Decoding cnidarian cell type gene regulation.

Area of Science:

• Evolutionary biology
• Genomics
• Cell biology

Background:

• Animal cell types arise from differential gene expression, controlled by transcription factors binding to cis-regulatory elements (CREs).
• Understanding the gene regulatory networks (GRNs) that define cell identities is crucial for deciphering cell type evolution, especially in early-branching animals like cnidarians.
• Cnidarians offer insights into the early evolution of cell type-specific genome regulation.

Purpose of the Study:

• To profile chromatin accessibility and identify CREs in the sea anemone Nematostella vectensis.
• To decode the regulatory grammar governing CRE activity and infer cell type relationships.
• To reconstruct GRNs defining cnidarian cell types and explore conserved principles of animal gene regulation.

Main Methods:

• Chromatin accessibility profiling in ~60,000 cells from Nematostella vectensis adults and embryos.
• Identification and activity quantification of 112,728 putative CREs across cell types.
• Training sequence-based models to predict CRE accessibility and integrating data with transcription factor expression to reconstruct GRNs.

Main Results:

• Discovery of 112,728 putative CREs with pervasive combinatorial enhancer usage and distinct promoter architectures.
• Development of predictive models that infer cell type similarities reflecting known ontogenetic relationships.
• Reconstruction of GRNs defining cnidarian cell types, revealing regulatory complexity in a simple animal.

Conclusions:

• The study elucidates the regulatory complexity underlying cell differentiation in cnidarians.
• Identified conserved principles in animal gene regulation, providing a foundation for comparative regulatory genomics.
• Highlights the importance of studying early-branching metazoans for understanding the evolution of animal cell type diversity.