Misexpression of the RNA-binding protein ELRB in Xenopus presumptive neurectoderm induces proliferation arrest and programmed cell death

Proteins of the ELAV/Hu family share the presence of three RNA binding doma ins. In Xenopus, three nervous system-specific elav/Hu related genes, elrB, elrC and elrD, have been identified so far. The temporally regulated expre ssion patterns of elrB, elrC and elrD suggest their involvement at differen t steps of neural differentiation. In the present study we misexpressed elr S by RNA injection in early Xenopus embryos and analyzed morphologically an d molecularly its effects on neural development. We showed that heterochron ous expression of elrB in presumptive neurectoderm down-regulates the expre ssion of neural markers, such as N-tubulin. as well as that of other Xenopu s elav-like genes, elrC and elrD, whereas ectopic expression of elrB in pre sumptive mesoderm has no effect on MyoD. Misexpression of elrB also induces severe defects in neural tube development, associated with massive cell lo ss resulting from early cell cycle arrest and programmed cell death. Our re sults are discussed in the context of early neural differentiation.