title: Transient expression of GAP-43 in nonneuronal cells of the embryonic chicken limb.
abstract: Growth associated protein (GAP)-43 is a membrane-bound phosphoprotein expressed in neurons and is particularly abundant during periods of axonal outgrowth in development and regeneration of the nervous system. In previous work, we cloned a full-length chicken GAP-43 cDNA and described the expression of its corresponding mRNA during early development of the chicken nervous system. We report here that the GAP-43 mRNA is also expressed transiently in developing limbs of chicken embryos, which contain axons of spinal cord and dorsal root ganglion neurons, but do not contain neuronal cell bodies. GAP-43 mRNA was first detectable by RNA blot analysis in limbs from Embryonic Day 5 (E5) embryos, reached maximal levels between E6 and E8, and diminished by E10. In situ hybridization analysis showed that the GAP-43 mRNA was localized in distal regions of developing limbs and was particularly abundant in the mesenchyme surrounding the digital cartilage. In some regions of the limb, GAP-43 immunoreactivity colocalized in cells that were also immunoreactive for meromyosin, a muscle-specific marker. These data suggest that both GAP-43 mRNA and the protein are expressed in nonneuronal cells of the developing limb, some of which may be part of the muscle cell lineage.
authors.affiliation: Department of Cell Biology and Anatomy, Oregon Health Sciences University, Portland 97201.
authors.forename: K M
authors.initials: KM
authors.lastname: Stocker
authors.forename: L
authors.initials: L
authors.lastname: Baizer
authors.forename: G
authors.initials: G
authors.lastname: Ciment
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D002642:Chick Embryo; D005121:Extremities / Q000196:embryology* / Q000294:innervation; D019922:GAP-43 Protein; D015870:Gene Expression; D005819:Genetic Markers; D006133:Growth Substances / Q000032:analysis* / Q000235:genetics; D007150:Immunohistochemistry; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000032:analysis* / Q000235:genetics; D010750:Phosphoproteins / Q000032:analysis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D014921:Wings, Animal / Q000196:embryology* / Q000294:innervation / Q000378:metabolism
chemical_list: D019922:GAP-43 Protein; D005819:Genetic Markers; D006133:Growth Substances; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger