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.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Animals
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Biological Evolution*
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Body Patterning* / genetics
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Camelus / anatomy & histology
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Camelus / embryology
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Cell Death
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Chondrogenesis* / genetics
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Extremities / anatomy & histology*
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Extremities / embryology*
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Fibroblast Growth Factor 8 / genetics
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Gene Expression Regulation, Developmental
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Hedgehog Proteins / genetics
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Homeodomain Proteins / genetics
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Horses / anatomy & histology
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Horses / embryology
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Mammals / anatomy & histology*
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Mammals / embryology*
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Mammals / genetics
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Mice
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Oncogene Proteins / genetics
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Patched Receptors
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Patched-1 Receptor
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Phylogeny
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Receptors, Cell Surface / genetics
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Rodentia / anatomy & histology
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Rodentia / embryology
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Swine / anatomy & histology
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Swine / embryology
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Trans-Activators / genetics
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Zinc Finger Protein GLI1
Substances
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Hedgehog Proteins
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Homeodomain Proteins
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Oncogene Proteins
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Patched Receptors
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Patched-1 Receptor
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Ptch1 protein, mouse
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Receptors, Cell Surface
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Trans-Activators
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Zinc Finger Protein GLI1
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Fibroblast Growth Factor 8