Upon neuronal commitment, they stop dividing and migrate to a final position where they remain for the rest of the individual’s life. To our knowledge, this concept was first clearly formulated by Swiss neurologist Wilhelm His (1831–1904). He made a simple observation that mitotic figures (which signify cell

division in histological preparation) are localized close NU7441 to the surface of the human cerebral ventricles but are virtually absent in the overlying cortex that is forming below the outer, pial surface (His, 1874 and His, 1904). He concluded that the germinal cells (which he called Kimzellen) produce over time all classes of neurons, which then migrate from the place of their origin to increasingly more distant locations. His’ concept that progenitors of Selleck Metformin the brain consist of two separate lines that generate neurons and glial cells was shared by Retzius (1893), but opposed by the proponents of the pluripotential germinal cells (e.g.,

Kölliker, 1879). In addition, in spite of some recent claims to priority, he also recognized asymmetrical cell division, by which one daughter cell remains attached to the VZ and her twin migrates away (Figure 1). For some of his discoveries, subsequently explained in more detail in his book published in 1904, His was a serious contender to coshare the Nobel Prize with Ramón y Cajal and Golgi, had he not died before it was awarded in 1906. His’ absence on the awards stage may in fact have prevented some additional controversies, as some of his ideas, particularly the concept of spongioblasts as progenitors of

glial cells, were contested and later proven incorrect. The introduction of the DNA replication marker 3H[thymidine] in the mid 20th century increased interest in germinal cells and enabled a better delineation of their positions in the vertebrate embryonic brain. As a result, the Boulder Committee formed by the American Association of Anatomists in 1970 standardized the heterogeneous and confusing nomenclature for the developing vertebrate central nervous system and suggested that the proliferative ventricular and subventricular zones are the whatever source of all neurons and macroglia of the central nervous system (reviewed in Bystron et al., 2008). This framework, which was based on the human cerebrum, has been widely adopted as a generic description for development of the entire vertebrate central nervous system. While the site of the active proliferative zones is not in question, the way they produce the diversity of neuronal and glial cells is. One of the dividing cell types in the developing brain that has a history of changes in its name and its role in development is the fetal glia, also discovered originally in the embryonic human brain by the old masters using the silver impregnation method (Golgi, 1885, Kölliker, 1879, Magini, 1888 and Ramón y Cajal, 1899).