February 10, 2012 Making a difference among multiple nuclei within a single cell
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Before you read this paper Cell-cell interaction during organogenesis often results in the formation of specific cell-cell junctions. The paper for this week deals with a junction between a muscle and the neuron that controls its activity. Such junction is called "neuromuscular junction", where a synaptic terminal of the axon contacts a specialized region of the muscle membrane. This region, or the "postsynaptic membrane", concentrates many proteins that are required for synaptic function, including acetylcholine receptors, which are transmembrane receptors of the neurotransmitter acetylcholine released from the nerve terminal. The question that the authors of this paper are interested in is "how to localize acetylcholine receptor proteins to the specific region of the muscle cell membrane, the region opposing the axon terminal". Before you read this paper, think about a more general problem " how to localize a protein species to a specific place within the cell", and consider different mechanisms that could be used for this purpose. I assume you are familiar about steps of gene expression: transcription translation, protein trafficking, etc, but you may also imagine cellular mechanisms that are not yet known to exist. Then read the paper --- which should be relatively straightforward. Was the possibility they addressed one of your scenarios? Does their experiment exclude any of the possibilities you considered? Based on the results obtained in this paper, what would like to know next? The title of this paper includes a phrase "synaptic nuclei" --- a term that you might be unfamiliar with. Because muscle fibers form by fusion of multiple myoblasts, they are multi-nucleated. Synaptic nuclei are the nuclei that are close to (just below) the synapse. Nuclei far from the synapse are called "extrasynaptic nuclei".
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