RNA velocity is a way of measuring the changes in gene expression. It is derived from ratio of spliced to unspliced RNA in the cell over time. Monitoring this value over time allows to see if the gene of interest is induced or repressed. It can be used to predict future changes in gene expression or cell differentiation
There are several software tools available for RNA velocity analysis.Each of these tools has its own strengths and applications, so the choice of tool would depend on the specific requirements of analysis:
Velocyto is a package for the analysis of expression dynamics in single cell RNA seq data. In particular, it enables estimations of RNA velocities of single cells by distinguishing unspliced and spliced mRNAs in standard single-cell RNA sequencing protocols. It is the first paper proposed the concept of RNA velocity. Velocyto works by solving the proposed differential equations for each gene.
scVelo is a method that solves the full transcriptional dynamics of splicing kinetics using a likelihood-based dynamical model. This generalizes RNA velocity to systems with transient cell states, which are common in development and in response to perturbations. scVelo was applied to understanding subpopulation kinetics in neurogenesis and pancreatic hormone secretion.
cellDancer is a scalable deep neural network that locally infers velocity for each cell from its neighbors and then relays a series of local velocities to provide single-cell resolution inference of velocity kinetics. Unlike previous models it does not infer the same velocity values for all the cells in the experiment.
MultiVelo is a differential equation model of gene expression that extends the RNA velocity framework to incorporate epigenomic data. MultiVelo uses a probabilistic latent variable model to estimate the switch time and rate parameters of chromatin accessibility and gene expression .
DeepVelo is a neural networkâÂÂbased ordinary differential equation that can model transcriptome dynamics by describing continuous-time gene expression changes within individual cells. DeepVelo has been applied to public datasets from different sequencing platforms to (i) formulate transcriptome dynamics on different time scales, (ii) measure the instability of cell states, and (iii) identify developmental driver genes via perturbation analysis.
UnitVelo is a statistical framework of RNA velocity that models the dynamics of spliced and unspliced RNAs via flexible transcription activities. UnitVelo supports the inference of a unified latent time across the transcriptome.