Impairment of neuromotor development and cognition associated with histopathological and neurochemical abnormalities in the cerebral cortex and striatum of glutaryl-CoA dehydrogenase deficient mice

Patients with glutaric acidemia type I (GA I) manifest motor and intellectual disabilities whose pathogenesis has been so far poorly explored. Therefore, we evaluated neuromotor and cognitive abilities, as well as histopathological and immunohistochemical features in the cerebral cortex and striatum of glutaryl-CoA dehydrogenase (GCDH) deficient knockout mice (Gcdh^−/−), a well-recognized model of GA I. The effects of a single intracerebroventricular glutaric acid (GA) injection in one-day-old pups on the same neurobehavioral and histopathological/immunohistochemical endpoints were also investigated. Seven-day-old Gcdh^−/− mice presented altered gait, whereas those receiving a GA neonatal administration manifested other sensorimotor deficits, including an abnormal response to negative geotaxis, cliff aversion and righting reflex, and muscle tone impairment. Compared to the WT mice, adult Gcdh−/− mice exhibited motor impairment, evidenced by poor performance in the Rota-rod test. Furthermore, neonatal GA administration provoked long-standing short- and long-term memory impairment in adult Gcdh^−/− mice. Regarding the histopathological features, a significant increase in vacuoles and neurodegenerative cells was observed in both the cerebral cortex and striatum of 15- and 60-day-old Gcdh−/− mice and was more pronounced in mice injected with GA. Neuronal loss (decrease of NeuN staining) was also significantly increased in the cerebral cortex and striatum of Gcdh^−/− mice, particularly in those neonatally injected with GA. In contrast, immunohistochemistry of MBP, astrocytic proteins GFAP and S100B, and the microglial marker Iba1 was not changed in 60-day-old Gcdh−/− mice, suggesting no myelination disturbance, reactive astrogliosis, and microglia activation, respectively. These data highlight the neurotoxicity of GA and the importance of early treatment aiming to decrease GA accumulation at early stages of development to prevent brain damage and learning/memory disabilities in GA I patients.