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Biology subjects

Xiang, Y.

Publications and source records attributed to Xiang, Y..

At least 91 records · Page 5Linked to original sources

Metabolic profiling stratifies colorectal cancer and reveals adenosylhomocysteinase as a therapeutic target

With colorectal cancer (CRC) being the second most common cause of cancer-related deaths worldwide1, there is an urgent need for better diagnostic tools and new, more targeted therapies. Here we used genetically engineered mouse models (GEMMs), and multimodal mass spectrometry-based metabolomics to study the impact of common genetic drivers of CRC on the metabolic landscape of the intestine. We show that unsupervised metabolic profiling can stratify intestinal tissues according to underlying genetic alterations, and use mass spectrometry imaging (MSI) to identify tumour, stromal and normal adjacent tissues. By identifying ions that drive variation between normal and transformed tissues, we found dysregulation of the methionine cycle to be a hallmark of APC-mutant CRC, and propose one of its enzymes, i.e. adenosylhomocysteinase (AHCY), as a new therapeutic target. Collectively, we show that the profound genotype-dependent alterations in both lipid and small molecule metabolism in CRC may be exploited for tissue classification with no need for ion identification, and we applied further data analysis to expose a novel metabolic vulnerability of CRC.

cancer biology↗

PD-L1 regulates inflammatory macrophage development from human pluripotent stem cells by maintaining interferon-gamma signal

PD-L1 (programmed death-ligand 1) serves as a pivotal immune checkpoint in both the innate and adaptive immune systems. PD-L1 is expressed in macrophages in response to interferon-gamma (IFN{gamma}). We examined whether PD-L1 might regulate macrophage development. We established PD-L1-/- human pluripotent stem cells, differentiated them into macrophages, and observed a 60% reduction of CD11B+CD45+ macrophages in PD-L1-/-, orthogonally verified with PD-L1 inhibitor BMS-1166 reduced macrophages to the same fold. Single-cell RNA sequencing further confirmed the 60% reduction of macrophages as well as the down-regulation of macrophage-defining transcription factors SPI1, KLF6, and MAFB. Further, PD-L1-/- macrophages reduced the level of inflammatory signals such as NF{kappa}B, TNF, and chemokines CXCL and CCL families. Whilst anti-inflammatory TGF-{beta} was upregulated. Finally, we identified that PD-L1-/- macrophages significantly down-regulated interferon-stimulated genes (ISGs) despite IFN{gamma} in differentiation media. Mechanistically, PD-L1-/- macrophages reduced IFNGR1 expression explaining that cells could not respond to IFN{gamma}. These data suggest that PD-L1 regulates inflammatory macrophage development by maintaining the IFN{gamma} signal.

immunology↗

Ring-finger protein 34 facilitates nervous necrosis virus evading antiviral innate immunity by targeting TBK1 and IRF3 for ubiquitination and degradation

Ubiquitination, as one of the most prevalent posttranslational modifications of proteins, enables a tight control on host immune responses. Many viruses hijack the host ubiquitin system to regulate host antiviral responses for their survival. Here, we found that fish pathogen nervous necrosis virus (NNV) recruited an E3 ubiquitin ligase ring finger protein 34 (RNF34) to inhibit RLRs-mediated interferons (IFN) response via ubiquitinating TBK1 and IRF3. Ectopic expression of RNF34 greatly enhances NNV replication and prevents IFN production, while deficiency of RNF34 led to the opposite effect. Furthermore, RNF34 targets TBK1 and IRF3 via its RING domain. Of note, the interactions between RNF34 and TBK1 or IRF3 were conserved in different fish species. Mechanically, RNF34 promote K27-linked ubiquitination and degradation of TBK1 and IRF3, which in turn diminishing TBK1-induced translocation of IRF3 from cytoplasm to nucleus. Ultimately, NNV capsid protein (CP) was found directly bind with RNF34 and this interaction was conserved in different fishes, and CP induced TBK1 and IRF3 degradation and IFN suppression was depended on RNF34. Our finding demonstrated a novel mechanism by which NNV CP evaded host innate immunity via RNF34, and provided a potential drug target for the control of NNV infection. Author SummaryUbiquitination plays an essential role in the regulation of innate immune responses to pathogens. NNV, a kind of RNA virus, is the causal agent of a highly destructive disease in a variety of marine and freshwater fish. Previous study reported NNV could hijack the ubiquitin system to manipulate the hosts immune responses, however, how NNV utilizes ubiquitination to facilitate its own replication is not well understood. Here, we identified a novel distinct role of E3 ubiquitin ligase RNF34 as an IFN antagonist to promote NNV infection. Nervous necrosis virus capsid protein utilized RNF34 to target TBK1 and IRF3 for K27 and K48-linked ubiquitination degradation. Importantly, the interactions between RNF34 and CP, TBK1 or IRF3 are conserved in different fishes, suggesting it is a general immune evasion strategy exploited by NNV to target the IFN response via RNF34.

immunology↗

Crosstalk between RNA m6A and DNA methylation regulates transposable element chromatin activation and cell fate in human pluripotent stem cells

Transposable elements (TEs) are parasitic DNA sequences accounting for over half of the human genome. Tight control of the repression and activation states of TEs is critical for genome integrity, development, immunity, and diseases, including cancer. However, precisely how this regulation is achieved remains unclear. To address this question, we develop a targeted proteomic proximity labeling approach to capture TE-associated proteins in human embryonic stem cells (hESCs). We find that the RNA N6-methyladenosine(m6A)-reader, YTHDC2, occupies genomic loci of the primate-specific TE, LTR7/HERV-H, specifically through its interaction with m6A-modified HERV-H RNAs. Unexpectedly, YTHDC2 recruits the DNA 5-methylcytosine(5mC)-demethylase, TET1, to remove 5mC from LTR7/HERV-H and prevent epigenetic silencing. Functionally, the YTHDC2/LTR7-axis inhibits neural differentiation of hESCs. Our results reveal both an underappreciated crosstalk between RNA m6A and DNA 5mC, the most abundant regulatory modifications of RNA and DNA in eukaryotes, and the fact that in hESCs this interplay controls TE activity and cell fate.

genetics↗

Organoid-based single-cell spatiotemporal gene expression landscape of human embryonic development and hematopoiesis

Single-cell level characterization of embryonic development is a major benchmark of human developmental biology. Spatiotemporal analysis of stem-cell-derived embryos offers conceptual and technical advances in the field. Here, we defined the single-cell spatiotemporal gene expression landscape of human embryonic development with stem-cell-derived organoids. We established the human embryonic organoid (HEMO) from expanded potential stem cells and achieved both embryonic and extraembryonic tissues in the same organoid. Time-series single-cell RNA sequencing paired with single-cell resolution spatial revealed human embryonic development signatures such as extraembryonic placenta, yolk sac hematopoiesis neural crest, blood vessels, and cardiac mesoderm. Hematopoietic tissues eventually predominated HEMO with erythropoiesis, mekagaryopiesis, and myelopoiesis. Cell-cell communication network analysis demonstrated that trophoblast-like tissues supplied WNT signaling in neural crest cells to facilitate maturation and migration. Single-cell resolution spatial transcriptomics defined the yolk sac erythro-megakaryopoietic niche. Vitronectin-integrin signaling, a major contributor to megakaryocyte maturation, was predominant in the yolk sac niche in HEMO and to human fetal samples. Overall, our study advances the spatiotemporal analysis of human embryonic development in stem-cell-derived organoids. HighlightsO_LIModeling human embryonic development from stem cells C_LIO_LIUsed of both 10X Chromium and 10X Visium to define the gene expression landscape of embryonic development and hematopoiesis C_LIO_LIWNT signaling as a regulator of neural crest maturation and EMT C_LIO_LIVTN-ITGA2B as the main contributor to Mk maturation within the yolk sac erythro-megakaryopoietic niche C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=158 HEIGHT=200 SRC="FIGDIR/small/505700v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@1710d00org.highwire.dtl.DTLVardef@10ca8e0org.highwire.dtl.DTLVardef@2310d1org.highwire.dtl.DTLVardef@252728_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

Cryo-EM complex structure of active GPR75 with a nanobody

Although there has been enormous progress in the last half-century in the drug discovery targeting obesity and associated co-morbidities, the clinical treatment of obesity remains tremendously challenging. GPR75 is an orphan receptor and is suggested to be a potential novel target for the control of obesity and related metabolic disorders. Inhibition of the GPR75 signaling pathway by small molecules, antibodies, or genetic manipulations may provide a therapeutic strategy for obesity. Here, we report the active-like Cryo-EM structure of human GPR75 with an intracellular nanobody, which reveals the receptor activation mechanism. The extensive interaction network required to achieve the active structure helps explain the allosteric coupling between the orthosteric pocket and the G-protein coupling domain. The well-defined orthosteric ligand binding pocket of human GPR75 provides a structural basis for anti-obesity drug discovery.

biophysics↗

Pore-forming protein βγ-CAT drives extracellular nutrient scavenging under cell starvation

Nutrient acquisition is essential for cells. {beta}{gamma}-CAT is a pore-forming protein (PFP) and trefoil factor complex assembled under tight regulation identified in toad Bombina maxima. Here, we reported that B. maxima cells secreted {beta}{gamma}-CAT under glucose and glutamine deficiency to scavenge extracellular proteins for their nutrient supply and survival. AMP-activated kinase signaling positively regulated the expression and secretion of {beta}{gamma}-CAT. The PFP complex promoted albumin and ovalbumin uptake through endolysosomal pathways. Elevated intracellular amino acids, enhanced ATP production, and eventually prolonged cell survival were observed in the presence of {beta}{gamma}-CAT and extracellular albumin or ovalbumin. Liposome assays indicated that high concentration of ATP (around 1-5 mM) negatively regulated the opening of {beta}{gamma}-CAT channels. Collectively, these results uncovered that {beta}{gamma}-CAT is an essential element in cell nutrient scavenging under cell starvation by driving vesicular uptake of extracellular proteins, providing a new paradigm for PFPs in cell nutrient acquisition and metabolic flexibility.

cell biology↗

Polyploidy, regular patterning of genome copies, and unusual control of DNA partitioning in the Lyme disease spirochete

Borrelia burgdorferi, the tick-transmitted spirochete agent of Lyme disease, has a highly segmented genome with a linear chromosome and various linear or circular plasmids. Here, by imaging several chromosomal loci and 16 distinct plasmids, we show that B. burgdorferi is polyploid during growth in culture and that the number of genome copies decreases during stationary phase. B. burgdorferi is also polyploid inside fed ticks and chromosome copies are regularly spaced along the spirochetes length in both growing cultures and ticks. This patterning involves the conserved DNA partitioning protein ParA whose localization is controlled by a potentially phage-derived protein, ParZ, instead of its usual partner ParB. ParZ binds its own coding region and acts as a centromere-binding protein. While ParA works with ParZ, ParB controls the localization of the condensin, SMC. Together, the ParA/ParZ and ParB/SMC pairs ensure faithful chromosome inheritance. Our findings underscore the plasticity of cellular functions, even those as fundamental as chromosome segregation.

microbiology↗

Spt6 directly interacts with Cdc73 and is required for Paf1C recruitment to active genes

Paf1C is a conserved transcription elongation factor that regulates transcription elongation efficiency, facilitates co-transcriptional histone modifications, and impacts molecular processes linked to RNA synthesis, such as polyA site selection. Coupling of the activities of Paf1C to transcription elongation requires its association with RNA polymerase II (Pol II). Mutational studies in yeast identified Paf1C subunits Cdc73 and Rtf1 as important mediators of Paf1C recruitment to Pol II on active genes. While the interaction between Rtf1 and the general elongation factor Spt5 is relatively well-understood, the interactions involving Cdc73 remain to be elucidated. Using an in vivo site-specific protein cross-linking strategy, we identified direct interactions between Cdc73 and two components of the elongation complex, the elongation factor Spt6 and the largest subunit of Pol II. Through in vitro protein binding assays and crosslinking/mass spectrometry, we show that Cdc73 and Spt6 can interact in the absence of additional factors and propose a binding interface. Rapid depletion of Spt6 dissociated Paf1 from chromatin and altered patterns of Paf1C-dependent histone modifications genome-wide. These results reveal previously unrecognized interactions between Cdc73 and the Pol II elongation complex and identify Spt6 as a key factor contributing to Paf1C recruitment to active genes in Saccharomyces cerevisiae.

molecular biology↗

Trophoblast and blood vessel organoid cultures recapitulate the role of WNT2B in promoting intravillous vascularization in human intrauterine and ectopic pregnancy

Tubal ectopic pregnancy (TEP), a pregnancy complication caused by aberrant implantation in fallopian tubes, accounts for 9-13% pregnancy-related deaths. The lack of models for human TEP hampers the understanding of its pathological mechanisms. Here, we employed multiple models to investigate the crosstalk between human trophoblast development and intravillous vascularization. We found that the severity of TEP, the size of placental villi, and the depth of trophoblast invasion are correlated with the extent of intravillous vascularization. We identified a key pro-angiogenic factor secreted by trophoblasts, WNT2B, that promotes villous vasculogenesis, angiogenesis, and vascular network expansion. In an organoid coculture model consisting of trophoblast organoids and blood vessel organoids, knockdown of WNT2B in trophoblast organoids compromises their pro-angiogenic effect on the development of blood vessel organoids. These organoid-based models reveal an important role for WNT-mediated angiogenesis in pregnancies and could be employed to investigate the commutations between trophoblasts and endothelial/endothelial progenitor cells.

cell biology↗

Dyslexia associated gene, KIAA0319, regulates cell cycle during human neuroepithelium development

Reading Disability (RD), also known as dyslexia, is defined as difficulty processing written language in individuals with normal intellectual capacity and educational opportunity. The prevalence of RD is between 5% and 17%, and the heritability ranges from 44% to 75%. Genetic linkage analysis and genome-wide association studies (GWAS) have identified several genes and regulatory elements linked to RD and reading ability. However, their functions and molecular mechanisms are not well understood. Prominent among these is KIAA0319, encoded in the DYX2 locus of human chromosome 6p22. Association of KIAA0319 has been independently replicated in multiple independent studies and languages. Rodent models suggest that KIAA0319 is involved in neuronal migration, but its precise function is unknown. This studies aim to determine the mechanisms by which KIAA0319 affects reading and language performance. We hypothesize that KIAA0319 plays a critical role in neuronal development. RT-qPCR and quantitative immunofluorescence in the cortical neurons differentiated from H7 hESC show regulatory effects on proliferation and differentiation of neuronal progenitor cells. Knockdown of KIAA0319 expression promotes early exit from the neuroepithelial cell stage and drives cells into cell cycle arrested neuronal progenitor cell stage. This suggests that KIAA0319 act by regulating neurogenesis in the reading related centers of the brain by targeting the cell cycle of proliferative cells. This demonstrates how subtle changes in expression could affect an isolated trait such as reading without global brain effects.

developmental biology↗

Conformational Flexibility in Neutralization of SARS-CoV-2 by Naturally Elicited Anti-SARS-CoV-2 Antibodies

As new variants of SARS-CoV-2 continue to emerge, it is important to assess the neutralizing capabilities of naturally elicited antibodies against SARS-CoV-2. In the present study, we evaluated the activity of nine anti-SARS-CoV-2 monoclonal antibodies (mAbs), previously isolated from convalescent donors infected with the Wuhan-Hu-1 strain, against the SARS-CoV-2 variants of concern (VOC) Alpha, Beta, Gamma, Delta and Omicron. By testing an array of mutated spike receptor binding domain (RBD) proteins, cell-expressed spike proteins from VOCs, and neutralization of SARS-CoV-2 VOCs as pseudoviuses, or as the authentic viruses in culture, we show that mAbs directed against the ACE2 binding site (ACE2bs) are far more sensitive to viral evolution compared to anti-RBD non-ACE2bs mAbs, two of which kept their potency against all VOCs tested. At the second part of our study, we reveal the neutralization mechanisms at high molecular resolution of two anti-SARS-CoV-2 neutralizing mAbs by structural characterization. We solved the structures of the Delta-neutralizing ACE2bs mAb TAU-2303 with the SARS-CoV-2 spike trimer and RBD at 4.5 [A] and 2.42 [A], respectively, revealing a similar mode of binding to that between the RBD and the ACE2 receptor. Furthermore, we provide five additional structures (at resolutions of 5.54 [A], 7.76 [A], 6.47 [A], 3.45 [A], and 7.32 [A]) of a second antibody, non-ACE2bs mAb TAU-2212, complexed with the SARS-CoV-2 spike trimer. TAU-2212 binds an exclusively quaternary epitope, and exhibits a unique, flexible mode of neutralization that involves transitioning between five different conformations, with both arms of the antibody recruited for cross linking intra- and inter-spike RBD subunits. Our study provides new mechanistic insights about how antibodies neutralize SARS-CoV-2 and its emerging variants and provides insight about the likelihood of reinfections.

immunology↗

Hetero-bivalent Nanobodies Provide Broad-spectrum Protection against SARS-CoV-2 Variants of Concern including Omicron

Following Delta, Omicron variant triggered a new wave of SARS-CoV-2 infection globally, adaptive evolution of the virus may not stop, the development of broad-spectrum antivirals is still urgent. We previously developed two hetero-bivalent nanobodies with potent neutralization against original WT SARS-CoV-2, termed aRBD-2-5 and aRBD-2-7, by fusing aRBD-2 with aRBD-5 or aRBD-7, respectively. Here, we resolved crystal structures of these nanobodies in complex with RBD, and found the epitope of aRBD-2 differs from that of aRBD-5, aRBD-7. aRBD-2 binds to a conserved epitope which renders its binding activity to all variants of concern (VOCs) including Omicron. Interestingly, although monovalent aRBD-5 and aRBD-7 lost binding to some variants, they effectively improved the overall affinity when transformed into the hetero-bivalent form after being fused with aRBD-2. Consistent with the high binding affinities, aRBD-2-5-Fc and aRBD-2-7-Fc exhibited ultra-potent neutralization to all five VOCs; particularly, aRBD-2-5-Fc neutralized authentic virus of Beta, Delta and Omicron with the IC50of 5.98[~]9.65 ng/mL or 54.3[~]87.6 pM. Importantly, aRBD-2-5-Fc provided in vivo prophylactic protection for mice against WT and mouse-adapted SARS-CoV-2, and provided full protection against Omicron in hamster model when administrated either prophylactically or therapeutically. Taken together, we found a conserved epitope on RBD, and hetero-bivalent nanobodies had increased affinity for VOCs over its monovalent form, and provided potent and broad-spectrum protection both in vitro and in vivo against all tested major variants, and potentially future emerging variants. Our strategy provides a new solution in the development of therapeutic antibodies for COVID-19 caused by newly emergent VOCs.

immunology↗

Reduced antigenicity of Omicron lowers host serologic response

SARS-CoV-2 Omicron variant of concern (VOC) contains fifteen mutations on the receptor binding domain (RBD), evading most neutralizing antibodies from vaccinated sera. Emerging evidence suggests that Omicron breakthrough cases are associated with substantially lower antibody titers than other VOC cases. However, the mechanism remains unclear. Here, using a novel geometric deep-learning model, we discovered that the antigenic profile of Omicron RBD is distinct from the prior VOCs, featuring reduced antigenicity in its remodeled receptor binding sites (RBS). To substantiate our deep-learning prediction, we immunized mice with different recombinant RBD variants and found that the Omicrons extensive mutations can lead to a drastically attenuated serologic response with limited neutralizing activity in vivo, while the T cell response remains potent. Analyses of serum cross-reactivity and competitive ELISA with epitope-specific nanobodies revealed that the antibody response to Omicron was reduced across RBD epitopes, including both the variable RBS and epitopes without any known VOC mutations. Moreover, computational modeling confirmed that the RBS is highly versatile with a capacity to further decrease antigenicity while retaining efficient receptor binding. Longitudinal analysis showed that this evolutionary trend of decrease in antigenicity was also found in hCoV229E, a common cold coronavirus that has been circulating in humans for decades. Thus, our study provided unprecedented insights into the reduced antibody titers associated with Omicron infection, revealed a possible trajectory of future viral evolution and may inform the vaccine development against future outbreaks.

immunology↗

Extensive in vitro and in vivo protein translation via in situ circularized RNAs

RNAs are a powerful therapeutic class. However their inherent transience impacts their activity both as an interacting moiety as well as a template. Circularization of RNA has been demonstrated as a means to improve persistence, however simple and scalable approaches to achieve this are lacking. Utilizing autocatalytic RNA circularization, here we engineer in situ circularized RNAs (icRNAs). This approach enables icRNA delivery as simple linear RNA that is circularized upon delivery into the cell, thus making them compatible with routine synthesis, purification, and delivery formulations. We confirmed extensive protein translation from icRNAs both in vitro and in vivo and explored their utility in three contexts: first, we delivered the SARS-CoV-2 Omicron spike protein in vivo as icRNAs and showed corresponding induction of humoral immune responses; second, we demonstrated robust genome targeting via zinc finger nucleases delivered as icRNAs; and third, to enable compatibility between persistence of expression and immunogenicity, we developed a novel long range multiplexed (LORAX) protein engineering methodology to screen progressively deimmunized Cas9 proteins, and demonstrated efficient genome and epigenome targeting via their delivery as icRNAs. We anticipate this highly simple and scalable icRNA methodology could have broad utility in basic science and therapeutic applications.

bioengineering↗

Interaction between photoperiod and variation in circadian rhythms in tomato

Many biological processes follow circadian rhythmicity and are controlled by the circadian clock. Predictable environmental changes such as seasonal variation in photoperiod can modulate circadian rhythms, allowing organisms to adjust to the time of the year. Modification of circadian clocks is especially relevant in crops to enhance their cultivability in specific regions by changing their sensibility to photoperiod. In tomato, the appearance of mutations in EMPFINDLICHER IM DUNKELROTEN LICHT 1 (EID1, Solyc09g075080) and NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED GENE 2 (LNK2, Solyc01g068560) during domestication delayed its circadian rhythms, and allowed its expansion outside its equatorial origin. Here we study how variation in circadian rhythms in tomato affects its perception of photoperiod. To do this, we create near isogenic lines carrying combinations of wild alleles of EID1 and LNK2 and perform transcriptomic profiling under two different photoperiods. We observe that EID1, but not LNK2, has a large effect on the tomato transcriptome and its response to photoperiod. This large effect of EID1 is likely a consequence of the global phase shift elicited by this gene in tomatos circadian rhythms.

plant biology↗

Control of Leaf Width by the APC/CTAD1-WL1-NAL1 Pathway in Rice

Leaf morphology is one of the most important features of the ideal plant architecture. However, the genetic and molecular mechanisms controlling leaf morphology in crops remain largely unknown, despite their central importance. Here we demonstrate that the APC/CTAD1-WL1-NAL1 pathway regulates leaf width in rice, and mutation of WL1 leads to width leaf variation. WL1 interacts with TAD1 and is degraded by APC/CTAD1, with the loss of TAD1 function resulting in narrow leaves. The WL1 protein directly binds to the regulatory region of NAL1 and recruits the corepressor TOPLESS-RELATED PROTEIN to inhibit NAL1 expression by down-regulating the level of histone acetylation of chromatin. Furthermore, biochemical and genetic analyses revealed that TAD1, WL1, and NAL1 function in a common pathway to control leaf width. Our study establishes an important framework for the APC/CTAD1-WL1-NAL1 pathway-mediated control of leaf width in rice and introduces novel perspectives for using this regulatory pathway for improving crop plant architecture.

plant biology↗

TrpA1 is a shear stress mechanosensing channel regulating intestinal homeostasis in Drosophila

Adult stem cells are essential for maintaining normal tissue homeostasis and supporting tissue repair. Although genetic and biochemical programs controlling adult stem cell behavior have been extensively investigated, how mechanosensing regulates stem cells and tissue homeostasis is not well understood. Here, we show that shear stress can activate enteroendocrine cells, but not other gut epithelial cell types, to regulate intestine stem cell-mediated gut homeostasis. This shear stress sensing is mediated by transient receptor potential A1 (TrpA1), a Ca2+-permeable ion channel that expressed only in enteroendocrine cells among all gut epithelial cells. Genetic depletion of TrpA1 or modification of its shear stress sensing function causes reduced intestine stem cell proliferation and intestine growth. We further show that among the TrpA1 splice variants, only select isoforms are activated by shear stress. Altogether, our results suggest the naturally occurring mechanical force such as fluid passing generated shear stress regulates intestinal stem cell-mediated tissue growth by activating enteroendocrine cells, and Drosophila TrpA1 as a new shear stress sensor.

developmental biology↗