title: Subtelomeric rearrangements in Indian children with idiopathic intellectual disability/developmental delay: Frequency estimation & clinical correlation using fluorescencein situhybridization (FISH).
abstract: OBJECTIVE
  Subtelomeres are prone to deleterious rearrangements owing to their proximity to unique sequences on the one end and telomeric repetitive sequences, which increase their tendency to recombine, on the other end. These subtelomeric rearrangements resulting in segmental aneusomy are reported to contribute to the aetiology of idiopathic intellectual disability/developmental delay (ID/DD). We undertook this study to estimate the frequency of subtelomeric rearrangements in children with ID/DD.
  
  
  METHODS
  One hundred and twenty seven children with idiopathic ID/DD were tested for subtelomeric rearrangements using karyotyping and FISH. Blood samples were cultured, harvested, fixed and GTG-banded using the standard protocols.
  
  
  RESULTS
  Rearrangements involving the subtelomeres were observed in 7.8 per cent of the tested samples. Detection of rearrangements visible at the resolution of the karyotype constituted 2.3 per cent, while those rearrangements detected only with FISH constituted 5.5 per cent. Five deletions and five unbalanced translocations were detected. Analysis of parental samples wherever possible was informative regarding the inheritance of the rearrangement.
  
  
  CONCLUSIONS
  The frequency of subtelomeric rearrangements observed in this study was within the reported range of 0-35 per cent. All abnormal genotypes were clinically correlated. Further analysis with array technologies presents a future prospect. Our results suggest the need to test individuals with ID/DD for subtelomeric rearrangements using sensitive methods such as FISH.
authors.affiliation: Department of Human Genetics, Sri Ramachandra University, Porur, India.
authors.forename: Shruthi
authors.initials: S
authors.lastname: Mohan
authors.affiliation: Department of Human Genetics, Sri Ramachandra University, Porur, India.
authors.forename: Teena
authors.initials: T
authors.lastname: Koshy
authors.affiliation: Department of Human Genetics, Sri Ramachandra University, Porur, India.
authors.forename: Perumal
authors.initials: P
authors.lastname: Vekatachalam
authors.affiliation: Department of Paediatric Genetics, Amrita Institute of Medical Sciences, Kochi, India.
authors.forename: Sheela
authors.initials: S
authors.lastname: Nampoothiri
authors.affiliation: Department of Paediatric Genetics, Amrita Institute of Medical Sciences, Kochi, India.
authors.forename: Dhanya
authors.initials: D
authors.lastname: Yesodharan
authors.affiliation: Department of Medical Genetics, CHILDS Trust Medical Research Foundation, Kanchi Kamakoti CHILDS Trust Hospital, Chennai, India.
authors.forename: Kalpana
authors.initials: K
authors.lastname: Gowrishankar
authors.affiliation: Department of Medical Genetics, CHILDS Trust Medical Research Foundation, Kanchi Kamakoti CHILDS Trust Hospital, Chennai, India.
authors.forename: Jeevan
authors.initials: J
authors.lastname: Kumar
authors.affiliation: Department of Paediatrics, Sri Ramachandra University, Porur, India.
authors.forename: Latha
authors.initials: L
authors.lastname: Ravichandran
authors.affiliation: Department of Radiology, Sri Ramachandra University, Porur, India.
authors.forename: Santhosh
authors.initials: S
authors.lastname: Joseph
authors.affiliation: Department of Radiology, Sri Ramachandra University, Porur, India.
authors.forename: Anupama
authors.initials: A
authors.lastname: Chandrasekaran
authors.affiliation: Department of Human Genetics, Sri Ramachandra University, Porur, India.
authors.forename: Solomon F D
authors.initials: SF
authors.lastname: Paul
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002869:Chromosome Aberrations; D002658:Developmental Disabilities / Q000235:genetics* / Q000473:pathology; D005260:Female; D015321:Gene Rearrangement / Q000235:genetics*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D007223:Infant; D008607:Intellectual Disability / Q000235:genetics* / Q000473:pathology; D059785:Karyotype; D008297:Male; D016615:Telomere / Q000235:genetics*