Subnuclear genome compartmentalization controls bivalent chromatin activity

Area of Science:

• Genomics
• Developmental Biology
• Epigenetics

Background:

• The nuclear genome's 3D architecture involves chromosomal domains associating with subnuclear compartments like the nuclear lamina and nuclear speckles.
• The role of higher-order spatial genome architecture in human development and its interplay with chromatin state and compartmentalization is not well understood.

Purpose of the Study:

• To map high-resolution genomic interactions with the lamina and speckles in human cortical neurogenesis.
• To investigate the association between subnuclear genome compartmentalization, chromatin state, and gene transcription during development.

Main Methods:

• Generation of high-resolution maps of genomic interactions with the nuclear lamina and nuclear speckles.
• Isolation of neurogenic lineage cells from mid-gestational human cortex.
• Analysis of chromatin state, specifically histone modifications like H3K27me3 and H3K4me3, and gene expression.

Main Results:

• Extensive remodeling of subnuclear genome compartmentalization during cortical neurogenesis.
• Relocation of hundreds of neuronal genes, including bivalent developmental genes, from the lamina to speckles.
• Genes at the lamina show low expression, while relocation to speckles enhances bivalent chromatin resolution and increases transcription over eightfold.
• Proximity to the nuclear periphery, not H3K27me3, maintains the poised state of lamina-embedded bivalent genes.
• The lamina's repressive environment segregates transcriptional machinery from the nuclear periphery.

Conclusions:

• Subnuclear genome compartmentalization, chromatin state, and transcription are intimately linked.
• Spatial genome organization is crucial for regulating gene expression during human neurodevelopment.
• Understanding a gene's spatial location is essential for comprehending its epigenomic regulation.