Project description:Most single cell RNA sequencing protocols start with single cells dispersed from intact tissue. High-throughput processing of the separated cells is enabled using microfluidics platforms. However, dissociation of tissue results in loss of information about cell location and morphology and potentially alters the transcriptome. An alternative approach for collecting RNA from single cells is to re-purpose the electrophysiological technique of patch clamp recording. A hollow patch pipette is attached to individual cells, enabling the recording of electrical activity, after which the cytoplasm may be extracted for single cell RNA-Seq (“Patch-Seq”). Since the tissue is not disaggregated, the location of cells is readily determined, and the morphology of the cells is maintained, making possible the correlation of single cell transcriptomes with cell location, morphology and electrophysiology. Recent Patch-Seq studies utilizes PCR amplification to increase amount of nucleic acid material to the level required for current sequencing technologies. PCR is prone to create biased libraries – especially with the extremely high degrees of exponential amplification required for single cell amounts of RNA. We compared a PCR-based approach with linear amplifications and demonstrate that aRNA amplification (in vitro transcription, IVT) is more sensitive and robust for single cell RNA collected by a patch clamp pipette.
Project description:We obtained full transcriptome data from single cortical neurons after whole-cell patch-clamp recording (termed “Patch-seq”). By applying “Patch-seq” to cortical neurons, we reveal a close link between biophysical membrane properties and genes coding for neurotransmitter receptors and channels, including well-established and hitherto undescribed subtypes.
Project description:In this project, we enabled mass spectrometry based proteomics characterization of single neurons in sections of the mouse brain. We accessed cells in a whole-cell patch clamp configuration and aspirated a portion of the neuronal soma into the patch clamp probe. The collected aspirate was expelled into a microvial, where proteins were extracted and processed for shot-gun analysis. The resulting trace amounts of protein digests were analyzed on a custom-built microanalytical capillary electrophoresis platform that was connected to an electrospray ionization high-resolution mass spectrometer. This “patch proteomics” technology identified ~150 proteins from triplicate measurement of single dopaminergic neurons in the mouse substantia nigra.
Project description:The classification of neurons into distinct types is an ongoing effort aimed at revealing and understanding the diversity of the components of the nervous system. Recently available methods allow us to determine the gene expression pattern of individual neurons in the mammalian cerebral cortex to generate powerful categorization schemes. For a thorough understanding of neuronal diversity such genetic categorization schemes need to be combined with traditional classification parameters like position, axonal projection or response properties to sensory stimulation. Here we describe a method to link the gene expression of individual neurons with their position, axonal projection or sensory response properties. Neurons are labeled in vivo based on their anatomical or functional properties and, using patch clamp pipettes, their RNA individually harvested in vitro for RNAseq. With this method we can determine the genetic expression pattern of functionally and anatomically identified individual neurons.
Project description:Investigated the DNA binding specificity of the C-clamp of dnTCF1E Used a doxycycline inducible system to investigate the role of the C-clamp in the genome-wide binding of dnTCF1E. Induced dnTCF1EWT and dnTCF1Emut (C-clamp mutant that is null for C-clamp DNA binding) over 2 time points (2 hours and 9 hours). A 0 hour (no doxycycline, uninduced) control was also included.
Project description:To investigate the DNA binding specificity of the CLAMP protein, we have designed a custom PBM to interrogate the binding of CLAMP to DNA sequences extracted from the Drosophila melanogaster genome. Specific regions were extracted based on ChIP-seq data, motif occurence and proximity to gene transcription start sites. N-terminal GST-tagged protein samples were made for the C-terminal four and six zinc finger portions of the protein CLAMP; samples were made by in vitro transcription translation (IVT). IVT reaction mixtures for the two CLAMP constructs were applied directly to the PBM microarray and incubated for 1hour. Microarray-bound protein was fluorescently labeled using Alexa488-conjugated antibodies targeting GST, and the microarray was scanned in using a standard microarray scanner. Median fluorescence intensity over eight replicate probes was reported for each unique DNA sequence on the microarray.
Project description:CLAMP is a GA-repeat motif binding transcription factor that regulates gene expression. We hypothesized that CLAMP also regulates RNA processing, specifically alternative splicing that occurs co-transcriptionally because CLAMP is bound to intronic regions that are rich in polypyrimidine tracts which contain GA-rich sequences. Furthermore, GA-rich repeat sequences are thought to have evolved from polypyrimidine tracts that regulate splicing. Also, MALDI-mass spectrometry data identifying putative CLAMP interactors found association with 33 RNA binding proteins, including 6 that regulate alternative splicing. Thus, to test our hypothesis that CLAMP shapes transcriptome diversity by regulating RNA transcript splicing, we performed mRNA-sequencing in the presence and absence of CLAMP in Kc (female) and S2 (male) cell lines and used a SUPPA based pipeline called time2splice (https://github.com/ashleymaeconard/time2splice) to analyze the sequencing data. Using both cell lines helped us to identify female (Kc) and male (S2) specific splicing events. We identified 452 genes differentially spliced beetween Kc and S2 cells. There are 46 and 113 CLAMP-dependent splicing events in Kc and S2 cells, respectively. Interestingly, 45 CLAMP-dependent events (belonging to 42 genes) are specific to Kc cells, i.e female-specific, whereas 112 CLAMP dependent events (belonging to 100 genes) in S2 cells are specific to S2 cells, i.e male-specific. Therefore, we identified a new role for the transcription factor CLAMP in regulated sex-specific splicing events in Kc and S2 cells.
Project description:ChIP-seq and mRNA-seq experiments were performed to understand the role of the CLAMP protein in dosage compensation ChIP-seq experiments compared the binding profiles of CLAMP in male and female cells and mRNA-seq data to define the role of CLAMP in regulating genes on the X-chromosome