Bi-allelic variants in OGDHL cause a neurodevelopmental spectrum disease featuring epilepsy, hearing loss, visual impairment, and ataxia.

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.

Parental psychosocial aspects and stressors involved in the management of inborn errors of metabolism.

Parents of children with inborn errors of metabolism (IEM) face numerous psychosocial challenges. An increased understanding and awareness of these stressors can ensure better overall outcomes for the entire family. We conducted semi-structured, in-person interviews with ten parents to identify psychosocial stressors, strategies, and supports they utilized to overcome their challenges. Our interview guide was designed to elicit familial experiences during the pre- and post-diagnosis periods. The themes and sub-themes were identified through qualitative descriptive textual analysis of audio-recorded transcripts. Major themes identified include ambiguity of illness, changing family and spousal dynamics, and navigating the healthcare system. Sub-themes revolved around disease effects, psychological stressors, health systems, support, and facing the disease. Healthcare professionals have an opportunity to minimize the impact of negative emotional outcomes by assisting families as they navigate the experience of having a child with an IEM. Our findings can be used to develop and continue a more well-rounded, family-oriented framework for IEM management.

Psychosocial impact on mothers receiving expanded newborn screening results.

Expanded newborn screening (NBS) for genetic disorders has improved diagnosis of numerous treatable diseases, positively impacting children's health outcomes. However, research about the psychological impact of expanded NBS on families, especially mothers, has been mixed. Our study examined associations between maternal experiences of expanded NBS and subsequent psychosocial functioning and parenting stress in mothers whose infants received either true negative (TN), true positive (TP) or false positive (FP) results after a 4- to 6-month period. The Parenting Stress Index and the Depression, Anxiety and Stress Scale were used to assess symptoms of anxiety, stress and depression in 3 sets of mothers, whose infants received TN (n = 31), TP (n = 8) or FP (n = 18) results. Multivariate analyses of variance (MANOVA) results revealed no significant differences among these three groups of mothers regarding overall anxiety, stress and depression. However, FP mothers experienced lower levels of stress related to their own health compared to TN group. Two potential trends were also identified; results suggested TN mothers might experience higher levels of isolation than mothers in the TP group and that FP mothers might report higher stress levels in relation to spousal relationships compared to the TN group. FP mothers seemed to report similar or better levels of psychosocial functioning than TN mothers. Our findings are encouraging with respect to impacts of NBS on maternal well-being. We also identify key areas for improvement (parental education) and research (isolation and spousal relationships).

Biotinidase deficiency: Spectrum of molecular, enzymatic and clinical information from newborn screening Ontario, Canada (2007-2014).

Untreated profound biotinidase deficiency results in a wide range of clinical features, including optic atrophy, cutaneous abnormalities, hearing loss and developmental delay. Ontario, Canada incorporated this treatable deficiency in newborn screening over the past 8years. This study elucidates the molecular, biochemical, and clinical findings from the pilot project. Information from initial screens, serum biotinidase activity level assays, molecular testing, and family history for 246 positive newborns screens were analyzed. A mutation spectrum was created for the province of Ontario, including common mutations such as D444H, D444H/A171T, Q456H, C33fs, and R157H. Individuals with partial deficiency were separated into 3 groups: D444H homozygotes (Group 1); compound heterozygotes for D444H with another profound allele (Group 2); compound heterozygotes with two non-D444H alleles (Group 3). Biochemical phenotype-genotype associations in partial deficiency showed a significant difference in serum biotinidase activity in between any given two groups. Three children with partial deficiency discontinued biotin for varied lengths of time. Two of whom became symptomatic with abnormal gait, alopecia, skin rashes and developmental delay. A need for more congruency in diagnostic, treatment and educational practices was highlighted across the province. Heterogeneity and variation in clinical presentations and management was observed in patients with the partial deficiency.