Integrative Single-Cell Transcriptomics Reveals Molecular Networks Defining Neuronal Maturation during Neurogenesis

Neurogenesis in the adult hippocampus contributes to information processing critical for cognition, adaptation, learning and memory, and is implicated in numerous neurological disorders. New neurons are continuously produced from neural stem cells via a well-controlled developmental process. The immature neuron stage defined by doublecortin (DCX) expression is the most sensitive to regulation by extrinsic factors. However, little is known about the dynamic biology within this critical interval that drives maturation and confers susceptibility to regulating signals. This study aims to test the hypothesis that DCX-expressing immature neurons in adult mouse hippocampus progress through developmental stages via activity of specific transcriptional networks. Using single-cell RNA-seq combined with a novel integrative bioinformatics approach, we discovered that individual immature neuron can be classified into distinct developmental subgroups based on characteristic gene expression profiles and subgroup-specific markers. Comparisons between immature and more mature subgroups revealed novel pathways involved in neuronal maturation. Genes enriched in more immature cells shared significant overlap with genes implicated in neurodegenerative diseases, while genes positively associated with neuronal maturation were enriched for autism-related gene sets. Our study thus discovers molecular signatures of individual adult-born immature neurons and unveils potential novel targets for therapeutic approaches to treat neurodevelopmental and neurological diseases. mRNA sequencing and expression estimation in 64 individual DCX-dsRed+ cells isolated from transgenic DCX-dsRed mice by FACS sorting