GSE191205
Heterogeneous fates of simultaneously-born neurons in the cortical ventricular zone
Neocortical excitatory neurons belong to diverse cell types, which can be distinguished by their dates of birth, laminar location, connectivity and molecular identities. During embryogenesis, apical progenitors (APs) located in the ventricular zone first give birth to deep-layer neurons, and next to superficial-layer neurons. While the overall sequential construction of neocortical layers is well-established, whether multiple neuron types are produced by APs at single time points of corticogenesis is unknown. To address this question, here we used FlashTag to fate-map simultaneously-born (i.e. isochronic) cohorts of AP-born neurons at successive stages of corticogenesis. We reveal that early in corticogenesis, isochronic neurons differentiate into heterogeneous laminar, hodological and molecular cell types. Later on, instead, simultaneously-born neurons have more homogeneous fates. Using single-cell gene expression analyses, we identify an early postmitotic surge in the molecular heterogeneity of nascent neurons during which some early-born neurons initiate and partially execute late-born neuron transcriptional programs. Together, these findings suggest that as corticogenesis unfolds, mechanisms allowing increased homogeneity in neuronal output are progressively implemented, resulting in progressively more predictable neuronal identities. Overall design: Patch-Seq of E13.5 born cells marked with FlashTag technology collected at P7 in Primary somatosensory area of the mouse brain.