Changes in pre-mRNA splicing factors during neural differentiation in P19 embryonal carcinoma cells

Alternative RNA splicing can be regulated in a highly cell- and tissue-spec ific or developmentally specific manner. In neurons, the functions of many gene products, such as those of trk genes are regulated by alternative spli cing. In this paper the mechanism of neural-specific RNA splicing is invest igated using trk genes as models. First, we confirm the splicing patterns o f trk transcripts during neural differentiation of P19 embryonal carcinoma (EC) cells. The full-length form of trk B was expressed in the neuronal sta te. In contrast, both the full-length and truncated forms of trk C were exp ressed constitutively in all differentiation states. However, two alternati vely spliced forms with either 42- or 117-nucleotide insertions in the tyro sine kinase domain were detected only in the neuronal state. Thus, the expr ession of functional trk B and C was found to be regulated by alternative s plicing during neural differentiation. To examine the molecular basis of neural-specific splicing, and how splicin g regulation is modulated in different neurons. The expression of a number of general splicing factors was studied. The mRNA levels of the splicing fa ctors ASF/SF2, U2AF SF3a, p54nrb and PTB was found to decrease rapidly duri ng differentiation. In contrast, Nova, an RNA-binding protein was expressed in the neuronal state. We also found that the levels of two SR proteins, m embers bf a family of splicing factors, increased in the neuronal state. Th ese results suggest that the stoichiometric balance among some splicing fac tors, including SR proteins, may be associated with the alternative splicin g of trk transcripts during differentiation. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.