title: Distinct populations within Isl1 lineages contribute to appendicular and facial skeletogenesis through the β-catenin pathway.
abstract: Isl1 expression marks progenitor populations in developing embryos. In this study, we investigated the contribution of Isl1-expressing cells that utilize the β-catenin pathway to skeletal development. Inactivation of β-catenin in Isl1-expressing cells caused agenesis of the hindlimb skeleton and absence of the lower jaw (agnathia). In the hindlimb, Isl1-lineages broadly contributed to the mesenchyme; however, deletion of β-catenin in the Isl1-lineage caused cell death only in a discrete posterior domain of nascent hindlimb bud mesenchyme. We found that the loss of posterior mesenchyme, which gives rise to Shh-expressing posterior organizer tissue, caused loss of posterior gene expression and failure to expand chondrogenic precursor cells, leading to severe truncation of the hindlimb. In facial tissues, Isl1-expressing cells broadly contributed to facial epithelium. We found reduced nuclear β-catenin accumulation and loss of Fgf8 expression in mandibular epithelium of Isl1(-/-) embryos. Inactivating β-catenin in Isl1-expressing epithelium caused both loss of epithelial Fgf8 expression and death of mesenchymal cells in the mandibular arch without affecting epithelial proliferation and survival. These results suggest a Isl1→β-catenin→Fgf8 pathway that regulates mesenchymal survival and development of the lower jaw in the mandibular epithelium. By contrast, activating β-catenin signaling in Isl1-lineages caused activation of Fgf8 broadly in facial epithelium. Our results provide evidence that, despite its broad contribution to hindlimb mesenchyme and facial epithelium, the Isl1-β-catenin pathway regulates skeletal development of the hindlimb and lower jaw through discrete populations of cells that give rise to Shh-expressing posterior hindlimb mesenchyme and Fgf8-expressing mandibular epithelium.
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA; Stem Cell Institute, University of Minnesota, 2001 Sixth Street SE, Minneapolis, MN 55455, USA.
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Akiyama
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA; Stem Cell Institute, University of Minnesota, 2001 Sixth Street SE, Minneapolis, MN 55455, USA.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Kawakami
authors.affiliation: Department of Pharmacology, Graduate School of Medicine, Kyoto University, Kyoto 606-8051, Japan.
authors.forename: M Mark
authors.initials: MM
authors.lastname: Taketo
authors.affiliation: Skaggs School of Pharmacy, and Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Sylvia M
authors.initials: SM
authors.lastname: Evans
authors.affiliation: Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Wada
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA; Department of Pediatrics, University of Minnesota, 2450 Riverside Avenue, Minneapolis, MN 55455, USA; Developmental Biology Center, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Petryk
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA; Stem Cell Institute, University of Minnesota, 2001 Sixth Street SE, Minneapolis, MN 55455, USA; Developmental Biology Center, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA; Lillehei Heart Institute, University of Minnesota, 312 Church Street SE, Minneapolis, MN 55455, USA. Electronic address: kawak005@umn.edu.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kawakami
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D051792:Basic Helix-Loop-Helix Proteins / Q000096:biosynthesis; D001934:Branchial Region / Q000196:embryology; D019070:Cell Lineage / Q000235:genetics; D049109:Cell Proliferation; D002470:Cell Survival; D015536:Down-Regulation; D054642:Dual Specificity Phosphatase 6 / Q000096:biosynthesis; D004622:Embryo, Mammalian / Q000378:metabolism; D004848:Epithelium / Q000196:embryology / Q000378:metabolism; D051524:Fibroblast Growth Factor 8 / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism; D006614:Hindlimb / Q000002:abnormalities / Q000196:embryology*; D018398:Homeodomain Proteins / Q000096:biosynthesis; D007569:Jaw Abnormalities / Q000196:embryology* / Q000235:genetics; D051741:Kruppel-Like Transcription Factors / Q000096:biosynthesis; D060850:LIM-Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008334:Mandible / Q000196:embryology; D008648:Mesoderm / Q000196:embryology; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D010012:Osteogenesis / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation; D000074290:Zinc Finger Protein Gli3; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D054642:Dual Specificity Phosphatase 6; D051524:Fibroblast Growth Factor 8; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D051741:Kruppel-Like Transcription Factors; D060850:LIM-Homeodomain Proteins; D009419:Nerve Tissue Proteins; D014157:Transcription Factors; D000074290:Zinc Finger Protein Gli3; D051176:beta Catenin; C095587:Barx1 protein, mouse; C496457:Fgf8 protein, mouse; C465571:Gli3 protein, mouse; C498766:Hand2 protein, mouse; C465570:Shh protein, mouse; C063843:insulin gene enhancer binding protein Isl-1; C517036:Dusp6 protein, mouse
keywords: Branchial arch; Isl1; Limb; Mandible; β-catenin