Biology subjects

Zhang, S.

Publications and source records attributed to Zhang, S..

At least 1,153 records · Page 64Linked to original sources

bioRxiv2019

Synaptotagmin-7 endows a population of chromaffin cell vesicles with enhanced calcium sensing and delayed content release properties

Synaptotagmin-7 (Syt-7) is one of two major calcium sensors for exocytosis in adrenal chromaffin cells, the other being synaptotagmin-1 (Syt-1). Despite its undoubted importance, questions remain as to the functional and physiological role of Syt-7 in secretion. We examined this issue using two distinct preparations - mouse chromaffin cells lacking endogenous Syt-7 (KO cells) and a reconstituted system employing cell-derived vesicles expressing either Syt-7 or Syt-1. First, we report using immunofluorescence that Syt-7 exhibits a punctate intracellular distribution consistent with its sorting to organelles, including dense core vesicles. We also find that the likelihood of vesicle fusion in KO cells is markedly lower than in WT cells. When fusion does occur, cargoes are discharged more rapidly when only Syt-1 is available to facilitate release. A distinctive characteristic of KO cells is that secretion runs down after prolonged cholinergic stimulation. In contrast, exocytosis persists in WT cells even with extended exposure to acetylcholine, suggesting a key role for Syt-7 in sustaining the secretory response. To determine the extent to which the aforementioned results are attributable purely to Syt-7, vesicles expressing only Syt-7 or Syt-1 were triggered to fuse on planar supported bilayers bearing plasma membrane SNARE proteins. Here, as in cells, Syt-7 confers substantially greater calcium sensitivity to vesicle fusion than Syt-1 and slows the rate at which cargos are released. Overall, this study demonstrates that by virtue of its high affinity for calcium, Syt-7 plays a central role in regulating secretory output from adrenal chromaffin cells.

biophysics↗

bioRxiv2019

In situ, fluorescence lifetime-based measurements of cell membrane micromechanics

Microscopic in situ measurements of the mechanical properties of lipid bilayers were derived from the mean and variance of the fluorescence lifetime distributions of 1-dioctadecyl-3,3,33-tetramethylindocarbocyanine perchlorate (DiI). In this method, DiI, incorporated into membranes, acts as a membrane-targeted molecular rotor whose fluorescence lifetime is sensitive to local lipid viscosity. A new model was developed in which changes in area per lipid were derived from the first and second moments of a stretched exponential distribution of fluorescence lifetimes of DiI, which were subsequently used to compute mean area per lipid and its variance, quantities directly related to bilayer compressibility and bending moduli. This method enabled molecular scale assays of surface micromechanics of membrane-bound entities, such as nanoliposomes and human red blood cells.\n\nSTATEMENT OF SIGNIFICANCEDespite the progress in cell deformability studies, and in understanding mechanical properties of purified lipid bilayers, there has not, to date, been a method to measure the mechanics of the lipid bilayer in cells in situ. The current manuscript describes such a method. Using a fluorescent molecular rotor, DiI, embedded in the membrane, along with time resolved fluorescence, we directly measure area per lipid, and its temporal and spatial variance, properties directly related to bilayer mechanical moduli. Such a method will allow investigators to start exploring the relationship between lipid bilayer mechanics and cellular health and disease.

biophysics↗

bioRxiv2019

Cell growth kinetics and accumulation of secondary metabolite of Bletilla striata Rchb.f. using cell suspension culture

Bletilla striata (Orchidaceae) is a well-recognized endangered medicinal plant due to inadequate natural reproduction with high market worth. To evaluate the cell growth kinetics and accumulation of secondary metabolites (SMs), the cell suspension culture is proved to be a valuable approach for acquiring the high yield of medicinal parts. An effective cell suspension culture for obtaining B. striata cell growth and its SMs was in vitro induction of callus from B. striata seeds. The cell growth kinetics and accumulation of SMs were analyzed using the mathematical model. Results cell growth kinetic model revealed that the growth curve of B. striata suspension cells was curved as sigmoid shape, indicating the changes of the growth curve of suspension cells. Improved Murashige and Skoog cell growth medium was the utmost favorable medium for B. striata callus formation with the highest cell growth during the stationary phase of cultivation period, the cell growth acceleration was started after 7 days and thereafter gradually decrease at 24 day and then reached to highest at 36 day of cultivation period in both dry weight and fresh weight. The coelonin concentration was peak during exponential growth stage and decreased afterward at the stationary phase in the cell suspension culture. The maximum content of coelonin (about 0.3323 mg/g cell dry weight) was observed on the 18th day of the cultivation cycle while the dactylorhin A and militarine reached highest at 24 day, and p-hydroxybenzyl alcohol at 39 day. This investigation also laid a foundation for multi-mathematical model to better describe the accumulation variation of SMs. The production of SMs had shown great specificity during cells growth and development. This research provided a well-organized way to more accumulation and production of SMs, on scale-up biosynthesis in B. striata cell suspension culture.

plant biology↗

bioRxiv2019

Temporal changes in genetic admixture are linked to heterozygosity and health diagnoses in humans

Reproduction between individuals from different ancestral populations creates genetically admixed offspring. Admixture can have positive and negative impacts on individual health, feeding back to population health. Historical and forced migrations, and recent mobility, have brought formerly disparate populations of humans together. Here we sought to better understand how temporal changes in genetic admixture influence levels of heterozygosity and health outcomes. We evaluated variation in ancestry over 100 birth years in 35,842 individuals from a genetic database linked to health records in a population in the Southeastern United States. Analysis of 2,678 ancestrally informative markers revealed increased admixture and heterozygosity for all clinically-defined race groups since 1990. Most groups also exhibited increasing long-range linkage disequilibrium over time. A phenome-wide association study of clinical outcomes detected protective associations with female reproductive disorders and increased risk for diseases with links to autoimmunity dysfunction. These mixed effects have important ramifications for human health.

genetics↗

bioRxiv2019

The anti-apoptotic proteins Bcl-2 and Bcl-xL suppress Beclin1/Atg6-mediated lethal autophagy in polyploid cells

Inhibition of Aurora-B kinase is a synthetic lethal therapy for tumors that overexpress the MYC oncoprotein. It is currently unclear whether co-occurring oncogenic alterations might influence this synthetic lethality by confering more or less potency in the killing of tumor cells. To identify such modifers, we utilized isogenic cell lines to test a variety of cancer genes that have been previously demonstrated to promote survival under conditions of cellular stress, contribute to chemoresistance and/or suppress MYC-primed apoposis. We found that Bcl-2 and Bcl-xL, two antiapoptotic members of the Bcl-2 family, can partially suppress the synthetic lethality, but not multinucleation, elicited by a panaurora kinase inhibitor, VX-680. We demonstrate that this suppression stems from the rescue of autophagic cell death, specifically of multinucleated cells, rather than a general inhibition of apoptosis. Bcl-2 inhibits VX-680-induced death of polyploid cells by interacting with the autophagy protein Beclin1/Atg6 and rescue requires localization of Bcl-2 to the endoplasmic reticulum. These findings expand on previous conclusions that autophagic death of polyploid cells is mediated by Atg6. Bcl-2 and Bcl-xL negatively modulate MYC-VX-680 synthetic lethality and it is the anti-autophagic activity of these two Bcl-2 family proteins, specifically in multinucleate cells, that contributes to resistance to Aurora kinase-targeting drugs.

cancer biology↗

bioRxiv2019

Phosphoprotein-based Biomarkers as Predictors for Cancer Therapy

Disparities in cancer patient responses have prompted widespread searches to identify differences in sensitive vs. non-sensitive populations and form the basis of personalized medicine. This customized approach is dependent upon the development of pathway-specific therapeutics in conjunction with biomarkers that predict patient responses. Here, we show that Cdk5 drives growth in subgroups of human patients with multiple types of neuroendocrine neoplasms. Phosphoproteomics and high throughput screening identified novel phosphorylation sites downstream of Cdk5. These phosphorylation events serve as biomarkers of Cdk5 activity and effectively pinpoint Cdk5-driven tumors. Toward achieving targeted therapy, we demonstrate that mouse models of neuroendocrine cancer are responsive to selective Cdk5 inhibitors and biomimetic nanoparticles are effective vehicles for enhanced tumor targeting and reduction of drug toxicity. Finally, we show that biomarkers of Cdk5-dependent tumors effectively predict response to anti-Cdk5 therapy in patient-derived xenografts. Thus, a phosphoprotein-based diagnostic assay combined with Cdk5-targeted therapy is a rational treatment approach for neuroendocrine malignancies.

cancer biology↗

bioRxiv2019

Symmetry breaking transition towards directional locomotion in Physarum microplasmodia

True slime mold Physarum polycephalum has been widely used as a model organism to study flow-driven amoeboid locomotion as well as the dynamics of its complex mechanochemical self-oscillations. The aim of this work is to quantify the mechanical aspects of symmetry breaking and its transition into directional flow-driven amoeboid locomotion in small (<[~] 200 {micro}m) fragments of Physarum polycephalum. To this end, we combined measurements of traction stresses, fragment morphology, and ectoplasmic microrheology with experimental manipulations of cell-substrate adhesion, cortical strength and microplasmodium size. These measurements show that initiation of locomotion is accompanied by the symmetry breaking of traction stresses and the polarization of ectoplasmic mechanical properties, with the rear part of the microplasmodium becoming significantly stiffer after the onset of locomotion. Our experimental data suggests that the initiation of locomotion in Physarum could be analogous to an interfacial instability process and that microplasmodial size is a critical parameter governing the instability. Specifically, our results indicate that the instability driving the onset of locomotion is strengthened by substrate adhesiveness and weakened by cortical stiffness. Furthermore, the Fourier spectral analysis of morphology revealed lobe number n = 2 as the consistent dominant mode number across various experimental manipulations, suggesting that the instability mechanism driving the onset of Physarum locomotion is robust with respect to changes in environmental conditions and microplasmodial properties.

biophysics↗

bioRxiv2019

CRISPR-assisted targeted enrichment-sequencing (CATE-seq)

The current targeted sequencing of genome is mainly dependent on various hybridization-based methods. However, the hybridization-based methods are still limited by the intrinsic shortcomings of nucleic acid hybridization. This study developed a new CRISPR-based targeted sequencing technique, CRISPR-assisted targeted enrichment-sequencing (CATE-seq). In this technique, the input genomic DNA (gDNA) was firstly bound by a complex of dCas9 and capture sgRNA (csgRNA). The DNA-dCas9-csgRNA complex was then captured on magnetic beads through an easy room-temperature annealing between a short universal capture sequence (24 bp) at the 3' end of csgRNA and capture oligonucleotide coupled on magnetic beads. The enriched DNAs were finally analyzed by next generation sequencing. Using this technique, three different scales of targeted enrichments were successfully performed, including enriching 35 target exons of 6 genes from 6 gDNA samples with 54 csgRNAs, 339 target exons of 186 genes from 9 gDNA samples with 367 csgRNAs, and 2031 target exons of 451 genes from 2 gDNA samples with 2302 csgRNAs. This technique has several significant advantages over the current hybridization-based methods, including high simplicity, specificity, sensitivity, throughput, and scalability.

cancer biology↗

bioRxiv2019

Single-cell profiling guided combinatorial immunotherapy for fast-evolving CDK4/6 inhibitor resistant HER2-positive breast cancer

Development of acquired resistance to targeted cancer therapy is one of the most significant clinical challenges. Acquiring resistance under drug selection pressure is a result of evolutionary adaptation to a complex and dynamic tumor microenvironment (TME). New therapy regimens combining CDK4/6 inhibitor are under active investigation in clinical trials to treat HER2+ breast cancer patients. In parallel with clinical trial settings, in this study, we sought to prospectively model the tumor evolution in response to a targeted therapy regimen in vivo and identify a clinically actionable strategy to combat potential acquired resistance. Notably, despite a promising initial response, acquired resistance emerged rapidly to the anti-Her2/Neu antibody plus CDK4/6 inhibitor Palbociclib combination treatment. By leveraging high-throughput single-cell analyses of the evolving tumors over the course of treatments, we revealed a distinct immunosuppressive immature myeloid cell (IMC) population infiltrated in the resistant TME. Guided by single-cell transcriptome analysis, we demonstrated a combinatorial immunotherapy of IMC-targeting tyrosine kinase inhibitor cabozantinib and immune checkpoint blockades enhanced anti-tumor immunity, and overcame the resistance. Further, sequential combinatorial immunotherapy enabled a sustained control of the rapidly evolving CDK4/6 inhibitor-resistant tumors. Our study demonstrates a translational framework for treating rapidly evolving tumors through preclinical modeling and single-cell analyses. Our findings provide a rationale for an immediate clinical proposition of combinatorial immunotherapy for HER2+ breast cancer as a strategy to mitigate the emergence of resistance.

cancer biology↗

bioRxiv2019

Rab11b-mediated integrin recycling promotes brain metastatic adaptation and outgrowth

GRAPHICAL ABSTRACT\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=162 SRC=\"FIGDIR/small/666750v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (68K):\norg.highwire.dtl.DTLVardef@16dc0c4org.highwire.dtl.DTLVardef@8ab7e2org.highwire.dtl.DTLVardef@12e5acforg.highwire.dtl.DTLVardef@4bf298_HPS_FORMAT_FIGEXP M_FIG C_FIG SUMMARYBreast cancer brain metastases (BCBM) have a 5-20 year latency and account for up to 30% of mortality. Developing new therapeutics requires a molecular understanding of adaptation to the brain microenvironment. Here, we combined RNA-sequencing of BCBM development with a reverse genetic screen in Drosophila melanogaster and identified Rab11b, an endosomal recycling protein, as a mediator of metastatic adaptation. We show that disseminated cells up-regulate Rab11b early after arrival in the brain, allowing control of the cell surface proteome through recycling of proteins required for successful interaction with the microenvironment, including integrin {beta}1. Rab11b-mediated control of integrin {beta}1 surface expression allows ligation to the brain ECM, activating mechanotransduction signaling to allow survival and proliferation. We propose a model in which up-regulation of Rab11b allows disseminated cells to recycle needed proteins during metastatic adaptation, without strictly requiring transcription and translation, to allow for metastatic outgrowth.\n\nManuscript SummaryRab11b up-regulation in the brain microenvironment promotes recycling of cargo proteins required for breast cancer brain metastasis, including increased surface expression of integrin {beta}1, which allows brain extracellular matrix attachment and mechanotransduction. Inhibition of the mevalonate pathway with statins prevents geranylgeranylation of Rab11b, decreasing cargo recycling, and inhibiting brain metastasis.

cancer biology↗

bioRxiv2019

RanGTP induces an effector gradient of XCTK2 and importin α/β for spindle microtubule cross-linking

High RanGTP around chromatin is important for governing spindle assembly during meiosis and mitosis by releasing the inhibitory effects of importin /{beta}. Here we examine how the Ran gradient regulates Kinesin-14 function to control spindle organization. We show that Xenopus Kinesin-14, XCTK2, and importin /{beta} form an effector gradient, which is highest at the poles that diminishes toward the chromatin and is inverse of the RanGTP gradient. Importin /{beta} preferentially inhibit XCTK2 anti-parallel microtubule cross-linking and sliding by decreasing the microtubule affinity of the XCTK2 tail domain. This change in microtubule affinity enables RanGTP to target endogenous XCTK2 to the spindle. We propose that these combined actions of the Ran pathway are critical to promote Kinesin-14 parallel microtubule cross-linking at the spindle poles to cluster centrosomes in cancer cells. Furthermore, our work illustrates that RanGTP regulation in the spindle is not simply a switch, but rather generates effector gradients where RanGTP gradually tunes the activities of spindle assembly factors.\n\nSummaryEms-McClung et al. visualize a RanGTP effector gradient of association between XCTK2 and importin /{beta} in the spindle. The importins preferentially inhibit XCTK2-mediate anti-parallel microtubule cross-linking and sliding, which allows XCTK2 to cross-link parallel microtubules and help focus spindle poles.

cell biology↗

bioRxiv2019

A mouse model of recurrent myocardial infarction reports diminished emergency hematopoiesis and cardiac inflammation

Recurrent MI is common in patients with coronary artery disease and associates with high mortality. Here we developed a surgical mouse model in which two subsequent MIs affect different left ventricular regions in the same mouse. Recurrent MI was induced by ligating the left circumflex followed by the left anterior descending branch of the coronary artery. We characterized the resulting ischemia by whole-heart fluorescent coronary angiography after optical organ clearing and by cardiac MRI. We report that a first MI induces bone marrow \"memory\" via a circulating signal, thereby affecting hematopoietic factor expression in bone marrow macrophages. This altered the organisms reaction to subsequent events. Inspite at least similar extent of injury reported by blood troponin, recurrent MI caused reduced emergency hematopoiesis and less leukocytosis than a first MI. Consequently, fewer leukocytes migrated to the ischemic myocardium. The hematopoietic response to lipopolysaccharide was also mitigated after a previous MI. Our data suggest that hematopoietic and innate immune responses are shaped by a preceding MI.

physiology↗

bioRxiv2019

Let-7 miRNAs control auditory sensory progenitor behavior in the vertebrate inner ear

The evolutionary conserved lethal-7 (let-7) family of microRNAs (miRNAs) is a well-known activator of terminal mitosis and differentiation. Surprisingly, we previously found that overexpression of let-7 miRNAs in the murine auditory organ accelerated the terminal mitosis of auditory sensory progenitors (pro-sensory cells) but failed to stimulate their differentiation into mechano-sensory hair cells (HCs). To further address the role of let-7 miRNAs in auditory sensory differentiation, we conducted gain and loss of function experiments in the developing chicken auditory organ, the basilar papilla (BP). Using a sponge approach, we show that the disruption of let-7 miRNA function in the developing BP delays pro-sensory cell exit and delays differentiation of auditory HCs, revealing that endogenous let-7 miRNAs limit pro-sensory cell self-renewal in the developing BP. However, consistent with the role of let-7 miRNAs in the murine auditory organ, let-7b overexpression in the developing BP delayed HC differentiation, suggesting that too low or too high let-7 miRNA levels disrupt HC differentiation. Furthermore, we provide evidence that the repressive role of let-7 miRNAs in HC differentiation may be due to its targeting of the chromatin remodeler CHD7. Mutation in the human CHD7 gene causes CHARGE syndrome, which amongst others is characterized by inner ear and hearing deficits. Using target prediction algorithms, we uncovered a highly predictive and evolutionary conserved let-7 binding site within the Chd7 transcript. Consistent with being a target of let-7 repression, we demonstrate that let-7b overexpression significantly reduced CHD7 protein expression in to the developing BP. Furthermore, utilizing an inducible let-7g transgenic mouse model, we show that let-7 miRNAs negatively regulate CHD7 protein expression in developing murine cochlear, retinal and brain tissue. CHD7 is dosage dependent and the here described regulation by let-7 miRNAs may be critical to fine tune CHD7 protein levels during sensory and neuronal development.\n\nSIGNIFICANCEThe evolutionary highly conserved let-7 miRNAs are essential for proper timing of cell state transitions during embryogenesis. Even though abundantly expressed in the vertebrate auditory organ, surprisingly little is known about their function in auditory sensory differentiation. Here, we demonstrate that endogenous let-7 miRNAs are essential for limiting auditory sensory progenitor (pro-sensory) cell self-renewal. Furthermore, we find that precocious let-7 miRNAs expression interferes with auditory hair cell differentiation and identify chromatin remodeler CHD7 as a potential target gene of let-7 repressive function in HC differentiation.

developmental biology↗

bioRxiv2019

Interfacial energy constraints are sufficient to align cells over large distances

During development and wound healing, cells need to form long-ranged ordered structures to ensure precise formation of organs and repair damage. This requires cells to locate specific partner cells to which to adhere. How such cell matching reliably happens is an open problem, particularly in the presence of biological variability. Here, we use an equilibrium energy model to simulate how cell matching can occur with subcellular precision. A single parameter - encapsulating the competition between selective cell adhesion and cell compressibility - can reproduce experimental observations of cell alignment in the Drosophila embryonic heart. This demonstrates that adhesive differences between cells (in the case of the heart, mediated by filopodia interactions) are sufficient to drive cell matching without requiring cell rearrangements. The biophysical model can explain observed matching defects in mutant conditions and when there is significant biological variability. We also demonstrate that a dynamic vertex model gives results consistent with the equilibrium energy model. Overall, this work shows that equilibrium energy considerations are consistent with observed cell matching in cardioblasts, and has potential application to other systems, such as neuron connections and wound repair. Statement of SignificanceCells often need to identify specific neighboring cells, such as during wound repair and forming neural connections. Here, we develop a biophysical model of such cell-cell interactions within the context of the developing heart. We demonstrate that precise cell matching can occur by minimizing the energy costs of interfacial interactions. This model can explain a breadth of experimental observations despite it being a steady-state approximation of a dynamic system. This opens the possibility that such approaches may be applicable to other systems, providing a powerful yet simple framework for understanding cell matching.

systems biology↗

bioRxiv2019

NEAT1 involves Alzheimer’s Disease (AD) progression via regulation of glycolysis and P-tau

Nuclear paraspeckles assembly transcript 1 (NEAT1) is a well-known long noncoding RNA (LncRNA) with unclear mechanism in Alzheimers disease (AD) progression. Here, we found that NEAT1 down-regulates in the early stage of AD patients and APPswe/PS1dE9 mouse. Moreover, knockdown of NEAT1 induced de-polymerization of microtubule (MT) and axonal retraction of nerve cells by dysregulation of the FZD3/GSK3{beta}/p-tau signaling pathway. Histone acetylation analysis at the Frizzled Class Receptor 3 (FZD3) promoter shows a marked decreased in the levels of the H3K27 acetylation (H3K27Ac) after NEAT1 knockdown. Our data demonstrates that P300/CBP recruited by NEAT1 to the FZD3 promoter and induced its transcription via histone acetylation. In recent years a growing number of evidences have shown an abnormal brain glucose homeostasis in AD. In the present study we also observed an abnormal brain glucose homeostasis and enhanced sirtuin1 (SIRT1) activity after knockdown of NEAT similarly as in AD. Our results provided insight into the role of NEAT1 in the maintenance of MT stability and its effect on glucose metabolism during early stages of AD.

neuroscience↗

bioRxiv2019

A general LC/MS-based RNA sequencing method for direct analysis of multiple-base modifications in RNA mixtures

A complete understanding of the structural and functional potential of RNA requires understanding of chemical modifications and noncanonical bases; this in turn requires advances in current sequencing methods to be able to sequence not only canonical ribonucleotides, but at the same time directly sequence these nonstandard moieties. Here, we present the first direct and modification type-independent RNA sequencing method via integration of a hydrophobic end-labeling strategy with of 2-D mass-retention time LC/MS analysis to allow de novo sequencing of RNA mixtures and enhance sample usage efficiency. Our method can directly read out the complete sequence, while identifying, locating, and quantifying base modifications accurately in both single and mixed RNA samples containing multiple different modifications at single-base resolution. Our method can also quantify stoichiometry/percentage of modified RNA vs. its canonical counterpart RNA, simulating a real biological sample where modifications exist but may not be 100% at a particular site of the RNA. This method is a critical step towards fully sequencing real complex cellular RNA samples of any type and containing any modification types and can also be used in the quality control of modified therapeutic RNAs.

biochemistry↗

bioRxiv2019

Subcellular analyses of planarian meiosis implicates a novel, double-membraned vesiculation process in nuclear envelope breakdown

AO_SCPLOWBSTRACTC_SCPLOWThe cell nuclei of Ophisthokonts, the eukaryotic supergroup defined by fungi and metazoans, is remarkable in the constancy of both their double-membraned structure and protein composition. Such remarkable structural conservation underscores common and ancient evolutionary origins. Yet, the dynamics of disassembly and reassembly displayed by Ophisthokont nuclei vary extensively. Besides closed mitosis in fungi and open mitosis in some animals, little is known about the evolution of nuclear envelope break down (NEBD) during cell division. Here, we uncovered a novel form of NEBD in primary oocytes of the flatworm Schmidtea mediterranea. From zygotene to metaphase II, both nuclear envelope (NE) and peripheral endoplasmic reticulum (ER) expand notably in size, likely involving de novo membrane synthesis. 3-D electron microscopy reconstructions demonstrated that the NE transforms itself into numerous double-membraned vesicles similar in membrane architecture to NE doublets in mammalian oocytes after germinal vesicle breakdown. The vesicles are devoid of nuclear pore complexes and DNA, yet are loaded with nuclear proteins, including a planarian homologue of PIWI, a protein essential for the maintenance of stem cells in this and other organisms. Our data contribute a new model to the canonical view of NE dynamics and support that NEBD is an evolutionarily adaptable trait in multicellular organisms.

cell biology↗

bioRxiv2019

Hairless as a novel component of the Notch signaling pathway

Suppressor of Hairless [Su(H)], the transcription factor at the end of the Notch pathway in Drosophila, utilizes the Hairless protein to recruit two co-repressors, Groucho (Gro) and C-terminal Binding Protein (CtBP), indirectly. Hairless is present only in the Pancrustacea, raising the question of how Su(H) in other protostomes gains repressive function. We show that Su(H) from a wide array of arthropods, molluscs, and annelids includes motifs that directly bind Gro and CtBP; thus, direct co-repressor recruitment is ancestral in the protostomes. How did Hairless come to replace this ancestral paradigm? Our discovery of a protein (S-CAP) in Myriapods and Chelicerates that contains a motif similar to the Su(H)-binding domain in Hairless has revealed a likely evolutionary connection between Hairless and Metastasis-associated (MTA) protein, a component of the NuRD complex. Sequence comparison and widely conserved microsynteny suggest that S-CAP and Hairless arose from a tandem duplication of an ancestral MTA gene.

evolutionary biology↗