Biology subjects

Su, B.

Publications and source records attributed to Su, B..

At least 55 records · Page 3Linked to original sources

bioRxiv2023

Generation of eco-friendly channel catfish, Ictalurus punctatus, harboring alligator cathelicidin gene with robust disease resistance by harnessing different CRISPR/Cas9-mediated systems

The CRISPR/Cas9 platform holds promise for modifying fish traits of interest as a precise and versatile tool for genome manipulation. To reduce introgression of transgene and control reproduction, catfish species have been studied for upscaled disease resistance and intervening of reproduction to lower the potential environmental risks of introgression of escapees as transgenic animals. Taking advantage of the CRISPR/Cas9-mediated system, we succeeded in integrating the cathelicidin gene from an alligator (Alligator sinensis; As-Cath) into the target luteinizing hormone (LH) locus of channel catfish (Ictalurus punctatus) using two delivery systems assisted by double-stranded DNA (dsDNA) and single-stranded oligodeoxynucleotides (ssODNs), respectively. In this study, high knock-in (KI) efficiency (22.38%, 64/286) but low on-target was achieved using the ssODN strategy, whereas adopting a dsDNA as the donor template led to an efficient on-target KI (10.80%, 23/213). On-target KI of As-Cath was instrumental in establishing the LH knockout (LH-_As-Cath+) catfish line, which displayed heightened disease resistance and reduced fecundity compared to the wild-type sibling fish. Furthermore, implanting with HCG and LHRHa can restore the fecundity, spawnability and hatchability of the new transgenic fish line. Overall, we replaced the LH gene with an alligator cathelicidin transgene and then administered hormone therapy to gain complete reproductive control of disease-resistant transgenic catfish in an environmentally sound manner. This strategy not only effectively improves the consumer-valued traits, but also guards against genetic contamination. This is a breakthrough in aquaculture genetics to confine fish reproduction and prevent the establishment of transgenic or domestic genotypes in the natural environment.

bioengineering↗

bioRxiv2022

Heritability enrichment in context-specific regulatory networks improves phenotype-relevant tissue identification

Systems genetics holds the promise to decipher complex traits by interpreting their associated SNPs through gene regulatory networks derived from comprehensive multi-omics data of cell types, tissues, and organs. Here, we propose SpecVar to integrate paired chromatin accessibility and gene expression data into context-specific regulatory network atlas and regulatory categories, conduct heritability enrichment analysis with GWAS summary statistics, identify relevant tissues, and depict shared heritability and regulations by relevance correlation. Our method improves power upon existing approaches by associating SNPs with context-specific regulatory elements to assess heritability enrichments and by explicitly prioritizing gene regulations underlying relevant tissues. Experiments on GWAS of six phenotypes show that SpecVar can improve heritability enrichment, accurately detect relevant tissues, and reveal causal regulations. Furthermore, SpecVar correlates the relevance patterns for pairs of phenotypes and better reveals shared heritability and regulations of phenotypes than existing methods. Studying GWAS of 206 phenotypes in UK-Biobank demonstrates that SpecVar leverages the context-specific regulatory network atlas to prioritize phenotypes relevant tissues and shared heritability for biological and therapeutic insights. SpecVar provides a powerful way to interpret SNPs via context-specific regulatory networks and is available at https://github.com/AMSSwanglab/SpecVar.

genetics↗

bioRxiv2022

Divergent MEK/ERK and AMPK signaling dictate lipogenic plasticity and dependence on fatty acid synthesis in Glioblastoma

Deregulated de novo lipid synthesis (DNLS) is a potential druggable vulnerability in Glioblastoma (GBM), a highly lethal and incurable cancer. Yet the molecular mechanisms that determine susceptibility to DNLS-targeted therapies remain unknown, and the lack of brain-penetrant inhibitors of DNLS has prevented their clinical evaluation as GBM therapeutics. Here, we report that YTX-7739, a clinical-stage, brain-penetrant inhibitor of stearoyl CoA desaturase (SCD), triggers lipotoxicity in patient-derived GBM stem-like cells (GSCs) and inhibits fatty acid desaturation in GSCs orthotopically implanted in mice. When administered as a single agent, or particularly in combination with the first line GBM chemotherapy, Temozolomide (TMZ), YTX-7739 showed therapeutic efficacy in orthotopic GSC mouse models owing to its lipotoxicity and its ability to impair DNA damage repair. Leveraging genetic, pharmacological, and physiological manipulation of key signaling nodes in gliomagenesis, we uncover that aberrant MEK/ERK signaling and its repression of the energy sensor AMP-activated protein kinase (AMPK) primarily drives therapeutic vulnerability to SCD and other DNLS inhibitors. Conversely, AMPK activation mitigates lipotoxicity and renders GSCs impervious to the loss of DNLS, both in culture and in vivo, by decreasing the saturation state of phospholipids and diverting toxic lipids into lipid droplets. Altogether, our findings reveal mechanisms of metabolic plasticity in GSCs and provide a framework for rational integration of DNLS-targeted therapies for the treatment of GBM.

cancer biology↗

bioRxiv2021

MEKK3-TGFβ crosstalk regulates inward arterial remodeling

Arterial remodeling is an important adaptive mechanism that maintains normal fluid shear stress in a variety of physiologic and pathologic conditions. Inward remodeling, a process that leads to reduction in arterial diameter, plays a critical role in progression of such common diseases as hypertension and atherosclerosis. Yet despite its pathogenic importance, molecular mechanisms controlling inward remodeling remain undefined. Mitogen-activated protein kinases (MAPKs) perform a number of functions ranging from control of proliferation to migration and cell fate transitions. While the MAPK ERK1/2 signaling pathway has been extensively examined in the endothelium, less is known about the role of the MEKK3/ERK5 pathway in vascular remodeling. To better define the role played by this signaling cascade, we studied the effect of endothelial-specific deletion of its key upstream MAP3K, MEKK3, in adult mice. The genes deletion resulted in a gradual inward remodeling of both pulmonary and systematic arteries leading to spontaneous hypertension in both vascular circuits and accelerated progression of atherosclerosis in hyperlipidemic mice. Molecular analysis revealed activation of TGF{beta} signaling both in vitro and in vivo. Endothelial-specific TGF{beta}R1 knockout prevented inward arterial remodeling in MEKK3 endothelial knockout mice. These data point to the unexpected participation of endothelial MEKK3 in regulation of TGF{beta}R1-Smad2/3 signaling and inward arterial remodeling in artery diseases. SignificanceInward remodeling of arteries to reduce lumen diameter is a major factor in disease progression and morbidity in multiple vascular diseases, including hypertension and atherosclerosis. However, molecular mechanisms controlling inward arterial remodeling remain largely undefined. In this study, we identify endothelial MEKK3 as an unexpected regulator of inward remodeling via inhibition of TGF{beta}-Smad2/3 signaling. Genetic deletion of MEKK3 in adult endothelium results in induction of TGF{beta}-Smad2/3 signaling, endothelial-to-mesenchymal transition and inward remodeling in both pulmonary and arterial circuits. The latter process results in pulmonary and systemic hypertension and accelerates atherosclerosis. These results provide a new basis for understanding the inward artery remodeling that leads to reduced blood flow to affected tissues and exacerbates hypertension in vascular disease.

pathology↗

bioRxiv2021

Spike mutations in SARS-CoV-2 variants confer resistance to antibody neutralization

New SARS-CoV-2 variants continue to emerge from the current global pandemic, some of which can replicate faster and with greater transmissibility and pathogenicity. In particular, UK501Y.V1 identified in UK, SA501Y.V2 in South Africa, and BR501Y.V3 in Brazil are raising serious concerns as they spread quickly and contain spike protein mutations that may facilitate escape from current antibody therapies and vaccine protection. Here, we constructed a panel of 28 SARS-CoV-2 pseudoviruses bearing single or combined mutations found in the spike protein of these three variants, as well as additional nine mutations that within or close by the major antigenic sites in the spike protein identified in the GISAID database. These pseudoviruses were tested against a panel of monoclonal antibodies (mAbs), including some approved for emergency use to treat SARS-CoV-2 infection, and convalescent patient plasma collected early in the pandemic. SA501Y.V2 pseudovirus was the most resistant, in magnitude and breadth, against mAbs and convalescent plasma, followed by BR501Y.V3, and then UK501Y.V1. This resistance hierarchy corresponds with Y144del and 242-244del mutations in the N-terminal domain as well as K417N/T, E484K and N501Y mutations in the receptor binding domain (RBD). Crystal structural analysis of RBD carrying triple K417N-E484K-N501Y mutations found in SA501Y.V2 bound with mAb P2C-1F11 revealed a molecular basis for antibody neutralization and escape. SA501Y.V2 and BR501Y.V3 also acquired substantial ability to use mouse and mink ACE2 for entry. Taken together, our results clearly demonstrate major antigenic shifts and potentially broadening the host range of SA501Y.V2 and BR501Y.V3, which pose serious challenges to our current antibody therapies and vaccine protection.

immunology↗

bioRxiv2020

Fusobacterium nucleatum facilitates cetuximab resistance in colorectal cancer via the PI3K/AKT and JAK/STAT3 pathways

Infectious pathogens contribute to about 20% of the total tumor burden. Fusobacterium nucleatum (Fn) has been associated with the initiation, progression, and therapy resistance in colorectal cancer (CRC). The over-abundance of Fn has been observed in patients with right-sided CRC than in those with left-sided CRC. While the KRAS/NRAS/BRAF wild-type status of the CRC conferred better response to cetuximab in patients with left-sided CRC than with right-sided CRC. However, treatment failure remains the leading cause of tumor relapse and poor clinical outcome in patients with CRC. Here, we have studied the association of Fn to cetuximab resistance. Our functional studies indicate that Fn facilitates resistance of CRC to cetuximab in vitro and in vivo. Moreover, Fn was found to target the PI3K/AKT and JAK/STAT3 pathways, which altered the response to cetuximab therapy. Therefore, assessing the levels and targeting Fn and the associated signaling pathways may allow modulating the treatment regimen and improve prognoses of CRC patients.

cancer biology↗

bioRxiv2020

E-cadherin promotes cell hyper-proliferation in breast cancer

The loss of the intercellular adhesion molecule E-cadherin is a hallmark of the epithelial- mesenchymal transition (EMT), during which tumor cells transition into an invasive phenotype. Accordingly, E-cadherin has long been considered a tumor suppressor gene. Using novel multi-compartment spheroids and multiple in vivo models, we show that E-cadherin promotes a hyper-proliferative phenotype in breast cancer cells via interaction with the transmembrane receptor EGFR. This interaction results in the activation of the MEK/ERK signaling pathway, leading to a significant increase in proliferation via the activation of transcription factors including c-Fos. Pharmacological inhibition of MEK activity in E-cadherin positive breast cancer cells significantly decreases both tumor growth and macro-metastasis in vivo. This work provides evidence for a novel role of E-cadherin in breast tumor growth and identifies a potential new target to treat hyper-proliferative E-cadherin-positive breast tumors.

cancer biology↗

bioRxiv2020

Large-scale single-cell analysis reveals critical immune characteristics of COVID-19 patients

Dysfunctional immune response in the COVID-19 patients is a recurrent theme impacting symptoms and mortality, yet the detailed understanding of pertinent immune cells is not complete. We applied single-cell RNA sequencing to 284 samples from 205 COVID-19 patients and controls to create a comprehensive immune landscape. Lymphopenia and active T and B cell responses were found to coexist and associated with age, sex and their interactions with COVID-19. Diverse epithelial and immune cell types were observed to be virus-positive and showed dramatic transcriptomic changes. Elevation of ANXA1 and S100A9 in virus-positive squamous epithelial cells may enable the initiation of neutrophil and macrophage responses via the ANXA1-FPR1 and S100A8/9-TLR4 axes. Systemic upregulation of S100A8/A9, mainly by megakaryocytes and monocytes in the peripheral blood, may contribute to the cytokine storms frequently observed in severe patients. Our data provide a rich resource for understanding the pathogenesis and designing effective therapeutic strategies for COVID-19. HIGHLIGHTSO_LILarge-scale scRNA-seq analysis depicts the immune landscape of COVID-19 C_LIO_LILymphopenia and active T and B cell responses coexist and are shaped by age and sex C_LIO_LISARS-CoV-2 infects diverse epithelial and immune cells, inducing distinct responses C_LIO_LICytokine storms with systemic S100A8/A9 are associated with COVID-19 severity C_LI

genomics↗

bioRxiv2020

PEA polymer-coated nanotopography delivers solid-state BMP2, enhances mesenchymal stem cell adhesion, prevents bacterial biofilm formation and protects cells from quorum sensing virulence factors

Post-operative infection is a major complication in patients recovering from orthopaedic surgery. As such, there is a clinical need to develop biomaterials for use in regenerative surgery that can promote mesenchymal stem cell (MSC) osteospecific differentiation and that can prevent infection caused by biofilm-forming pathogens. Nanotopographical approaches to pathogen control are being identified, including in orthopaedic materials such as titanium and its alloys. These topographies use high aspect ratio nanospikes or nanowires to prevent bacterial adhesion but these features puncture adhering cells, thus also reducing MSC adhesion. Here, we use a poly(ethyl acrylate) (PEA) polymer coating on titanium nanowires to spontaneously organise fibronectin (FN) and to deliver bone morphogenetic protein 2 (BMP2) to enhance MSC adhesion and osteospecific signalling. This nanotopography when combined with the PEA coating enhanced osteogenesis and reduced adhesion of Pseudomonas aeruginosa in culture. Using a novel MSC-Pseudomonas aeruginosa co-culture, we also show that the coated nanotopographies protect MSCs from cytotoxic quorum sensing and signalling molecules. We conclude that the PEA polymer-coated nanotopography can both support MSCs and prevent pathogens from adhering to a biomaterial surface, thus protecting from biofilm formation and bacterial infection and supporting osteogenic repair.

bioengineering↗

bioRxiv2020

Inferring MHC interacting SARS-CoV-2 epitopes recognized by TCRs towards designing T cell-based vaccines

The coronavirus disease 2019 (COVID-19) is triggered by severe acute respiratory syndrome mediated by coronavirus 2 (SARS-CoV-2) infection and was declared by WHO as a major international public health concern. While worldwide efforts are being advanced towards vaccine development, the structural modeling of TCR-pMHC (T Cell Receptor-peptide-bound Major Histocompatibility Complex) regarding SARS-CoV-2 epitopes and the design of effective T cell vaccine based on these antigens are still unresolved. Here, we present both pMHC and TCR-pMHC interfaces to infer peptide epitopes of the SARS-CoV-2 proteins. Accordingly, significant TCR-pMHC templates (Z-value cutoff > 4) along with interatomic interactions within the SARS-CoV-2-derived hit peptides were clarified. Also, we applied the structural analysis of the hit peptides from different coronaviruses to highlight a feature of evolution in SARS-CoV-2, SARS-CoV, bat-CoV, and MERS-CoV. Peptide-protein flexible docking between each of the hit peptides and their corresponding MHC molecules were performed, and a multi-hit peptides vaccine against the S and N glycoprotein of SARS-CoV-2 was designed. Filtering pipelines including antigenicity, and also physiochemical properties of designed vaccine were then evaluated by different immunoinformatics tools. Finally, vaccine-structure modeling and immune simulation of the desired vaccine were performed aiming to create robust T cell immune responses. We anticipate that our design based on the T cell antigen epitopes and the frame of the immunoinformatics analysis could serve as valuable supports for the development of COVID-19 vaccine.

immunology↗

bioRxiv2020

miR-200 deficiency promotes lung cancer metastasis by activating cancer-associated fibroblasts

Lung adenocarcinoma, the most prevalent lung cancer subtype, is characterized by its high propensity to metastasize. Despite the importance of metastasis in lung cancer mortality, its underlying cellular and molecular mechanisms remain largely elusive. Here, we identified miR-200 miRNAs as potent suppressors for lung adenocarcinoma metastasis. miR-200 expression is specifically repressed in mouse metastatic lung adenocarcinomas, and miR-200 decrease strongly correlates with poor patient survival. Consistently, deletion of mir-200c/141 in the KrasLSL-G12D/+; Trp53flox/flox lung adenocarcinoma mouse model significantly promoted metastasis, generating a desmoplastic tumor stroma highly reminiscent of metastatic human lung cancer. miR-200 deficiency in lung cancer cells promotes the proliferation and activation of adjacent cancer-associated fibroblasts (CAFs), which in turn elevates the metastatic potential of cancer cells. miR-200 regulates the functional interaction between cancer cells and CAFs, at least in part, by targeting Notch ligand Jagged1 and Jagged2 in cancer cells and inducing Notch activation in adjacent CAFs. Hence, the interaction between cancer cells and CAFs constitutes an essential mechanism to promote metastatic potential.

cancer biology↗

bioRxiv2020

Effect of mechanical properties of monofilament twines on the catch efficiency of biodegradable gillnets.

Gillnets made of the biodegradable resin polybutylene succinate co-adipate-co-terephthalate (PBSAT) were tested under commercial fishing conditions to compare their fishing performance with that of conventional nylon polyamide (PA) gillnets. Both types of gillnets were made of 0.55 mm Ø monofilaments. However, since the biodegradable nets are weaker than nylon PA nets when using the same monofilament diameter, we also used biodegradable nets made of 0.60 mm Ø monofilament that had a similar tensile strength to the 0.55 mm Ø nylon PA nets. The relative catch efficiency of the different gillnet types was evaluated over the 2018 autumn fishing season for saithe and cod in northern Norway. For cod, both biodegradable gillnets (0.55 and 0.60 mm) had a significantly lower catch efficiency compared to the traditional nylon PA net (0.55 mm) with estimated catch efficiencies of 62.38% (CI: 50.55–74.04) and 54.96% (CI: 35.42–73.52) compared with the nylon PA net, respectively. Similarly for saithe, both biodegradable gillnets (0.55 and 0.60 mm) had a lower estimated catch efficiency compared to the traditional nylon PA net (0.55 mm) with estimated catch efficiencies of 83.40% (71.34–94.86) and 83.87% (66.36–104.92), compared with the nylon PA net, respectively. Tensile strength does not explain the differences in catch efficiency between the two gillnet types, since increasing the twine diameter of the biodegradable gillnets (to match the strength of nylon PA gillnets) did not yield similar catch efficiencies. However, the elasticity and stiffness of the materials may be responsible for the differences in catch efficiency between the nylon PA and biodegradable gillnets.View Full Text

scientific communication and education↗

bioRxiv2020

Transcriptional Difference between SARS-COV-2 and other Human Coronaviruses Revealed by Sub-genomic RNA Profiling

BackgroundFundamental to viral biology is identification and annotation of viral genes and their function. Determining the level of coronavirus gene expression is inherently difficult due to the positive stranded RNA genome and the identification of sub-genomic RNAs (sgRNAs) that are required for expression of most viral genes. In the COVID-19 epidemic so far, few genomic studies have looked at viral sgRNAs and none have systematically examined the sgRNA profiles of large numbers of SARS-CoV2 datasets in conjuction with data for other coronaviruses. ResultsWe developed a bioinformatic pipeline to analyze the sgRNA profiles of coronaviruses and applied it to 588 individual samples from 20 independent studies, covering more than 10 coronavirus species. Our result showed that SARS-CoV, SARS-CoV-2 and MERS-CoV each had a core sgRNA repertoire generated via a canonical mechanism. Novel sgRNAs that encode peptides with evolutionarily conserved structures were identified in several coronaviruses and were expressed in vitro and in vivo. Two novel peptides may have direct functional relevance to disease, by alluding interferon responses and disrupting IL17E (IL25) signaling. Relevant to coronavirus infectivity and transmission, we also observed that the level of Spike sgRNAs were significantly higher in-vivo than in-vitro, while the opposite held true for the Nucleocapside protein. ConclusionsOur results greatly expanded the predicted number of coronaviruses proteins and identified potential viral peptide suggested to be involved in viral virulence. These methods and findings shed new light on coronavirus biology and provides a valuable resource for future genomic studies of coronaviruses.

bioinformatics↗

bioRxiv2019

De novo assembly of a Tibetan genome and identification of novel structural variants associated with high altitude adaptation

Structural variants (SVs) may play important roles in human adaption to extreme environments such as high altitude but have been under-investigated. Here, combining long-read sequencing with multiple scaffolding techniques, we assembled a high-quality Tibetan genome (ZF1), with a contig N50 length of 24.57 mega-base pairs (Mb) and a scaffold N50 length of 58.80 Mb. The ZF1 assembly filled 80 remaining N-gaps (0.25 Mb in total length) in the reference human genome (GRCh38). Markedly, we detected 17,900 SVs, among which the ZF1-specific SVs are enriched in GTPase activity that is required for activation of the hypoxic pathway. Further population analysis uncovered a 163-bp intronic deletion in the MKL1 gene showing large divergence between highland Tibetans and lowland Han Chinese. This deletion is significantly associated with lower systolic pulmonary arterial pressure, one of the key adaptive physiological traits in Tibetans. Moreover, with the use of the high quality de novo assembly, we observed a much higher rate of genome-wide archaic hominid (Altai Neanderthal and Denisovan) shared non-reference sequences in ZF1 (1.32%-1.53%) compared to other East Asian genomes (0.70%-0.98%), reflecting a unique genomic composition of Tibetans. One such archaic-hominid shared sequence, a 662-bp intronic insertion in the SCUBE2 gene, is enriched and associated with better lung function (the FEV1/FVC ratio) in Tibetans. Collectively, we generated the first high-resolution Tibetan reference genome, and the identified SVs may serve as valuable resources for future evolutionary and medical studies.

genomics↗

bioRxiv2019

Map3k2-Regulated Intestinal Stromal Cells (MRISC) Define a Distinct Sub-cryptic Stem Cell Niche for Damage Induced Wnt Agonist R-spondin1 Production

Intestinal stem cell propagation and differentiation are essential for rapid repair of tissue damage in the gut. While intestinal stromal cells were recently identified as key mediators of this process, the cellular and molecular mechanisms by which this diverse population induces tissue repair remains poorly understood. Here we show that Map3k2 has a colon stromal cell specific function critically required for maintenance of Lgr5+ intestinal stem cells and protection against acute intestinal damage. This Map3k2-specific function is mediated by enhancing Wnt agonist R-spondin1 production. We further reveal a unique novel cell population, named Map3k2-regulated intestinal stromal cells (MRISC), as the primary cellular source of R-spondin1 following intestinal injury. Together, our data identify a novel intestinal stem cell niche organized by MRISC, which specifically dependent on the Map3k2-signaling pathway to augment the production of Wnt agonist R-spondin1 and promote regeneration of the acutely damaged intestine.\n\nHighlightsO_LIMap3k2 protects mice from DSS-induced colitis by promoting intestinal stem cell regeneration.\nC_LIO_LIMap3k2-MAPK pathway cross-talks with Wnt signaling pathway via upregulation of R-spondin1.\nC_LIO_LIMap3k2-Regulated Intestinal Stromal Cells (MRISC) marked by co-expression of CD90, CD34 and CD81 defines a novel colonic stem cell niche.\nC_LI

cell biology↗

bioRxiv2019

Long-read assembly of the Chinese rhesus macaque genome and identification of ape-specific structural variants

Rhesus macaque (Macaca mulatta) is a widely-studied nonhuman primate. Here we present a high-quality de novo genome assembly of the Chinese rhesus macaque (rheMacS) using long-read sequencing and multiplatform scaffolding approaches. Compared to the current Indian rhesus macaque reference genome (rheMac8), the rheMacS genome assembly improves sequence contiguity by 75-fold, closing 21,940 of the remaining assembly gaps (60.8 Mbp). To improve gene annotation, we generated more than two million full-length transcripts from ten different tissues by long-read RNA sequencing. We sequence resolve 53,916 structural variants (96% novel) and identify 17,000 ape-specific structural variants (ASSVs) based on comparison to the long-read assembly of ape genomes. We show that many ASSVs map within ChIP-seq predicted enhancer regions where apes and macaque show diverged enhancer activity and gene expression. We further characterize a set of candidate ASSVs that may contribute to ape- or great-ape-specific phenotypic traits, including taillessness, brain volume expansion, improved manual dexterity, and large body size. This improved rheMacS genome assembly serves as an ideal reference for future biomedical and evolutionary studies.

genomics↗

bioRxiv2019

Fate mapping via Ms4a3 expression history traces monocyte-derived cells

Most tissue-resident macrophage (RTM) populations are seeded by waves of embryonic hematopoiesis and are self-maintained independently of a bone-marrow contribution during adulthood. A proportion of RTMs, however, is constantly replaced by blood monocytes and their functions compared to embryonic RTM remains unclear. The kinetics and extent of the contribution of circulating monocytes to RTM replacement during homeostasis, inflammation and disease is highly debated. Here, we identified Ms4a3 as a specific marker expressed by granulocyte-monocyte progenitors (GMPs) and subsequently generated Ms4a3TdT reporter and Ms4a3Cre-RosaTdT fate mapper models to follow monocytes and their progenies. Our Ms4a3Cre-RosaTdT model traced efficiently blood monocytes (97%) and granulocytes (100%), but no lymphocytes or tissue dendritic cells. Using this model, we precisely quantified the contribution of monocytes to the RTM pool during homeostasis and inflammation. The unambiguous identification of monocyte-derived cells will permit future studies of their function under any condition.

immunology↗

bioRxiv2018

A novel nonsense mutation c.424G>T (p. G142X) in the first exon of XLas leading to osteopetrosis

GNAS is one of the most complex gene loci in the human genome and encodes multiple gene products. XLas, the extra-large isoform of alpha-subunit of the stimulatory guanine nucleotide-binding protein (Gas), is paternally inherited. Although XLas can mimic the action of Gas, its significance remains largely unknown in humans. Here we report a patient presented with increased bone mass, hypophosphatemia, and elevated parathyroid hormone levels. His serum calcium was in the lower limit of normal range. DEXA scan revealed progressive increase in the bone density of this patient. Whole exome sequencing of this subject found a novel nonsense mutation c.424G>T (p. G142X) in the first exon of XLas, which was inherited from his father and transmitted to his daughter. This mutation was predicted to exclusively influence the expression of XLas, while may have no significant effects on other gene products of this locus. SaOS2 cells transfected with mutant XLas failed to generate cAMP under parathyroid hormone stimulation, indicating skeletal resistance to this hormone. This subject showed higher circulating SOST, DKK1 and OPG levels, while lower RANKL levels and RANKL/OPG ratio, leading to reduced bone resorption. It is speculated that this patient may belong to a very rare type of pseudohypoparathyroidism with selective skeletal resistance but normal renal tubular response to parathyroid hormone. Our findings indicate that XLas plays a critical role in bone metabolism and GNAS locus should be considered as a candidate gene for high bone mass.\n\nAuthor summaryGNAS has been regarded as one of the most complex gene loci and encodes multiple transcripts, including Gs, XLs, NESP55 and A/B transcripts. These isoforms share the same 2-13 exons with alternative first exons. Previously reported mutations often disrupt multiple protein-coding transcripts in addition to that encoding Gs, making it difficult to distinguish the contributions of each transcript to disease phenotypes. Here we first report a novel nonsense mutation c.424G>T (p. G142X) in the first exon of XLas in a subject presenting with high bone mass, unclosed cranial suture, and persistent hypophosphatemia, and elevated parathyroid hormone (PTH) levels. This is the first report of a mutation located in the first exon of XLas in humans, which was predicted to exclusively influence the expression of XLas, while may have no significant effects on other gene products of this locus. SaOS2 cells transfected with mutant XLas failed to generate cAMP under PTH stimulation, indicating skeletal resistance to this hormone. Our study suggests that XLas has an important physiological role in humans, and is involved in skeletal PTH/cAMP pathway. Our findings also indicate GNAS locus should be considered as a candidate gene for high bone mass.\n\nFundingThe National Natural Science Foundation of China.\n\nDeclaration of InterestsThe authors declare no competing interests.

genetics↗