Project description:Here, we examined diversity in the cell-type composition of the mouse anterior thalamic nuclei (ATN) using single-cell RNA-seq and single-cell spatial transcriptomics.
Project description:We profiled the transcriptome of 22 thalamic nuclei. Nuclei were retrogradely labeled from their forebrain target areas, microdissected and fluorescent cells pooled. Anterograde tracing was used when identification of nuclear boundaries was ambiguous. We found that thalamic nuclei share a common axis of variance closely linked to the mediolateral spatial axis of thalamus. This axis was enriched in functionally relevant genes such as neurotransmitter receptors and ion channels, and was closely linked to functional and morphological properties of the neurons.
Project description:The thalamus is the principal information hub of the vertebrate brain, with essential roles in sensory and motor information processing, attention, and memory. The complex array of thalamic nuclei develops from a restricted pool of neural progenitors. We apply longitudinal single-cell RNA-sequencing and regional abrogation of Sonic hedgehog (Shh) to map the developmental trajectories of thalamic progenitors, intermediate progenitors, and post-mitotic neurons as they coalesce into distinct thalamic nuclei. These data reveal that the complex architecture of the thalamus is established early during embryonic brain development through the coordinated action of four cell differentiation lineages derived from Shh-dependent and independent progenitors. We systematically characterize the gene expression programs that define these thalamic lineages across time and demonstrate how their disruption upon Shh depletion causes pronounced locomotor impairment resembling infantile Parkinson’s disease. These results reveal key principles of thalamic development and provide mechanistic insights into neurodevelopmental disorders resulting from thalamic dysfunction.
Project description:A hippocampal-diencephalic-cortical network supports memory function. The anterior thalamic nuclei (ATN) form a key anatomical hub within this system. Consistent with this, injury to the mammillary body-ATN axis is associated with examples of clinical amnesia. However, there is only limited and indirect support that the output of ATN neurons actively enhances memory. Here, in rats, we first showed that mammillothalamic tract (MTT) lesions caused a persistent impairment in spatial working memory. MTT lesions also reduced rhythmic electrical activity across the memory system. Next, we introduced 8.5 Hz optogenetic theta-burst stimulation of the ATN glutamatergic neurons. The exogenously-triggered, regular pattern of stimulation produced an acute and substantial improvement of spatial working memory in rats with MTT lesions and enhanced rhythmic electrical activity. Neither behaviour nor rhythmic activity was affected by endogenous stimulation derived from the dorsal hippocampus. Analysis of immediate early gene activity, after the rats foraged for food in an open field, showed that exogenously-triggered ATN stimulation also increased Zif268 expression across memory-related structures. These findings provide clear evidence that increased ATN neuronal activity supports memory. They suggest that ATN-focused gene therapy may be feasible to counter clinical amnesia associated with dysfunction in the mammillary body-ATN axis.
Project description:The thalamus is organized into nuclei that have distinct input and output connectivities with the cortex. While first-order (FO) nuclei – also called core nuclei – relay input from sensory organs on the body surface and project to primary sensory areas, higher-order (HO) nuclei – matrix nuclei – instead receive their driver input from the cortex and project to secondary and associative areas within cortico-thalamo-cortical loops. Input-dependent processes have been shown to play a critical role in the emergence of FO thalamic neuron identity from a ground state HO neuron identity, yet how this identity emerges during development remains unknown. Here, using single-nucleus RNA sequencing of the developing embryonic thalamus we show that FO thalamic identity emerges after HO identity, and that peripheral input is critical for the maturation of excitatory, but not inhibitory FO-type neurons. Our findings reveal that subsets of HO neurons are developmentally co-opted into FO-type neurons, providing a mechanistic framework for the diversification of thalamic neuron types during development and evolution.
Project description:We collected single-cell RNAseq data from neurons of five thalamocortical projection systems (motor, somatosensory, visual, auditory, and prefrontal). Cells of each projection system were retrogradely labeled from their cortical target area, microdissected, and collected individually. By combining single-cell transcriptomics with in situ RNA hybridization, we found heterogeneity not only between thalamic nuclei but also within nuclei, with graded transitions between cell identities.
Project description:To identify genes expressed in specific developing thalamic nuclei during embryonic stages, a genetic dual labelling strategy was established to mark and isolate the cells. Transcription profiles were determined for the principal sensory thalamic populations by genome-wide analysis. We identified genes expressed in distinct thalamic nuclei with a potential function in the specification of individual sensory-modality thalamocortical connections.