This analysis was performed as previously described 12. In brief, all datasets were reduced to a set of six common cell types: pyramidal neurons, interneurons, astrocytes, microglia and oligodendrocyte precursors. Specificity was recalculated using only these six cell types. Comparisons were then made between pairs of datasets (denoted in the graph with the format ‘X versus Y’). The difference in specificity for a set of dendrite enriched genes is calculated between the datasets. Differences in specificity are also calculated for random sets of genes selected from the background gene set. The probability and z-score for the difference in specificity for the dendritic genes is thus estimated. Dendritically enriched transcripts were obtained from Supplementary Table 10 of Cajigas et al. 96. For the KI dataset 12, we used S1 pyramidal neurons. For the Zeisel 2018 dataset 30 we used all ACTE* cells as astrocytes, TEGLU* as pyramidal neurons, TEINH* as interneurons, OPC as oligodendrocyte precursors and MGL* as microglia. For the Saunders dataset 41, we used all Neuron.Slc17a7 cell types from FC, HC or PC as pyramidal neurons; all Neuron.Gad1Gad2 cell
