Mushroom Body is a Quadruple Structure - Figure 1

Summary of the structural organisation of the mushroom body.

I: Three models of the mushroom body neuroblast progeny.

MB region specific (Model A)

All MB regions (Model B)

Not limited to MBs (Model C)

A:	The first possibility is that each MBNb is specified uniquely to generate neurones that project to a specific region of the MB neuropile, e.g. the alpha lobe.
B:	Another possibility is that each MBNb may not be limited to a specific substructure, but contribute to all of the cellular repertoire of the MB.
C:	The last possibility is that the progeny of the MBNb are not confined to the MB, but may project to other regions of the brain.

Our clonal analysis (Fig. 2 for method, Fig. 3 for results) shows that each MBNb clone contributes to all of the cellular repertoire of the MB. (Model A is rejected.) We found no MBNb clone that projects to other regions of the brain. (Model C is rejected.) Thus, we conclude that model B is the likely model of the MB formation in the adult Drosophila brain.

II: Fourfold structure of the mushroom body.

A

B

A:

Each MBNb generates a clonal unit that contains glia and all the types of Kenyon cells (KC in different colours). After arborizing in the calyx (ca), the fibres make the pedunculus (ped) that de-fasciculates into the lateral (L) and medial (M) bundles. Fibres in the medial bundle form the alpha and beta lobes, while those in the lateral bundle contribute to the spur (sp) as well as alpha' and gamma lobes. Flippase-mediated clones reveal such clonal units (Fig. 3). Partial ablation experiments show that any of the MBNb can autonomously generate such a unit even when all other MBNbs are absent (Fig. 6).

B:

The intact MB is a four-fold structure of these clonal units. Since each unit contains all the cell types, a marker that detects a certain subset of cells (black) will reveal cells in all the four clusters (cf. Figs. 4, 5)

Go to Index | Fig. 1 | Fig. 2 | Fig. 3 | Fig. 4 | Fig. 5 | Fig. 6

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