Where in the brain are the genes expressed

The need to determine the distribution of a given cellular or molecular marker within the brain is common to a wide range of neuroscience investigations. Localization is an essential parameter both for the interpretation of findings in an anatomical and functional context, as well as for comparing findings across specimens. Knowledge of temporal and spatial gene expression patterns in the brain is of particular importance for understanding correlations between genotype and phenotype, during development, in normal adults, as well as in disease. In situ hybridization and similar measurements of molecular distributions, selectively label cells expressing particular genes or gene products in tissue sections. However, lack of structural background information in the surrounding tissue makes the identification of anatomical boundaries difficult. Variations in the used section plane complicate matters further. As a result, studies of gene expression distributions tend to be restricted to limited regions, and reported findings are typically difficult to compare.