bioRxiv Science⌕ Search

Biology subjects

Megas, S.

Publications and source records attributed to Megas, S..

2 recordsLinked to original sources

Integrating multi-covariate disentanglement with counterfactual analysis on synthetic data enables cell type discovery and counterfactual predictions.

Single-cell gene expression is influenced by diverse covariates such as genomics protocol, tissue origin, donor attributes, and microenvironment, which are challenging to disentangle. We present CellDISECT, a novel method combining disentangled representations and causal inference for multi-batch, multi-covariate single-cell data analysis. CellDISECT employs a mixture of expert variational autoencoders to learn covariate-specific and unsupervised latent spaces, enabling counterfactual predictions and biological discovery. Drawing inspiration from LLM training on synthetic data, CellDISECT generates synthetic counterfactuals during training and their quality is scored in the loss function. This semi-autoencoding of counterfactuals during training increases model performance in counterfactual predictions at test time. Benchmarking across datasets, CellDISECT outperformed existing methods in disentanglement, counterfactual in-silico prediction of responses to perturbations, and cell type discovery. CellDISECT predicted responses of cells to changing tissue microenvironments and identified a novel pre-natal megakaryocyte subpopulation with immune characteristics distinct from classical platelet-producing MKs, highlighting its unique capabilities in single-cell analysis to help identify novel subpopulations and reduce concerns of technical effects during integration.

genomics↗

A multiomic atlas of human early skeletal development

Bone and joint formation in the developing skeleton rely on co-ordinated differentiation of progenitors in the nascent developing limbs and joints. The cell states, epigenetic processes and key regulatory factors underlying their lineage commitment to osteogenic and other mesenchymal populations during ossification and joint formation remain poorly understood and are largely unexplored in human studies. Here, we apply paired single-nuclei transcriptional and epigenetic profiling of 336,000 droplets, in addition to spatial transcriptomics, to construct a comprehensive atlas of human bone, cartilage and joint development in the shoulder, hip, knee and cranium from 5 to 11 post-conception weeks. Spatial mapping of cell clusters to our highly multiplexed in situ sequencing (ISS) data using our newly developed tool ISS-Patcher revealed new cellular mechanisms of zonation during bone and joint formation. Combined modelling of chromatin accessibility and RNA expression allowed the identification of the transcriptional and epigenetic regulatory landscapes that drive differentiation of mesenchymal lineages including osteogenic and chondrogenic lineages, and novel chondrocyte cell states. In particular, we define regionally distinct limb and cranial osteoprogenitor populations and trajectories across the fetal skeleton and characterise differential regulatory networks that govern intramembranous and endochondral ossification. We also introduce SNP2Cell, a tool to link cell-type specific regulatory networks to numerous polygenic traits such as osteoarthritis. We also conduct in silico perturbations of genes that cause monogenic craniosynostosis and implicate potential pathogenic cell states and disease mechanisms involved. This work forms a detailed and dynamic regulatory atlas of human fetal skeletal maturation and advances our fundamental understanding of cell fate determination in human skeletal development.

developmental biology↗