Pericentromeric

Pericentromeric refers to the region of a chromosome that lies adjacent to the centromere on each arm. These regions are distinct from the centromeric core and are commonly described as constitutive heterochromatin in many organisms.

In many species, the pericentromeric domain is rich in repetitive DNA sequences, such as satellite DNA, and contains remnants of transposable elements. The chromatin is typically highly condensed and marked by heterochromatin-associated histone modifications (for example, H3K9me3) and binding by HP1 proteins. Pericentromeric DNA is often late-replicating and has low gene density, which supports a stable genome structure near the centromere.

Functionally, the pericentromeric region contributes to chromosome architecture and stability. It helps maintain proper sister-chromatid cohesion and can suppress recombination in the surrounding region, preserving centromere identity. In many organisms, pericentromeric heterochromatin participates in nuclear organization and may influence kinetochore function indirectly by shaping the local chromatin environment.

Variation in size and composition of pericentromeric blocks is common across species and even among chromosomes within a species. Their repetitive content makes them challenging to assemble in reference genomes. Studying pericentromeric regions often relies on methods such as fluorescence in situ hybridization, long-read sequencing, and chromatin profiling.

Alterations in pericentromeric regions, including rearrangements and changes in heterochromatin state, can contribute to chromosomal instability and missegregation. The study of pericentromeric regions informs understanding of chromosome evolution, genome organization, and species-specific chromosomal biology.