Sox6 expression distinguishes dorsally and ventrally biased dopamine neurons in the substantia nigra with distinctive properties and embryonic origins.

Dopamine (DA) neurons in the ventral tier of the substantia nigra pars compacta (SNc) degenerate prominently in Parkinson's disease, while those in the dorsal tier are relatively spared. Defining the molecular, functional, and developmental characteristics of each SNc tier is crucial to understand their distinct susceptibility. We demonstrate that Sox6 expression distinguishes ventrally and dorsally biased DA neuron populations in the SNc. The Sox6+ population in the ventral SNc includes an Aldh1a1+ subset and is enriched in gene pathways that underpin vulnerability. Sox6+ neurons project to the dorsal striatum and show activity correlated with acceleration. Sox6- neurons project to the medial, ventral, and caudal striatum and respond to rewards. Moreover, we show that this adult division is encoded early in development. Overall, our work demonstrates a dual origin of the SNc that results in DA neuron cohorts with distinct molecular profiles, projections, and functions.

The Notch signaling pathway: its role in focal CNS demyelination and apotransferrin-induced remyelination.

Oligodendroglial damage and demyelination are common pathological features characterizing white matter and neurodegenerative disorders. Identifying the signaling pathways involved in myelin repair through oligodendroglial progenitor maturation is essential for the development of new therapies. This article investigated the role of the Notch signaling pathway in CNS demyelination and apotransferrin-induced remyelination in a focal lysolecithin-induced demyelination model in rats. Notch was found activated in Nestin-expressing neural progenitor cells and in NG2-expressing oligodendroglial precursor cells in the subventricular zone and corpus callosum of lysolecithin-demyelinated rats. Notch activation seemed to be driven by Jagged1, which led to a high expression of downstream gene Hes5 in the subventricular zone of demyelinated rats. Apotransferrin injection induced remyelination, while the injection of the γ-secretase inhibitor reversed this effect. In addition, 24 h after apotransferrin injection, evidence showed Notch activation concomitantly with an increase in F3/contactin levels and the up-regulation of the myelin-associated glycoprotein gene in the subventricular zone and corpus callosum of demyelinated rats. Collected evidence supports the participation of both canonical and non-canonical Notch signaling pathways in demyelination/remyelination. Notch activation was found to trigger Hes5 expression as a consequence of focal demyelination, which might promote oligodendroglial precursor cell proliferation. During apotransferrin-induced remyelination, Notch activation seemed to be mediated by the expression of F3/contactin, which might induce apotransferrin-mediated oligodendroglial maturation. Evidence of the participation of Notch signaling in the demyelination/remyelination process will help further understand demyelinating disorders such as Multiple Sclerosis and the use of aTf should be taken into consideration as a possible therapeutic intervention.