Telomere Dysfunction in Human Astrocytes Drives Acrocentric Chromosome Instability and Nucleolar Reorganization

Area of Science:

• Cellular and Molecular Biology
• Genomics and Genetics
• Cancer Research

Background:

• Loss of tumor suppressors p53 and Rb allows cells to divide despite telomere erosion, leading to telomere crisis.
• The longitudinal dynamics of structural genomic damage during telomere crisis are not fully understood.

Purpose of the Study:

• To investigate the long-term effects of telomere erosion and crisis on genomic structure and organization in human cells.
• To elucidate the role of the nucleolus in response to telomere dysfunction and subsequent genomic instability.

Main Methods:

• Transduction of normal human astrocytes (NHA) with HPV18 E6/E7 to induce crisis.
• Multicolor fluorescence in situ hybridization (FISH) for chromosomal abnormality detection.
• Immunofluorescence microscopy for nucleolar structure analysis.
• Hi-C and KaryoScope (alignment-free k-mer approach) for chromatin contact analysis.

Main Results:

• NHA E6/E7 cells exhibited telomere shortening, anaphase bridges, and a growth plateau characteristic of crisis.
• FISH identified frequent, subclonal abnormalities in acrocentric chromosomes (13, 21, 22), often missed by short-read sequencing.
• Nucleoli transitioned from compact spheres to dispersed necklace-like structures.
• Hi-C and KaryoScope revealed a persistent depletion of inter-chromosomal contacts among acrocentric chromosomes.

Conclusions:

• Telomere crisis induces significant genomic rearrangements, particularly affecting acrocentric chromosomes.
• Nucleolar structural reorganization is a hallmark of telomere dysfunction and is linked to altered higher-order chromatin organization.
• The nucleolus acts as a critical nexus connecting telomere erosion to large-scale genomic instability and rearrangements.