The cis-regulatory dynamics of embryonic development at single-cell resolution

Area of Science:

• Developmental Biology
• Genomics
• Epigenetics

Background:

• Understanding gene regulatory networks controlling cell fate is crucial for developmental biology.
• Single-cell gene expression studies offer insights into lineage commitment, but regulatory mechanisms remain unclear.
• Investigating chromatin accessibility dynamics provides a deeper understanding of developmental processes.

Purpose of the Study:

• To investigate the dynamics of chromatin regulatory landscapes during embryogenesis at single-cell resolution.
• To uncover cis-regulatory programs governing metazoan germ layer and cell type specification.
• To identify tissue-specific regulatory elements and validate their germ-layer specificity.

Main Methods:

• Employed single-cell combinatorial indexing assay for transposase accessible chromatin with sequencing (sci-ATAC-seq).
• Profiled chromatin accessibility in over 20,000 single nuclei from fixed Drosophila melanogaster embryos across three key developmental stages.
• Validated predicted enhancers for germ-layer specificity in transgenic embryos.

Main Results:

• Observed spatial heterogeneity in regulatory genome accessibility before gastrulation, correlating with future cell fates.
• Demonstrated that individual cell types can be inferred by chromatin accessibility patterns during mid-embryogenesis.
• Identified 30,075 distal regulatory elements with tissue-specific accessibility, achieving 90% validation accuracy for enhancers.

Conclusions:

• Single-cell profiling of embryos effectively resolves dynamic chromatin landscape changes during development.
• Uncovered conserved regulatory element usage between endoderm and non-myogenic mesoderm, suggesting a shared mesendoderm program.
• Provides a high-resolution map of regulatory elements crucial for metazoan development.