title: Zebrafish Numb homologue: phylogenetic evolution and involvement in regulation of left-right asymmetry.
abstract: Numb and its homologue, Numb-like (Numbl), play important roles in mammalian development, but their role in embryonic development of lower vertebrates remains unknown. We cloned a zebrafish numb homologue (znumb) by searching database. znumb shows approximately 60% identity with mammalian Numb orthologs. Interstingly, znumb lacks two specific sequence motifs unique to Numbl orthologs. However, chromosomal localization of znumb gene revealed colinearity with genes located around mouse and human Numbl genes. Furthermore, multi-species comparisons of conserved phosphotyrosine-binding (PTB) domain sequences in Numb and Numbl proteins suggest that znumb is more closely related to Numbl than Numb. znumb mRNA was expressed in a wide variety of zebrafish adult tissues. Overexpression of znumb in embryos resulted in an absence, or reversal, of the normal leftward shift of the developing heart tube. Furthermore, no or bi-lateral transcripts of lefty2 were observed in znumb-expressing embryos, suggesting that the Notch signaling was essential for left-right field formation and maintenance in zebrafish, and that znumb perturbed this process through down-regulation of endogenous Notch signaling.
authors.affiliation: Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Niikura
authors.forename: Yoko
authors.initials: Y
authors.lastname: Tabata
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tajima
authors.forename: Ituro
authors.initials: I
authors.lastname: Inoue
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Arai
authors.forename: Sumiko
authors.initials: S
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D003001:Cloning, Molecular; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian; D019143:Evolution, Molecular; D018507:Gene Expression Regulation, Developmental; D007605:Juvenile Hormones / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D007605:Juvenile Hormones; D008565:Membrane Proteins; D051880:Receptors, Notch; D029961:Zebrafish Proteins; C060606:numb protein, Drosophila; C513665:numb protein, zebrafish