Publications by authors named "Yichen Si"

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease with no effective pharmacological interventions. While single-cell transcriptomics has advanced our understanding of AAA, it lacks spatial context. Here, we employed Seq-Scope, an ultra-high-resolution spatial transcriptomic technology, to decipher the spatial landscape of angiotensin II-induced AAA in Apoe-/- mice.

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Spatial transcriptomics (ST) enables systematic profiling of whole-transcriptome gene expression in tissues while preserving spatial context. Recent advances in sequencing- and imaging-based ST technologies have ushered in the era of microscopic-resolution ST (μST), allowing transcriptome mapping at cellular and even subcellular scales with unprecedented precision. Despite these advances, μST faces substantial challenges, including sparse transcript discovery per submicron (or micron)-sized spatial units and data fragmentation across platforms, hindering integration and analysis.

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Sequencing-based spatial transcriptomics (sST) enables transcriptome-wide gene expression mapping but falls short of reaching the optical resolution (200-300 nm) of imaging-based methods. Here, we present Seq-Scope-X (Seq-Scope-eXpanded), which empowers submicrometer-resolution Seq-Scope with tissue expansion to surpass this limitation. By physically enlarging tissues, Seq-Scope-X minimizes transcript diffusion effects and increases spatial feature density by an additional order of magnitude.

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Spatial transcriptomics technologies aim to advance gene expression studies by profiling the entire transcriptome with intact spatial information from a single histological slide. However, the application of spatial transcriptomics is limited by low resolution, limited transcript coverage, complex procedures, poor scalability and high costs of initial setup and/or individual experiments. Seq-Scope repurposes the Illumina sequencing platform for high-resolution, high-content spatial transcriptome analysis, overcoming these limitations.

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Article Synopsis
  • Spatial transcriptomics (ST) technologies allow for in-depth gene expression analysis at a very fine scale, but traditional methods face challenges due to complex tissue structures and irregular cell shapes.
  • The new method, FICTURE, offers a segmentation-free approach that can analyze large-scale transcriptome data with submicron precision, making it compatible with different types of ST data.
  • FICTURE is significantly more efficient than existing methods and improves our understanding of intricate tissue architectures in challenging areas like vascular and fibrotic tissues, enhancing the exploration of high-resolution spatial transcriptomics.
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Spatial transcriptomics (ST) technologies represent a significant advance in gene expression studies, aiming to profile the entire transcriptome from a single histological slide. These techniques are designed to overcome the constraints faced by traditional methods such as immunostaining and RNA hybridization, which are capable of analyzing only a few target genes simultaneously. However, the application of ST in histopathological analysis is also limited by several factors, including low resolution, a limited range of genes, scalability issues, high cost, and the need for sophisticated equipment and complex methodologies.

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Article Synopsis
  • - The study focuses on skeletal muscle's vital role in movement and metabolism, emphasizing the challenge of mapping gene expression in muscle tissue due to current technological limitations.
  • - Researchers utilized a new technique called Seq-Scope, which allows for high-resolution observation of gene expression in mouse soleus muscle, analyzing differences between healthy and denervated conditions that simulate aging.
  • - Findings reveal detailed insights into muscle composition and gene expression related to muscle injury, contributing greatly to the understanding of muscle function decline with age and paving the way for potential new treatments to enhance muscle health.
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Spatial transcriptomics (ST) technologies have advanced to enable transcriptome-wide gene expression analysis at submicron resolution over large areas. Analysis of high-resolution ST data relies heavily on image-based cell segmentation or gridding, which often fails in complex tissues due to diversity and irregularity of cell size and shape. Existing segmentation-free analysis methods scale only to small regions and a small number of genes, limiting their utility in high-throughput studies.

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Understanding the DNA methylation patterns in the human genome is a key step to decipher gene regulatory mechanisms and model mutation rate heterogeneity in the human genome. While methylation rates can be measured e.g.

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Article Synopsis
  • Autoantibodies against type I interferons (IFNs) are present in some patients with critical COVID-19, affecting 19% of those with critical disease and 6% of severe cases, but not in moderate cases.
  • Analysis of over 600,000 immune cells from patients showed that those with critical disease had a lack of IFN-stimulated responses, particularly in dendritic cells, which produced these autoantibodies.
  • There was also increased expression of the LAIR1 receptor on monocytes, which inversely correlated with the immune response, suggesting that both autoantibodies and LAIR1 contribute to immune suppression in critical COVID-19.
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Spatial barcoding technologies have the potential to reveal histological details of transcriptomic profiles; however, they are currently limited by their low resolution. Here, we report Seq-Scope, a spatial barcoding technology with a resolution comparable to an optical microscope. Seq-Scope is based on a solid-phase amplification of randomly barcoded single-molecule oligonucleotides using an Illumina sequencing platform.

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Article Synopsis
  • Type I interferon (IFN-I) autoantibodies were detected in 19% of critical COVID-19 patients, 6% of severe cases, and none in moderate cases, indicating a higher prevalence in more severe infections.
  • A study analyzing over 600,000 blood cells from various groups revealed that critical COVID-19 patients have an impaired IFN-I stimulated gene (ISG-I) response, particularly in myeloid cells.
  • There is a notable inverse relationship between an inhibitory receptor (LAIR-1) and ISG-I expression, suggesting that this suppressed response may contribute to the severity of COVID-19 through multiple mechanisms.
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Genotype imputation is an indispensable step in human genetic studies. Large reference panels with deeply sequenced genomes now allow interrogating variants with minor allele frequency < 1% without sequencing. Although it is critical to consider limits of this approach, imputation methods for rare variants have only done so empirically; the theoretical basis of their imputation accuracy has not been explored.

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