structural equation model
Definition
A structural equation model (SEM) is a multivariate statistical framework that tests hypothesized causal relationships among observed and latent variables through a system of simultaneous equations. In biological research, SEMs combine path analysis and factor analysis to model complex networks of direct and indirect effects, such as how genetic variants influence disease phenotypes through intermediate molecular mechanisms. SEMs are particularly valuable for integrating multi-omics data, testing mediation pathways, and quantifying the strength of causal links while accounting for measurement error and confounding variables in biological systems.
Visualize structural equation model in Nodes Bio
Researchers can use Nodes Bio to visualize SEM results as directed network graphs where nodes represent variables (genes, proteins, metabolites, phenotypes) and edges show estimated causal effects with path coefficients as weights. This enables intuitive exploration of direct versus indirect pathways, identification of key mediators, and comparison of alternative causal models across different experimental conditions or disease states.
Visualization Ideas:
- Multi-layer causal networks showing genetic variants, molecular intermediates, and phenotypic outcomes with path coefficients
- Mediation pathway diagrams highlighting direct and indirect effects between exposures and disease endpoints
- Comparative SEM networks displaying alternative causal models with goodness-of-fit statistics for model selection
Example Use Case
A research team investigating type 2 diabetes uses SEM to model how genetic variants in TCF7L2 influence glucose homeostasis. Their model includes latent variables for beta-cell function and insulin sensitivity, with observed measurements of gene expression, protein levels, and clinical markers. The SEM reveals that TCF7L2 variants primarily affect glucose control through beta-cell dysfunction rather than insulin resistance, with GLP-1 receptor signaling as a key mediating pathway, informing targeted therapeutic strategies.