NB 2-1 Details
Videos
NB 2-1 delaminates as an S4 NB.
This lineage has not been described in other insects.
NB 2-1 expresses castor (cas), huckebein (hkb), Klumpfuss (Klu), ventral nervous system defective (vnd) and mirror-lacZ (mrr-lacZ) as it delaminates (Cui and Doe, 1992; Doe, 1992; Chu-LaGraff et al, 1995; White et al, 1983; McDonald et al, 1998; McNeill et al, 1997; Broadus et al, 1995).
Bossing et al (1996) describe the lineage as consisting of approximately 8 interneurons and an obligate subclone of approximately 4 epidermal cells. They find a tangle of ipsilateral projections and a single interneuronal projection through the anterior commissure.
A. Motoneurons:
There are no motoneurons in this clone. We did observe a short axon that looked as though it could be a motoraxon in young clones, but we never saw a motoraxon exit the CNS.
B. Interneurons:
There are no intersegmental interneurons in this clone. At stage 15, we found the NB 2-1 clone to consist of 9 cells, consistent with the results of Bossing et al, 1996. These cells were interneurons, averaging 4.7 microns in diameter (n=10 cells measured in 2 clones). By stage 16, there were 13 cells and they averaged 4.5 microns in diameter (n=8 cells measured in 2 clones). By stage 17, there were 15 cells in this lineage, divisible into large and small diameter groups. Approximately 25% of the cells were 2.2 microns in diameter, the remaining cells averaged 4.0 microns in diameter. We found these cells to cross the midline in a single projection in a posterior fascicle of the anterior commissure. It extended to the contralateral posterior commissure and then bifurcated.
C. Glia:
In both of the stage 17 clones we scored, we observed a segmental nerve glial cell. We observed a sub-perineurial glial cell once (see movies).
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.
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.
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.
Doe, C. Q. (1992). Molecular markers for identified neuroblasts and ganglion mother cells in the Drosophila central nervous system. Development 116: 855- 863.
McDonald, J.A., Holbrook, S., Isshiki, T., Weiss, J., Doe, C.Q., and Mellerick, D.M. (1998). Dorsoventral patterning in the Droosphila central nervous system: the vnd homeobox gene specifies ventral column identity. Genes Dev 12: 3603-12.
McNeill, H., Yang, C.H., Brodsky, M., Ungos, J., and Simon, M.A. (1997). Mirror encodes a novel PBX-class of homeoprotein that functions in the definition of the dorsal-ventral border in the Drosophila eye. Genes Dev 11(8): 1073-82.
White, K., DeCelles, N.L., and Enlow, T.C. (1983). Genetic and developmental analysis of the locus vnd in Drosophila melanogaster. Genetics 104(3): 433-48.
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.