Search bioRxiv⌕ Search

Biology subjects

Kumar, A.

Publications and source records attributed to Kumar, A..

At least 541 records · Page 30Linked to original sources

Genome-wide SNP data unravel the ancestry and signatures of divergent selection in Ghurrah pigs of India

The evolution and domestication of pigs is a complex and ongoing process. Despite its rich biodiversity and proximity to the geographical origins of Sus scrofa domesticus, the place of Indian pigs in the global phylogeny is unclear. Using microarray-derived (porcine 60K SNP chip) genotypes of 11 Ghurrah pigs from North-Western India and a public dataset comprising 2113 pigs of 146 breeds, we determined the genomic ancestry of Ghurrah pigs and compared their genetic constitution to European and Asian breeds to ascertain signatures of divergent selection. Results showed that Ghurrah pigs contain genes of Asian and European ancestry with signs of inter-species introgression. Using Admixture LD - decay statistics, the European admixture event was dated to the recent past, coinciding with the start of cross-breeding efforts in India. The complex Asian ancestry pattern of the breed resembled that of wild boars of South - Central China and Thailand, possibly suggesting introgression from an Indian wild boar relative. FST and XP - EHH comparisons with Asian breeds highlighted divergent selection in genomic regions associated with odontogenesis and skeletal muscle development. Comparisons with European commercial breeds revealed that genomic regions governing olfaction and response to sensory stimulation were under selection in Ghurrah pigs. QTL for meat and carcass traits also showed divergent selection between European breeds and Ghurrah pigs. Our results present the first genomic characterization of an Indian pig breed using dense microarray-derived genotypes and highlight the importance of further genomic characterization of Indian domestic and wild pigs.

genomics↗

Degenerating Drosophila Larval Epidermal Cells Drive Thorax Closure

Adult thorax formation in Drosophila begins during pre-pupal development by fusion of its two contralateral progenitor halves, the heminotal epithelia (HE). HEs migrate and replace an underlying cell layer of thoracic larval epidermal cells (LECs) during a morphogenetic process called thorax closure. The LEC layer has so far been proposed to be a passive substrate over which HEs migrate before their zipping. By contrast, here we show that the pull forces generated within the LEC layer drive HE migration. During thorax closure, the LECs display actomyosin-mediated contraction, via enrichment of non-muscle myosin-II and actin, besides squamous-to-pseudostratified columnar epithelial transition and tissue shrinkage. This shrinkage of the LEC layer is further accompanied by cell extrusion and death, that prevent overcrowding of LECs, thereby promoting further shrinkage. The pull forces thus generated by the shrinking LEC layer are then relayed to the HEs by their mutual adhesions via {beta}PS1 (Mys) and PS3 (Scb) integrins. Suppression of cell death in the LEC layer by a gain of p35 leads to cell overcrowding, which impedes HE migration and zipping. Further, knockdown of sqh, the light chain of non-muscle myosin II, in LECs or integrins (mys or scb) in either the LEC layer or in the HEs, or both abrogate thorax closure. Mathematical modeling also reveals the biophysical underpinnings of the forces that drive this tissue closure process wherein a degenerating LEC layer mediates its succession by the future adult primodia. These essential principles of thorax closure appear ancient in origin and recur in multiple morphogenetic contexts and tissue repair.

developmental biology↗

SARS-CoV-2 NSP1 C-terminal region (residues 130-180) is an intrinsically disordered region

Nonstructural protein 1 (NSP1) of SARS-CoV-2 plays a key role in downregulation of RIG-I pathways and interacts with 40 S ribosome. Recently, the cryo-EM structure in complex with 40S ribosome is deciphered. However, the structure of full length NSP1 without any partner has not been studies. Also, the conformation of NSP1-C terminal region in isolation is not been studied. In this study, we have investigated the conformational dynamics of NSP1C-terminal region (NSP1-CTR; amino acids 130-180) in isolation and under different solvent environments. The NSP1-CTR is found to be intrinsically disordered in aqueous solution. Further, we used alpha helix inducer, trifluoroethanol, and found induction of alpha helical conformation using CD spectroscopy. Additionally, in the presence of SDS, NSP1-CTR is showing a conformational change from disordered to ordered, possibly gaining alpha helix in part. But in presence of neutral lipid DOPC, a slight change in conformation is observed. This implies the possible role of hydrophobic interaction and electrostatic interaction on the conformational changes of NSP1. The changes in structural conformation were further studied by fluorescence-based studies, which showed significant blue shift and fluorescence quenching in the presence of SDS and TFE. Lipid vesicles also showed fluorescence-based quenching. In agreement to these result, fluorescence lifetime and fluorescence anisotropy decay suggests a change in conformational dynamics. The zeta potential studies further validated that the conformational dynamics is mostly because of hydrophobic interaction. In last, these experimental studies were complemented through Molecular Dynamics (MD) simulation which have also shown a good correlation and testify our experiments. We believe that the intrinsically disordered nature of the NSP1-CTR will have implications in disorder based binding promiscuity with its interacting proteins.

biophysics↗

Ratio of hydrophobic-hydrophilic and positive-negative residues at lipid-water-interface influences surface expression and channel-gating of TRPV1

During evolution, TRPV1 has lost, retained or selected certain residues at Lipid-Water-Interface (LWI) and formed specific patterns there. The ratio of "hydrophobic-hydrophilic" and "positive-negative charged" residues at the inner LWI remains conserved throughout vertebrate evolution and play important role in regulating TRPV1 trafficking, localization and functions. Arg575 is an important residue as Arg575Asp mutant has reduced Capsaicin-sensitivity, surface expression, colocalization with lipid-raft markers, cell area, and increased cell lethality. This lethality is due to the disruption of the ratio between positive-negative charges there. Such lethality can be rescued by either using TRPV1-specfic inhibitor 5-IRTX or by restoring the positive-negative charge ratio at that position, i.e. by introducing Asp576Arg mutation in Arg575Asp backbone. We propose that Arg575Asp mutant confers TRPV1 in a "constitutive-open-like" condition. These findings have broader implication in understanding the molecular basis of thermo-gating and channel-gating and the microenvironments involved in such process that goes erratic in different diseases.

cell biology↗

Different evolutionary pathways of HIV-1 between fetus and mother perinatal transmission pairs indicate unique immune selection pressure in fetuses

Study of evolution and selection pressure on HIV-1 in fetuses will lead to a better understanding of the role of immune responses in shaping virus evolution and vertical transmission. Detailed genetic analyses of HIV-1 env gene from 12 in utero transmission pairs show that most infections (67%) occur within two months from childbirth. In addition, env sequences from long-term infected fetuses were highly divergent and formed separate phylogenetic lineages from their cognate maternal viruses. Host selection sites unique to infant viruses were identified in regions frequently targeted by broadly neutralizing antibodies and T cell immune responses. The identification of unique selection sites in the env gene of fetal viruses indicates that the immune system in fetuses is capable of exerting selection pressure on viral evolution. Studying selection and evolution of HIV-1 or other viruses in fetuses can be an alternative approach to investigate adaptive immunity in fetuses.

microbiology↗

Complete mitogenome of Kashmir musk deer (Moschus cupreus) and its comparative phylogenetic relationships

The endangered Kashmir musk deer (Moschus cupreus) is native to the high altitudinal region of the Himalayas. In this study, we sequenced, annotated and characterized the complete mitogenome of M. cupreus to gain insight into the molecular phylogeny and evolution of musk deer. The mitogenome of M. cupreus, which is 16,354 bp long comprised 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs) and non-coding control region. The M. cupreus mitogenome composition was highly A+T biased 68.42%, and exhibited a positive AT skew (0.082) and negative GC skew (0.307). The phylogenetic analysis suggested that KMD is the most primitive extant species in the genus Moschus whereas Alpine musk deer (M. chrysogaster) and Himalayan musk deer (M. leucogaster) are closely related. This result confirmed the placement of M. cupreus within the monotypic family Moschidae of musk deer. This study provides a better understanding of lineage identification and musk deer evolution for further research.

genetics↗

Genetic evidence indicates new distribution record of endangered Kashmir musk deer (Moschus cupreus) with range expansion in Uttarakhand, India

Kashmir musk deer, KMD (Moschus cupreus) is one the most threatened species reported from the Himalayan region of Kashmir, Pakistan and Afghanistan. A comprehensive and reliable distribution range of musk deer is still lacking. Recently, a molecular study confirmed the presence of KMD in Mustang in Nepal, west of Annapurna Himalayas. Here, we investigated the phylogenetic relationship of musk deer from Jammu and Kashmir (J&K), Kedarnath Wildlife Sanctuary (KWLS), and Nanda Devi Biosphere Reserve (NDBR), Uttarakhand region, India based on mitochondrial control region. The Bayesian phylogenetic analysis indicated a close genetic relationship between samples from J&K, KWLS and NDBR with identified lineages of KMD from Nepal with high posterior probabilities (PP[~]100). It confirmed that the musk deer lineage from the Uttarakhand region of KWLS (1025-3662 m) and NDBR (1800-7817 m) to be of KMD (M. cupreus) and hence a distinct Evolutionary Significant Unit (ESU). Besides, as per the IUCN database, the Western Himalayan region also holds the population of M. leucogaster and M. chrysogaster. Hence, we suggest extensive sampling for proper identification and validation of the geographic limits of musk deer species. We report for the first time the existence of KMD from the Uttarakhand region that we recommend to be updated in the IUCN database. It will assist in the effective conservation and management of this enigmatic endangered species.

genetics↗

Alternative catalytic mechanisms driven by structural plasticity is an emerging theme in HAS-GTPases, Era and FeoB

GTP hydrolysis is the underlying basis for functioning of biological switches or GTPases. Extensively studied GTPases, Ras and EF-Tu, use a conserved Gln/His that facilitates the activation of attacking water for nucleophilic attack. However, this is insufficient to explain catalysis in Hydrophobic Amino acid Substituted (HAS)-GTPases that naturally possess a hydrophobic residue in lieu of Gln/His. We had previously reported a bridging water-chain mediated catalytic mechanism for HAS-GTPase FeoB; which utilizes two distantly-located but conserved glutamates. Curiously, mutating these does not abolish GTP hydrolysis. Similarly, in this study we report our observations on another HAS-GTPase Era, wherein the mutants of catalytically important residues continue to hydrolyze GTP. We attempt to rationalize these inquisitive observations on GTP hydrolysis by FeoB and Era mutants. We propose a general theory that appears common to at least three classes of GTPases, where alternative mechanisms emerge when the primary mechanism is disrupted. Based on the analysis of crystal structures of FeoB and Era mutants, bound to the transition state analogue GDP.AlFx, this work suggests that in the absence of catalytically important residues, the active site waters in both FeoB and Era undergo re-arrangements, which in turn helps in sustaining GTP hydrolysis. Similar employment of alternative mechanisms was also suggested for the catalytic mutants of hGBP1. Importantly, such alternatives underscore the robustness of GTP hydrolysis mechanisms in these systems, and raise important questions regarding the need for persistent GTP hydrolysis and the physiological relevance of structural plasticity seen here.

biochemistry↗

C3' Stereocentre of Furanose Determines the Helicity of Double-Stranded Nucleic Acids: Towards Etiology of Nucleic Acids

The conformational landscape of 29-mer long four stereo variants of furanosal nucleic acids and their C2 deoxy counterparts were explored using molecular dynamics and well-tempered metadynamics simulations. The ribose containing double-stranded nucleic acids exhibit helical structure, however inversion of C3 and/or C2 stereocentre of ribose results in structural modification. The free energy surfaces relative to the average twist angle and end-to-end distances suggests that the configuration at the C3 position plays a pivotal role in determining the helicity. The C3 stereocentre acts as toggle-switch for helix to non-helical structures in double-stranded nucleic acids. Thus, the ribose containing double-stranded nucleic acids result in well-organized helical structures, while those containing xylose and lyxose show a variety of structures, which include (circular) ladder configurations. Based on the present set of results, it can be inferred that ribose containing double-stranded nucleic acids form well-defined helical structures in contrast to their C2 and C3 epimers.

biophysics↗

Phylogeography and population genetic structure of red muntjacs: Evidence of enigmatic Himalayan red muntjac from India

We investigated the phylogeographic pattern of red muntjac across its distribution range, intending to address the presence of distinct lineages from Northwest India. The Complete mitogenome analysis revealed that India holds three mitochondrial lineages of red muntjac, whereas four were identified from its entire distribution range: Himalayan red muntjac (M. (m.) aureus), Northern red muntjac (M. vaginalis), Srilankan and Western Ghat India (M. malabaricus) and Southern red muntjac (M. muntjak) from Sundaland. The newly identified Himalayan red muntjac found in the Northwestern part of India, which was previously described based on their morphological differences. Estimates of the divergence dating indicate that the Northwest and Northern lineage split during the late Pleistocene approximately 0.83 Myr (CI95%:0.53 to 1.26), which is the younger lineages, whereas M. malabaricus is the most primitive lineage among all the red muntjac. Microsatellite results also supported the mitochondrial data and evident the presence of three distinct genetic clusters within India. The pronounced climate fluctuation during the Quaternary period was considered as a critical factor influencing the current spatial distribution of forest-dwelling species that restricted themselves in northwest areas. Based on molecular data, this study provided evidence of a new lineage within the red muntjac group from India that required to be managed as an evolutionary significant unit (ESUs). It highlighted a need for the taxonomic revision of Himalayan red muntjac (M. (m.) aureus) and also suggested its conservation status under IUCN Red List.

evolutionary biology↗

High throughput detection and genetic epidemiology of SARS-CoV-2 using COVIDSeq next generation sequencing

The rapid emergence of coronavirus disease 2019 (COVID-19) as a global pandemic affecting millions of individuals globally has necessitated sensitive and high-throughput approaches for the diagnosis, surveillance and for determining the genetic epidemiology of SARS-CoV-2. In the present study, we used the COVIDSeq protocol, which involves multiplex-PCR, barcoding and sequencing of samples for high-throughput detection and deciphering the genetic epidemiology of SARS-CoV-2. We used the approach on 752 clinical samples in duplicates, amounting to a total of 1536 samples which could be sequenced on a single S4 sequencing flow cell on NovaSeq 6000. Our analysis suggests a high concordance between technical duplicates and a high concordance of detection of SARS-CoV-2 between the COVIDSeq as well as RT-PCR approaches. An in-depth analysis revealed a total of six samples in which COVIDSeq detected SARS-CoV-2 in high confidence which were negative in RT-PCR. Additionally, the assay could detect SARS-CoV-2 in 21 samples and 16 samples which were classified inconclusive and pan-sarbeco positive respectively suggesting that COVIDSeq could be used as a confirmatory test. The sequencing approach also enabled insights into the evolution and genetic epidemiology of the SARS-CoV-2 samples. The samples were classified into a total of 3 clades. This study reports two lineages B.1.112 and B.1.99 for the first time in India. This study also revealed 1,143 unique single nucleotide variants and added a total of 73 novel variants identified for the first time. To the best of our knowledge, this is the first report of the COVIDSeq approach for detection and genetic epidemiology of SARS-CoV-2. Our analysis suggests that COVIDSeq could be a potential high sensitivity assay for detection of SARS-CoV-2, with an additional advantage of enabling genetic epidemiology of SARS-CoV-2.

genomics↗

IL-4 receptor targeting as an effective immunotherapy against triple-negative breast cancer

In many solid tumors including triple-negative breast cancer (TNBC), IL-4 receptor (IL-4R) upregulation has been shown to promote cancer cell proliferation, apoptotic resistance, metastatic potential and a Th2 response in the tumor microenvironment (TME). Immunosuppressive cells in the TME including myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) also express the IL4-R. We hypothesized that selective depletion of IL4-R bearing cells in TNBC may have dual cytotoxic and immunotherapeutic benefit. To selectively target IL-4R+ cells, we genetically constructed, expressed and purified DABIL-4, a fusion protein toxin consisting of the catalytic and translocation domains of diphtheria toxin fused to murine IL-4. We found that DABIL-4 has potent and specific cytotoxic activity against TNBC cells in vitro. In murine TNBC models, DABIL-4 significantly reduced tumor growth, splenomegaly and lung metastases, and this was associated with reductions in MDSC, TAM and regulatory T-cells (Tregs) populations with a concomitant increase in the proportion of IFN{gamma}+ CD8 T-cells. The anti-tumor activity of DABIL-4 was absent in IL-4R KO mice directly implicating IL-4R directed killing as the mechanism of anti-tumor activity. Moreover, NanoString analysis of DABIL-4 treated TNBC tumors revealed marked decline in mRNA transcripts that promote tumorigenesis and metastasis. Our findings demonstrate that DABIL-4 is a potent targeted antitumor agent which depletes both IL-4R bearing tumor cells as well as immunosuppressive cell populations in the TME. STATEMENT OF SIGNIFICANCEIn solid tumors like breast cancer, Interleukin-4 receptor (IL-4R) expression in the tumor microenvironment aids tumor growth and metastasis. IL-4R expression upon host immune cells further dampens antitumor immunity. In this study, we have genetically constructed a fusion protein toxin, DABIL-4, composed of the catalytic and translocation domains of diphtheria toxin and murine IL-4. DABIL-4 showed specific cytotoxicity against triple-negative breast cancer (TNBC) cells in vitro. DABIL-4 also markedly inhibited TNBC tumor growth and metastasis in vivo. The primary activity of DABIL-4 was found to be depletion of IL-4R+ immune cells in combination with direct elimination of tumor cells. In conclusion, DABIL-4 targeting of both tumor and immunosuppressive host cells is a versatile and effective treatment strategy for TNBC.

immunology↗

The SWELL1-LRRC8 complex regulates endothelial AKT-eNOS-mTOR signaling and vascular function

The endothelium responds to a multitude of chemical and mechanical factors in regulating vascular tone, angiogenesis, blood pressure and blood flow. The endothelial volume regulatory anion channel (VRAC) has been proposed to be mechano-sensitive, to activate in response to fluid flow/hydrostatic pressure and putatively regulate vascular reactivity and angiogenesis. Here, we show that the Leucine Rich Repeat Containing Protein 8a, LRRC8a (SWELL1) functionally encodes VRAC in human umbilical vein endothelial cells (HUVECs). Endothelial SWELL1 (SWELL1) expression positively regulates AKT-eNOS signaling while negatively regulating mTOR signaling, via a SWELL1-GRB2-Cav1-eNOS signaling complex. Endothelium-restricted SWELL1 KO (SWELL1 KO) mice exhibit enhanced tube formation from ex-vivo aortic ring explants in matrigel angiogenesis assays, develop hypertension in response to chronic angiotensin II infusion and have impaired retinal blood flow with both diffuse and focal blood vessel narrowing in the setting of Type 2 diabetes (T2D). These data demonstrate that SWELL1 antithetically regulates AKT-eNOS and mTOR signaling in endothelium and is required for maintaining vascular function, particularly in the setting of T2D.

cell biology↗

Computational Properties of the Visual Microcircuit

The neocortex is organized around layered microcircuits consisting of a variety of excitatory and inhibitory neuronal types which perform rate-and oscillation based computations. Using modeling, we show that both superficial and deep layers of the primary mouse visual cortex implement two ultrasensitive and bistable switches built on mutual inhibitory connectivity motives between SST, PV and VIP cells. The switches toggle pyramidal neurons between high and low firing rate states that are synchronized across layers through translaminar connectivity. Moreover, inhibited and disinhibited states are characterized by low- and high frequency oscillations, respectively, with layer-specific differences in frequency and power which show asymmetric changes during state transitions. These findings are consistent with a number of experimental observations and embed firing rate together with oscillatory changes within a switch interpretation of the microcircuit.

neuroscience↗

3D-Visualization of Amyloid-β Oligomer and Fibril Interactions with Lipid Membranes by Cryo-Electron Tomography

Amyloid-{beta} (A{beta}) monomers assemble into mature fibrils via a range of metastable oligomeric and protofibrillar intermediates. These A{beta} assemblies have been shown to bind to lipid bilayers. This can disrupt membrane integrity and cause a loss of cellular homeostasis, that triggers a cascade of events leading to Alzheimers disease. However, molecular mechanisms of A{beta} cytotoxicity and how the different assembly forms interact with the membrane remain enigmatic. Here we use cryo-electron tomography (cryoET) to obtain three-dimensional nano-scale images of various A{beta} assembly types and their interaction with liposomes. A{beta} oligomers bind extensively to the lipid vesicles, inserting and carpeting the upper-leaflet of the bilayer. Furthermore, curvilinear protofibrils also insert into the bilayer, orthogonally to the membrane surface. A{beta} oligomers concentrate at the interface of vesicles and form a network of A{beta}-linked liposomes. While crucially, monomeric and fibrillar A{beta} have relatively little impact on the membrane. Changes to lipid membrane composition highlights a significant role for GM1-ganglioside in promoting A{beta}-membrane interactions. The different effects of A{beta} assembly forms observed align with the highlighted cytotoxicity reported for A{beta} oligomers. The wide-scale incorporation of A{beta} oligomers and curvilinear protofibrils into the lipid bilayer suggests a mechanism by which membrane integrity is lost.

biophysics↗

Accessible, Reproducible, and Scalable Machine Learning for Biomedicine

Supervised machine learning, where the goal is to predict labels of new instances by training on labeled data, has become an essential tool in biomedical data analysis. To make supervised machine learning more accessible to biomedical scientists, we have developed Galaxy-ML, a platform that enables scientists to perform end-to-end reproducible machine learning analyses at large scale using only a web browser. Galaxy-ML extends Galaxy, a biomedical computational workbench used by tens of thousands of scientists across the world, with a machine learning tool suite that supports end-to-end analysis.

bioinformatics↗

SWELL1-LRRC8 complex regulates skeletal muscle cell size, intracellular signalling, adiposity and glucose metabolism

Maintenance of skeletal muscle is beneficial in obesity and Type 2 diabetes. Mechanical stimulation can regulate skeletal muscle differentiation, growth and metabolism, however the molecular mechanosensor remains unknown. Here, we show that SWELL1 (LRRC8a) functionally encodes a swell-activated anion channel that regulates PI3K-AKT, ERK1/2, mTOR signaling, muscle differentiation, myoblast fusion, cellular oxygen consumption, and glycolysis in skeletal muscle cells. SWELL1 over-expression in SWELL1 KO myotubes boosts PI3K-AKT-mTOR signaling to supra-normal levels and fully rescues myotube formation. Skeletal muscle targeted SWELL1 KO mice have smaller myofibers, generate less force ex vivo, and exhibit reduced exercise endurance, associated with increased adiposity under basal conditions, and glucose intolerance and insulin resistance when raised on a high-fat diet, compared to WT mice. These results reveal that the SWELL1-LRRC8 complex regulates insulin-PI3K-AKT-mTOR signalling in skeletal muscle to influence skeletal muscle differentiation in vitro and skeletal myofiber size, muscle function, adiposity and systemic metabolism in vivo.

cell biology↗

Various RNA-binding proteins and their conditional networks explain miRNA biogenesis and help to reveal the potential SARS-CoV-2 host miRNAome system

Formation of mature miRNAs and their expression is a highly controlled process. It is very much dependent upon the post-transcriptional regulatory events. Recent findings suggest that several RNA binding proteins beyond Drosha/Dicer are involved in the processing of miRNAs. Deciphering of conditional networks for these RBP-miRNA interactions may help to reason the spatio-temporal nature of miRNAs which can also be used to predict miRNA profiles. In this direction, >25TB of data from different platforms were studied (CLIP-seq/RNA-seq/miRNA-seq) to develop Bayesian causal networks capable of reasoning miRNA biogenesis. The networks ably explained the miRNA formation when tested across a large number of conditions and experimentally validated data. The networks were modeled into an XGBoost machine learning system where expression information of the network components was found capable to quantitatively explain the miRNAs formation levels and their profiles. The models were developed for 1,204 human miRNAs whose accurate expression level could be detected directly from the RNA-seq data alone without any need of doing separate miRNA profiling experiments like miRNA-seq or arrays. A first of its kind, miRbiom performed consistently well with high average accuracy (91%) when tested across a large number of experimentally established data from several conditions. It has been implemented as an interactive open access web-server where besides finding the profiles of miRNAs, their downstream functional analysis can also be done. miRbiom will help to get an accurate prediction of human miRNAs profiles in the absence of profiling experiments and will be an asset for regulatory research areas. The study also shows the importance of having RBP interaction information in better understanding the miRNAs and their functional projectiles where it also lays the foundation of such studies and software in future.

bioinformatics↗