NB 7-4 details
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NB 7-4 delaminates at S1 in the posterior-most row of the lateral column.
In Schistocerca, NB 7-4 generates the sibling intersegmental interneurons Q1/Q2, C/G, and Q5/Q6. All cross the posterior commissure. Q1, Q2, and C then extend posteriorly while G, Q5, and Q6 extend anteriorly (Raper et al., 1983 a,b). The C and G interneurons have been identified in the adult metathorax and are called IN 314 and IN 714, respectively (reviewed in Boyan and Ball, 1993).
In Drosophila NB 7-4 expresses engrailed (en) and achaete (ac) as it delaminates (Lundell et al, 1996; Skeath et al, 1992; Doe, 1992). At S2, it adds seven-up-lacZ (svp-lacZ) and muscle-specific homeobox-1 (msh) expression (Broadus et al, 1995; Buescher et al, 1997; Isshiki et al, 1997) and loses ac expression. By S3, it adds Klumpfuss (Klu) and castor (cas) expression (Yang et al, 1997; Cui and Doe, 1992; Cui and Doe, 1995). Expression of en, svp-lacZ, msh, Klu, and cas continues in NB 7-4 throughout S4 and S5.
Schmidt et al. (1997) described the NB 7-4 lineage as consisting of 8-12 interneurons that cross the posterior commissure and then extend both anterior and posterior, and 3-4 glial cells (2 channel glia and a lateral sub-perineural glial cell).
A. Interneurons
The intersegmental interneurons are similarly sized (4.8 um; n=12) and project across the posterior commissure; putative homologs of Q1, Q2, and C project posteriorly, while the putative homologs of G, Q5, and Q6 project anteriorly. In addition, many local interneurons project across the posterior commissure and turn anteriorly in a medial fascicle of the connective (see Fig. 7-4B, asterisk).
B. Glia
Similar to Schmidt et al. (1997), we observe a variable number of glia, including channel glia, sub-perineural glia and cell body glia (Fig. 7-4 A,B)
References:
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