Project description:The mammalian brain contains diverse neuron cell types with distinct physiological, morphological and molecular characteristics. However, a comprehensive assessment of the epigenetically distinct neuronal classes is currently missing. Cytosine DNA methylation is a stable epigenetic mark that distinguishes neuron types and marks gene regulatory elements. We developed an efficient single-nucleus methylome sequencing approach that allows robust high-throughput neuron-type classification. We generated >6,000 single-nucleus methylomes and identified 16 mouse and 21 human neuronal subpopulations in the frontal cortex. Both CG and non-CG methylation exhibited cell type-specific distributions that recapitulate and extend findings from single neuron transcriptome profiling. Moreover, we found approximately 500,000 neuron-type-specific regulatory elements showing strong differential methylation in mouse and human cortex. Distinct methylation signatures identified an unique human Parvalbumin-expressing inhibitory sub-type and a layer 6 specific excitatory sub-type in mouse. Comparative epigenomic analysis showed stronger conservation of gene regulatory elements in inhibitory compared with excitatory neurons. These findings demonstrate the utility of single nucleus methylome profiling for both expanding the atlas of brain cell types and identifying regulatory elements that potentially drive these differences.
Project description:Reciprocal deletion and duplication of 16p11.2 is the most common copy number variation (CNV) associated with Autism Spectrum Disorder (ASD) and other developmental disorders, and has significant effect on brain size. We used cortical organoids derived from ASD cases to investigate neurodevelopmental pathways dysregulated by dosage changes of 16p11.2 CNV. We show that organoids recapitulate patients’ macrocephaly and microcephaly phenotypes. Deletions and duplications have “mirror” effects on cell proliferation, maturation and synapse number, consistent with “mirror” effects on brain development in humans. Neuronal migration was decreased in both, deletion and duplication organoids. Transcriptomic and proteomic profiling revealed synaptic defects and neuronal migration as key drivers of 16p11.2 functional effect. We implicate upregulation of small GTPase RhoA involved in regulation of cytoskeletal dynamics, neuron migration and neurite outgrowth as one of the pathways impacted by the 16p11.2 CNV in ASD. Treatment with the RhoA inhibitor Rhosin rescued neuron migration, but not synaptic defects. This study identifies pathways dysregulated by the 16p11.2 CNV during early neocortical development using cortical organoid models. Grant ID: Simons Foundation, #345469 Grant Title: Translational dysregulation of the RhoA pathway in autism Affiliation: University of California San Diego Name: Lilia M. Iakoucheva; Alysson R. Muotri
Project description:The functions and protein expressions of the blood-brain barrier are changed during brain development after birth. The purpose of the present study was to develop a method to isolate brain capillaries from a single frozen neonatal mouse brain and elucidate the enrichment of brain capillaries by quantitative proteomic analysis. The brain capillary fraction was prepared by the optimized method from a single frozen mouse neonatal brain (postnatal day 7). The brain capillary fractions and brain lysates were digested by trypsin and analyzed by DIA.
Project description:Normal brain function critically depends on the interaction between highly specialized neurons that operate within anatomically and functionally distinct brain regions. The fidelity of neuronal specification is contingent upon the robustness of the transcriptional program that supports the neuron type-specific patterns of gene expression. Changes in neuron type-specific gene expression are commonly associated with neurodegenerative disorders including Huntingtonâs and Alzheimerâs disease. The neuronal specification is driven by gene expression programs that are established during early stages of neuronal development and remain in place in the adult brain. Here we show that the Polycomb repressive complex 2 (PRC2), which supports neuron specification during early differentiation, contributes to the suppression of the transcription program that can be detrimental for the adult neuron function. We show that PRC2 deficiency in adult striatal neurons and in cerebellar Purkinje cells impairs the maintenance of neuron-type specific gene expression. The deficiency in PRC2 has a direct impact on a selected group of genes that is dominated by self-regulating transcription factors normally suppressed in these neurons. The age-dependent progressive transcriptional changes in PRC2-deficient neurons are associated with impaired neuronal function and survival and lead to the development of fatal neurodegenerative disorders in mice. Medium Spiny neuronal nuclei were isolated from adult mouse striata via NeuN-specific Flourescence Activated Nuclei Sorting.
Project description:Isolated brain capillaries are essential for analyzing the changes of protein expressions at the blood-brain barrier (BBB) under pathological conditions. The standard brain capillary isolation methods require the use of at least 5 mouse brains in order to obtain a sufficient amount and purity of brain capillaries. The purpose of this study was to establish a brain capillary isolation method from a single mouse brain for protein expression analysis.
Project description:Differential encoding in prefrontal cortex projection neuron classes across cognitive tasks We perform single nucleus RNAsequencing using a smartseq2 protocol on mouse prefrontal cortex neurons labeled by tdTomato in an Rbp4-cre;Ai14 mouse. Some cells were retrolabeled from various brain regions.
Project description:Purpose Corneal neovascularization (CNV) impairs corneal transparency and visual acuity. The study aims to deepen our understanding of the molecules involved in CNV induced by alkali burns, facilitate a better grasp of CNV mechanisms, and uncover potential therapeutic targets. Methods Mice were selected for establishing CNV models via alkali burns. On days 3, 7, and 14 after the burns, corneal observations and histological investigations were conducted. An integrated analysis of RNA sequencing (RNA-seq)-based transcriptomics and label-free quantitative proteomics was performed in both normal and burned corneas. Bioinformatics approaches, encompassing GO and KEGG analysis, were applied to discern differentially expressed genes (DEGs) and crucial signaling pathways. Four potentially CNV-related genes were validated using qRT-PCR and Western blot. Results Significant CNV was observed on the seventh day. Forty-one genes were differentially expressed in neovascularized corneas, with 15 upregulated and 26 downregulated at both mRNA and protein levels. Bioinformatics analysis revealed that these DEGs participated in diverse biological processes, encompassing retinol and retinoic acid metabolism, neutrophil chemotaxis, and actin filament assembly, along with significant enrichment pathways like cytochrome P450, tyrosine, and phenylalanine metabolism. The upregulation of lymphocyte cytosolic protein 1 (LCP1) and cysteine and glycine-rich protein 2 (CSRP2) genes and the downregulation of transglutaminase 2 (TGM2) and transforming growth factor-beta-induced (TGFBI) genes were confirmed. Conclusions We analyzed gene expression differences in mouse corneas seven days after alkali burns, finding 41 genes with altered expression. The exact role of these genes in CNV is not fully understood, but exploring angiogenesis-related molecules offers potential for CNV treatment or prevention.