Developmental patterns of Ki-67, Oct-4 and α-tubulin proteins expression in the human spinal cord

The aim of this study was to analyze immunohistochemically the relationships between factors involved in processes of cell proliferation (Ki-67), differentiation (Oct-4) and primary cilia formation (α-tubulin) in the two parts of the developing human spinal cord (SC) of different origin in 11 human concepti (developmental weeks 5–10). Proliferation was highest in weeks 7–8 in the dorsal ventricular zones of the cranial (85.5%) and caudal (12.1%) SC. In the ventricular (VZ), intermediate (IZ) and marginal zones (MZ) of the cranial SC, α-tubulin and Oct-4 were moderately to strongly expressed. During weeks 5–6, moderate expression of α-tubulin and Oct-4 characterized the ventral part, with mild expression in the dorsal part of the caudal SC. In weeks 7–8, their expression increased in the VZ and IZ, and decreased in the MZ. In both parts of the SC Ki-67 and α-tubulin co-localized in the VZ. Oct-4 and Ki-67 co-localized only in the ependymal cells. In the cranial SC α-tubulin and Oct-4 co-localized (VZ and IZ), while the MZ expressed only α-tubulin. In the caudal SC, α-tubulin and Oct-4 co-localized in the VZ, while in the IZ some cells were only α-tubulin-positive. We suggest the importance of temporal–spatial expression of Ki-67 for the thickening of the cranial SC lateral wall. While in the cranial part of the SC, proliferation followed a ventral–dorsal direction, the caudal SC had a more irregular pattern. α-Tubulin was associated with cilia formation (ependymal cells) and axonic elongation of neuroblasts (MZ). Primary cilia signaling are important in control of SC proliferation and differentiation. Oct-4 expression in the SC coincided with presence of dividing neuroepithelial cells in the VZ and neuroblasts in the IZ, and could control the level of SC differentiation.