Overexpression of muscle specific kinase increases the transcription and aggregation of acetylcholine receptors in Xenopus embryos.
Muscle specific kinase (MuSK) mediates agrin-induced acetylcholine receptor (AChR) aggregation on muscle membrane at the neuromuscular junction (NMJ). To examine whether MuSK enhances NMJ formation during embryonic development in vivo, the level of expression of MuSK was manipulated in Xenopus embryos and the functional consequence at the NMJ was assessed. We found that overexpression of MuSK enhanced the formation of NMJ by increasing the aggregation of AChRs at innervated regions in developing embryos. The area of AChR aggregation increased by approximately 2-fold in MuSK injected embryos during the critical stages of NMJ formation. Interestingly, overexpression of MuSK in Xenopus embryos was found to induce the level of AChR transcript. Deletion of the Kringle domain in the MuSK construct did not attenuate the observed induction of AChR transcription and aggregation. Taken together, our findings provide the first demonstration that increased level of MuSK expression in vivo significantly elevate the aggregation and transcription of AChR at the NMJ in developing Xenopus embryos.
Fu
A K
AK
Department of Biochemistry, Molecular Neuroscience Center and Biotechnology Research Institute, Hong Kong University of Science and Technology, Hong Kong, Clear Water Bay, China.
Cheung
J
J
Smith
F D
FD
Ip
F C
FC
Ip
N Y
NY
D000818:Animals; D004625:Embryo, Nonmammalian / Q000378:metabolism; D005260:Female; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D049452:Green Fluorescent Proteins; D007202:Indicators and Reagents / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D008297:Male; D016296:Mutagenesis / Q000502:physiology; D009469:Neuromuscular Junction / Q000201:enzymology; D010766:Phosphorylation; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*; D011950:Receptors, Cholinergic / Q000235:genetics* / Q000378:metabolism*; D013569:Synapses / Q000201:enzymology; D015533:Transcriptional Activation / Q000502:physiology*; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D014982:Xenopus laevis
D007202:Indicators and Reagents; D008164:Luminescent Proteins; D011950:Receptors, Cholinergic; D049452:Green Fluorescent Proteins; D014443:Tyrosine; C095714:MUSK protein, human; D020794:Receptor Protein-Tyrosine Kinases