Cycloleucine-induced vacuolation of myeline is associated with inhibition of protein methylation

Chickens injected with cycloleucine developed vacuolation of myelin similar to that seen in humans with vitamin B12 deficiency. Cycloleucine, an inhibitor of the formation of S-adenosylmethionine, decreased the incorporation of methyl groups into methylarginine in myelin basic protein in vivo. The need for methylcobalamin for the conversion of homocysteine to methionine and the requirement that myelin basic protein be methylated, offer a rational explanation for the myelin lesions observed in cases of vitamin B12 deficiency where there is increasing evidence that methyl-, rather than adenosylcobalamin is required to prevent dysmyelination. © 1981.