Bi-allelic GOT2 Mutations Cause a Treatable Malate-Aspartate Shuttle-Related Encephalopathy.

TitleBi-allelic GOT2 Mutations Cause a Treatable Malate-Aspartate Shuttle-Related Encephalopathy.
Publication TypeJournal Article
Year of Publication2019
Authorsvan Karnebeek, CDM, Ramos, RJ, Wen, X-Y, Tarailo-Graovac, M, Gleeson, JG, Skrypnyk, C, Brand-Arzamendi, K, Karbassi, F, Issa, MY, van der Lee, R, Drögemöller, BI, Koster, J, Rousseau, J, Campeau, PM, Wang, Y, Cao, F, Li, M, Ruiter, J, Ciapaite, J, Kluijtmans, LAJ, Willemsen, MAAP, Jans, JJ, Ross, CJ, Wintjes, LT, Rodenburg, RJ, Huigen, MCDG, Jia, Z, Waterham, HR, Wasserman, WW, Wanders, RJA, Verhoeven-Duif, NM, Zaki, MS, Wevers, RA
JournalAm J Hum Genet
Volume105
Issue3
Pagination534-548
Date Published2019 Sep 05
ISSN1537-6605
Abstract

Early-infantile encephalopathies with epilepsy are devastating conditions mandating an accurate diagnosis to guide proper management. Whole-exome sequencing was used to investigate the disease etiology in four children from independent families with intellectual disability and epilepsy, revealing bi-allelic GOT2 mutations. In-depth metabolic studies in individual 1 showed low plasma serine, hypercitrullinemia, hyperlactatemia, and hyperammonemia. The epilepsy was serine and pyridoxine responsive. Functional consequences of observed mutations were tested by measuring enzyme activity and by cell and animal models. Zebrafish and mouse models were used to validate brain developmental and functional defects and to test therapeutic strategies. GOT2 encodes the mitochondrial glutamate oxaloacetate transaminase. GOT2 enzyme activity was deficient in fibroblasts with bi-allelic mutations. GOT2, a member of the malate-aspartate shuttle, plays an essential role in the intracellular NAD(H) redox balance. De novo serine biosynthesis was impaired in fibroblasts with GOT2 mutations and GOT2-knockout HEK293 cells. Correcting the highly oxidized cytosolic NAD-redox state by pyruvate supplementation restored serine biosynthesis in GOT2-deficient cells. Knockdown of got2a in zebrafish resulted in a brain developmental defect associated with seizure-like electroencephalography spikes, which could be rescued by supplying pyridoxine in embryo water. Both pyridoxine and serine synergistically rescued embryonic developmental defects in zebrafish got2a morphants. The two treated individuals reacted favorably to their treatment. Our data provide a mechanistic basis for the biochemical abnormalities in GOT2 deficiency that may also hold for other MAS defects.

DOI10.1016/j.ajhg.2019.07.015
Alternate JournalAm. J. Hum. Genet.
PubMed ID31422819
PubMed Central IDPMC6732527
Grant ListR01 NS048453 / NS / NINDS NIH HHS / United States
R01 NS098004 / NS / NINDS NIH HHS / United States
U54 HG006504 / HG / NHGRI NIH HHS / United States
UM1 HG008900 / HG / NHGRI NIH HHS / United States