Abstract
This immunohistochemical study compares the localization of the neuronal class III β-tubulin isotype (βIII) to that of calbindin-D28k in 40 human fetal and postnatal cerebella ranging from 12 weeks gestation to adulthood. In the external granule layer of the developing cerebellar cortex, βIII staining was present in the premigratory (postmitotic) zone of horizontal neurons but was absent in “epithelioid” cells of the subpial proliferative mitotic zone. In the molecular layer, intense βIII staining was associated with parallel fibers, stellate/basket neurons and migrating fusiform granule neurons. βIII staining was also present in internal granule neurons. In contrast, βIII was not detectable in fetal and neonatal Purkinje neurons and Golgi II neurons, but was evident in these neurons from juvenile and adult cerebella. Calbindin-D28k staining was present in Purkinje neurons also delineating their somatic spines (“pseudopodia”), lateralizing and apical dendrites (including dendritic spines), subpopulations of small to intermediate-sized Golgi II neurons in the internal granule layer (“synarmotic cells” of Landau), large to medium-sized subcortical Golgi II neurons and neurons of cerebellar roof nuclei, at various gestational stages and postnatally. It was absent in the external granule layer, parallel fibers, stellate/basket and internal granule neurons. Variable degrees of βIII and calbindin-D28k staining were detected in subpopulations of immature neuroepithelial cells of the ventricular matrix at the roof of the fourth ventricle. Glial (including Bergmann glia) and mesenchymal cells were not stained for either antigenic determinants. The differential expression of calbindin-D28k and βIII defines distinct populations of neurons in the developing human cerebellar cortex and supports the ontogenetic concept of Ramon y Cajal.