Biology subjects

Tang, T.

Publications and source records attributed to Tang, T..

At least 55 records · Page 3Linked to original sources

bioRxiv2021

Functional evaluation of proteolytic activation for the SARS-CoV-2 variant B.1.1.7: role of the P681H mutation

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the agent causing the COVID-19 pandemic. SARS-CoV-2 B.1.1.7 (Alpha), a WHO variant of concern (VOC) first identified in the UK in late 2020, contains several mutations including P681H in the spike S1/S2 cleavage site, which is predicted to increase cleavage by furin, potentially impacting the viral cell entry. Here, we studied the role of the P681H mutation in B.1.1.7 cell entry. We performed assays using fluorogenic peptides mimicking the Wuhan-Hu-1 and B.1.1.7 S1/S2 sequence and observed no significant difference in furin cleavage. Functional assays using pseudoparticles harboring SARS-CoV-2 spikes and cell-to-cell fusion assays demonstrated no differences between Wuhan-Hu-1, B.1.1.7 or a P681H point mutant. Likewise, we observed no differences in viral growth between USA-WA1/2020 and a B.1.1.7 isolate in cell culture. Our findings suggest that while the B.1.1.7 P681H mutation may slightly increase S1/S2 cleavage this does not significantly impact viral entry or cell-cell spread. HighlightsO_LISARS-CoV-2 B.1.1.7 VOC has a P681H mutation in the spike that is predicted to enhance viral infection C_LIO_LIP681H does not significantly impact furin cleavage, viral entry or cell-cell spread C_LIO_LIOther mutations in the SARS-CoV-2 B.1.1.7 VOC may account for increased infection rates C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=134 SRC="FIGDIR/small/438731v2_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@c148d7org.highwire.dtl.DTLVardef@1954eeeorg.highwire.dtl.DTLVardef@171130dorg.highwire.dtl.DTLVardef@99bd45_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2021

Targeting properdin - Structure and function of a novel family of tick-derived complement inhibitors

Activation of the serum-resident complement system begins a cascade that leads to activation of membrane-resident complement receptors on immune cells, thus coordinating serum and cellular immune responses. Whilst many molecules act to control inappropriate activation, Properdin is the only known positive regulator of the human complement system. By stabilising the alternative pathway C3 convertase it promotes complement self-amplification and persistent activation boosting the magnitude of the serum complement response by all triggers. We have identified a novel family of alternative pathway complement inhibitors, hereafter termed CirpA. Functional and structural characterisation reveals that CirpA family directly bind to properdin, inhibiting its ability to promote complement activation, and leading to potent inhibition of the complement response in a species specific manner. For the first time this study provides a full functional and structural characterization of a properdin inhibitor, opening avenues for future therapeutic approaches.

immunology↗

bioRxiv2021

Weak effect of Gypsy retrotransposon bursts on Sonneratia alba salt stress gene expression

Background and AimsTransposable elements (TEs) are an important source of genetic diversity and can be co-opted for the regulation of host genes. However, to what extent the pervasive TE colonization of plant genomes has contributed to stress adaptation remains controversial. Plants inhabiting harsh environments in nature provide a unique opportunity to answer this question. MethodsWe compared TE compositions and their evolutionary dynamics in the genomes of two mangrove species: the pioneer Sonneratia alba and its less salt-tolerant relative S. caseolaris. Age distribution, strength of purifying selection and the removal rate of LTR (long terminal repeat) retrotransposons were estimated. Phylogenetic analysis of LTR retrotransposons and their distribution in the genome of S. alba were surveyed. Small RNA sequencing and whole-genome bisulfite sequencing was conducted using leaves of S. alba. Expression pattern of LTR retrotransposons and their nearby genes were examined using RNA-seq data of S. alba under different salt treatments. Key ResultsS. alba possesses more TEs than S. caseolaris. Particularly, many more young Gypsy LTR retrotransposons have accumulated in S. alba than in S. caseolaris despite an increase in purifying selection against TE insertions. The top two most abundant Gypsy families in S. alba preferentially insert in gene-poor regions. They are under relaxed epigenetic repression, probably due to the presence of CHROMO domains in their 3-ends. Although a considerable number of TEs in S. alba showed differential expression under salt stress, only four copies were significantly correlated with their nearby genes in expression levels. One such TE-gene pair involves Abscisic acid 8-hydroxylase 3 functioning in abscisic acid catabolism. ConclusionsThis study sheds light on the evolutionary dynamics and potential function of TEs in an extremophile. Our results suggest that the conclusion on co-option of TEs should be cautious even though activation of TEs by stress might be prevalent.

evolutionary biology↗

bioRxiv2021

Meeting experiments at the diffraction barrier: an in-silico widefield fluorescence microscopy

Fluorescence microscopy allows the visualization of live cells and their components, but even with advances in super- resolution microscopy, atomic resolution remains unattainable. On the other hand, molecular simulations (MS) can easily access atomic resolution, but comparison with experimental microscopy images has not been possible. In this work, a novel in-silico widefield fluorescence microscopy is proposed, which reduces the resolution of MS to generate images comparable to experiments. This technique will allow cross-validation and compound the knowledge gained from experiments and MS. We demonstrate that in-silico images can be produced with different optical axis, object focal planes, exposure time, color combinations, resolution, brightness and amount of out-of-focus fluorescence. This allows the generation of images that resemble those obtained from widefield, confocal, light-sheet, two-photon and super-resolution microscopy. This technique not only can be used as a standalone visualization tool for MS, but also lays the foundation for other in-silico microscopy methods.

biophysics↗

bioRxiv2021

Can we harness digital technologies and physiology to hasten genetic gain in U.S. maize breeding?

Genetic gain in breeding programs depends on the predictive skill of genotype-to-phenotype algorithms and precision of phenotyping, both integrated with well-defined breeding objectives for a target population of environments (TPE). The integration of physiology and genomics could improve predictive skill by capturing additive and non-additive interaction effects of genotype (G), environment (E), and management (M). Precision phenotyping at managed stress environments (MSEs) can elicit physiological expression of processes that differentiate germplasm for performance in target environments, thus enabling algorithm training. Gap analysis methodology enables design of GxM technologies for target environments by assessing the difference between current and attainable yields within physiological limits. Harnessing digital technologies such as crop growth model-whole genome prediction (CGM-WGP) and gap analysis, and MSEs, can hasten genetic gain by improving predictive skill and definition of breeding goals in the U.S. maize production TPE. A half-diallel maize experiment resulting from crossing 9 elite maize inbreds was conducted at 17 locations in the TPE and 6 locations at MSEs between 2017 and 2019. Analyses over 35 families represented by 2367 hybrids demonstrated that CGM-WGP offered a predictive advantage (y) compared to WGP that increased with occurrence of drought as measured by decreasing whole-season evapotranspiration (ET; log(y) = 0.80({+/-}0.6) - 0.006({+/-}0.001) x ET; r2 = 0.59; df = 21). Predictions of unobserved physiological traits using the CGM, akin to digital phenotyping, were stable. This understanding of germplasm response to ET enables predictive design of opportunities to close productivity gaps. We conclude that enabling physiology through digital methods can hasten genetic gain by improving predictive skill and defining breeding objectives bounded by physiological realities.

plant biology↗

bioRxiv2021

Extracellular vesicles mediate the intercellular exchange of nanoparticles

In order to exert their therapeutic effects, nanoparticles (NPs) often need to travel into the tissues composed of multilayered cells. Accumulative evidence has revealed the crucial role of transcellular transport route (entry into one cell, exocytosis, and re-entry into another) in this process. While NP endocytosis and subcellular transport have been intensively characterized, the exocytosis and re-entry steps are poorly understood, which becomes a barrier to improve NP delivery into complex tissues. Here, we termed the exocytosis and re-entry steps together as intercellular exchange. We developed a collagen-based 3D assay to specifically monitor and quantify the intercellular exchange events of NPs, and distinguish the contributions of several potential mechanisms. Our results showed that NPs can be exocytosed freely or enclosed inside extracellular vesicles (EVs) for re-entry, while direct cell-cell contact is hardly involved. EVs account for a significant fraction of NP intercellular exchange, and its importance in NP transport was demonstrated in vitro and in vivo. Intriguingly, while freely released NPs engage with the same cellular receptors for re-entry, EV-enclosed ones bypass this dependence. These studies provide an easy and precise system to investigate the intercellular exchange stage of NP delivery, and shed the first light in the importance of EVs in NP transport between cells and across complex tissues.

pharmacology and toxicology↗

bioRxiv2021

iRGD-liposomes enhance tumor delivery and therapeutic efficacy of antisense oligonucleotide drugs against primary prostate cancer and bone metastasis

Nucleotide-based drugs, such as antisense oligonucleotides (ASOs), have unique advantages in treating human diseases as they provide virtually unlimited ability to target any gene. However, their clinical translation faces many challenges, one of which is poor delivery to the target tissue in vivo. This problem is particularly evident in solid tumors. Here, we functionalized liposomes with a tumor-homing and -penetrating peptide, iRGD, as a carrier of an ASO against androgen receptor (AR) for prostate cancer treatment. The iRGD-liposomes exhibited a high loading efficiency of AR-ASO, and an efficient knockdown of AR gene products was achieved in vitro, including AR splice variants. In vivo, iRGD-liposomes significantly increased AR-ASO accumulation in the tumor tissue and decreased AR expression relative to free ASOs in prostate tumors established as subcutaneous xenografts. Similar results were obtained with intra-tibial xenografts modeling metastasis to bones, the predominant site of metastasis for prostate cancer. In treatment studies, iRGD-liposomes markedly improved the AR-ASO efficacy in suppressing the growth of both subcutaneous xenografts and intra-tibial xenografts. The inhibitory effect on tumor growth was also significantly prolonged by the delivery of the AR-ASO in the iRGD-liposomes. Meanwhile, iRGD-liposomes did not increase ASO accumulation or toxicity in healthy organs. Overall, we provide here a delivery system that can significantly increase ASO accumulation and efficacy in solid tumors. These benefits are achieved without significant side effects, providing a way to increase the antitumor efficacy of ASOs.

cancer biology↗

bioRxiv2020

Two decades of creating drought tolerant maize and underpinning prediction technologies in the US corn-belt: Review and perspectives on the future of crop design

Over the last decade, society witnessed the largest expansion of agricultural land planted with drought tolerant (DT) maize (Zea mays L.) Dedicated efforts to drought breeding led to development of DT maize. Here we show that after two decades of sustained breeding efforts the rate of crop improvement under drought is in the range 1.0-1.6% yr-1, which is higher than rates (0.7% yr-1) reported prior to drought breeding. Prediction technologies that leverage biological understanding and statistical learning to improve upon the quantitative genetics framework will further accelerate genetic gain. A review of published and unpublished analyses conducted on data including 138 breeding populations and 93 environments between 2009 and 2019 demonstrated an average prediction skill (r) improvement around 0.2. These methods applied to pre-commercial stages showed accuracies higher that current statistical approaches (0.85 vs. 0.70). Improvement in hybrid and management choice can increase water productivity. Digital gap analyses are applicable at field scale suggesting the possibility of transition from evaluating hybrids to designing genotype x management (GxM) technologies for target cropping systems in drought prone areas. Due to the biocomplexity of drought, research and development efforts should be sustained to advance knowledge and iteratively improve models. HighlightCrop improvement rate in maize increased after implementation of drought breeding efforts. Harnessing crop, quantitative genetics and gap models will enable the transition from genetic evaluation to crop design.

plant biology↗

bioRxiv2020

Proteolytic activation of the SARS-CoV-2 spike S1/S2 site: a re-evaluation of furin cleavage

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uses its spike (S) protein to mediate viral entry into host cells. Cleavage of the S protein at the S1/S2 and/or S2 site(s) is associated with viral entry, which can occur at either the cell plasma membrane (early pathway) or the endosomal membrane (late pathway), depending on the cell type. Previous studies show that SARS-CoV-2 has a unique insert at the S1/S2 site that can be cleaved by furin, which appears to expand viral tropism to cells with suitable protease and receptor expression. Here, we utilize viral pseudoparticles and protease inhibitors to study the impact of the S1/S2 cleavage on infectivity. Our results demonstrate that S1/S2 pre-cleavage is essential for early pathway entry into Calu-3 cells, a model lung epithelial cell line, but not for late pathway entry into Vero E6 cells, a model cell line. The S1/S2 cleavage was found to be processed by other proteases beyond furin. Using bioinformatic tools, we also analyze the presence of a furin S1/S2 site in related CoVs and offer thoughts on the origin of the insertion of the furin-like cleavage site in SARS-CoV-2.

microbiology↗

bioRxiv2020

Reproductive resilience but not root architecture underpin yield improvement in maize

Plants capture soil resources to produce the grains required to feed a growing population. Because plants capture water and nutrients through roots, it was proposed that changes in root systems architecture (RSA) underpin the three-fold increase in maize grain yield over the last century1,2,3,4. Within this framework, improvements in reproductive resilience due to selection are caused by increased water capture1. Here we show that both root architecture and yield have changed with decades of maize breeding, but not the water capture. Consistent with Darwinian agriculture5 theory, improved reproductive resilience6,7 enabled farmers increase the number of plants per unit land8,9,10, capture soil resources, and produced more dry matter and grain. Throughout the last century, selection operated to adapt roots to crowding, enabling reallocation of C from large root systems to the growing ear and the small roots of plants cultivated in high plant populations in modern agriculture.

plant biology↗

bioRxiv2020

FDA approved calcium channel blockers inhibit SARS CoV 2 infectivity in epithelial lung cells

COVID-19 is caused by a novel coronavirus, severe acute respiratory syndrome coronavirus (CoV)-2 (SARS-CoV-2). The virus is responsible for an ongoing pandemic and concomitant public health crisis around the world. While vaccine development is proving to be highly successful, parallel drug development approaches are also critical in the response to SARS-CoV-2 and other emerging viruses. Coronaviruses require Ca2+ ions for host cell entry and we have previously shown that Ca2+ modulates the interaction of the viral fusion peptide with host cell membranes. In an attempt to accelerate drug development, we tested a panel of L-type calcium channel blocker (CCB) drugs currently developed for other conditions, to determine whether they would inhibit SARS-CoV-2 infection in cell culture. All the CCBs tested showed varying degrees of inhibition, with felodipine and nifedipine strongly limiting SARS-CoV-2 entry and infection in epithelial lung cells at concentrations where cell toxicity was minimal. Further studies with pseudo-typed particles displaying the SARS-CoV-2 spike protein suggested that inhibition occurs at the level of virus entry. Overall, our data suggest that certain CCBs have potential to treat SARS-CoV-2 infections and are worthy of further examination for possible treatment of COVID-19.

microbiology↗

bioRxiv2020

Single-cell atlas of a non-human primate reveals new pathogenic mechanisms of COVID-19

Stopping COVID-19 is a priority worldwide. Understanding which cell types are targeted by SARS-CoV-2 virus, whether interspecies differences exist, and how variations in cell state influence viral entry is fundamental for accelerating therapeutic and preventative approaches. In this endeavor, we profiled the transcriptome of nine tissues from a Macaca fascicularis monkey at single-cell resolution. The distribution of SARS-CoV-2 facilitators, ACE2 and TMRPSS2, in different cell subtypes showed substantial heterogeneity across lung, kidney, and liver. Through co-expression analysis, we identified immunomodulatory proteins such as IDO2 and ANPEP as potential SARS-CoV-2 targets responsible for immune cell exhaustion. Furthermore, single-cell chromatin accessibility analysis of the kidney unveiled a plausible link between IL6-mediated innate immune responses aiming to protect tissue and enhanced ACE2 expression that could promote viral entry. Our work constitutes a unique resource for understanding the physiology and pathophysiology of two phylogenetically close species, which might guide in the development of therapeutic approaches in humans. Bullet pointsO_LIWe generated a single-cell transcriptome atlas of 9 monkey tissues to study COVID-19. C_LIO_LIACE2+TMPRSS2+ epithelial cells of lung, kidney and liver are targets for SARS-CoV-2. C_LIO_LIACE2 correlation analysis shows IDO2 and ANPEP as potential therapeutic opportunities. C_LIO_LIWe unveil a link between IL6, STAT transcription factors and boosted SARS-CoV-2 entry. C_LI

cell biology↗

bioRxiv2020

Surgery and Radioactive Iodine Therapeutic Strategy for Patients Greater than 60 Years of Age with Differentiated Thyroid Cancer

PurposeThe purpose of the current study was to determine whether older patients with differentiated thyroid cancer (DTC) who received surgical treatment had a better cause-specific survival (CSS) than patients who were recommended surgery, but declined, and whether patients who underwent post-operative RAI-131 therapy had an impact on CSS based on TNM staging and number of lymph node metastases for all total or near-total thyroidectomy patients. Patients and MethodsAll DTC patients information were obtained from the SEER*Stat 8.3.6 program, and only patients [≥] 60 years or older were considered. The patients were divided into two groups (underwent surgery and surgery recommend, but not performed). Furthermore, patients were grouped as follows: T4; N1b; M1; T1-3N0-1a; specific number of lymph node metastases; and total or near-total thyroidectomy. ResultsThe 120-month cause-specific survival (CSS) rate of females and males showed a gradual declining trend from 60-64 to [≥]80 years of age in the group that underwent surgery. The CSS rate of females and males showed a marked downward and irregular trend with an increase in age in the recommended, but no surgery group. Univariate analysis indicated that the surgery group had a higher 120-month CSS in females in most stages and males, compared with the no surgery group. RAI-131 therapy was associated with an improved 80-month CSS in T4/N1b/M1 females (P<0.0183) and males (P<0.0011). There was no CSS difference in females or males between the T1-3N0 and T1-3N1a patients. There was no statistical difference between the two subgroups. ConclusionsSurgical treatment should be recommended for elderly DTC patients because surgery can lead to a better CSS. High-risk patients achieve a higher benefit-to-risk ratio with RAI-131 therapy. To avoid the adverse effects associated with RAI-131 therapy, a multidisciplinary discussion should be arranged for intermediate- and low-risk patients.

cancer biology↗

bioRxiv2020

The Nonequilibrium Mechanism of Noise Enhancer synergizing with Activator in HIV Latency Reactivation

Reactivating HIV latency and then simultaneously eliminating it by antiretroviral therapy has become a leading strategy in curing HIV. Recently, single-cell screening experiments have shown the drug synergy between two categories of biomolecules, Activators (AC) and Noise Enhancers (NE): NE can amplify the reactivation of latent HIV induced by AC, although NE itself cannot reactivate HIV latency. Based on an established LTR-two-state effective model, we uncover two necessary conditions for this type of drug synergy: The decreasing of the turning-on rate of LTR induced by NE is highly inhibited when presented with AC; The timescale of LTR turning off without AC/NE presented should be no slower than the timescale of Tat transactivation. Then we propose a detailed LTR-four-state mechanistic model with both AC/NE regulation kinetics and Tat transactivation circuit. We show that, in order to achieve drug synergy, the system of HIV gene state transition must operate out of thermodynamic equilibrium, which is caused by energy input. The direction of energy input determines whether the inhibition of NE upon the reactivation rate of LTR-off states (unbinding of RNAP) can be successfully prevented in the presence of AC. The drug synergy can also be significantly enhanced if the energy input is appropriately distributed to more than one reaction. Our model reveals a generic nonequilibrium mechanism underpinning the noise enhanced drug synergy, which may apply to identify the same drug synergy on reactivating a diverse class of lentivirus latency. Significance StatementThe "kick and kill" strategy has become a promising way to cure HIV by eliminating latent HIV reservoirs, the main barrier to a clinical cure. Two categories of biomolecules, Activators (AC) and Noise Enhancers (NE), have been found to have synergy on reactivating latent HIV (kick strategy). We uncover the underlying non-equilibrium mechanism of such drug synergy by developing mathematical models based on genetic regulatory kinetics. We find that controlling the magnitude and direction of energy input into genetic regulatory kinetics can prevent NE from reducing the turn-on rate of the inactivated gene state in the presence of AC, which produces the synergy. This general nonequilibrium mechanism can be useful for identifying other drug synergies on lentivirus latency reactivation.

systems biology↗

bioRxiv2019

Ca2+ ions promote fusion of Middle East Respiratory Syndrome coronavirus with host cells and increase infectivity

Middle East respiratory syndrome coronavirus (MERS-CoV) is a major emerging zoonotic infectious disease. Since its first outbreak in 2012, the virus has repeatedly transmitted from camels to humans with 2,468 confirmed cases, causing 851 deaths. To date, there are no efficacious drugs and vaccines against MERS-CoV, increasing its potential to cause a public health emergency. A critical step in the life cycle of MERS-CoV is the fusion with the host cell with its spike (S) protein as main determinant of viral entry. Proteolytic cleavage of S exposes its fusion peptide (FP), which initiates membrane fusion. Previous studies on the related severe acute respiratory syndrome coronavirus (SARS-CoV) FP have shown that calcium (Ca2+) plays an important role for fusogenic activity via a Ca2+ binding pocket with conserved glutamic acid (E) and aspartic acid (D) residues. SARS-CoV and MERS-CoV FP share a high sequence homology and here, we investigated whether Ca2+ is required for MERS-CoV fusion by substituting E and D residues in the MERS-CoV FP with neutrally charged alanines. Upon verifying mutant cell surface expression and proteolytic cleavage, we tested the mutants ability to mediate infection of pseudo-particles (PPs) on host cells without and with Ca2+. Our results demonstrate that intracellular Ca2+ enhances MERS-CoV WT PPs infection by approximately two-fold and that E891 is a crucial residue for Ca2+ interaction. Electron spin resonance revealed that this enhancement could be attributed to Ca2+ increasing MERS-CoV FP fusion-relevant membrane ordering. Intriguingly, isothermal calorimetry titration showed that MERS-CoV FP binds one Ca2+, as opposed to SARS-CoV FP which binds two. Our data suggests that there are significant differences in FP-Ca2+ interactions of MERS-CoV and SARS-CoV FP despite their high sequence similarity and that the number of Ca2+ ions interacting with the FP has implications on the fusion dynamics of the virus.

microbiology↗

bioRxiv2019

Contrast-Enhanced, Molecular Imaging of Vascular Inflammation in the Mouse Model by Simultaneous PET/MRI

Despite advances in diagnosis and management, cardiovascular diseases (CVDs) remain the leading cause of death in the US. Atherosclerosis is the most common form of CVD and the vulnerability of atherosclerotic plaques to rupture is a primary determinant for risk of catastrophic ischemic events. Current imaging of atherosclerotic disease focuses on assessing plaque size and the degree of luminal stenosis, which are not good predictors of plaque stability. Functional methods to identify biomarkers of inflammation in plaques could facilitate assessment of plaque instability to allow early intervention. In this study, we validate the use of a purpose-built, magnetic resonance imaging (MRI)-compatible positron emission tomography (PET) insert for multimodal, molecular imaging of vulnerable plaques in mice. We illustrate the application of PET to screen for inflamed regions to guide the application of MRI. Molecular MRI visualizes regions of vascular inflammation and is coupled with anatomical MRI to generate detailed maps of the inflammatory marker within the context of an individual vessel. As a testbed for this imaging methodology, we developed a multimodal, iron oxide nanoparticle (NP) targeting vascular cell adhesion molecule-1 (VCAM-1) for simultaneous PET/MRI of vascular inflammation performed on a mouse carotid ligation model. In vitro cell studies confirmed that the NPs are not cytotoxic to liver cells. In vivo simultaneous PET/MRI imaging identified regions of inflammation. Three-dimensional rendering of the MRI data facilitated high-resolution visualization of patterns of inflammation along the injured vessel. Histology validated the co-localization of the NPs with VCAM-1 expression at sites of induced inflammation. The results of this work validate the utility of the simultaneous PET/MR insert as a research tool for small animals and lays groundwork to further advance the potential clinical utility of integrated imaging systems.

bioengineering↗

bioRxiv2019

Three-dimensional Structural Interrelations between Cells, Extracellular Matrix and Mineral in Vertebrate Mineralization

The spatial-temporal relationship between cells, extracellular matrices and mineral deposits is fundamental for an improved understanding mineralization mechanisms in vertebrate tissues. By utilizing focused ion beam-scanning electron microscopy with serial surface imaging, normally mineralizing avian tendons have been studied with nanometer resolution in three dimensions with volumes exceeding tens of microns in range. These parameters are necessary to yield fine ultrastructural details while encompassing tissue domains sufficient to provide a comprehensive overview of the interrelationships between the tissue structural constituents. Investigation reveals a novel complex cellular network in highly mineralized tendon aspects, where [~]100 nm diameter canaliculi emanating from cell (tenocyte) lacunae surround extracellular collagen fibril bundles. Canaliculi are linked to smaller channels of [~]40 nm diameter, occupying spaces between fibrils. Close to the tendon mineralization front, calcium-rich globules appear between the fibrils and, with time, mineral propagates along and within collagen. These close associations between tenocytes, canaliculi, small channels, collagen and mineral suggest a new concept for the mineralization process, where ions and/or mineral precursors may be transported through spaces between fibrils before they crystallize along the surface of and within the fibrils.\n\nSignificance StatementThe basic mechanism by which vertebrate collagenous tissues are mineralized is still not fully elucidated, despite the importance of this process for skeletal formation and regeneration. Through three-dimensional imaging of the cellular network together with the extracellular matrix and mineral deposits, the present work investigates normally mineralizing avian leg tendon as a model system for vertebrates in general. The data support a mechanism where mineral ions and possible mineral precursors are initially present in interfibrillar collagen spaces and are subsequently translocated to neighboring collagen fibrils. Mineral particles then nucleate in association with collagen to form the well known collagen-mineral composite material of the skeleton.

bioengineering↗

bioRxiv2019

Essential role of Bone morphogenetic protein 15 in porcine ovarian and follicular development and ovulation

Bone morphogenetic protein 15 (BMP15) is a multifunctional oocyte-specific secreted factor. It controls female fertility and follicular development in both species-specific and dosage-sensitive manners. Previous studies found that BMP15 played a critical role on follicular development and ovulation rate of mono-ovulatory mammalian species, but has minimal impact on poly-ovulatory mice. However, whether this is true in non-rodent poly-ovulatory species need to be validated. To investigate this question, we generated a BMP15 knockdown pig model. We found that BMP15 knockdown gilts showed markedly reduced fertility accompanied with phenotype of dysplastic ovaries containing significantly declined number of follicles, increased number of abnormal follicles, and abnormally enlarged antral follicles resulting in disordered ovulation. Molecular and transcriptome analysis revealed that knockdown of BMP15 significantly suppressed cell proliferation, differentiation, Fshr expression, leading to premature luteinization and reduced estradiol production in GCs, and simultaneously decreased the quality and meiotic maturation of oocyte. Our results provide in vivo evidences for the essential role of BMP15 in porcine ovarian and follicular development, and new insight into the complicated regulatory function of BMP15 in female fertility of poly-ovulatory species.

developmental biology↗