One important application for the generated dataset is to gain insight into normal and abnormal human neurodevelopment by analyzing trajectories of individual genes or groups of genes associated with a particular neurobiological category or disease. To test this strategy, we compared our expression data of DCX (a gene expressed in neuronal progenitor cells and migrating immature neurons), as well as genes associated with dendrite (MAP1A, MAPT, CAMK2A) and synapse (SYP, SYPL1, SYPL2, SYN1) development, with independently generated, non-transcriptome human datasets. The DCX expression trajectory was remarkably reminiscent of the reported changes in the density of DCX-immunopositive cells in the postnatal human hippocampus (Fig. 5a)36,40. In our transcriptome dataset, DCX expression progressively increased until early midfetal development (period 5) and then gradually declined with age until early childhood (period 10). Likewise, expression trajectories of dendrite and synapse development gene groups closely paralleled the growth of basal dendrites of DFC pyramidal neurons41 (Spearman correlation, r=0.810 for layer 3 and r=0.700 for layer 5; Fig. 5b) and DFC synaptogenesis42 (r=0.946; Fig. 5c), respectively. Steep increases in both processes occurred between late midfetal and
