title: Terminal 18q deletions are stabilized by neotelomeres.
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.
authors.affiliation: Department of Morphology and Genetics, Universidade Federal de São Paulo, Rua Botucatu 740, CEP 04023-900, São Paulo, Brazil.
authors.forename: Roberta Santos
authors.initials: RS
authors.lastname: Guilherme
authors.affiliation: Department of Human Genetics, Emory University School of Medicine, 615 Michael Street Northeast, GA 30322, Atlanta, USA.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Hermetz
authors.affiliation: Department of Biophysics, Universidade Federal de São Paulo, Rua Três de Maio 100, CEP 04023-900, São Paulo, Brazil.
authors.forename: Patrícia Teixeira
authors.initials: PT
authors.lastname: Varela
authors.affiliation: Department of Morphology and Genetics, Universidade Federal de São Paulo, Rua Botucatu 740, CEP 04023-900, São Paulo, Brazil.
authors.forename: Ana Beatriz Alvarez
authors.initials: AB
authors.lastname: Perez
authors.affiliation: Department of Morphology and Genetics, Universidade Federal de São Paulo, Rua Botucatu 740, CEP 04023-900, São Paulo, Brazil.
authors.forename: Vera Ayres
authors.initials: VA
authors.lastname: Meloni
authors.affiliation: Department of Human Genetics, Emory University School of Medicine, 615 Michael Street Northeast, GA 30322, Atlanta, USA.
authors.forename: M Katharine
authors.initials: MK
authors.lastname: Rudd
authors.affiliation: Department of Pathology, Laboratório de Citogenômica, Universidade de São Paulo, Avenida Dr. Enéas Carvalho de Aguiar 255, CEP 05403-000, São Paulo, Brazil.
authors.forename: Leslie Domenici
authors.initials: LD
authors.lastname: Kulikowski
authors.affiliation: Department of Morphology and Genetics, Universidade Federal de São Paulo, Rua Botucatu 740, CEP 04023-900, São Paulo, Brazil.
authors.forename: Maria Isabel
authors.initials: MI
authors.lastname: Melaragno
keywords: Breakpoint sequencing; Neotelomere; Stabilization mechanism; Telomere capture; Telomere healing; Terminal 18q deletion