Naxd, or NAD(P)HX dehydratase, is a highly conserved enzyme essential for the intracellular repair of redox-inactive derivatives NAD(P)HX, which are formed from the damage of central cofactors NAD(P)H by hydration [1,3,5]. This repair process is crucial for maintaining normal cellular metabolism and function. The gene plays a significant role in metabolic pathways related to the maintenance of NAD(P)H homeostasis. Genetic models are valuable for studying Naxd as they can help reveal its precise function in vivo.

Pathogenic variants in Naxd are associated with a metabolite repair disorder. Naxd-deficiency patients show distinct clinical features depending on the sub-cellular compartment affected by the enzymatic deficiency. Variants affecting both cytosolic and mitochondrial isoforms present with neurological defects, seizures, and skin lesions, while those affecting only the mitochondrial isoform present with myopathy, moderate neuropathy, and cardiac issues without skin lesions, seizures, or neurological degeneration [1]. Additionally, Naxd-deficiency can lead to progressive neurological deterioration, often associated with febrile illness, along with skin lesions, elevated lactate levels, and brain neuroimaging abnormalities [3]. In some cases, niacin-based therapies have shown promise in improving outcomes and normalizing metabolic abnormalities [2,4].

In conclusion, Naxd is essential for the repair of damaged NAD(P)HX, thus maintaining normal cellular metabolism. Studies on Naxd-deficiency, often through patient-based genetic analysis (since no KO/CKO mouse models were mentioned in the provided references), have revealed its role in various disease-related phenotypes, mainly neurological and metabolic disorders. Understanding Naxd function is crucial for the early identification of related diseases and the development of more effective therapeutic interventions.