Mechanism of pectoral fin outgrowth in zebrafish development.
Fins and limbs, which are considered to be homologous paired vertebrate appendages, have obvious morphological differences that arise during development. One major difference in their development is that the AER (apical ectodermal ridge), which organizes fin/limb development, transitions into a different, elongated organizing structure in the fin bud, the AF (apical fold). Although the role of AER in limb development has been clarified in many studies, little is known about the role of AF in fin development. Here, we investigated AF-driven morphogenesis in the pectoral fin of zebrafish. After the AER-AF transition at ∼36 hours post-fertilization, the AF was identifiable distal to the circumferential blood vessel of the fin bud. Moreover, the AF was divisible into two regions: the proximal AF (pAF) and the distal AF (dAF). Removing the AF caused the AER and a new AF to re-form. Interestingly, repeatedly removing the AF led to excessive elongation of the fin mesenchyme, suggesting that prolonged exposure to AER signals results in elongation of mesenchyme region for endoskeleton. Removal of the dAF affected outgrowth of the pAF region, suggesting that dAF signals act on the pAF. We also found that the elongation of the AF was caused by morphological changes in ectodermal cells. Our results suggest that the timing of the AER-AF transition mediates the differences between fins and limbs, and that the acquisition of a mechanism to maintain the AER was a crucial evolutionary step in the development of tetrapod limbs.
Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aobayama Aoba-ku, Sendai 980-8578, Japan.
Tohru
T
Yano
Gembu
G
Abe
Hitoshi
H
Yokoyama
Koichi
K
Kawakami
Koji
K
Tamura
D058500:Animal Fins / Q000098:blood supply / Q000196:embryology*; D000818:Animals; D030801:Animals, Genetically Modified; D001057:Apolipoproteins E / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D005075:Biological Evolution; D048430:Cell Shape; D017931:DNA Primers / Q000235:genetics; D004475:Ectoderm / Q000166:cytology / Q000196:embryology; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015027:Zebrafish / Q000033:anatomy & histology / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
D001057:Apolipoproteins E; D017931:DNA Primers; D018398:Homeodomain Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; C501122:dlx5a protein, zebrafish; C479567:fibroblast growth factor 24, zebrafish; D049452:Green Fluorescent Proteins; D005346:Fibroblast Growth Factors