Comparative analysis of Drd1+ Medium Spiny Neurons, Drd2+ Medium Spiny Neurons, Motor Neurons, and Purkinje Neurons. Mus musculus

The cellular heterogeneity of the brain confounds efforts to elucidate the biological properties of distinct neuronal populations. Using Bacterial Artificial Chromosome (BAC) transgenic mice which express EGFP-tagged ribosomal protein L10a in defined cell populations, we have developed a methodology to affinity purify polysomal mRNAs from genetically defined cell populations in the brain. The utility of this approach is illustrated by the comparative analysis of four types of neurons, revealing hundreds of genes that distinguish these four cell populations. We find that even two morphologically indistinguishable, intermixed subclasses of medium spiny neuron display vastly different translational profiles and present examples of the physiological significance of such differences. This genetically targeted Translating Ribosome Affinity Purification (TRAP) methodology is a generalizable method useful for the identification of molecular changes in any genetically defined cell type in response to genetic alterations, disease, or pharmacological perturbations. Keywords: Cell Type Comparison Overall design: For each cell population, three independent TRAP replicates were collected, and total RNA from both the immunoprecipitate and unbound fractions were seperately amplified and hybridized. For each tissue, several representative unnbound fractions are provided to serve as controls. Biological replicates are GCRMA normalized within groups. Following averaging of replicates, we recommend further global normalization between groups, using affymetrix biotinylated controls, to correct for any broad biases in scanning and hybridization. Finally for many analyses, we also recommend filtering to remove those probesets with low IP/UB fold change values from each cell type. Researchers can contact us for spreadsheets where these additional steps have been completed.