Molecular mechanism of neural crest cell differentiation, proliferation and death

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The murine Ncx (Tlx2,Enx,Hox11L1) gene is expressed in neural crest derived tissues and regulates neuronal cell death in enteric neurons. We have used chromatin immunoprecipitation method to screen for target genes for Ncx. This screen led to the identification of novel gene termed Nczf. Nczf contains an N-terminal KRAB box domain and 11 Kruppel C2H2 type zinc finger motifs at C terminus. Promoter region of the Nczf gene contains 5 consensus sequences for Ncx binding motifs. Transient transfection assays of the 5'-flanking region fused to the luciferase reporter gene with various amount of Ncx expression vector showed dose dependent increase of the Nczf promoteractivity. Expression of Nczf mRNA was detected in enteric neurons like that of Ncx. The amount of Nczf mRNA roughly correlated with that of the Ncx in enteric ganglia during embryonic development. Nczf localized in the nucleus and functioned as a transcriptional repressor. The consensus binding sequence of core nucleotides contains (A/T/C)CTTT(A/G)TTNT. In a gel mobility shift assay, the probe containing these sequences bound to the fusion protein. In silico analysis, these consensus sequences were found on regulatory regions of the endothelin receptor B and the microphthalmia-associated transcription factor genes, which are involved in neural crest development. Furthermore, overexpression of Nczf incultured neuroblastoma and fibroblast cell lines caused apoptotic cell death. These results suggest that Nczf functions as a sequence specific transcription repressor to regulate neural crest cell development.