NF1 and glioblastoma: More specifically, in parental SF268 glioblastoma cells and in cells expressing NLS-neurofibromin, asters clearly bore MTs extending towards the cell cortex (astral MTs) and inwards (polar, interpolar MTs), while in cells lacking NLS neurofibromin projections to the cortex were absent (Figure 6 left column, a and c versus b).