Average shape standard atlas for the adult Drosophila ventral nerve cord.

Neuroanatomy benefits from quantification of neural structures, i.e., neurons, circuits, and brain parts, within a common reference system. Recent improvements in imaging techniques and increased computational power have made the creation of Web-based databases possible, which serve as common platforms for incorporating anatomical data. This study establishes a standard average shape atlas for the ventral nerve cord (VNC) of Drosophila melanogaster. This atlas allows for the registration of morphological, developmental, and genetic data into one quantitative 3D reference system. The standard is based on an average adult Drosophila VNC neuropil as labeled in 24 whole-mount preparations with the commercially available antibody (nc82) recognizing the Drosophila Bruchpilot protein (Brp). For the standardization procedure no expert knowledge of brain anatomy is required and global thresholding as well as straightforward affine and elastic registration procedures minimize user interactions. Successful registration is demonstrated for tracts and commissures, gene expression patterns, and geometric reconstructions of individual neurons. Any structure that is counterstained with anti-Brp can be registered into the standard, allowing for fast comparison of data from different experiments and different laboratories. In addition, standard transformations can be applied to gray scale image data, so that any confocal image stack that is colabeled with anti-Brp can be analyzed within standardized 3D reference coordinates. This allows for the creation of putative neural connectivity maps and the comparison of expression patterns derived from different preparations. The standard and protocols for histological methods, segmentation, and registration procedures will be made available on the Web.