NB 7-1

Segregation wave: S1

The late embryonic NB 7-1 clone comprises 16 to 22 neuronal cells in the lateral cortex. About 3 motoneurons form a fascicle that exits through the anterior root of the intersegmental nerve (7-1M). Immediately outside the nerve cord the fascicle splits into two branches. One branch arborizes over up to three muscles of the ventral external oblique group (most likely muscle VO1, VO2, and VO3). The second branch exhibits extensive arborisations and swellings along the whole dorsoventral length of the segment border muscle (SBM; Bate, 1993). In 3 out of 10 cases an additional branch from this fascicle contacts a muscle of the dorsal oblique group (most likely muscle DO2). Considering the projection pattern and some cells in the clone occupying a position ventromedial to the aCC motoneuron, these motoneurons might correspond to the previously described U1-U3 neurons (Goodman and Doe, 1993). Most cells of the NB 7-1 lineage represent interneurons that form two major contralateral fascicles (7-1Ica, 7-1Icp). Beside the CQ neurons an interneuron positioned dorsomedially can be detected with an antibody against the eve protein. Expression and position just below and between aCC and pCC suggests this cell to represent the Òfriend of pCCÓ (fpCC, Goodman and Doe, 1993; ÒFPÓ cell of Jacobs and Goodman, 1989) or Òcandidate fpCCÓ (Broadus et al., 1995). The axon of the fpCC interneuron first extends ipsilateral anterior to reach the anterior commissure where it turns contralaterally. The position of the CQ neurons inside the cluster does not allow to identify their individual projections. A few cells of the NB 7-1 clone are located in the posterior region of the gooseberry expression domain.

Flybrain    Development    Neuroblast Lineage    NB 7-1

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