Biology subjects

Kallas, T.

Publications and source records attributed to Kallas, T..

3 recordsLinked to original sources

bioRxiv2025

Single-Cell Protein Interactomes by the Proximity Network Assay

Cellular functions depend on dynamic interactions of proteins and their spatial organisation. While transcriptomic and proteomic methods of molecular parts-lists have enabled single-cell profiling based on abundance, scalable technologies allowing high-resolution measurements of protein organization and interactions at scale are lacking. Here we present the Proximity Network Assay (PNA), a DNA-based method for constructing three-dimensional nanoscale maps of 155 plasma membrane proteins in single cells without the use of optics. PNA employs barcoded antibodies and in situ rolling circle amplification to generate >40,000 spatial nodes per cell, which are linked through proximity-dependent gap-fill ligation and decoded by DNA sequencing forming single cell Proximity Networks. PNA captures abundance, self-clustering, and [~]12,000 pairwise colocalization relationships per single-cell, validating established protein interactions. This new modality provides a framework to uncover novel spatial biomarkers, reveal functional mechanisms, and advance translational studies in immunology, oncology, and cell therapy.

bioengineering↗

bioRxiv2023

Molecular Pixelation: Single cell spatial proteomics by sequencing

The spatial distribution of cell surface proteins govern vital processes of the immune system such as inter-cell communication and mobility. However, tools for studying these at high multiplexing scale, resolution, and throughput needed to drive novel discoveries are lacking. We present Molecular Pixelation, a DNA-sequencing based method for single cell analysis to quantify protein abundance, spatial distribution, and colocalization of targeted proteins using Antibody Oligonucleotide Conjugates (AOCs). Relative locations of AOCs are inferred by sequentially associating these into local neighborhoods using DNA-pixels containing unique pixel identifier (UPI) sequences, forming >1,000 connected spatial zones per single cell in three dimensions. DNA-sequencing reads are computationally arranged into spatial single cell maps for 76 proteins without cell compartmentalization. By studying immune cell dynamics and using spatial statistics on graph representations of the data, previously known and novel patterns of protein spatial polarization and co-localization were found in chemokine-stimulated T-cells.

immunology↗

bioRxiv2016

BLISS: quantitative and versatile genome-wide profiling of DNA breaks in situ

We present a method for genome-wide DNA double-strand Breaks (DSBs) Labeling In Situ and Sequencing (BLISS) which, compared to existing methods, introduces several key features: 1) high efficiency and low input requirement by in situ DSB labeling in cells or tissue sections directly on a solid surface; 2) easy scalability by performing in situ reactions in multi-well plates; 3) high sensitivity by linearly amplifying tagged DSBs using in vitro transcription; and 4) accurate DSB quantification and control of PCR biases by using unique molecular identifiers. We demonstrate the ability to use BLISS to quantify natural and drug-induced DSBs in low-input samples of cancer cells, primary mouse embryonic stem cells, and mouse liver tissue sections. Finally, we applied BLISS to compare the specificity of CRISPR-associated RNA-guided endonucleases Cas9 and Cpf1, and found that Cpf1 has higher specificity than Cas9. These results establish BLISS as a versatile, sensitive, and efficient method for genome-wide DSB mapping in many applications.

molecular biology↗