title: Differential regulation of gene expression in the digit forming area of the mouse limb bud by SHH and gremlin 1/FGF-mediated epithelial-mesenchymal signalling.
abstract: Spatially and temporally coordinated changes in gene expression are crucial to orderly progression of embryogenesis. We combine mouse genetics with experimental manipulation of signalling to analyze the kinetics by which the SHH morphogen and the BMP antagonist gremlin 1 (GREM1) control gene expression in the digit-forming mesenchyme of mouse limb buds. Although most mesenchymal cells respond rapidly to SHH signalling, the transcriptional upregulation of specific SHH target signals in the mesenchyme occurs with differential temporal kinetics and in a spatially restricted fashion. In particular, the expression of the BMP antagonist Grem1 is always upregulated in mesenchymal cells located distal to the SHH source and acts upstream of FGF signalling by the apical ectodermal ridge. GREM1/FGF-mediated feedback signalling is, in turn, required to propagate SHH and establish the presumptive digit expression domains of the Notch ligand jagged 1 (Jag1) and 5'Hoxd genes in the distal limb bud mesenchyme. Their establishment is significantly delayed in Grem1-deficient limb buds and cannot be rescued by specific restoration of SHH signalling in mutant limb buds. This shows that GREM1/FGF feedback signalling is required for regulation of the temporal kinetics of the mesenchymal response to SHH signalling. Finally, inhibition of SHH signal transduction at distinct time points reveals the differential temporal dependence of Grem1, Jag1 and 5'Hoxd gene expression on SHH signalling. In particular, the expression of Hoxd13 depends on SHH signal transduction significantly longer than does Hoxd11 expression, revealing that the reverse co-linear establishment, but not maintenance of their presumptive digit expression domains, depends on SHH signalling.
authors.affiliation: Developmental Genetics, DKBW Centre for Biomedicine, University of Basel Medical School, Mattenstrasse 28, CH-4058 Basel, Switzerland.
authors.forename: Lia
authors.initials: L
authors.lastname: Panman
authors.forename: Antonella
authors.initials: A
authors.lastname: Galli
authors.forename: Nadege
authors.initials: N
authors.lastname: Lagarde
authors.forename: Odysse
authors.initials: O
authors.lastname: Michos
authors.forename: Gwen
authors.initials: G
authors.lastname: Soete
authors.forename: Aimee
authors.initials: A
authors.lastname: Zuniga
authors.forename: Rolf
authors.initials: R
authors.lastname: Zeller
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D016207:Cytokines; D005246:Feedback; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005838:Genotype; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D000072100:Jagged-1 Protein; D018878:Limb Buds / Q000196:embryology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D010641:Phenotype; D000072099:Serrate-Jagged Proteins; D015398:Signal Transduction
chemical_list: D002135:Calcium-Binding Proteins; D016207:Cytokines; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D000072100:Jagged-1 Protein; D008565:Membrane Proteins; D000072099:Serrate-Jagged Proteins; C113178:Grem1 protein, mouse; C000606274:Jag1 protein, mouse; C465570:Shh protein, mouse; C107836:Tlx2 protein, mouse