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. 1998 Feb 1;18(3):987–998. doi: 10.1523/JNEUROSCI.18-03-00987.1998

Fig. 3.

Fig. 3.

ArgK is strongly expressed in muscle pioneer cells and their extending processes. A, C,E, The two retractor unguis muscle pioneer cells express argK protein (antibody label) at the onset of their differentiation (A, black arrow), while they are extending their processes to the site of retractor unguis muscle insertion in the femur (C, black arrow), and as they shorten (E, black arrow) with the invagination of the tube of epithelial cells that will form the muscle apodeme (C, E, white arrows). B, In situ hybridization reveals argK mRNA throughout the cytoplasm of the retractor unguis muscle pioneers early in their differentiation. D, In mesothoracic limb buds at the 33% stage, argK is expressed in all limb muscle pioneer cells (and in the CNS); it is not expressed in afferent neurons, epithelial cells, or mesodermal cells (other than muscle pioneers). F, At the 55% stage, argK is still expressed in muscle pioneer cells (white arrow) of the extensor tibia (and other) muscles, but not in extensor tibia myoblasts or in afferent neurons or ectoderm. Scale bars: A, C, E, 50 μm; B, 25 μm; D, 100 μm;F, 200 μm.