27 - Differentiation of the oligodendrocyte fate neuroblasts in the prenatal human cortex development.
Aims. Development of the cerebral cortex starts with neural stem/progenitor cell proliferation, neuroblast migration and glial/neural lineage differentiation. To define periods and regional dynamics of oligodendrocyte differentiation within the main cortical subdivisions immunomorphological analysis of human foetal brains was undertaken.
Methods. This study is a part of the human brain development project: brain samples aged from 8pcw to birth was studied with the oligodendroglia-specific markers (Olig2, MBP).
Results. Olig2-immunoreactivity patterns at the prefoetal stage evidence for lateral (LGE) and medial (MGE) ganglionic eminences, septal ventricular zone (sVZ) are main sources for telencephalon oligodendrocyte fate neuroblasts. The MGE seems to be a main source for the neocortical, insular and paleocortical oligodendrocytes and sVZ – for the dorsal presumptive archaecortex, and later (since the end of early foetal stage) caudal ganglionic eminence also gives rise to cortical oligodendrocytes. The dorsal paleocortical ventricular zone (since 13gw) also demonstrates Olig2-immunoreactivity and could partially participate in formation of the paleocortical oligodendrocyte population. The Olig2-immunoreactive neuroblast ratio gradually increases from the early to late foetal stages within marginal zone and cortical plate of the main pallial subdivisions with paleocortical advanced timeline. MBP-immunoreactivity was firstly observed within pallium in the lateral olfactory tract fibres at 29-30gw, which evidences for the prior maturation of the paleocortical structures within pallium.
Conclusions. At the prefoetal stage (8-12pcw), oligodendroglial distribution within cortex is determined by the neuroblast sources and at the later stages – by the proper developmental timetable of the certain region and seems to correlate with the pathways’ maturation.