CHANGES IN MORPHOLOGY AND SPATIAL POSITION OF COILED BODIES DURING NGF-INDUCED NEURONAL DIFFERENTIATION OF PC12 CELLS

Interphase nuclei are organized into structural and functional domains . The coiled body, a nuclear organelle of unknown function, exhibits c ell type-specific changes in number and morphology. Its association wi th nucleoli and with small nuclear ribonucleoproteins (snRNPs) indicat es that it functions in RNA processing. In cycling cells, coiled bodie s are round structures not associated with nucleoli. In contrast, in n eurons, they frequently present as nucleolar ''caps.'' To test the hyp othesis that neuronal differentiation is accompanied by changes in the spatial association of coiled bodies with nucleoli and in their morph ology, PC12 cells were differentiated into a neuronal phenotype with n erve growth factor (NGF) and coiled bodies detected by immunocytochemi cal localization of p80-coilin and snRNPs. The fraction of cells that showed coiled bodies as nucleolar caps increased from 1.6 +/- 0.9% (me an +/- SEM) in controls to 16.5 +/- 1.6% in NGF-differentiated culture s. The fraction of cells with ring-like coiled bodies increased from 1 7.2 +/- 5.0% in controls to 57.8 +/- 4.4% in differentiated cells. Thi s was accompanied by a decrease, from 81.2 +/- 5.7% to 25.7 +/- 3.1%, in the fraction of cells with small, round coiled bodies. SnRNPs remai ned associated with typical coiled bodies and with ring-like coiled bo dies during NGF-induced recruitment of snRNPs to the nuclear periphery . Together with the observation that :oiled bodies are also present as nucleolar caps in sensory neurons,;he results indicate that coiled bo dies alter their morphology and increase their association with nucleo li during NGF-induced neuronal differentiation.