Target contact regulates expression of synaptotagmin genes in spinal motor neurons in vivo.
During neuromuscular development, neuronal contact with peripheral targets is associated with an increase in synaptic vesicle protein (SVP) gene expression, suggesting that target contact and upregulation of SVP genes are causally related. To test this idea, we analyzed the developmental expression pattern of synaptotagmin (syt) mRNAs in the chick lateral motor column (LMC) using in situ hybridization. Syt I mRNA in the LMC is upregulated from Embryonic Day 4.5 (E4.5) to E5.5, coincident with the time these neurons begin to make contact with their muscle targets. In contrast, levels of mRNA for neurofilament do not change during this time. Extirpation of the limb bud prior to motor axon outgrowth eliminates the increase in syt I mRNA ipsilaterally. Later in development, there is a switch in syt isoform abundance in the LMC, with syt II mRNA being upregulated between E15 and E20 and syt I mRNA being downregulated. Our results suggest that contact with targets upregulates syt I gene expression during neuromuscular synapse formation in vivo, and that a later stage of synaptic maturation involves changes in SVP isoform abundance.
Campagna
J A
JA
Department of Molecular & Cellular Pharmacology, University of Miami School of Medicine, Florida 33101, USA.
Prevette
D
D
Oppenheim
R W
RW
Bixby
J L
JL
D000818:Animals; D002135:Calcium-Binding Proteins; D002642:Chick Embryo / Q000502:physiology; D005314:Embryonic and Fetal Development; D005786:Gene Expression Regulation; D008562:Membrane Glycoproteins / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics; D009046:Motor Neurons / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009434:Neural Pathways / Q000196:embryology; D016900:Neurofilament Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D013116:Spinal Cord / Q000166:cytology / Q000196:embryology*; D050861:Synaptotagmin II; D050857:Synaptotagmins
D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins; D012333:RNA, Messenger; D050861:Synaptotagmin II; C061195:neurofilament protein M; D050857:Synaptotagmins