NB 3-5 details
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NB 3-5 delaminates at S1 in the anterior-most row of the lateral column.
No information about the lineage derived from NB 3-5 is available from other insects.
NB 3-5 expresses achaete (ac) as it delaminates; it loses ac expression by S3 as it begins to express seven-up-lacZ (svp-lacZ) (Doe, 1992; Broadus, et al, 1995). By S5 it has added Klumpfuss (Klu) and zinc-finger homeobox gene-1 (zfh-1) expression (MacDonald and Doe, 1998; Yang, et al, 1997; Fortini et al, 1991; Skeath et al, 1998). In addition, as is true for NB 3-3, muscle specific homeobox gene 1 (msh) can be faintly detected in NB 3-5, but only as perdurance of neurectodermal gene expression; there is no de novo synthesis in the neuroblast (T. Isshiki, personal communication).
Schmidt et al (1997) describe the lineage as containing 19-24 interneurons that project both ipsilaterally and contralaterally. They describe these projections as occasionally extending anteriorly further than one segment. They also note a prominent ipsilateral fascicle that we do not observe.
A. Motoneurons:
In the first thoracic segment (T1) this lineage contains a large motoneuron (7.2 mm) that projects ipsilaterally via the posterior root of the ISN and forms synapses on muscles 1, 3, and 9 (Fig. 3-5). This motoneuron is not generated in any other thoracic or abdominal segments.
B. Interneurons:
The majority of the interneurons are intersegmental. They project across the anterior commissure in at least three separate fascicles and then defasciculate and form large, diffuse anterior projections in the contralateral connective (Fig. 3-5B,D). In thoracic segments, there is an ipsilateral anterior projection that is only occasionally present in abdominal segments, and there are almost twice as many cells as in abdominal segments. The first thoracic segment appears to generate only local interneurons with a similar projection pattern.
C. Glia:
Abdominal clones contain a nerve root glial cell that ensheathes the axons (Fig. 3-5D); this is similar to nerve root glia from NBs 2-1, 2-5 and 3-5, but different from the more rounded nerve root glia derived from NB 1-1 and NB 7-1.
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.
Doe, C. Q. (1992) Molecular markers for identified neuroblasts and ganglion mother cells in the Drosophila central nervous system. Development 116: 855-863.
Fortini, M.E., Lai, Z.C., and Rubin, G.M (1991). Drosophila zfh-1 and zfh-2 genes encode novel proteins containing both zinc-finger and homeodomain motifs. Mech Dev 34(2-3):113-22.
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.
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.
Skeath, J. B. (1998). The Drosophila EGF-Receptor controls the formation and specification of NBs along the dorso-ventral axis of the Drosophila embryo. Development 125: 3301-12.
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.