Complexity of polysomal polyadenylated RNA in undifferentiated and differentiated neuroblastoma cells

Using cDNA probes, we have analysed the sequence complexity and the frequency distribution of the polysomal poly(A)-containing RNA from neuroblastoma cells at two different developmental states: either as round, immature neuroblasts, or as differentiated cells exhibiting the morphological properties of mature neurons. The total complexities measured for mRNA from undifferentiated and differentiated cells are identical and correspond to approximately 7000 average-sized sequences of 1750 nucleotides distributed in the same three abundance classes. We have determined the homology between the mRNA populations corresponding to the two developmental states by heterologous cross-hybridization: all the sequence from differentiated cells are present in the polysomes of undifferentiated cells. Conversely, the mRNA from differentiated cells fails to hybridize with about 15% of hybridizable cDNA corresponding to undifferentiated cells. This difference probably results from the disappearance of some mRNA species and may be related to the terminal differentiation of neuroblastoma cells.