Laminachromatin

Laminachromatin refers to regions of chromatin that are in close physical association with the nuclear lamina, a structure formed by a fibrous meshwork of lamins underlying the inner nuclear membrane. In many metazoan cells, large portions of the genome are organized into lamina-associated domains (LADs) that contact the lamina. Laminachromatin is typically gene-poor and transcriptionally inactive, and it displays late replication timing and enrichment for repressive histone marks such as H3K9me2/3 and H3K27me3.

The lamina-chromatin contacts are mediated by lamin proteins (notably Lamin B1 and somatic Lamin A/C) and lamina-associated proteins (LBR, Emerin, LAP2 family, MAN1), which anchor chromatin to the periphery via protein-protein and protein-DNA interactions. These connections help shape higher-order genome organization by juxtaposing peripheral, repressed chromatin with more internal, active domains.

Functionally, laminachromatin contributes to global genome organization by partitioning the genome into peripherally anchored LADs and interior euchromatic regions. This organization is thought to help stabilize repressed genes, regulate replication timing, and coordinate development. The composition and size of laminachromatin domains can change during differentiation, development, aging, and in disease states. Alterations of lamina-chromatin interactions have been implicated in laminopathies and in altered nuclear architecture observed in cancer cells.

Methods such as DamID, lamin ChIP, and Hi-C-based mapping have been used to study laminachromatin and LADs, revealing extensive interactions between the nuclear envelope and the genome.