Project description:The mammalian cerebral cortex contains an extraordinary diversity of cell types that emerge through the implementation of different developmental programs. Delineating when and how cellular diversification occurs is particularly challenging for cortical inhibitory neurons, as they represent a relatively small proportion of all cortical cells, migrate tangentially from their embryonic origin to the cerebral cortex, and have a protracted development. Here we combine single-cell RNA sequencing and spatial transcriptomics to characterize the emergence of neuronal diversity among somatostatin-expressing (SST+) cells, the most diverse subclass of inhibitory neurons in the mouse cerebral cortex. We found that SST+ inhibitory neurons segregate during embryonic stages into long-range projection (LRP) neurons and two types of interneurons, Martinotti cells and non-Martinotti cells, following distinct developmental trajectories. Two main subtypes of LRP neurons and several subtypes of interneurons are readily distinguishable in the embryo, although interneuron diversity is further refined during early postanal life. Our results suggest that the timing for cellular diversification is unique for different subtypes of SST+ neurons and particularly divergent for LRP neurons and interneurons. Thus, the diversification of SST+ inhibitory neurons involves a temporal cascade of unique molecular programs driving their divergent developmental trajectories.
Project description:Somatostatin interneurons are the earliest born population of inhibitory cells. They are crucial to support normal brain development and function; however, the mechanisms underlying their integration into nascent cortical circuitry are not well understood. In this study, we begin by demonstrating that the maturation of somatostatin interneurons is activity dependent. We then investigated the relationship between activity, alternative splicing and synapse formation within this population. Specifically, we discovered that the Nova family of RNA-binding proteins are activity-dependent and are essential for the maturation of somatostatin interneurons, as well as their afferent and efferent connectivity. Moreover, in somatostatin interneurons, Nova2 preferentially mediates the alternative splicing of genes required for axonal formation and synaptic function. Hence, our work demonstrates that the Nova family of proteins are centrally involved in coupling developmental neuronal activity to cortical circuit formation.
Project description:CUT&RUN for MEF2C in mature PV+ and SST+ cortical interneurons to characterize the differential usage of this transcription factor by these populations.
Project description:We hypothesized that the occurrence of IVH would reduce interneuron neurogenesis in the medial ganglionic eminence and diminish the population of parvalbumin+ and somatostatin+ cortical interneurons. Since Sonic Hedgehog promotes the production of cortical interneurons, we also postulated that the activation of Sonic Hedgehog signaling might restore neurogenesis, cortical interneuron population, and neurobehavioral function in premature newborns with IVH.
Project description:Interneurons navigate along multiple tangential paths to settle into appropriate cortical layer. They undergo saltatory migration, which is paced by intermittent nuclear jumps whose regulation relies on interplay between extracellular cues and genetic-encoded information. However, it remains unclear how cycles of pause and movement are coordinated at the molecular level. Post-translational modification of proteins contributes to cell migration regulation. The present study uncovers that carboxypeptidase 1, which promotes deglutamylation, is a pivotal regulator of pausing of cortical interneurons. Moreover, we show that pausing during migration controls the flow of interneurons invading the cortex by generating heterogeinity in movement at the population level. Interfering with the regulation of pausing not only affects the size of the cortical interneuron cohort but also secondarily impairs the generation of age-matched upper layer projection neurons.
Project description:Total RNA-sequencing of FACs isolated nucleus accumbens somatostatin interneuron nuclei Somatostatin interneuron loss in multiple cortical brain regions has been observed postmortem in humans with several neuropsychiatric disorders and their loss is proposed to underlie some common pathological changes in circuit function across numerous syndromes. However, somatostatin interneurons in the nucleus accumbens (NAc), a key brain reward region, remain poorly understood due to the fact that these cells account for <1% of NAc neurons. Here, we used Flouresence activated cell sorting to isolate nuclei of somatostatin-expressing interneurons in the Nucleus Accumbens from individual SST-TLG498 reporter mice that express membrane bound EGFP-F specifically in somatostatin-expressing neurons. We then performed cell-type specific Total RNA-sequencing to characterize the entire transcriptome of NAc somatostatin interneurons after repeated exposure (7 days) to either saline or cocaine. We identified a wide variety of coding and non-coding transcripts that were expressed at high levels and were differentially expressed between saline and cocaine treated mice. Repeated cocaine administration induces transcriptome-wide changes in gene expression within NAc somatostatin interneurons, with particular regulation of transcripts related to neural plasticity. Our results identify alterations in NAc induced by cocaine in a sparse population of somatostatin interneurons, and illustrate the value of studying brain diseases using cell type-specific whole transcriptome RNA-sequencing to identify novel neurpathophysiology.
Project description:Cortical interneurons display a remarkable diversity in their morphology, physiological properties and connectivity. Elucidating the molecular determinants underlying this heterogeneity is essential for understanding interneuron development and function. We discovered that alternative splicing differentially regulates the integration of somatostatin- and parvalbumin-expressing interneurons into nascent cortical circuits through the cell-type specific tailoring of mRNAs. Specifically, we identified a role for the activity-dependent splicing regulator Rbfox1 in the development of cortical interneuron subtype specific efferent connectivity. Our work demonstrates that Rbfox1 mediates largely non-overlapping alternative splicing programs within two distinct but related classes of interneurons.
Project description:In the cerebral cortex, projection neurons and interneurons work coordinately to establish functional neural networks and to control the balance between excitatory versus inhibitory synaptic activities for normal cortical functions. While the specific mechanisms that control productions of projection neurons and interneurons are beginning to be revealed, a global characterization of the molecular differences between these two groups of neurons is in need for a more comprehensive understanding of their developmental specifications as well as their cortical functions. Previous studies have shown that the majority of cortical projection neurons are produced by radial glial cells (RGCs) through intermediate progenitor cells (IPCs) which can be marked by the expression of transcription factor Tbr2(Eomes). In this study, taking advantage of lineage tracing power of combining Tbr2(Eomes)-GFP and DCX-mRFP transgenic reporter mice, we prospectively separated IPC-derived neurons (IPNs) from non-IPC-derived neurons (non-IPNs) of the embryonic cortex. Molecular characterizations revealed that IPNs and non-IPNs were enriched with projection neurons and interneurons, respectively. Transcriptome analyses documented distinct groups of genes differentially expressed between these two groups of neurons. These data present a useful resource for further investigation of the molecular regulations and functions of projection neurons and interneurons.
Project description:In the mammalian cortex, about 60% of GABAergic interneurons, mainly including parvalbumin-expressing (PV+) and somatostatin (SST+) interneurons are generated from the medial ganglionic eminence (MGE) in the subpallium and tangentially migrate to the cortex. Here we analyze the role of the Sp9 transcription factor in regulating the development of MGE-derived cortical interneurons. We show that SP9 is widely expressed in the MGE subventricular zone (SVZ) and in MGE-derived migrating interneurons. By analyzing Sp9 null and conditional mutant mice, we demonstrate that Sp9 promotes MGE progenitor proliferation in the SVZ and is required for the normal patterning of tangential migration and the laminar distribution of MGE-derived cortical GABAergic interneurons. Loss of Sp9 function results in a ~50% reduction of MGE-derived cortical interneurons, an ectopic aggregation of MGE-derived neurons in the embryonic ventral telencephalon, and an increased ratio of SST+/PV+ cortical interneurons. Finally, we provide evidence that Sp9 regulates MGE derived cortical interneuron development through promoting expression of the Lhx6 and Lhx8 transcription factors.