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Fan, M.

Publications and source records attributed to Fan, M..

43 records · Page 3Linked to original sources

A machine learning approach to define antimalarial drug action from heterogeneous cell-based screens

Drug resistance threatens the effective prevention and treatment of an ever-increasing range of human infections. This highlights an urgent need for new and improved drugs with novel mechanisms of action to avoid cross-resistance. Current cell-based drug screens are, however, restricted to binary live/dead readouts with no provision for mechanism of action prediction. Machine learning methods are increasingly being used to improve information extraction from imaging data. Such methods, however, work poorly with heterogeneous cellular phenotypes and generally require time-consuming human-led training. We have developed a semi-supervised machine learning approach, combining human- and machine-labelled training data from mixed human malaria parasite cultures. Designed for high-throughput and high-resolution screening, our semi-supervised approach is robust to natural parasite morphological heterogeneity and correctly orders parasite developmental stages. Our approach also reproducibly detects and clusters drug-induced morphological outliers by mechanism of action, demonstrating the potential power of machine learning for accelerating cell-based drug discovery. One Sentence SummaryA machine learning approach to classifying normal and aberrant cell morphology from plate-based imaging of mixed malaria parasite cultures, facilitating clustering of drugs by mechanism of action.

microbiology↗

Adeno-Associated Virus Technologies and Methods for Targeted Neuronal Manipulation

Cell-type-specific expression of molecular tools and sensors is critical to construct circuit diagrams and to investigate the activity and function of neurons within the nervous system. Strategies for targeted manipulation include combinations of classical genetic tools such as Cre/loxP and Flp/FRT, use of cis-regulatory elements, targeted knock-in transgenic mice, and gene delivery by AAV and other viral vectors. The combination of these complex technologies with the goal of precise neuronal targeting is a challenge in the lab. This report will discuss the theoretical and practical aspects of combining current technologies and establish best practices for achieving targeted manipulation of specific cell types. Novel applications and tools, as well as areas for development, will be envisioned and discussed.

neuroscience↗

Differential functions of splicing factors in breast-cancer initiation and metastasis

Misregulation of alternative splicing is a hallmark of human tumors; yet to what extent and how it contributes to malignancy are only beginning to be unraveled. Here, we define which members of the splicing factor SR and SR-like families contribute to breast cancer, and uncover differences and redundancies in their targets and biological functions. We first identify splicing factors frequently altered in human breast tumors, and then assay their oncogenic functions using breast organoid models. Importantly we demonstrate that not all splicing factors affect mammary tumorigenesis. Specifically, upregulation of either SRSF4, SRSF6 or TRA2{beta} promotes cell transformation and invasion. By characterizing the targets of theses oncogenic factors, we identify a shared set of spliced genes associated with well-established cancer hallmarks. Finally, we demonstrate that the splicing factor TRA2{beta} is regulated by the MYC oncogene, plays a role in metastasis maintenance in vivo, and its levels correlate with breast-cancer-patient survival.

cancer biology↗

Time-resolved genome-scale profiling reveals a causal expression network

We present an approach for inferring genome-wide regulatory causality and demonstrate its application on a yeast dataset constructed by independently inducing hundreds of transcription factors and measuring timecourses of the resulting gene expression responses. We discuss the regulatory cascades in detail for a single transcription factor, Aft1; however, we have 201 TF induction timecourses that include >100,000 signal-containing dynamic responses. From a single TF induction timecourse we can often discriminate the direct from the indirect effects of the induced TF. Across our entire dataset, however, we find that the majority of expression changes are indirectly driven by unknown regulators. By integrating all timecourses into a single whole-cell transcriptional model, potential regulators of each gene can be predicted without incorporating prior information. In doing so, the indirect effects of a TF are understood as a series of direct regulatory predictions that capture how regulation propagates over time to create a causal regulatory network. This approach, which we call CANDID (Causal Attribution Networks Driven by Induction Dynamics), resulted in the prediction of multiple transcriptional regulators that were validated experimentally.

systems biology↗

SCFAs-induced GLP-1 Secretion Links the Regulation of Gut Microbiome on Hepatic Lipogenesis in Chickens

Chickens represent a specific case in lipid metabolism that liver is the main site of lipid synthesis. As ovipara, their gut microbiota could be strongly influenced by environment and diets after hatching. The aim of this study is to elucidate the linkage of gut microbiota and fat synthesis in broilers. The broilers were subjected to dietary treatments of combined probiotics (Clostridium butyrate 4x108 cfu/kg, Bifidobacterium 2x108 cfu/kg, Lactobacillus plantarum 2x108 cfu/kg and Lactococcus faecalis 2x108 cfu/kg, PB) and guar gum (1 g/kg, GG). The result showed that dietary supplementation of PB and GG changed the cecal microbiota diversity, altered short chain fatty acids (SCFAs) contents, and suppressed lipogenesis in liver and abdominal fat tissues. In intestinal epithelial cells (IECs), acetate, propionate, and butyrate upregulated the expression of glucagon-like peptide-1 (GLP-1) via MAPK pathways, especially via the ERK and p38 MAPK pathways. GLP-1 suppressed lipid accumulation in primary hepatocytes with the involvement of AMPK/ACC signaling. In conclusion, the result suggests that SCFAs-induced GLP-1 secretion links the regulation of gut microbiome on hepatic lipogenesis in chickens. IMPORTANCEIntestinal microbes metabolize SCFAs and stimulate intestinal epithelium L cells to produce GLP-1. Recent evidence showed that GLP-1 reduced fat deposition by reducing appetite and increasing satiety. However, how SCFAs stimulate the secretion of GLP-1 and whether GLP-1 directly affects fat metabolism is not clear. Poultry adipocytes have limited ability to produce fat, and 90% of carcass fat is synthesized in the liver. In addition, large intake of feeds easily leads to fatty liver diseases in chickens. The aim of this study is to investigate how SCFAs mediate secretion of GLP-1 and whether GLP-1 could directly affect hepatic deposition in broiler chickens. The hepatic lipogenesis regulated by the intestinal microbiota of chickens is of great significance to the study of intestinal microbiota and fat deposition in poultry, and this work could provide reference for intestinal microorganism and fat metabolism in mammals and humans.

microbiology↗

Improved yield of AAV2 and rAAV2-retro serotypes following sugar supplementation during the viral production phase

Hyperosmolarity has been used as a means to improve yields in various processes such as antibody production in hybridoma cells and retroviral and adenoviral production systems. In this study we demonstrate that treatment of AAVpro 293T packaging cells with the sugars sucrose or sorbitol during adeno-associated virus (AAV) production improves the yields of AAV2 and rAAV2-retro serotypes 1.8-fold and 1.5-fold, respectively. Using an iodixanol gradient centrifugation strategy followed by a column-based buffer exchange, we show that the sugar supplements are not carried over to the final viral preparation and have no effect on the purity or infectivity of the virus. Given the wide availability, low cost, and ease of use of these sugars, we believe that this strategy can be easily adopted by vector cores and laboratories to improve yields of their AAV preparations.

cell biology↗