Computer-generated three-dimensional reconstructions of serially sectionedmouse embryos

We have been involved with a group of computer scientists and anatomists in the development of computer-based methodologies that not only combine the advantages of scanning electron microscopy and conventional histology, but provide the additional dimension of tissue recognition. The latter is achie ved by the appropriate labelling of tissues and structures by delineation o r 'painting'. Individually segmented anatomically defined tissues can be hi ghlighted in a particular colour and viewed either in isolation or in combi nation with other appropriately labelled tissues and organs. Tissues can be shown in any orientation either as a transparent overlay on computer-gener ated histological sections or as 3-D images without the histological backgr ound. An additional feature of the system is that computer graphics technol ogy combined with 3-D glasses now also allows the viewer to see the object under analysis in stereo. This facility has been found to be particularly h elpful in drawing attention to topological relationships that had not previ ously been readily noted. As the mouse is now the mammalian model of choice in many areas of developmental research, it is of critical importance that a basic level of skill is available in the research community in the inter pretation of serially sectioned material, for example, for the rapidly expa nding held in which gene expression studies play a significant role. It is equally important that there is an understanding of the dynamic changes tha t occur in relation to the differentiation of the various organ systems see n in these early stages of development. What we emphasise here is the addit ional information that it is possible to gain from the use of this tool whi ch, in our view, could not readily have been gained from the analysis of sc anning electron micrographs or by studying conventional serial histological sections of similar stages of mouse embryonic development. The methodology has been developed as part of a large project to prepare a database of mou se developmental anatomy covering all stages from fertilisation to birth in order to allow the accurate spatial mapping of gene expression and cell li neage data onto the digital Atlas of normal mouse development. In this pape r we show how this digital anatomical Atlas also represents a valuable teac hing aid and research tool in anatomy.