Biology subjects

Zeng, C.

Publications and source records attributed to Zeng, C..

67 records · Page 4Linked to original sources

bioRxiv2020

Incorporating Prior Knowledge into Regularized Regression

MotivationAssociated with genomic features like gene expression, methylation, and genotypes, used in statistical modeling of health outcomes, there is a rich set of meta-features like functional annotations, pathway information, and knowledge from previous studies, that can be used post-hoc to facilitate the interpretation of a model. However, using this meta-feature information a-priori rather than post-hoc can yield improved prediction performance as well as enhanced model interpretation. ResultsWe propose a new penalized regression approach that allows a-priori integration of external meta-features. The method extends LASSO regression by incorporating individualized penalty parameters for each regression coefficient. The penalty parameters are in turn modeled as a log-linear function of the meta-features and are estimated from the data using an approximate empirical Bayes approach. Optimization of the marginal likelihood on which the empirical Bayes estimation is based is performed using a fast and stable majorization-minimization procedure. Through simulations, we show that the proposed regression with individualized penalties can outperform the standard LASSO in terms of both parameters estimation and prediction performance when the external data is informative. We further demonstrate our approach with applications to gene expression studies of bone density and breast cancer. Availability and implementationThe methods have been implemented in the R package xtune freely available for download from CRAN.

bioinformatics↗

bioRxiv2020

The Sigma-2 Receptor/TMEM97, PGRMC1, and LDL Receptor complex are responsible for the cellular uptake of Aβ42 and its protein aggregates

BackgroundOur lab has recently shown that the Sigma-2 Receptor/Transmembrane Protein 97 (TMEM97) and Progesterone Receptor Membrane Component 1 (PGRMC1) form a complex with the Low Density Lipoprotein Receptor (LDLR), and this intact complex is required for efficient uptake of lipoproteins such as LDL and apolipoprotein E (apoE). These receptors are expressed in the nervous system where they have implications in neurodegenerative diseases such as Alzheimers Disease (AD), where apoE is involved in neuronal uptake and accumulation of A{beta}42, eventually cascading into neurodegeneration, synaptic dysfunction, and ultimately, dementia. HypothesisWe hypothesize that the intact Sigma-2 receptor complex -TMEM97, PGRMC1, and LDLR-- is necessary for internalization of apoE and A{beta}42 monomers (mA{beta}42) and oligomers (oA{beta}42), and the disruption of the receptor complex inhibits uptake. ResultsThe results of this study suggest that the intact Sigma-2 receptor complex is a binding site for mA{beta}42 and oA{beta}42, in the presence or absence of apoE2, apoE3, and apoE4. The loss or pharmacological inhibition of one or both of these proteins results in the disruption of the complex leading to decreased uptake of mA{beta}42 and oA{beta}42 and apoE in primary neurons. ConclusionThe TMEM97, PGRMC1, and LDLR complex is a pathway for the cellular uptake of A{beta}42 via apoE dependent and independent mechanisms. This study suggests that the complex may potentially be a novel pharmacological target to decrease neuronal A{beta}42 internalization and accumulation, which may represent a new strategy for inhibiting the rate of neurotoxicity, neurodegeneration, and progression of AD.

neuroscience↗

bioRxiv2020

Common postzygotic mutational signature in multiple healthy adult tissues related to embryonic hypoxia

Postzygotic mutations are acquired in all of the normal tissues throughout an individuals lifetime and hold clues for identifying mutagenesis causing factors. The process and underlying mechanism of postzygotic mutations in normal tissues is still poorly understood. In this study, we investigated postzygotic mutation spectra in healthy individuals by optimized ultra-deep exome sequencing of time series samples from the same volunteer and samples from different individuals. In cells of blood, sperm, and muscle, we resolved three common types of mutational signature. Two of them are known to represent clock-like mutational processes, and their proportions in mutation profiles associated with polymorphisms of epigenetic regulation genes, suggesting the contribution of personal genetic backgrounds to underlying biological process. Notably, the third signature, characterized by C>T transitions at GpCpN sites, tends to be a feature of diverse normal tissues. Mutations of this type were likely to occur early in embryo development even before the tissue differentiation, as indicated by their relatively high allele frequencies, sharing variants between multiple tissues, and lacking of age-related accumulation. Almost all tumors shown in public datasets did not have this signature detected except for 19.6% of clear cell renal cell carcinoma samples, which featured by activation of the hypoxia-induced signaling pathway. Moreover, in vitro activation of HIF signaling pathway successfully introduced the corresponding mutation profile of this signature in a culture-expanded human embryonic stem cell line. Therefore, embryonic hypoxia may explain this novel signature across multiple normal tissues. Our study suggest hypoxic conditions in the early stage of embryo development may be a crucial factor for the C>T transitions at GpCpN sites and individual genetic background also related to shaping human postzygotic mutation profiles.

genetics↗

bioRxiv2019

The impact of alternative splicing on RNA subcellular localization

Alternative splicing, a ubiquitous phenomenon in eukaryotes, is a regulatory mechanism for the biological diversity of individual genes. Most studies have focused on the effects of alternative splicing for protein synthesis. However, the transcriptome-wide influence of alternative splicing on RNA subcellular localization has rarely been studied. By analyzing RNA-seq data obtained from subcellular fractions across 13 human cell lines, we identified 8720 switching genes between the cytoplasm and the nucleus. Consistent with previous reports, intron retention was observed to be enriched in the nuclear transcript variants. Interestingly, we found that short and structurally stable introns were positively correlated with nuclear localization. Motif analysis reveals that fourteen RNA-binding protein (RBPs) are prone to be preferentially bound with such introns. To our knowledge, this is the first transcriptome-wide study to analyze and evaluate the effect of alternative splicing on RNA subcellular localization. Our findings reveal that alternative splicing plays a promising role in regulating RNA subcellular localization.

genetics↗

bioRxiv2019

MeCP2 deletion impaired layer 2/3-dominant dynamic reorganization of cortical circuit during motor skill learning

Rett Syndrome (RTT) is a severe neurodevelopmental disorder caused by loss of function of the X-linked Methyl-CpG-binding protein 2 (MECP2). Several case studies report that gross motor function can be improved in children with RTT through treadmill walking, but whether the MeCP2-deficient motor circuit can support actual motor learning remains unclear. We used two-photon calcium imaging to simultaneously observe layer (L) 2/3 and L5a excitatory neuronal activity in the motor cortex (M1) while mice adapted to changing speeds on a computerized running wheel. Despite circuit hypoactivity and weakened functional connectivity across L2/3 and L5a, the Mecp2-null circuits firing pattern evolved with improved performance over two weeks. Moreover, trained mice became less anxious and lived 20% longer than untrained mice. Since motor deficits and anxiety are core symptoms of Rett, which is not diagnosed until well after symptom onset, these results underscore the benefit of motor learning.

neuroscience↗

bioRxiv2019

Diagnostic value of galactomannan in bronchoalveolar lavage fluid for chronic respiratory disease with pulmonary aspergillosis

ObjectiveTo explore the diagnostic value of the bronchoalveolar lavage fluid galactomannan (BALF GM) test for chronic respiratory disease with pulmonary aspergillosis, and establish the optimal cut-off value.\n\nMethodsA total of 180 chronic respiratory disease patients seen at the Respiratory Medicine Department of Peking University Shenzhen Hospital from September 2017 to September 2018 were analyzed. According to the diagnostic criteria, we divided the patients into the case group (n = 70, comprising 5, 20, and 45 proven, probable, and possible cases, respectively) and the control group (n = 110). Bronchoalveolar lavage fluid was collected, and the BALF GM test results were analyzed.\n\nResultsA non-parametric rank-sum test showed that the mean rank of the case group was 140.80, which was higher than that of the control group (58.49). The Z-value was 10.335 (P = 0.000), indicating that the general distribution of BALF GM differed between the two groups. A BALF GM cut-off value of 0.485 showed the highest diagnostic efficacy for pulmonary aspergillosis. The sensitivity, specificity, positive predictive value, and negative predictive value were 92.9%, 100%, 92.8%, and 100%, respectively. As the cut-off value increased, the specificity and sensitivity of the BALF GM test increased and decreased, respectively.\n\nConclusionsThe BALF GM test can be used confirm the diagnosis of patients with pulmonary aspergillosis and chronic respiratory disease. The optimum BALF GM cut-off value was 0.485. Antifungal therapy is important for treating pulmonary aspergillus infection in patients with chronic respiratory disease.

microbiology↗

bioRxiv2019

Single cell chromatin accessibility reveals pancreatic islet cell type- and state-specific regulatory programs of diabetes risk

Genetic risk variants for complex, multifactorial diseases are enriched in cis-regulatory elements. Single cell epigenomic technologies create new opportunities to dissect cell type-specific mechanisms of risk variants, yet this approach has not been widely applied to disease-relevant tissues. Given the central role of pancreatic islets in type 2 diabetes (T2D) pathophysiology, we generated accessible chromatin profiles from 14.2k islet cells and identified 13 cell clusters including multiple alpha, beta and delta cell clusters which represented hormone-producing and signal-responsive cell states. We cataloged 244,236 islet cell type accessible chromatin sites and identified transcription factors (TFs) underlying both lineage- and state-specific regulation. We measured the enrichment of T2D and glycemic trait GWAS for the accessible chromatin profiles of single cells, which revealed heterogeneity in the effects of beta cell states and TFs on fasting glucose and T2D risk. We further used machine learning to predict the cell type-specific regulatory function of genetic variants, and single cell co-accessibility to link distal sites to putative cell type-specific target genes. We localized 239 fine-mapped T2D risk signals to islet accessible chromatin, and further prioritized variants at these signals with predicted regulatory function and co-accessibility with target genes. At the KCNQ1 locus, the causal T2D variant rs231361 had predicted effects on an enhancer with beta cell-specific, long-range co-accessibility to the insulin promoter, and deletion of this enhancer reduced insulin gene and protein expression in human embryonic stem cell-derived beta cells. Our findings provide a cell type- and state-resolved map of gene regulation in human islets, illuminate likely mechanisms of T2D risk at hundreds of loci, and demonstrate the power of single cell epigenomics for interpreting complex disease genetics.

genomics↗

bioRxiv2019

A network of microRNAs acts to promote cell cycle exit and differentiation of human pancreatic endocrine cells

Pancreatic endocrine cell differentiation is orchestrated by transcription factors that operate in a gene regulatory network to activate endocrine lineage genes and repress lineage-inappropriate genes. MicroRNAs (miRNAs) are important modulators of gene expression, yet their role in endocrine cell differentiation has not been explored system-wide. Here we characterize miRNA-regulatory networks active in human endocrine cell differentiation by combining small RNA sequencing, miRNA overexpression experiments, and network modeling approaches. This analysis identifies Let-7g, Let-7a, miR-200a, and miR-375 as endocrine-enriched miRNAs with high impact on driving endocrine differentiation-associated gene expression changes. These miRNAs target different sets of transcription factors, which converge on a network of genes involved in cell cycle regulation. When expressed in human embryonic stem cell-derived pancreatic progenitors these miRNAs induce cell cycle exit and promote endocrine cell differentiation. Our study delineates the role of miRNAs in human endocrine cell differentiation and identifies miRNAs that could facilitate endocrine cell reprogramming.

developmental biology↗

bioRxiv2018

Differential phase partition of a PICS complex is required for piRNA processing and chromosome segregation in C. elegans

Piwi-interacting RNAs (piRNAs) play significant roles in suppressing transposons and non-self nucleic acids, maintaining genome integrity, defending against viral infections, and are essential for fertility in a variety of organisms. In C. elegans, most piRNA precursors are transcribed by RNA polymerase II in the nucleus and are subjected to a number of processing and maturation steps. However, the biogenesis of piRNAs are still not fully understood. We used functional proteomics to study piRNA biogenesis in C. elegans and identified a PICS complex that is required for piRNA processing and chromosome segregation. The PICS complex contains two known piRNA biogenesis factors TOFU-6 and PID-1, and three new proteins PICS-1, TOST-1, and ERH-2, which exhibit dynamic localization among different subcellular compartments. In the germline of gravid animals, the PICS complex contains TOFU-6/PICS-1/ERH-2/PID-1 and largely concentrate at the perinuclear granule zone and engages in piRNA processing. During early embryogenesis, the TOFU-6/PICS-1/ERH-2/TOST-1 complex accumulates in the nucleus and play essential roles in chromosome segregation and cell division. Interestingly, the function of these factors in mediating chromosome segregation is independent of piRNA production. Therefore, we speculate that a differential phase partition of PICS factors may help cells to coordinate distinct cellular processes.

genetics↗

bioRxiv2018

PREMONition: An algorithm for predicting the circadian clock-regulated molecular network

A transcriptional feedback loop is central to clock function in animals, plants and fungi. The clock genes involved in its regulation are specific to - and highly conserved within - the kingdoms of life. However, other shared clock mechanisms, such as phosphorylation, are mediated by proteins found broadly among living organisms, performing functions in many cellular sub-systems. Use of homology to directly infer involvement/association with the clock mechanism in new, developing model systems, is therefore of limited use. Here we describe the approach PREMONition, PREdicting Molecular Networks, that uses functional relationships to predict molecular circadian clock associations. PREMONition is based on the incorporation of proteins encoded by known clock genes (when available), rhythmically expressed clock-controlled genes and non-rhythmically expressed but interacting genes into a cohesive network. After tuning PREMONition on the networks derived for human, fly and fungal circadian clocks, we deployed the approach to predict a molecular clock network for Saccharomyces cerevisiae, for which there are no readily-identifiable clock gene homologs. The predicted network was validated using gene expression data and a growth assay for sensitivity to light, a zeitgeber of circadian clocks of most organisms. PREMONition may be used to identify candidate clock-regulated processes and thus candidate clock genes in other organisms.

bioinformatics↗

bioRxiv2018

Novel 5-Hydroxymethylcytosine Markers for Pancreatic Cancer

OBJECTIVESRobust biomarkers for pancreatic cancer (PaC) early detection/prognosis are critical for improved patient survival. Our goal was to explore the biomarker potential of 5-hydroxymethylcytosines (5hmC), an epigenetic marker with a distinct role in cancer pathobiology, yet under-investigated due largely to technical constraints.\n\nMETHODSWe used the TAB-Array assay, a state-of-the-art technology to directly profile 5hmC at single base resolution with the Illumina EPIC array (>850,000 CpG sites) in 17 pairs of tumor/adjacent tissue samples from US patients.\n\nRESULTSWe demonstrated distinctive distributions of 5hmC in tissues, and substantial differences between tumor and adjacent tissues, suggesting their diagnostic/prognostic value of for PaC.\n\nCONCLUSIONThis study established the potential of 5hmC as a novel epigenetic biomarker for PaC.

cancer biology↗

bioRxiv2018

The USTC complex co-opts an ancient machinery to drive piRNA transcription in C. elegans

Piwi-interacting RNAs (piRNAs) engage Piwi proteins to suppress transposons and non-self nucleic acids, maintain genome integrity, and are essential for fertility in a variety of organisms. In C. elegans most piRNA precursors are transcribed from two genomic clusters that contain thousands of individual piRNA transcription units. While a few genes have been shown to be required for piRNA biogenesis the mechanism of piRNA transcription remains elusive. Here we used functional proteomics approaches to identify an upstream sequence transcription complex (USTC) that is essential for piRNA biogenesis. The USTC complex contains PRDE-1, TOFU-4, TOFU-5 and SNPC-4. The USTC complex form a unique piRNA foci in germline nuclei and coat the piRNA cluster genomic loci. USTC factors associate with the Ruby motif just upstream of type I piRNA genes. USTC factors are also mutually dependent for binding to the piRNA clusters and to form the piRNA foci. Interestingly, USTC components bind differentially to piRNAs in the clusters and other non-coding RNA genes. These results reveal USTC as a striking example of the repurposing of a general transcription factor complex to aid in genome defence against transposons.

developmental biology↗

bioRxiv2018

Phosphorothioate-modified DNA oligonucleotides inactivate CRISPR-Cpf1 mediated genome editing

CRISPR-Cpf1, a microbial adaptive immune system discovered from Prevotella and Francisella 1, employs a single-stranded CRISPR RNA (crRNA) to induce double stranded DNA breaks1. To modulate genome editing activity of Cpf1 in human cells, we designed a series of crRNA variants including DNA-crRNA and RNA-crRNA duplexes, and identified that phosphorothioate (PS)-modified DNA-crRNA duplex completely blocked the function of Cpf1 mediated gene editing. More importantly, without prehybridization, this PS-modified DNA was able to regulate Cpf1 activity in a time-and dose-dependent manner. Mechanistic studies indicate that PS-modified DNA oligonucleotides hinder the binding between Cpf1-crRNA complex and target DNA substrate. Consequently, phosphorothioate-modified DNA oligonucleotides provide a tunable platform to inactivate Cpf1 mediated genome editing.

bioengineering↗