@article {916, title = {Biallelic variants in HPDL, encoding 4-hydroxyphenylpyruvate dioxygenase-like protein, lead to an infantile neurodegenerative condition.}, journal = {Genet Med}, volume = {23}, year = {2021}, month = {2021 03}, pages = {524-533}, abstract = {

PURPOSE: Dioxygenases are oxidoreductase enzymes with roles in metabolic pathways necessary for aerobic life. 4-hydroxyphenylpyruvate dioxygenase-like protein (HPDL), encoded by HPDL, is an orphan paralogue of 4-hydroxyphenylpyruvate dioxygenase (HPD), an iron-dependent dioxygenase involved in tyrosine catabolism. The function and association of HPDL with human diseases remain unknown.

METHODS: We applied exome sequencing in a cohort of over 10,000 individuals with neurodevelopmental diseases. Effects of HPDL loss were investigated in vitro and in vivo, and through mass spectrometry analysis. Evolutionary analysis was performed to investigate the potential functional separation of HPDL from HPD.

RESULTS: We identified biallelic variants in HPDL in eight families displaying recessive inheritance. Knockout mice closely phenocopied humans and showed evidence of apoptosis in multiple cellular lineages within the cerebral cortex. HPDL is a single-exonic gene that likely arose from a retrotransposition event at the base of the tetrapod lineage, and unlike HPD, HPDL is mitochondria-localized. Metabolic profiling of HPDL mutant cells and mice showed no evidence of altered tyrosine metabolites, but rather notable accumulations in other metabolic pathways.

CONCLUSION: The mitochondrial localization, along with its disrupted metabolic profile, suggests HPDL loss in humans links to a unique neurometabolic mitochondrial infantile neurodegenerative condition.

}, keywords = {4-Hydroxyphenylpyruvate Dioxygenase, Animals, Dioxygenases, Exons, Mice, Mice, Knockout, Phenotype}, issn = {1530-0366}, doi = {10.1038/s41436-020-01010-y}, author = {Ghosh, Shereen G and Lee, Sangmoon and Fabunan, Rudy and Chai, Guoliang and Zaki, MAH S and Abdel-Salam, Ghada and Sultan, Tipu and Ben-Omran, Tawfeg and Alvi, Javeria Raza and McEvoy-Venneri, Jennifer and Stanley, Valentina and Patel, Aakash and Ross, Danica and Ding, Jeffrey and Jain, Mohit and Pan, Daqiang and L{\"u}bbert, Philipp and Kammerer, Bernd and Wiedemann, Nils and Verhoeven-Duif, Nanda M and Jans, Judith J and Murphy, David and Toosi, Mehran Beiraghi and Ashrafzadeh, Farah and Imannezhad, Shima and Karimiani, Ehsan Ghayoor and Ibrahim, Khalid and Waters, Elizabeth R and Maroofian, Reza and Gleeson, Joseph G} } @article {690, title = {Bi-allelic GOT2 Mutations Cause a Treatable Malate-Aspartate Shuttle-Related Encephalopathy.}, journal = {Am J Hum Genet}, volume = {105}, year = {2019}, month = {2019 Sep 05}, pages = {534-548}, 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.

}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2019.07.015}, author = {van Karnebeek, Clara D M and Ramos, R{\'u}ben J and Wen, Xiao-Yan and Tarailo-Graovac, Maja and Gleeson, Joseph G and Skrypnyk, Cristina and Brand-Arzamendi, Koroboshka and Karbassi, Farhad and Issa, Mahmoud Y and van der Lee, Robin and Dr{\"o}gem{\"o}ller, Britt I and Koster, Janet and Rousseau, Justine and Campeau, Philippe M and Wang, Youdong and Cao, Feng and Li, Meng and Ruiter, Jos and Ciapaite, Jolita and Kluijtmans, Leo A J and Willemsen, Michel A A P and Jans, Judith J and Ross, Colin J and Wintjes, Liesbeth T and Rodenburg, Richard J and Huigen, Marleen C D G and Jia, Zhengping and Waterham, Hans R and Wasserman, Wyeth W and Wanders, Ronald J A and Verhoeven-Duif, Nanda M and Zaki, Maha S and Wevers, Ron A} }