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Targeted Gene Expression in Central Complex Structures

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IrreC-rst misexpression in central brain structures does not alter their development

Christian Reiter, Zhiping Nie, K.-F. Fischbach
Institut für Biologie III; Schänzlestr.1, D-79104 Freiburg

Table of contents

IrreC-rst, a transmembrane protein of the immunoglobulin superfamily with 5 immunoglobulin-like domains, is required for normal axonal projections in both optic chiasms (Boschert et al., 1990; Ramos et al., 1993). Normally it is not expressed in developing central complex structures. When misexpressed in these structures (by use of the Gal4/UAS-system; Brand and Perrimon, 1993), it does not seem to affect their development. We cloned the irreC-rst cDNA HB3 into the pUAST vector, behind UAS binding sites for the yeast transcription factor Gal4 and established five independent UAS-HB3 transformant lines, that were subsequently crossed to Gal4-lines. The IrreC-rst protein in F1 hybrids was detected by mab24A5.1 (Schneider et al., 1995) which is directed against the extracellular domain of IrreC-rst. We viewed pupal brain whole mounts in the confocal microscope.

GAL4 line 507 was obtained from Gerhard Technau and Joachim Urban

JPEG-file 182 K / GIF-file 293 K

Abbreviations in blown up Figure: ac, antennal commissure; al, antennal lobe; alpha, alpha-lobe of mushroom body; an, antennal nerve; beta, beta lobe of mushroom body; ca, central canal of ellipsoid body; fb, fan shaped body; ir, inner ring of ellipsoid body; oes, oesophagus; or, outer ring of ellipsoid body; p, peduncle of mushroom body.

GAL4 line KL124, obtained from Klemens Stoertkuhl, labels ring neurons of the ellipsoid body

The outer ring of the ellipsoid body (eb) formed by the terminals of R2 and R4 neurons (Hanesch et al., 1989) is beautifully stained in GAL4 line KL124 ectopically expressing UAS-HB3 (see below). The IrreC-rst protein is transported into the axonal terminals. In the cell bodies (cb), cell body fibres and putative dendritic regions (lateral triangles, ltr) only patchy IrreC-rst immunoreactivity is visible.

Labels in blown up version only.

JPEG-file 98 K / GIF-file 176 K

Conclusions

In summary, in the above GAL4-lines, gross anatomical anomalies of central brain structures misexpressing IrreC-rst during their develoment have not been detected (a complete different story is IrreC-rst misexpression in the optic lobes, in preparation). Interestingly, the IrreC-rst protein accumulates at the axonal terminals of ring neurons, while only patchy expression is visible at the level of their cell bodies and along their axons. This corresponds to what is found in the optic lobe, where IrreC-rst is normally expressed during axonal growth and synaptogenesis of certain columnar neurons (Schneider, 1995).

References

Boschert, U., Ramos, R.G.P., Tix, S., Technau, G.M., Fischbach, K.F. (1990). J. Neurogenetics, 6: 153-171
Brand, A.H., Perrimon, N. (1993). Development 118:401-415
Hanesch, U., Fischbach, K.-F., and Heisenberg, M. (1989). Cell Tissue Res. 257, 343-366
Ramos, R. C., Igloi, G. L., Lichte, B., Baumann, U., Maier, D., Schneider, T., Brandstätter, J. H., Fröhlich, A., and Fischbach, K. F. (1993). Genes Dev. 7, 2533-2547.
Schneider T., Reiter Ch., Lichte B., Nie Z., Eule E., Bader B., Schimansky T., Ramos R.G.P., and Fischbach K.-F. (1995) Neuron, 15, 259-271

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