PMID: 32929747.


TANGO2 disease is a severe inherited disorder associating multiple symptoms such as metabolic crises, encephalopathy, cardiac arrhythmias, and hypothyroidism. The mechanism of action of TANGO2 is currently unknown. Here, we describe a cohort of 20 French patients bearing mutations in the TANGO2 gene. We found that the main clinical presentation was the association of neurodevelopmental delay (n = 17), acute metabolic crises (n = 17) and hypothyroidism (n = 12), with a large intrafamilial clinical variability. Metabolic crises included rhabdomyolysis (15/17), neurological symptoms (14/17), and cardiac features (12/17; long QT (n = 10), Brugada pattern (n = 2), cardiac arrhythmia (n = 6)) that required intensive care. We show previously uncharacterized triggers of metabolic crises in TANGO2 patients, such as some anesthetics and possibly l-carnitine. Unexpectedly, plasma acylcarnitines, plasma FGF-21, muscle histology, and mitochondrial spectrometry were mostly normal. Moreover, in patients' primary myoblasts, palmitate and glutamine oxidation rates, and the mitochondrial network were also normal. Finally, we found variable mitochondrial respiration and defective clearance of oxidized DNA upon cycles of starvation and refeeding. We conclude that TANGO2 disease is a life-threatening disease that needs specific cardiac management and anesthesia protocol. Mechanistically, TANGO2 disease is unlikely to originate from a primary mitochondrial defect. Rather, we suggest that mitochondrial defects are secondary to strong extrinsic triggers in TANGO2 deficient patients.

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