Biology subjects

Naik, A.

Publications and source records attributed to Naik, A..

33 records · Page 2Linked to original sources

bioRxiv2023

SynerGPT: In-Context Learning for Personalized Drug Synergy Prediction and Drug Design

Predicting synergistic drug combinations can help accelerate discovery of cancer treatments, particularly therapies personalized to a patients specific tumor via biopsied cells. In this paper, we propose a novel setting and models for in-context drug synergy learning. We are given a small "personalized dataset" of 10-20 drug synergy relationships in the context of specific cancer cell targets. Our goal is to predict additional drug synergy relationships in that context. Inspired by recent work that pre-trains a GPT language model (LM) to "in-context learn" common function classes, we devise novel pre-training schemes that enable a GPT model to in-context learn "drug synergy functions". Our model--which does not use any textual corpora, molecular fingerprints, protein interaction or any other domain-specific knowledge-- is able to achieve competitive results. We further integrate our in-context approach with a genetic algorithm to optimize model prompts and select synergy candidates to test after conducting a patient biopsy. Finally, we explore a novel task of inverse drug design which can potentially enable the design of drugs that synergize specifically to target a given patients "personalized dataset". Our findings can potentially have an important impact on precision cancer medicine, and also raise intriguing questions on non-textual pre-training for LMs.

bioinformatics↗

bioRxiv2023

BEERS2: RNA-Seq simulation through high fidelity in silico modeling

Simulation of RNA-seq reads is critical in the assessment, comparison, benchmarking, and development of bioinformatics tools. Yet the field of RNA-seq simulators has progressed little in the last decade. To address this need we have developed BEERS2, which combines a flexible and highly configurable design with detailed simulation of the entire library preparation and sequencing pipeline. BEERS2 takes input transcripts (typically fully-length mRNA transcripts with polyA tails) from either customizable input or from CAMPAREE simulated RNA samples. It produces realistic reads of these transcripts as FASTQ, SAM, or BAM formats with the SAM or BAM formats containing the true alignment to the reference genome. It also produces true transcript-level quantification values. BEERS2 combines a flexible and highly configurable design with detailed simulation of the entire library preparation and sequencing pipeline and is designed to include the effects of polyA selection and RiboZero for ribosomal depletion, hexamer priming sequence biases, GC-content biases in PCR amplification, barcode read errors, and errors during PCR amplification. These characteristics combine to make BEERS2 the most complete simulation of RNA-seq to date. Finally, we demonstrate the use of BEERS2 by measuring the effect of several settings on the popular Salmon pseudoalignment algorithm.

bioinformatics↗

bioRxiv2023

Modulation of SLFN11 induces changes in DNA Damage response

BackgroundLack of Schlafen family member 11 (SLFN11) expression has been recently identified as a dominant genomic determinant of response to DNA damaging agents in numerous cancer types. Thus, strategies aimed at increasing SLFN11 could be used to restore chemosensitivity of refractory cancers. As oncogenic downregulation is often driven by methylation of the promotor region, we explore the demethylation effect of 5-aza-2-deoxycytidine (decitabine), on the SLFN11 gene methylation. Since SLFN11 has been reported as an interferon inducible gene, and interferon is secreted during an active anti-tumor immune response, we investigated the in vitro effect of IFN-{gamma} on SLFN11 expression in breast cancer cell lines. A second broader approach to show cross talk between immune cells and SLFN11 expression is indirect co-culture of breast cancer cells with activated PBMCs and evaluate if this can drive SLFN11 upregulation. Finally, as a definitive and specific way to modulate SLFN11 expression we implemented SLFN11 dCas9 (dead CRISPR associated protein 9) systems to specifically increase or decrease SLFN11 expression. ResultsWe first confirmed a correlation previously reported between methylation of SLFN11 promoter and its expression across multiple cell lines. We showed in-vitro that decitabine and IFN-{gamma} could increase moderately the expression of SLFN11 in both BT- 549 and T47D cell lines, but not in strongly methylated cell lines such as MDA-MB-231. Though, in-vitro, the co-culture of the same cell lines with CD8-CD25 activated PBMC failed to increase SLFN11 expression. On the one hand, the use of a CRISPR-dCas9 UNISAM system could increase SLFN11 expression significantly (up to 5-fold), stably and specifically in BT-549 and T47D cancer cell lines. Though, this system also failed to force a strong expression of SLFN11 in cell lines with robust SLFN11 promoter methylation such as MDA-MB-231. On the other hand, the use of CRISPR-dCas9 KRAB could significantly reduce the expression of SLFN11 in BT-549 and T47D. We then used the modified cell lines to confirm the alteration in chemo sensitivity of those cells to treatment with DNA Damaging Agents (DDAs) such as Cisplatin and Epirubicin or DNA Damage Response (DDRs) drugs like Olaparib. RNAseq was used to elucidate the mechanisms of action affected by the alteration in SLFN11 expression. ConclusionTo our knowledge this is the first report of the stable non-lethal increase of SLFN11 expression in a cancer cell line. Our results show that induction of SLFN11 expression can enhance DDA and DDR sensitivity in breast cancer cells and dCas9 systems may represent a novel approach to increase SLFN11 and achieve higher sensitivity to chemotherapeutic agents, improving outcome or decreasing required drug concentrations. SLFN11-targeting therapies might be explored pre-clinically to develop personalized approaches.

cancer biology↗

bioRxiv2023

Time-Resolved Chemical Phenotyping of Whole Plant Roots with Printed Electrochemical Sensors and Machine Learning

Plants are non-equilibrium systems consisting of time-dependent biological processes. Phenotyping of chemical responses, however, is typically performed using plant tissues, which behave differently to whole plants, in one-off measurements. Single point measurements cannot capture the information rich time-resolved changes in chemical signals in plants associated with nutrient uptake, immunity or growth. In this work, we report a high-throughput, modular, real-time chemical phenotyping platform for continuous monitoring of chemical signals in the often-neglected root environment of whole plants: TETRIS (Time-resolved Electrochemical Technology for plant Root In-situ chemical Sensing). TETRIS consists of screen-printed electrochemical sensors for monitoring concentrations of salt, pH and H2O2 in the root environment of whole plants. TETRIS can detect time-sensitive chemical signals and be operated in parallel through multiplexing to elucidate the overall chemical behavior of living plants. Using TETRIS, we determined the rates of uptake of a range of ions (including nutrients and heavy metals) in Brassica oleracea acephala. We also modulated ion uptake using the ion channel blocker LaCl3, which we could monitor using TETRIS. We developed a machine learning model to predict the rates of uptake of salts, both harmful and beneficial, demonstrating that TETRIS can be used for rapid mapping of ion uptake for new plant varieties. TETRIS has the potential to overcome the urgent "bottleneck" in high-throughput screening in producing high yielding plant varieties with improved resistance against stress.

bioengineering↗

bioRxiv2022

Structural surfaceomics reveals an AML-specific conformation of Integrin-β2 as a CAR-T therapy target

Safely expanding indications for cellular therapies has been challenging given a lack of highly cancer-specific surface markers. Here, we explore the hypothesis that tumor cells express cancer-specific surface protein conformations, invisible to standard target discovery pipelines evaluating gene or protein expression, that can be identified and immunotherapeutically targeted. We term this strategy, integrating cross-linking mass spectrometry (XL-MS) with glycoprotein surface capture, "structural surfaceomics". As a proof of principle, we apply this technology to acute myeloid leukemia, a hematologic malignancy with dismal outcomes and no known optimal immunotherapy target. We identify the activated conformation of integrin-{beta}2 as a structurally-defined, widely-expressed, AML-specific target. We develop and characterize recombinant antibodies to this protein conformation, and show that chimeric antigen receptor (CAR) T-cells eliminate AML cells and patient-derived xenografts without notable toxicity versus normal hematopoietic cells. Our findings validate an AML conformation-specific target antigen while demonstrating a toolkit for applying these strategies more broadly.

cancer biology↗

bioRxiv2021

Circadian regulation of lung repair and regeneration

Optimal lung repair and regeneration is essential for recovery from viral infections such as that induced by influenza A virus (IAV). We have previously demonstrated that lung inflammation induced by IAV is under circadian control. However, it is not known if the circadian clock exerts its influence on lung repair and regenerative processes independent of acute inflammation from IAV. Here, we demonstrate for the first time that lung organoids have a functional clock as they mature and that the absence of an intact circadian clock impairs regenerative capacity. Using several models of circadian disruption, we show that with the absence of an intact clock lung proliferation is disrupted. Further, we find that the circadian clock acts through direct control of the Wnt/{beta}-catenin pathway. We speculate, that adding the circadian dimension to the critical process of lung repair and regeneration will lead to novel therapies and improve outcomes. Finally, we use data from UK Biobank to demonstrate at the population level, the role of poor circadian rhythms in mediating negative outcomes following lung infection.

cell biology↗

bioRxiv2021

Probing neuropeptide volume transmission in vivo by a novel all-optical approach

Neuropeptides are essential signaling molecules in the nervous system involved in modulating neural circuits and behavior. Although hypothesized to signal via volume transmission through G-protein coupled receptors (GPCR), remarkably little is known about their extrasynaptic diffusion. Here, we developed an all-optical approach to probe neuropeptide volume transmission in mouse neocortex. To control neuropeptide release, we engineered photosensitive nanovesicles with somatostatin-14 (SST) that is released with near-infrared light stimulation. To detect SST, we created a new cell-based neurotransmitter fluorescent engineered reporter (CNiFER) using the SST2 GPCR. Under two-photon imaging, we determined the time to activate SST2R at defined distances as well as the maximal distance and loss rate for SST volume transmission in neocortex. Importantly, we determined that SST transmission is significantly faster in neocortex with a chemically degraded extracellular matrix, a diseased condition indicated in neuroinflammation and Parkinsons disease. These new neurotechnologies can reveal important biological signaling processes previously not possible, and provide new opportunities to investigate volume transmission in the brain.

neuroscience↗

bioRxiv2021

Targeting LDHC dysregulates the cell cycle and improves sensitivity to cisplatin and olaparib

The cancer testis antigen (CTA) lactate dehydrogenase C (LDHC) is a promising anti-cancer target with tumor-specific expression, immunogenicity and a role in metabolic reprogramming. Interrogation of the TCGA breast cancer cohort demonstrates upregulation of LDHC expression, conferring unfavorable prognosis. Although the role of LDHC is well characterized in spermatocytes, its role in tumors remains largely unknown. We investigated whether LDHC is involved in regulating genomic stability and may be targeted to affect tumor cellular fitness. Silencing LDHC in four breast cancer cell lines significantly increased the presence of giant cells and nuclear aberrations, DNA damage and apoptosis. LDHC silenced cells demonstrated aberrant cell cycle progression with differential expression of cell cycle checkpoint and DNA damage response regulators. In addition, LDHC silencing induced microtubule destabilization, culminating in increased mitotic catastrophe and reduced long-term survival. Notably, cisplatin and olaparib treatment further reduced survival of LDHC silenced cells. This study supports the therapeutic potential of targeting LDHC to mitigate cancer cell survival, and improve sensitivity to DNA damaging and DNA damage repair inhibiting agents.

cancer biology↗

bioRxiv2020

V-NeuroStack: 3D Time Stacks for Identifying Patterns in Calcium Imaging Data

BackgroundUnderstanding functional correlations between the activities of neuron populations is vital for the analysis of neuronal networks. Analyzing large-scale neuroimaging data obtained from hundreds of neurons simultaneously poses significant visualization challenges. We developed V-NeuroStack, a novel network visualization tool to visualize data obtained using calcium imaging of spontaneous activity of cortical neurons in a mouse brain slice. New MethodV-NeuroStack creates 3D time stacks by stacking 2D time frames for a period of 600 seconds. It provides a web interface that enables exploration and analysis of data using a combination of 3D and 2D visualization techniques. Comparison with existing MethodsPrevious attempts to analyze such data have been limited by the tools available to visualize large numbers of correlated activity traces. V-NeuroStack can scale data sets with at least a few thousand temporal snapshots. ResultsV-NeuroStacks 3D view is used to explore patterns in the dynamic large-scale correlations between neurons over time. The 2D view is used to examine any timestep of interest in greater detail. Furthermore, a dual-line graph provides the ability to explore the raw and first-derivative values of a single neuron or a functional cluster of neurons. ConclusionsV-NeuroStack enables easy exploration and analysis of large spatio-temporal datasets using two visualization paradigms: (a) Space-Time cube (b)Two-dimensional networks, via web interface. It will support future advancements in in vitro and in vivo data capturing techniques and can bring forth novel hypotheses by permitting unambiguous visualization of large-scale patterns in the neuronal activity data.

neuroscience↗

bioRxiv2019

Enhanced cytokine responsiveness in natural killer cells from a pilot cohort of uninfected seronegative women exposed to hepatitis C virus contaminated anti-D immunoglobulin

BackgroundSome people exposed to hepatitis C virus (HCV) appear to be capable of preventing infection in the absence of detectable antibody responses. These exposed seronegative (ESN) people appear naturally resistant to HCV infection. Here, we aimed to examine innate immune mechanisms in ESN individuals amongst rhesus negative Irish women exposed to HCV via contaminated anti-D immunoglobulin between 1977-79 and 1991-94.\n\nMethodsA total of 16 ESN individuals were recruited, along with 9 age- and gender-matched healthy controls. All tested negative for HCV-specific antibodies using conventional diagnostic assays. Peripheral blood cells were analysed for presence of adaptive immune response markers, innate immune responsiveness and natural killer cell phenotype and function.\n\nResultsThe innate immune cell profile of ESN women in the present study was characterised by a significant decrease in monocyte frequency and elevated levels of interleukin-8 and -18 compared to age- and gender-matched healthy controls. NK cells from ESN women had normal expression of NK cell receptors but increased IFN{gamma}-production upon cytokine and target cell stimulation as well as enhanced natural killer (NK) cell STAT3 phosphorylation in response to Type I IFN.\n\nConclusionsWe describe for the first time ESN individuals amongst Irish women with past exposure to HCV via contaminated anti-D immunoglobulin. NK cells from these ESN individuals are more responsive to cytokine signalling compared with age- and gender-matched controls. Human ESN cohorts can provide unique insights into the biological mechanisms associated with antigen-independent natural resistance to viral infection.

immunology↗

bioRxiv2019

An Addressable Microfluidics device for Noninvasive Manipulation of Cells and Chemicals within Live Cultures

According to the U.S. Department of Health & Human Services, nearly 115,000 people in the U.S needed a lifesaving organ transplant in 2018, while only [~]10% of them have received it. Yet, almost no artificial FDA-approved products are commercially available today - three decades after the inception of tissue engineering. It is hypothesized here that the major bottlenecks restricting its progress stem from lack of access to the inner pore space of the scaffolds. Specifically, the inability to deliver nutrients to, and clear waste from, the center of the scaffolds limits the size of the products that can be cultured. Likewise, the inability to monitor, and control, the cells after seeding them into the scaffold results in nonviable tissue, with an unacceptable product variability. To resolve these bottlenecks, we present a prototype addressable microfluidics device capable of minimally disruptive fluid and cell manipulations within living cultures. As proof-of-concept, we demonstrate its ability to perform additive manufacturing by seeding cells in spatial patterns (including co-culturing multiple cell types); and subtractive manufacturing by removing surface adherent cells via focused flow of trypsin. Additionally, we show that the device can sample fluids and perform cell "biopsies" (which can be subsequently sent for ex-situ analysis), from any location within its Culture Chamber. Finally, the on-chip plumbing is completely automated using external electronics. This opens the possibility to perform long-term computer-driven tissue engineering experiments, where the cell behavior is modulated in response to the minimally disruptive observations (e.g. fluid sampling and cell biopsies) throughout the entire duration of the cultures. It is expected that the proof-of-concept technology will eventually be scaled up to 3D addressable microfluidic scaffolds, capable of overcoming the limitations bottlenecking the transition of tissue engineering technologies to the clinical setting.

bioengineering↗

bioRxiv2019

Gli3 loss-of-function compromises vomeronasal neurogenesis, formation of olfactory ensheathing cells in the nasal mucosa, and GnRH-1 neuronal migration

During mammalian development, gonadotropin-releasing-hormone-1 neurons (GnRH-1ns) migrate from the developing vomeronasal organ (VNO) into the brain asserting control of pubertal onset and fertility. Recent data suggest that correct development of the olfactory ensheathing cells (OEC) is imperative for normal GnRH-1 neuronal migration. However, the full ensemble of molecular pathways that regulate OEC development remains to be fully deciphered. Loss-of-function of the transcription factor Gli3 is known to disrupt olfactory development, however, if Gli3 plays a role in GnRH-1 neuronal development is unclear. By analyzing Gli3 extra-toe mutants (Gli3Xt/Xt), we found that Gli3 loss-of-function compromises the onset of achaete-scute family bHLH transcription factor 1 (Ascl-1) positive vomeronasal progenitors and the formation of OEC in the nasal mucosa. Surprisingly, GnRH-1 neurogenesis was intact in Gli3Xt/Xt mice but they displayed significant defects in GnRH-1 neuronal migration. In contrast, Ascl-1null mutants showed reduced neurogenesis for both vomeronasal and GnRH-1ns but less severe defects in OEC development. These observations suggest that Gli3 is critical for OEC development in the nasal mucosa and subsequent GnRH-1 neuronal migration. However, the non-overlapping phenotypes between Ascl-1 and Gli3 mutants indicate that Ascl-1, while crucial for GnRH-1 neurogenesis, is not required for normal OEC development. Since Kallmann syndrome (KS) is characterized by abnormal GnRH migration, we examined whole exome sequencing data from KS subjects. We identified and validated a GLI3 loss-of-function variant in a KS individual. These findings provide new insights into GnRH-1 and OECs development and demonstrate that human GLI3 mutations contribute to KS etiology.\n\nSignificance statementThe transcription factor Gli3 is necessary for correct development of the olfactory system. However, if Gli3 plays a role in controlling GnRH-1 neuronal development has not been addressed. We found that Gli3 loss-of-function compromises the onset of Ascl1+ vomeronasal progenitors, formation of olfactory ensheathing cells in the nasal mucosa and impairs GnRH-1 neuronal migration to the brain. By analyzing Ascl1 null mutants we dissociated the neurogenic defects observed in Gli3 mutants from lack of olfactory ensheathing cells in the nasal mucosa, moreover, we discovered that Ascl1 is necessary for GnRH-1 ontogeny. Analyzing human whole exome sequencing data, we identified a GLI3 loss-of-function variant in a KS individual. Our data suggest that GLI3 is a candidate gene contributing to KS etiology.

developmental biology↗

bioRxiv2019

Local climate and social inequality drive spatio-temporal variation in malaria risk across a complex urban landscape

BackgroundCities are becoming increasingly important habitats for mosquito-borne infections. The pronounced heterogeneity of urban landscapes challenges our understanding of the spatio-temporal dynamics of these diseases, and of the influence of climate and socio-economic factors at different spatial scales. Here, we quantify this joint influence on malaria risk by taking advantage of an extensive dataset in both space and time for reported Plasmodium falciparum cases in the city of Surat, Northwest India. MethodsWe analyzed 10 years of monthly falciparum cases resolved at three nested spatial resolutions (for 7 zones, 32 units and 478 workers units subdivisions, respectively). With a Bayesian hierarchical mixed model that incorporates effects of population density, poverty, humidity and temperature, we investigate the main drivers of spatio-temporal malaria risk at the intermediate scale of districts. The significance of covariates and the model fit is then examined at lower and higher resolutions. FindingsThe spatial variation of urban malaria cases is strongly stationary in time, whereby locations exhibiting high and low yearly cases remain largely consistent across years. Local socio-economic variation can be summarized with two main principal components, representing poverty and population density respectively. The model that incorporates these two factors together with local temperature and global relative humidity, best explains monthly malaria patterns at the intermediate resolution. The effects of local temperature and population density remain significant at the finest spatial scale. We further identify the specific areas where such increased resolution improves model fit. InterpretationMalaria risk patterns within the city are largely driven by fixed spatial structures, highlighting the key role of local climate conditions and social inequality. As a result, malaria elimination efforts in the Indian subcontinent can benefit from identifying, predicting and targeting disease hotspots within cities. Spatio-temporal statistical models for the mesoscale of administrative units can inform control efforts, and be complemented with bespoke plans in the identified areas where finer scale data could be of value. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSUrban areas have become the new dominant ecosystem around the globe. Developing countries comprise the most urbanized regions of the world, with 80% of their population living in cities and an expected increase to 90% by 2050. The large and heterogeneous environments of today challenge the understanding and control of infectious disease dynamics, including of those transmitted by vectors. Malaria in the Indian subcontinent has an important urban component given the existence of a truly urban mosquito vector Anopheles stephensi. A literature search in Mendeley of "urban malaria" and "India" returned 161 publications, in their majority on diagnostics or brief reports on the disease, and on cross-sectional rather than longitudinal studies addressing the spatio-temporal variation of disease risk for a whole city, the subject of our work. A relevant exception is a study for the city of Ahmedabad; this not address multiple seasons across different spatial scales, and climatic conditions are not considered jointly with socio-economic drivers in the modeling. A second Mendeley search on A. stephensi returned 11 publications into two distinct groups: early entomological studies for India and recent reports of the mosquito in the Horn of Africa. This geographical expansion makes the specter of urban malaria a future possibility for the African continent where the disease remains so far rural and peri-urban. Added value of this studyThis paper relies on an extensive surveillance data set of Plasmodium falciparum cases for Surat (India) to investigate the variation and drivers of malaria risk in an heterogenous urban environment. A statistical model for the spatio-temporal variability of cases is developed, which includes both climatic and socio-economic drivers, with the latter summarized into two major axes of variation. Model fits are compared across three spatial resolutions, ranging from a few zones to a few hundred units. Seasonal hotspots are shown to be largely stationary in time, which allows identification of dominant drivers, including population density and local temperatures, whereas humidity acts globally modulating year-to-year burden. More granular statistical models and datasets like the one analyzed here are needed to capture the effects of socioeconomic and climatic drivers, and to predict current and future malaria incidence patterns within cities. Implications of all the available evidenceThe analysis identifies relevant resolution which can vary across the city for targeted intervention, including vector control, that would focus on reducing and eliminating transmission hotspots. The modeling framework, incorporating predictors representing climate at local vs. aggregate levels, and major axes of socio-economic variation, should apply to other vector-borne diseases and other cities for which surveillance records are available. The importance of spatially-explicit and sustained surveillance data for informing these models cannot be overstated.

ecology↗

bioRxiv2018

Cortex-wide neural interfacing via transparent polymer skulls

Neural computations occurring simultaneously in multiple cerebral cortical regions are critical for mediating cognition, perception and sensorimotor behaviors. Enormous progress has been made in understanding how neural activity in specific cortical regions contributes to behavior. However, there is a lack of tools that allow simultaneous monitoring and perturbing neural activity from multiple cortical regions. To fill this need, we have engineered \"See-Shells\" - digitally designed, morphologically realistic, transparent polymer skulls that allow long-term (>200 days) optical access to 45 mm2 of the dorsal cerebral cortex in the mouse. We demonstrate the ability to perform mesoscopic imaging, as well as cellular and subcellular resolution two-photon imaging of neural structures up to 600 {micro}m through the See-Shells. See-Shells implanted on transgenic mice expressing genetically encoded calcium (Ca2+) indicators allow tracking of neural activities from multiple, non-contiguous regions spread across millimeters of the cortex. Further, neural probes can access the brain through perforated See-Shells, either for perturbing or recording neural activity from localized brain regions simultaneously with whole cortex imaging. As See-Shells can be constructed using readily available desktop fabrication tools and modified to fit a range of skull geometries, they provide a powerful tool for investigating brain structure and function.

neuroscience↗

bioRxiv2016

Protein phosphatase 1 down regulates ZYG-1 levels to limit centrioleduplication

In humans perturbations of centriole number are associated with tumorigenesis and microcephaly, therefore appropriate regulation of centriole duplication is critical. The C. elegans homolog of Plk4, ZYG-1, is required for centriole duplication, but our understanding of how ZYG-1 levels are regulated remains incomplete. We have identified the two PP1 orthologs, GSP-1 and GSP-2, and their regulators I-2szy-2 and SDS-22 as key regulators of ZYG-1 protein levels. We find that down-regulation of PP1 activity either directly, or by mutation of szy-2 or sds-22 can rescue the loss of centriole duplication associated with a zyg-1 hypomorphic allele. Suppression is achieved through an increase in ZYG-1 levels, and our data indicate that PP1 normally regulates ZYG-1 through a post-translational mechanism. While moderate inhibition of PP1 activity can restore centriole duplication to a zyg-1 mutant, strong inhibition of PP1 in a wild-type background leads to centriole amplification via the production of more than one daughter centriole. Our results thus define a new pathway that limits the number of daughter centrioles produced each cycle.\n\nAuthor SummaryThe centrosomes are responsible for organizing the mitotic spindle a microtubule-based structure that centers, then segregates, the chromosomes during cell division. When a cell divides it normally possesses two centrosomes, allowing it to build a bipolar spindle and accurately segregate the chromosomes to two daughter cells. Appropriate control of centrosome number is therefore crucial to maintaining genome stability. Centrosome number is largely controlled by their regulated duplication. In particular, the protein Plk4, which is essential for duplication, must be strictly limited as an overabundance leads to excess centrosome duplication. We have identified protein phosphatase 1 as a critical regulator of the C. elegans Plk4 homolog (known as ZYG-1). When protein phosphatase 1 is down-regulated, ZYG-1 levels increase leading to centrosome amplification. Thus our work identifies a novel mechanism that limits centrosome duplication.

cell biology↗