NB 2-3 Details
NB 2-3:
NB 2-3 delaminates as an S5 NB.
This lineage has not been described in other insects.
NB 2-3 expresses mirror-lacZ (mrr-lacZ) and runt as it forms (McNeill et al, 1997; Doe, 1992; Broadus et al, 1995; Dormand and Brand, 1998).
Its lineage was not identified by Bossing et al. (1995, 1996) or Schmidt et al., (1997). We generated 15 NB 2-3 clones, but only 6 thoracic clones developed. In abdominal segments, only a large labeled NB is detectable at stage 17, it either fails to divide or all its progeny die.
A. Motoneurons:
The thoracic NB 2-3 generates three very large round cells (9.5 mm; n=7) at the dorsal side of the clone. The large size of these cells (characteristic of motoneurons), and their presence specifically in thoracic segments, suggests that they may be latent leg motoneurons that will extend axons during leg-disk eversion. Consistent with this proposal, Truman et al. (1993) observe that the thorax-specific leg motoneurons are born during embryonic development, but wait for leg imaginal disc eversion before pioneering leg innervation. Other adult leg motoneurons may derive from the NB 1-1 lineage, which generates two large axonless cells adjacent to aCC and pCC only in thoracic segments (Fig. 1-1). B. Interneurons: In 5 of 6 clones, we observe 2-4 small interneurons (3.2 mm; n=6) at the ventral side of the clone; they project across the anterior commissure and bifurcate in the connective (Fig. 2-3).
References:
Bossing, T., Technau, G. M., and Doe, C.Q. (1995). Huckebein is required for glial development and axon path-finding in the NB 1-1 and NB 2-2 lineages in the Drosophila central nervous system. Mech Dev 55: 53-64.
Bossing, T., Udolph, G., Doe, C. Q., and Technau, G. M. (1996). The Embryonic CNS lineages of Drosophila melanogaster I. Neuroblast lineages derived from the ventral half of the neurectoderm. Dev Biol 179: 41-64.
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.
Dormand, E.L., and Brand, A.H. (1998). Runt determines cell fate in the Drosophila embryonic CNS. Development 125(9):1659-67.
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.
Truman, J., Taylor, B. J., and Awad, T. A. (1993). " Formation of the Adult Nervous System." in The Development of Drosophila Melanogaster Cold Spring Harbor Laboratory Press: pages 1245-1276.