Ontogenetic oligodendrocyte maturation through gestational iron deprivation: The road not taken

Developmental iron deficiency (dID) models facilitate the study of specific oligodendrocyte (OL) requirements for their progression to a mature state and subsequent contribution to myelination. In the current work, we used the dID model in transgenic mice expressing green fluorescence protein under the CNPase promoter allowing the identification of cells belonging to the oligodendroglial lineage, and the visualization of the entire myelin structure and single OL morphology. The present work evaluates dID effects on OL complexity in different brain areas. Control animals showed an increase in OL complexity both during development and along the anterior-posterior axis. In contrast, dID animals exhibited an initial increase in CNPase+ cells with prevalence of immature-OL (i-OL), an effect later compensated during development by selective death of those i-OL. As a consequence, developmental behavior was impaired in terms of body balance, muscle response, and sensorimotor functions. To explore why i-OL fail to mature in dID, expression levels of transcriptional factors involved in the maturation of the OL lineage were studied. In nuclear fractions, dID animals showed an increase in Hes5, which prevents the maturation of i-OL, and a decrease in Sox10, a positive regulator of OL maturation. The cytoplasmic fractions showed a decrease in Olig1, which is critical for precursor cell differentiation into premyelinating OL. Overall, the expression levels of Hes5, Sox10, and Olig1 in dID conditions correlated with an unfavorable OL maturation profile. In sum, the current results provide further evidence of dID impact on myelination, keeping OL away from the maturational path.