nb 5-4 details
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NB 5-4 delaminates during S4 in an intermediate column.
No information about NB 5-4 is available from other insects.
NB 5-4 expresses muscle-specific homeobox gene 1(msh), gooseberry distal (gsb-d), wingless (wg), and huckebein (hkb) (Buescher et al, 1997; Isshiki et al, 1997; Skeath et al, 1995; Chu-LaGraff and Doe, 1993;Chu-LaGraff et al, 1995; Doe, 1992; Broadus et al, 1995 ) as it delaminates. By S5, it adds Klumpfuss (Klu) and seven-up-lacZ (svp-lacZ) (Yang et al, 1997; Broadus et al, 1995).
Schmidt et al. (1997) propose that NB 5-4 generates 5-9 neurons (thoracic) or 3-4 motoneurons (abdominal) that have an ipsilateral projection to an unknown target. We propose instead that the clone consists of 2-3 neurosecretory cells and abdomen-specific interneurons.
A.Neurosecretory cells:
In both Schistocerca and Manduca, abdominal segments contain crustacean cardioactive peptide (CCAP; also called CAP2A) -immunoreactive neurons with similar complex dendritic arborizations that project medially and dorsally before turning laterally and anastomosing with the TN (Broadie et al., 1990; Dircksen et al., 1991; reviewed in Burrows, 1996). Some confusion exists in the literature concerning the neuroanatomy of these cells. Some CCAP/CAP+ cells originate in the periphery and extend axons into the TN from positions outside the CNS (Taghert, et al., 1988; Nassel, 1996, for review) whereas others arise from medial and postero-lateral positions within the ganglion (Broadie et al., 1990; Tublitz and Sylwester, 1990; Dircksen et al., 1991; Tublitz and Loi, 1993; Loi and Tublitz, 1993). We observe that both thoracic and abdominal lineages contain 2-3 large cells (4.8 x 7.2 um, n=4) that project towards the midline, bifurcate, and extend bilaterally out the CNS in the TN (or possibly SNa); these cells also have a short dense projection into the ipsilateral connective (Fig. 5-4). These cells match the cell body position and axon projection pattern of the CCAP/CAP+ neurosecretory cells.
B. Interneurons
Abdominal clones contain an additional 2-4 smaller cells (4.5 _m; n=4) that only contain the local interneuronal projection described above (Fig. 5-4).
References:
Broadie, K., Sylwester, A., Bate, M., and Tublitz, N. J. (1990). Immunological, biochemical and physiological analyses of cardioacceleratory peptide 2 (CAP2) activity in the embryo of the tobacco hawkmoth, Manduca sexta. Development 108: 59-71.
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.
Burrows, M. (1996). Oxford University Press, The Neurobiology of an Insect Brain. New York.
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Chu-LaGraff, Q., and Doe, C.Q. (1993). Neuroblast specification and formation regulated by wingless in the Drosophila CNS. Science 261(5128): 1594-7.
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Taghert, P. H., Carr, J. N., and Wall, J. B. (1988). The formation of a neurohaemal organ during embryogenesis. in Advances in Insect Physiology (ed. P.D. Evans and V.B. Wigglesworth) Academic Press: New York. pgs 87-117.
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