NB 3-4 details
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NB 3-4 delaminates during S5.
No information about the NB 3-4 lineage is available from other insects.
NB 3-4 expresses seven-up-lacZ (svp-lacZ), Mirror-lacZ (Mrr-lacZ), muscle specific homeobox gene 1 (msh), Klumpfuss (Klu) and castor (cas) as it delaminates (Broadus et al, 1995; McNeill et al, 1997; Cui and Doe, 1992, 1995; Buescher, et al, 1997; Isshiki et al, 1997; Yang, et al, 1997). Schmidt et al (1997) in their lineage studies did not determine the complement of cells derived from NB 3-4.
NBs 3-4 and 4-4 generate clones that appear to be indistinguishable (see NB 4-4). We cannot rule out the possibility that only one NB generates this clone, with the other NB generating a different clone that we have misidentified, never observed, or is lost through cell death prior to differentiating. NB 3-4/4-4 clones die with greater than normal frequency (50% survival compared to the usual 80% survival) and so we cannot rule the latter possibility out.
We find that at stage 17 there are 10-18 neurons: one motoneuron, at least two intersegmental interneurons, and local interneurons. We found epidermal subclones in 50% of our lineages and PNS subclones in 10% of our lineages.
A. Motoneurons.
NB 3-4 produces a single small motoneuron (5.2 mm at stage 15) which is located at the posterior ventral boundary of the clone and projects into the anterior root of the ISN by stage 15. It exits the CNS via SNd to innervate muscles 15, 16 and 17 and possibly 14, 28, and 30 (Fig. 3-4/4-4, single arrows). There is a small dendritic arborization in the ipsilateral longitudinal connective.
B. Interneurons.
At least two intersegmental interneurons form by stage 17, one extending anterior ipsilaterally and the other crossing the anterior commissure before extending anteriorly. Local interneurons share the same projection patterns, but do not extend beyond the segment border. The ipsilateral longitudinal connective has the intersegmental interneuronal axon in the medial fascicle and the local axon in the lateral one. In the contralateral longitudinal connective, the situation is reversed, with the local projection closer to the midline than the intersegmental one. Cell sizes are bimodal: most are large (5.2 mm; n=20), but 15% are smaller (3.2 mm; n=5).
References
Broadus, J., Skeath, J.B., Spana, E. P., Bossing, T., Technau, G.M., and Doe, C.Q. (1995). New neuroblast markers and the origin of the aCC/pCC neurons in the Drosophila central nervous system. Mech Dev 53: 393-402.
Buescher, M., and Chia, W. (1997). Mutations in lottchen cause cell fate transformations in both neuroblast and glioblast lineages in the Drosophila embryonic central nervous system. Development 124(3): 673-81.
Chu-LaGraff, Q., Schmid, A., Leidel, J., Broenner, G., Jaeckle, H., and Doe, C. Q. (1995). huckebein specifies aspects of CNS precursor identity required for motoneuron axon pathfinding. Neuron 15: 1041-1051.
Cui, X., and Doe, C.Q. (1992). ming is expressed in neuroblast sublineages and regulates gene expression in the Drosophila central nervous system. Development 116(4): 943-52.
Cui, X., and Doe, C.Q. (1995). The role of the cell cycle and cytokinesis in regulating neuroblast sublineage gene expression in the Drosophila CNS. Development 121(10): 3233-43
Isshiki, T., Takeichi, M., and Nose, A. (1997). The role of the msh homeobox gene during Drosophila neurogenesis: implication for the dorsoventral specification of the neurectoderm. Development 124(16): 3099-3109.
McDonald, J., and Doe, C. Q. (1997). Establishing NB specific gene expression in the Drosophila CNS: huckebein is activated by wingless and hedgehog and repressed by engrailed and gooseberry. Development 124: 1079-87.
McNeill, H., Yang, C.H., Brodsky, M., Ungos, J., and Simon, M.A. (1997). Mirror encodes a novel PBX-class ofhomeoprotein that functions in the definition of the dorsal-ventral border in the Drosophila eye. Genes Dev 11(8): 1073-82.
Schmidt, H., Rickert, C., Bossing, T., Vef, O., Urban, J., and Technau, G. M. (1997). The embryonic Central Nervous System lineages of Drosophila melanogaster II. Neuroblast lineages derived from the dorsal part of the neurectoderm. Dev Biol 189: 186-204.
Yang, X., Bahri, S., Klein, T., and Chia, W. (1997). Klumpfuss, a putative Drosophila zinc finger transcription factor, acts to differentiate between the identities of two secondary precursor cells within one neuroblast lineage. Genes Dev 11(11):1396-1408.