title: Nrarp functions to modulate neural-crest-cell differentiation by regulating LEF1 protein stability.
abstract: Nrarp (Notch-regulated ankyrin repeat protein) is a small protein that has two ankyrin repeats. Although Nrarp is known to be an inhibitory component of the Notch signalling pathway that operates in different developmental processes, the in vivo roles of Nrarp have not been fully characterized. Here, we show that Nrarp is a positive regulator in the Wnt signalling pathway. In zebrafish, knockdown of Nrarp-a expression by an antisense morpholino oligonucleotide (MO) results in altered Wnt-signalling-dependent neural-crest-cell development. Nrarp stabilizes LEF1 protein, a pivotal transcription factor in the Wnt signalling cascade, by blocking LEF1 ubiquitination. In accordance with this, the knockdown phenotype of lef1 is similar to that of nrarp-a, at least in part, in its effect on the development of multiple tissues in zebrafish. Furthermore, activation of LEF1 does not affect Notch activity or vice versa. These findings reveal that Nrarp independently regulates canonical Wnt and Notch signalling by modulating LEF1 and Notch protein turnover, respectively.
authors.affiliation: Unit on Nervous System Development, Laboratory of Cell Regulation, Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Ishitani
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Ajay B
authors.initials: AB
authors.lastname: Chitnis
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Itoh
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D006801:Humans; D009432:Neural Crest / Q000166:cytology* / Q000502:physiology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D051880:Receptors, Notch / Q000502:physiology; D015398:Signal Transduction; D014157:Transcription Factors / Q000502:physiology*; D025801:Ubiquitin; D051155:Wnt1 Protein / Q000502:physiology; D029867:Xenopus Proteins / Q000378:metabolism* / Q000502:physiology; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins / Q000502:physiology*
chemical_list: C507321:LEF1 protein, zebrafish; C434261:Nrarp protein, Xenopus; D016376:Oligonucleotides, Antisense; D051880:Receptors, Notch; D014157:Transcription Factors; D025801:Ubiquitin; D051155:Wnt1 Protein; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; C499041:nrarpa protein, zebrafish