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Intellectual disability v9.122 OGDHL Ida Ertmanska changed review comment from: As reviewed by Arina Puzriakova, there are at least 10 individuals from 9 unrelated families with biallelic variants in OGDHL (PMIDs: 28017472; 34800363). The individuals present with a complex neurodevelopmental disorder, also known as Yoon-Bellen syndrome. The phenotype is highly variable between the cases and includes developmental delay / intellectual disability.

PMID: 38031187 Lin et al. 2023 - authors re-evaluate the evidence for the association between Yoon-Bellen neurodevelopmental syndrome and the OGDHL gene. The article reports further 14 individuals from 12 unrelated, diverse families, with biallelic OGDHL variants. Patients presented with a range of heterogeneous symptoms: neurodevelopmental disorder, neurodegeneration, infantile-onset epileptic encephalopathy, skeletal dysplasia, childhood-onset epilepsy, multiple congenital anomalies, dysmorphism, non-syndromic hearing loss, neuromuscular disorders, and congenital heart defects. 9/14 reported patients had developmental delay/intellectual disability. Due to the highly variable phenotype, authors propose 3 possible hypotheses: ‘biallelic OGDHL variants lead to a highly variable monogenic disorder, variants in OGDHL are following a complex pattern of inheritance, or they may not be causative at all’.

In total, 17/21 families reported in the above articles have history of consanguinity. In most cases, additional likely pathogenic mutations were discovered in other genes, which complicates the phenotypic understanding.

Functional evidence: A zebrafish knockout of Ogdhl (78% identical gene ortholog) resulted in a range of phenotypes: smaller head, eye, and body, and heart edema. No seizure manifestation, visual impairment, or hearing deficiencies were observed. Authors note elevated neuronal cell death in the eye, hindbrain, and spinal cord of knockout animals. The phenotype was rescued by injection of human OGDHL. Moreover, OGDHL, OGDH, and DHTKD1 are isoenzymes – through double and triple gene knockouts, authors provide evidence indicating a complex compensatory relationship (PMID: 38031187).

This gene should remain Green for Intellectual disability. There is strong evidence for the association between OGDHL and Yoon-Bellen neurodevelopmental syndrome. However, care should be taken not to attribute all clinical symptoms to OGDHL dysfunction.; to: As reviewed by Arina Puzriakova, there are at least 10 individuals from 9 unrelated families with biallelic variants in OGDHL (PMIDs: 28017472; 34800363). The individuals present with a complex neurodevelopmental disorder, also known as Yoon-Bellen syndrome. The phenotype is highly variable between the cases and includes developmental delay / intellectual disability.

PMID: 38031187 Lin et al. 2023 - authors re-evaluate the evidence for the association between Yoon-Bellen neurodevelopmental syndrome and the OGDHL gene. The article reports further 14 individuals from 12 unrelated, diverse families, with biallelic OGDHL variants. Patients presented with a range of heterogeneous symptoms: hypotonia (9/14), short stature and variable dysmorphic facial features (each 8/14), failure to thrive (7/14), developmental delay/intellectual disability (9/14), seizures (4/14), hearing loss (4/14), and microcephaly (3/14). Due to the highly variable phenotype, authors propose 3 possible hypotheses: ‘biallelic OGDHL variants lead to a highly variable monogenic disorder, variants in OGDHL are following a complex pattern of inheritance, or they may not be causative at all’.

In total, 17/21 families reported in the above articles have history of consanguinity. In most cases, additional likely pathogenic mutations were discovered in other genes, which complicates the phenotypic understanding.

Functional evidence: A zebrafish knockout of Ogdhl (78% identical gene ortholog) resulted in a range of phenotypes: smaller head, eye, and body, and heart edema. No seizure manifestation, visual impairment, or hearing deficiencies were observed. Authors note elevated neuronal cell death in the eye, hindbrain, and spinal cord of knockout animals. The phenotype was rescued by injection of human OGDHL. Moreover, OGDHL, OGDH, and DHTKD1 are isoenzymes – through double and triple gene knockouts, authors provide evidence indicating a complex compensatory relationship (PMID: 38031187).

This gene should remain Green for Intellectual disability. There is strong evidence for the association between OGDHL and Yoon-Bellen neurodevelopmental syndrome. However, care should be taken not to attribute all clinical symptoms to OGDHL dysfunction.