Increased susceptibility to 4-HNE-induced toxicity and impaired development in a model of ALDH4A1-deficient pediatric epilepsy carrying the S352L variant

Certain human mutations in the mitochondrial aldehyde dehydrogenase 4A1 (ALDH4A1) lead to a severe, paediatric form of epilepsy and developmental abnormalities, yet the precise molecular mechanism leading to the clinical phenotypes remains unexplained. ALDH4A1 metabolizes glutamic-γ-semialdehyde (GSA). Mutations in ALDH4A1, which lead to inactive enzyme variants, cause GSA to accumulate and vitamin B6 inactivation. Patients with severe ALDH4A1 deficiency have paediatric epilepsy and are resistant to prescribed therapies. We develop knock-in cell culture and mouse models of the S352L variant to help characterize this human pathology. The knock-in models show that ALDH4A1 is necessary for clearing a non-canonical substrate, 4-hydroxynonenal (4-HNE), without becoming inactivated, like the main clearance mechanism of 4-HNE, ALDH2, and that ALDH4A1 deficiency alters transcriptional profiles in genes that regulate brain development, including LGI1 and FOXB1. Protein levels, including those in the proline metabolic pathway (e.g., spermine synthase), are also downregulated in both S352L iPSCs and the brains of S352L homozygous mice. This work identifies additional metabolic and transcriptional pathways regulated by ALDH4A1, and potential pathways that can be targeted to treat patients with ALDH4A1 deficiency.