Asymmetric cell division is an important mechanism for creating diversity in a cellular population. Stem cells commonly perform asymmetric division to generate both a daughter stem cell for self-renewal and a more dif...Asymmetric cell division is an important mechanism for creating diversity in a cellular population. Stem cells commonly perform asymmetric division to generate both a daughter stem cell for self-renewal and a more differentiated daughter cell to populate the tissue. During asymmetric cell division, protein cell fate determinants asymmetrically localize to the opposite poles of a dividing cell to cause distinct cell fate. However, it remains unclear whether cell fate determination is robust to fluctuations and noise during this spatial allocation process. To answer this question, we engineered Caulobacter, a bacterial model for asymmetric division, to express synthetic scaffolds with modular protein interaction domains. These scaffolds perturbed the spatial distribution of the PleC-DivJ- DivK phospho-signaling network without changing their endogenous expression levels. Surprisingly, enforcing symmetrical distribution of these cell fate de terminants did not result in symmetric daughter fate or any morphological defects. Further computational analysis suggested that PleC and DivJ form a robust phospho-switch that can tolerate high amount of spatial variation. This insight may shed light on the presence of similar phospho-switches in stem cell asymmetric division regulation. Overall, our study demonstrates that synthetic protein scaffolds can provide a useful tool to probe biological systems for better understanding of their operating principles.展开更多
High-speed high-resolution imaging of the whole-brain hemodynamics is critically important to facilitating neurovascular research.High imaging speed and image quality are crucial to visualizing real-time hemodynamics ...High-speed high-resolution imaging of the whole-brain hemodynamics is critically important to facilitating neurovascular research.High imaging speed and image quality are crucial to visualizing real-time hemodynamics in complex brain vascular networks,and tracking fast pathophysiological activities at the microvessel level,which will enable advances in current queries in neurovascular and brain metabolism research,including stroke,dementia,and acute brain injury.Further,real-time imaging of oxygen saturation of hemoglobin(sO_(2))can capture fast-paced oxygen delivery dynamics,which is needed to solve pertinent questions in these fields and beyond.Here,we present a novel ultrafast functional photoacoustic microscopy(UFF-PAM)to image the whole-brain hemodynamics and oxygenation.UFF-PAM takes advantage of several key engineering innovations,including stimulated Raman scattering(SRS)based dual-wavelength laser excitation,water-immersible 12-facet-polygon scanner,high-sensitivity ultrasound transducer,and deep-learning-based image upsampling.A volumetric imaging rate of 2 Hz has been achieved over a field of view(FOV)of 11×7.5×1.5 mm^(3) with a high spatial resolution of~10 μm.Using the UFF-PAM system,we have demonstrated proof-of-concept studies on the mouse brains in response to systemic hypoxia,sodium nitroprusside,and stroke.We observed the mouse brain's fast morphological and functional changes over the entire cortex,including vasoconstriction,vasodilation,and deoxygenation.More interestingly,for the first time,with the whole-brain FOV and micro-vessel resolution,we captured the vasoconstriction and hypoxia simultaneously in the spreading depolarization(SD)wave.We expect the new imaging technology will provide a great potential for fundamental brain research under various pathological and physiological conditions.展开更多
Colorectal cancer is a leading cause of cancer deaths.Most colorectal cancer patients eventually develop chemoresistance to the current standard-of-care therapies.Here,we used patient-derived colorectal cancer organoi...Colorectal cancer is a leading cause of cancer deaths.Most colorectal cancer patients eventually develop chemoresistance to the current standard-of-care therapies.Here,we used patient-derived colorectal cancer organoids to demonstrate that resistant tumor cells undergo significant chromatin changes in response to oxaliplatin treatment.Integrated transcriptomic and chromatin accessibility analyses using ATAC-Seq and RNA-Seq identified a group of genes associated with significantly increased chromatin accessibility and upregulated gene expression.CRISPR/Cas9 silencing of fibroblast growth factor receptor 1(FGFR1)and oxytocin receptor(OXTR)helped overcome oxaliplatin resistance.Similarly,treatment with oxaliplatin in combination with an FGFR1 inhibitor(PD166866)or an antagonist of OXTR(L-368,899)suppressed chemoresistant organoids.However,oxaliplatin treatment did not activate either FGFR1 or OXTR expression in another resistant organoid,suggesting that chromatin accessibility changes are patient-specific.The use of patient-derived cancer organoids in combination with transcriptomic and chromatin profiling may lead to precision treatments to overcome chemoresistance in colorectal cancer.展开更多
文摘Asymmetric cell division is an important mechanism for creating diversity in a cellular population. Stem cells commonly perform asymmetric division to generate both a daughter stem cell for self-renewal and a more differentiated daughter cell to populate the tissue. During asymmetric cell division, protein cell fate determinants asymmetrically localize to the opposite poles of a dividing cell to cause distinct cell fate. However, it remains unclear whether cell fate determination is robust to fluctuations and noise during this spatial allocation process. To answer this question, we engineered Caulobacter, a bacterial model for asymmetric division, to express synthetic scaffolds with modular protein interaction domains. These scaffolds perturbed the spatial distribution of the PleC-DivJ- DivK phospho-signaling network without changing their endogenous expression levels. Surprisingly, enforcing symmetrical distribution of these cell fate de terminants did not result in symmetric daughter fate or any morphological defects. Further computational analysis suggested that PleC and DivJ form a robust phospho-switch that can tolerate high amount of spatial variation. This insight may shed light on the presence of similar phospho-switches in stem cell asymmetric division regulation. Overall, our study demonstrates that synthetic protein scaffolds can provide a useful tool to probe biological systems for better understanding of their operating principles.
基金This work was sponsored by the National Institutes of Health(R01 EB028143,RO1 NS111039,RF1 NS115581,R21 EB027304,R21EB027981,R43 CA243822,R43 CA239830,R44 HL138185)American Heart Association Collaborative Sciences Award(18CSA34080277)Chan Zuckerberg Initiative Grant on Deep Tissue Imaging 2020-226178 by Silicon Valley Community Foundation.
文摘High-speed high-resolution imaging of the whole-brain hemodynamics is critically important to facilitating neurovascular research.High imaging speed and image quality are crucial to visualizing real-time hemodynamics in complex brain vascular networks,and tracking fast pathophysiological activities at the microvessel level,which will enable advances in current queries in neurovascular and brain metabolism research,including stroke,dementia,and acute brain injury.Further,real-time imaging of oxygen saturation of hemoglobin(sO_(2))can capture fast-paced oxygen delivery dynamics,which is needed to solve pertinent questions in these fields and beyond.Here,we present a novel ultrafast functional photoacoustic microscopy(UFF-PAM)to image the whole-brain hemodynamics and oxygenation.UFF-PAM takes advantage of several key engineering innovations,including stimulated Raman scattering(SRS)based dual-wavelength laser excitation,water-immersible 12-facet-polygon scanner,high-sensitivity ultrasound transducer,and deep-learning-based image upsampling.A volumetric imaging rate of 2 Hz has been achieved over a field of view(FOV)of 11×7.5×1.5 mm^(3) with a high spatial resolution of~10 μm.Using the UFF-PAM system,we have demonstrated proof-of-concept studies on the mouse brains in response to systemic hypoxia,sodium nitroprusside,and stroke.We observed the mouse brain's fast morphological and functional changes over the entire cortex,including vasoconstriction,vasodilation,and deoxygenation.More interestingly,for the first time,with the whole-brain FOV and micro-vessel resolution,we captured the vasoconstriction and hypoxia simultaneously in the spreading depolarization(SD)wave.We expect the new imaging technology will provide a great potential for fundamental brain research under various pathological and physiological conditions.
基金WethankDukeCenterforGenomicandComputational Biology sequencingcorefacilityforresearchsupport.This work wassupportedbyNIHNCIU01CA217514andU01 CA214300.
文摘Colorectal cancer is a leading cause of cancer deaths.Most colorectal cancer patients eventually develop chemoresistance to the current standard-of-care therapies.Here,we used patient-derived colorectal cancer organoids to demonstrate that resistant tumor cells undergo significant chromatin changes in response to oxaliplatin treatment.Integrated transcriptomic and chromatin accessibility analyses using ATAC-Seq and RNA-Seq identified a group of genes associated with significantly increased chromatin accessibility and upregulated gene expression.CRISPR/Cas9 silencing of fibroblast growth factor receptor 1(FGFR1)and oxytocin receptor(OXTR)helped overcome oxaliplatin resistance.Similarly,treatment with oxaliplatin in combination with an FGFR1 inhibitor(PD166866)or an antagonist of OXTR(L-368,899)suppressed chemoresistant organoids.However,oxaliplatin treatment did not activate either FGFR1 or OXTR expression in another resistant organoid,suggesting that chromatin accessibility changes are patient-specific.The use of patient-derived cancer organoids in combination with transcriptomic and chromatin profiling may lead to precision treatments to overcome chemoresistance in colorectal cancer.
