Central nervous system dysfunction in a mouse model of Fa2H deficiency

Fatty acid 2-hydroxylase (FA2H) is responsible for the synthesis of myelin galactolipids containing hydroxy fatty acid (hFA) as the N-acyl chain. Mutations in the FA2H gene cause leukodystrophy, spastic paraplegia, and neurodegeneration with brain iron accumulation. Using the Cre-lox system, we developed two types of mouse mutants, Fa2h^-/- mice (Fa2h deleted in all cells by germline deletion) and Fa2h^flox/flox Cnp1-Cre mice (Fa2h deleted only in oligodendrocytes and Schwann cells). We found significant demyelination, profound axonal loss, and abnormally enlarged axons in the CNS of Fa2h^-/- mice at 12 months of age, while structure and function of peripheral nerves were largely unaffected. Fa2h^-/- mice also exhibited histological and functional disruption in the cerebellum at 12 months of age. In a time course study, significant deterioration of cerebellar function was first detected at 7 months of age. Further behavioral assessments in water T-maze and Morris water maze tasks revealed significant deficits in spatial learning and memory at 4 months of age. These data suggest that various regions of the CNS are functionally compromised in young adult Fa2h^-/- mice. The cerebellar deficits in 12-month-old Fa2h^flox/flox Cnp1-Cre mice were indistinguishable from Fa2h^-/- mice, indicating that these phenotypes likely stem from the lack of myelin hFA-galactolipids. In contrast, Fa2h^flox/flox Cnp1-Cre mice did not show reduced performance in water maze tasks, indicating that oligodendrocytes are not involved in the learning and memory deficits found in Fa2h^-/- mice. These findings provide the first evidence that FA2H has an important function outside of oligodendrocytes in the CNS.