Thy-1-like immunoreactivity in developing chicken skeletal muscle: identification of a cross-reactive slow-fiber specific molecule that is not Thy-1

Protein phosphorylation in fast and slow chicken skeletal muscles: effect of denervation

We have identified proteins in adult chicken skeletal muscle whose phosphorylation can be used as markers for the mature fast and slow muscle phenotype. These include phosphorylase, phosphorylase kinase, and a cyclic adenosine 3',5'-monophosphate (cAMP)-stimulated, calmodulin-inhibited 28-kDa band (markers for fast muscle), a calmodulin-stimulated 50-kDa band, and two cAMP-stimulated bands at 44 and 46 kDa (markers for slow muscle), and the relative concentrations of the regulatory subunits of cAMP-dependent protein kinase (RI and RII). After denervation the pattern of phosphorylation in fast muscle changed to resemble that of slow muscle: phosphorylation of the fast phenotype markers decreased; the slow phenotype markers, barely detectable in normal fast muscle, appeared as significant phosphoproteins; and the concentration of RII increased with no change in RI. This is consistent with denervation-induced changes observed using other phenotypic markers and indicates the potential for using these phosphoprotein markers in studies of muscle development and pathophysiology.

Molecular cloning and primary structure of the avian Thy-1 glycoprotein

We have previously characterised, both biochemically and immunohistochemically, a 23 kDa putative avian Thy-1 protein homologue. In this report we have examined the carbohydrates present on the protein and determined the partial protein sequence of enzymatically and CNBr-produced peptides. The protein sequences enabled us to clone an essentially full-length (1854 bp) cDNA using PCR and colony screening of an embryonic day (ED) 18 forebrain pUEX-1 cDNA library. Analysis of deduced amino acid sequence shows the 23 kDa protein to be 110 amino acids in length compared to mouse (112) and human and rat (111) while still retaining the conserved cysteine residues. The N-glycosylation site at position 61 is the same as that in the human protein, but is different from that in the rodent (position 75). Northern blot analysis of Thy-1 mRNA expression in the forebrain, cerebellum and tectum show that all three tissues have low levels at ED4 (forebrain and tectum) and ED8 (cerebellum), rising most rapidly between ED16 and the first few days post-hatch. Analysis of various tissues at hatch and adult show expression to be predominantly neuronal with very low levels in some other organs, mainly at hatch, indicating the possibility of subsets of cells, which we have also seen in histological sections, in these tissues expressing Thy-1 mRNA. Bone marrow and blood cells were also negative for Thy-1 protein.