In vitro differentiation in a human cortical neuronal cell line (HCN-1A): Ultrastructure and immunocytochemistry

Abstract

The study of neuronal differentiation would be facilitated by the availability of a homogeneous neuronal cell line capable of differentiation. Ronnett, et al. have cloned a cell line (HCN-1A) from the cerebral cortex of a megalencephalic patient. These cells undergo process formation after treatment with nerve growth factor and cAMP and, after differentiation, express numerous neuronal markers. Subsequent to treatment, the normally epithelioid HCN-1A cells became highly branched, often within the first two hours (FIG. 1A), creating a meshwork of closely associated processes with several orders of branching (FIG 1B). Not all cells remained in the differentiated state, resulting in phenotypically mixed cultures (FIG. 1A). Light microscopy of treated cells suggested that process formation occurred via cytoplasmic retraction rather than neurite outgrowth. In situ TEM analysis revealed that the cell bodies (FIG. 2A) of treated and untreated cells both possessed a number of neuronal characteristics including large euchromatic nuclei with prominent nucleoli, numerous profiles of rough endoplasmic reticulum (FIG. 2B), and prominent Golgi lamellae (FIG. 2C). Processes (FIG. 2D) were not ultrastructurally identifiable as axonal versus dendritic. Longitudinally arranged microtubules and intermediate filaments were both present in the majority of processes.