Medaka unextended-fin mutants suggest a role for Hoxb8a in cell migration and osteoblast differentiation during appendage formation.
Hoxb8 has been suggestively implicated in the formation of the zone of polarizing activity (ZPA) in the limb bud. However, as hoxb8-/- mice did not show any defects in their limb development, the role of Hoxb8 during limb development has not been fully elucidated. Here, we report the identification of the medaka hoxb8a mutant, unextended-fin (ufi), in which all the fin tissues were malformed. Since the abnormal phenotype was observed in the caudal fin, the ufi phenotype suggests that the medaka Hoxb8a has a fundamental role in the formation of appendages protruding from the trunk. Our analyses revealed that the expression of wnt5a, a regulator of cell migration that signals through the non-canonical Wnt/Ca2+ pathway, was down-regulated in the ufi fin-folds. In fact, we found that the proximal-distal cell migration was impaired in ufi mutants and that the defect could be reversed by the injection of a Wnt5a protein. Moreover, we show herein that the numbers of proliferating cells and osteoblastic cells were increased in the ufi mutants. According to these results, we propose that the medaka Hoxb8a protein functions in the outgrowth of appendages through the regulation of cell migration and osteoblast differentiation.
Department of Biological Information, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
Sae
S
Sakaguchi
Yuki
Y
Nakatani
Naofumi
N
Takamatsu
Hiroshi
H
Hori
Atsushi
A
Kawakami
Keiji
K
Inohaya
Akira
A
Kudo
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020013:Calcium Signaling; D002454:Cell Differentiation; D002465:Cell Movement; D049109:Cell Proliferation; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D005121:Extremities / Q000254:growth & development; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism*; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D020319:Oligodeoxyribonucleotides, Antisense / Q000008:administration & dosage / Q000235:genetics; D009990:Oryzias / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010641:Phenotype; D017386:Sequence Homology, Amino Acid
D029941:Fish Proteins; D018398:Homeodomain Proteins; D020319:Oligodeoxyribonucleotides, Antisense