title: Differential cell affinity and sorting of anterior and posterior cells during outgrowth of recombinant avian limb buds.
abstract: To examine the role of position-specific differences in cell-cell affinity, recombinant limb buds composed of dissociated and reaggregated cells derived from anterior (A) and posterior (P) limb bud fragments were analyzed. Dissociated anterior and/or posterior cells were differentially labeled, and their behavior was analyzed during recombinant limb bud outgrowth. We find that anterior and posterior cells sort out from one another to form alternating anterior and posterior stripes of cells that extend distally along the proximal-distal axis. These alternating stripes are prominent across the A/P axis in whole-mount preparations of recombinant limb buds after 48 h of outgrowth when the presumptive autopod is dorsal-ventrally flattened and digit rudiments are not evident. After 96 h, when digital and interdigital regions are clearly defined, we find evidence that A/P stripes do not follow obvious anatomical boundaries. The formation of A/P stripes is not inhibited by grafts of ZPA tissue, suggesting that polarizing activity does not influence cell-cell affinity early in limb outgrowth. In vitro studies provide evidence that cell sorting is not dependent on the limb bud ectoderm or the AER; however, cells sort out without organizing into stripes. Gene expression studies using anterior-specific (Alx-4) and posterior-specific (Shh, Bmp-2, and Hoxd-13) marker genes failed to reveal expression domains that corresponded to stripe formation. Control recombinant limb buds composed of anterior, central, or posterior mesenchyme formed digits in a position-specific manner. A/P recombinant limb buds that develop to later stages form digits that are characteristic of central recombinant limbs. These data provide the first definitive evidence of A/P cell sorting during limb outgrowth in vivo and suggest that differential cell affinities play a role in modulating cell behavior during distal outgrowth.
authors.affiliation: Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: Minoru
authors.initials: M
authors.lastname: Omi
authors.forename: Rosalie
authors.initials: R
authors.lastname: Anderson
authors.forename: Ken
authors.initials: K
authors.lastname: Muneoka
mesh_terms: D000818:Animals; D019521:Body Patterning; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000235:genetics; D002465:Cell Movement; D002642:Chick Embryo; D005121:Extremities / Q000196:embryology* / Q000637:transplantation; D018507:Gene Expression Regulation, Developmental; D005819:Genetic Markers; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins / Q000235:genetics; D017403:In Situ Hybridization; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D016042:Transplantation, Heterotopic
chemical_list: D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D005819:Genetic Markers; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta