Publication Date
12-2-2021
Journal
American Journal of Human Genetics
DOI
10.1016/j.ajhg.2021.11.003
PMID
34800363
PMCID
PMC8715183
PubMedCentral® Posted Date
11-19-2021
PubMedCentral® Full Text Version
Post-print
Published Open-Access
yes
Keywords
Alleles, Animals, Ataxia, Cells, Cultured, Child, Cohort Studies, DNA Mutational Analysis, Drosophila melanogaster, Epilepsy, Family Health, Female, Fibroblasts, Hearing Loss, Humans, Ketoglutarate Dehydrogenase Complex, Male, Mutation, Neurodevelopmental Disorders, RNA Splicing, Vision Disorders, OGDHL, mitochondria, α-ketoglutarate, bi-allelic, developmental and epileptic encephalopathy, DEE, exome sequencing, Drosophila, CRISPR-Cas9 gene editing, neurodevelopmental disease
Abstract
The 2-oxoglutarate dehydrogenase-like (OGDHL) protein is a rate-limiting enzyme in the Krebs cycle that plays a pivotal role in mitochondrial metabolism. OGDHL expression is restricted mainly to the brain in humans. Here, we report nine individuals from eight unrelated families carrying bi-allelic variants in OGDHL with a range of neurological and neurodevelopmental phenotypes including epilepsy, hearing loss, visual impairment, gait ataxia, microcephaly, and hypoplastic corpus callosum. The variants include three homozygous missense variants (p.Pro852Ala, p.Arg244Trp, and p.Arg299Gly), three compound heterozygous single-nucleotide variants (p.Arg673Gln/p.Val488Val, p.Phe734Ser/p.Ala327Val, and p.Trp220Cys/p.Asp491Val), one homozygous frameshift variant (p.Cys553Leufs∗16), and one homozygous stop-gain variant (p.Arg440Ter). To support the pathogenicity of the variants, we developed a novel CRISPR-Cas9-mediated tissue-specific knockout with cDNA rescue system for dOgdh, the Drosophila ortholog of human OGDHL. Pan-neuronal knockout of dOgdh led to developmental lethality as well as defects in Krebs cycle metabolism, which was fully rescued by expression of wild-type dOgdh. Studies using the Drosophila system indicate that p.Arg673Gln, p.Phe734Ser, and p.Arg299Gly are severe loss-of-function alleles, leading to developmental lethality, whereas p.Pro852Ala, p.Ala327Val, p.Trp220Cys, p.Asp491Val, and p.Arg244Trp are hypomorphic alleles, causing behavioral defects. Transcript analysis from fibroblasts obtained from the individual carrying the synonymous variant (c.1464T>C [p.Val488Val]) in family 2 showed that the synonymous variant affects splicing of exon 11 in OGDHL. Human neuronal cells with OGDHL knockout exhibited defects in mitochondrial respiration, indicating the essential role of OGDHL in mitochondrial metabolism in humans. Together, our data establish that the bi-allelic variants in OGDHL are pathogenic, leading to a Mendelian neurodevelopmental disease in humans.
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