Terminal 18q deletions are stabilized by neotelomeres.

Mol Cytogenet

Department of Morphology and Genetics, Universidade Federal de São Paulo, Rua Botucatu 740, CEP 04023-900, São Paulo, Brazil.

Published: May 2015

AI Article Synopsis

  • Human chromosomes are protected by tandem repeat sequences (TTAGGG)n at their ends, which are crucial for maintaining chromosomal integrity and preventing fusions, especially after breakage.
  • This study focused on nine patients with terminal deletions on chromosome 18, utilizing various techniques like G-banding, genomic arrays, and FISH to investigate the breakpoints and telomeric features of the deleted chromosomes.
  • The analysis revealed that all sequenced deleted chromosomes had telomeric sequences attached to their breakpoints, suggesting that these chromosomes likely stabilized through a healing process that led to the formation of new telomeres (neotelomeres).

Article Abstract

Background: All human chromosomes are capped by tandem repeat (TTAGGG)n sequences that protect them against end-to-end fusion and are essential to chromosomal replication and integrity. Therefore, after a chromosomal breakage, the deleted chromosomes must be stabilized by retaining the telomere or acquiring a new cap, by telomere healing or telomere capture. There are few reports with molecular approaches on the mechanisms involved in stabilization of 18q terminal deletions.

Results: In this study we analyzed nine patients with 18q terminal deletion identified by G-banding and genomic array. FISH using PNA probe revealed telomeric signals in all deleted chromosomes tested. We fine-mapped breakpoints with customized arrays and sequenced six terminal deletion junctions. In all six deleted chromosomes sequenced, telomeric sequences were found directly attached to the breakpoints. Little or no microhomology was found at the breakpoints and none of the breaks sequenced were located in low copy repeat (LCR) regions, though repetitive elements were found around the breakpoints in five patients. One patient presented a more complex rearrangement with two deleted segments and an addition of 17 base pairs (bp).

Conclusions: We found that all six deleted chromosomes sequenced were probably stabilized by the healing mechanism leading to a neotelomere formation.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4427916PMC
http://dx.doi.org/10.1186/s13039-015-0135-6DOI Listing

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