Embryonic progenitor pools generate diversity in fine-scale excitatory cortical subnetworks

The mammalian neocortex is characterized by a variety of neuronal cell types and precise arrangements of synaptic connections, but the processes that generate this diversity are poorly understood. Here we examine how a pool of embryonic progenitor cells consisting of apical intermediate progenitors (aIPs) contribute to diversity within the upper layers of mouse cortex. In utero labeling combined with single-cell RNA-sequencing reveals that aIPs can generate transcriptionally defined glutamatergic cell types, when compared to neighboring neurons born from other embryonic progenitor pools. Whilst sharing layer-associated morphological and functional properties, simultaneous patch clamp recordings and optogenetic studies reveal that aIP-derived neurons exhibit systematic biases in both their intralaminar monosynaptic connectivity and the post-synaptic partners that they target within deeper layers of cortex. Multiple cortical progenitor pools therefore represent an important factor in establishing diversity amongst local and long-range fine-scale glutamatergic connectivity, which generates subnetworks for routing excitatory synaptic information.


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Policy information about availability of data All manuscripts must include a data availability statement. This statement should provide the following information, where applicable: -Accession codes, unique identifiers, or web links for publicly available datasets -A list of figures that have associated raw data -A description of any restrictions on data availability Colin J. Akerman Aug 23, 2019 All commercial software for data collection is detailed in the manuscript. These included: pClamp9 (Molecular Devices, RRID:SCR_011323) and WinWCP software (University of Strathclyde, UK, RRID:SCR_014713).
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nature research | reporting summary
October 2018 Field-specific reporting Please select the one below that is the best fit for your research. If you are not sure, read the appropriate sections before making your selection. Sample sizes were chosen based on accepted standards in the field. These are sufficient to generate meaningful conclusions given biologically relevant effect sizes and typical data variance for the measures used.
No data was excluded.
Three approaches were taken with regards to reproducibility. Firstly, intrinsic electrophysiological properties of both aIP-and OP-derived neurons were recorded separately by two of the authors (TE and SVA) and both data sets confirmed the observation that intrinsic electrophysiological properties are similar between SNP-and OP-derived neurons. Secondly, progenitor-based differences in intralaminar synaptic connectivity were detected in two separate cortical layers. A bias in intralaminar connectivity was initially observed within layer L2/3 of cortex and, at this point, intralaminar connectivity was then assessed within layer 4 of cortex and progenitor-based differences were replicated. Thirdly, progenitor-based differences in extralaminar synaptic connectivity were observed in two pathways: ipsilateral translaminar connections from layer 2/3 to layer 5 and contralateral translaminar connections from layer 2/3 to layer 5.
All patch clamp recordings were performed randomly, in the sense that aIP-and OP-derived neurons were both assessed in individual recording sessions, in randomized configurations, and using different recording headstages. This approach avoided potential biases in cellular and circuit properties that could be associated with individual animals, the time of recording or equipment.
Wherever possible, we used blinding during data analysis. Most experiments involved large data sets and analysis employed automated, or semi-automated computer scripts, in which the experimenter was blinded to cell type or brain region. For example, the analysis of all intracellular recording data (electrophysiological properties and synaptic connectivity) was performed blinded to a neuron's progenitor type of origin, and anatomical data was analyzed blinded to injection location and progenitor of origin.
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Provide details on animals observed in or captured in the field; report species, sex and age where possible. Describe how animals were caught and transported and what happened to captive animals after the study (if killed, explain why and describe method; if released, say where and when) OR state that the study did not involve wild animals.