title: Patterning and post-patterning modes of evolutionary digit loss in mammals.
abstract: A reduction in the number of digits has evolved many times in tetrapods, particularly in cursorial mammals that travel over deserts and plains, yet the underlying developmental mechanisms have remained elusive. Here we show that digit loss can occur both during early limb patterning and at later post-patterning stages of chondrogenesis. In the 'odd-toed' jerboa (Dipus sagitta) and horse and the 'even-toed' camel, extensive cell death sculpts the tissue around the remaining toes. In contrast, digit loss in the pig is orchestrated by earlier limb patterning mechanisms including downregulation of Ptch1 expression but no increase in cell death. Together these data demonstrate remarkable plasticity in the mechanisms of vertebrate limb evolution and shed light on the complexity of morphological convergence, particularly within the artiodactyl lineage.
authors.affiliation: 1] Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA [2] Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, USA. [3].
authors.forename: Kimberly L
authors.initials: KL
authors.lastname: Cooper
authors.affiliation: 1] Department of Animal Biology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA [2].
authors.forename: Karen E
authors.initials: KE
authors.lastname: Sears
authors.affiliation: 1] Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA [2].
authors.forename: Aysu
authors.initials: A
authors.lastname: Uygur
authors.affiliation: Department of Animal Biology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Maier
authors.affiliation: cole Normale Supérieure de Lyon, 69007 Lyon, France.
authors.forename: Karl-Stephan
authors.initials: KS
authors.lastname: Baczkowski
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Margaret
authors.initials: M
authors.lastname: Brosnahan
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Doug
authors.initials: D
authors.lastname: Antczak
authors.affiliation: The Camel Reproduction Centre, Dubai, United Arab Emirates.
authors.forename: Julian A
authors.initials: JA
authors.lastname: Skidmore
authors.affiliation: Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Clifford J
authors.initials: CJ
authors.lastname: Tabin
mesh_terms: D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning / Q000235:genetics; D002162:Camelus / Q000033:anatomy & histology / Q000196:embryology; D016923:Cell Death; D020219:Chondrogenesis / Q000235:genetics; D005121:Extremities / Q000033:anatomy & histology* / Q000196:embryology*; D051524:Fibroblast Growth Factor 8 / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics; D006736:Horses / Q000033:anatomy & histology / Q000196:embryology; D008322:Mammals / Q000033:anatomy & histology* / Q000196:embryology* / Q000235:genetics; D051379:Mice; D015513:Oncogene Proteins / Q000235:genetics; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; D010802:Phylogeny; D011956:Receptors, Cell Surface / Q000235:genetics; D012377:Rodentia / Q000033:anatomy & histology / Q000196:embryology; D013552:Swine / Q000033:anatomy & histology / Q000196:embryology; D015534:Trans-Activators / Q000235:genetics; D000071676:Zinc Finger Protein GLI1
chemical_list: D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D015513:Oncogene Proteins; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; C000606240:Ptch1 protein, mouse; D011956:Receptors, Cell Surface; D015534:Trans-Activators; D000071676:Zinc Finger Protein GLI1; D051524:Fibroblast Growth Factor 8