{"doi":"10.1242/dev.122.8.2319","title":"The limb field mesoderm determines initial limb bud anteroposterior asymmetry and budding independent of <i>sonic hedgehog</i> or apical ectodermal gene expressions","abstract":"<jats:title>ABSTRACT</jats:title>\n               <jats:p>We have analyzed the pattern of expression of several genes implicated in limb initiation and outgrowth using limbless chicken embryos. We demonstrate that the expressions of the apical ridge associated genes, Fgf-8, Fgf-4, Bmp-2 and Bmp-4, are undetectable in limbless limb bud ectoderm; however, FGF2 protein is present in the limb bud ectoderm. Shh expression is undetectable in limbless limb bud mesoderm. Nevertheless, limbless limb bud mesoderm shows polarization manifested by the asymmetric expression of Hoxd-11, -12 and -13, Wnt-5a and Bmp-4 genes. The posterior limbless limb bud mesoderm, although not actually expressing Shh, is competent to express it if supplied with exogenous FGF or transplanted to a normal apical ridge environment, providing further evidence of mesodermal asymmetry. Exogenous FGF applied to limbless limb buds permits further growth and determination of recognizable skeletal elements, without the development of an apical ridge. However, the cells competent to express Shh do so at reduced levels; nevertheless, Bmp-2 is then rapidly expressed in the posterior limbless mesoderm. limbless limb buds appear as bi-dorsal structures, as the entire limb bud ectoderm expresses Wnt-7a, a marker for dorsal limb bud ectoderm; the ectoderm fails to express En-1, a marker of ventral ectoderm. As expected, C-Lmx1, which is downstream of Wnt-7a, is expressed in the entire limbless limb bud mesoderm. We conclude that anteroposterior polarity is established in the initial limb bud prior to Shh expression, apical ridge gene expression or dorsalventral asymmetry. We propose that the initial pattern of gene expressions in the emergent limb bud is established by axial influences on the limb field. These permit the bud to emerge with asymmetric gene expression before Shh and the apical ridge appear. We report that expression of Fgf8 by the limb ectoderm is not required for the initiation of the limb bud. The gene expressions in the pre-ridge limb bud mesoderm, as in the limb bud itself, are unstable without stimulation from the apical ridge and the polarizing region (Shh) after budding is initiated. We propose that the defect in limbless limb buds is the lack of a dorsalventral interface in the limb bud ectoderm where the apical ridge induction signal would be received and an apical ridge formed. These observations provide evidence for the hypothesis that the dorsal-ventral ectoderm interface is a precondition for apical ridge formation.</jats:p>","journal":"Development","year":1996,"id":32597,"datarank":5.615791656706326,"base_score":4.770684624465665,"endowment":4.770684624465665,"self_citation_contribution":0.7156026936698499,"citation_network_contribution":4.900188963036476,"self_endowment_contribution":0.7156026936698499,"citer_contribution":4.900188963036476,"corpus_percentile":null,"corpus_rank":null,"citation_count":117,"citer_count":91,"citers_with_citation_signal":82,"citers_with_endowment":82,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":172208,"name":"Alric López-Martínez","orcid":null,"position":1,"is_corresponding":false},{"id":172209,"name":"B. Kay Simandl","orcid":null,"position":2,"is_corresponding":false},{"id":172210,"name":"Concepción Rodriguez","orcid":null,"position":3,"is_corresponding":false},{"id":172211,"name":"Juan Carlos Izpisúa Belmonte","orcid":null,"position":4,"is_corresponding":false},{"id":172212,"name":"Randall Dahn","orcid":null,"position":5,"is_corresponding":false},{"id":172213,"name":"John F. Fallon","orcid":null,"position":6,"is_corresponding":false},{"id":172207,"name":"Maria A. Ros","orcid":null,"position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"base_score":4.770684624465665,"endowment":4.770684624465665,"datacite_reuse_total":0,"file_count":0,"downloads":0,"views":0,"has_version_chain":false,"is_dataset":false,"is_oa":false,"pmid":"8756277","pmcid":null,"openalex_id":"https://openalex.org/W2183330297","authors":[],"funders":[{"funder_name":"NICHD NIH HHS","grant_id":"HD32551","title":null},{"funder_name":"OHS HRSA HHS","grant_id":"ST32GM07507","title":null}],"total_grants":2,"fwci":7.4244,"citation_percentile":0.97900706,"influential_citations":0,"citation_trend":[{"year":2013,"count":2},{"year":2014,"count":2},{"year":2015,"count":2},{"year":2016,"count":1},{"year":2018,"count":1},{"year":2020,"count":1},{"year":2021,"count":1},{"year":2024,"count":3},{"year":2026,"count":1}],"oa_status":"closed","license":"http://www.biologists.com/user-licence-1-1/","oa_locations":[{"url":"https://journals.biologists.com/dev/article-pdf/122/8/2319/3120985/develop_122_8_2319.pdf","host_type":"publisher"},{"url":"https://doi.org/10.1242/dev.122.8.2319","host_type":"journal"},{"url":"https://pubmed.ncbi.nlm.nih.gov/8756277","host_type":"repository"}],"fields_of_study":["Developmental Biology and Gene Regulation","Hedgehog Signaling Pathway Studies","Congenital limb and hand anomalies","Animals","Biomarkers","Chick Embryo","Ectoderm","Fibroblast Growth Factor 2","Gene Expression","Genes, Homeobox","Hedgehog Proteins","Limb Buds","Mesoderm","Proteins","Proto-Oncogene Proteins","Trans-Activators","Wnt Proteins","Wnt-5a Protein"],"mesh_terms":["Wnt-5a Protein","Animals","Chick Embryo","Ectoderm","Genes, Homeobox","Mesoderm","Proteins","Proto-Oncogene Proteins","Biomarkers","Trans-Activators","Gene Expression","Fibroblast Growth Factor 2","Limb Buds","Wnt Proteins","Hedgehog Proteins"],"keywords":["Zone of polarizing activity","Apical ectodermal ridge","Limb bud","Ectoderm","Limb development","Mesoderm","Biology","Anatomy","Intermediate mesoderm","FGF and mesoderm formation","Lateral plate mesoderm","Sonic hedgehog","Cell biology","Embryogenesis","Embryo","Genetics","Gene","Embryonic stem cell","Signal transduction"],"sdg_mappings":[{"sdg_number":0,"sdg_label":"Life in Land"}],"linked_datasets":[],"clinical_trials":[],"software_tools":[],"database_accessions":[],"source":"live","citation_network_status":"fetched"},"created_at":"2026-06-09T13:36:48.496196Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}