title: Interstitial deletion of proximal 8q including part of the centromere from unbalanced segregation of a paternal deletion/marker karyotype with neocentromere formation at 8p22.
abstract: OBJECTIVE
  The 'McClintock mechanism' of chromosome breakage and centromere misdivision, in which a deleted chromosome with its concomitant excised marker or ring chromosome is formed, has been described in approximately one dozen reports. We report a case of a girl with short stature, developmental delay, and dysmorphic features.
  
  
  METHODS
  Analysis was performed on the proband and father using cytogenetic chromosome analysis and the Affymetrix 6.0 SNP microarray. Fluorescence in situ hybridization (FISH) using a chromosome 8 alpha-satellite probe and immunofluorescence with antibodies to CENP-C were used to examine the centromere positions in these chromosomes.
  
  
  RESULTS
  An abnormal chromosome 8 with a cytogenetically visible deletion was further defined by SNP array as a 10.6-Mb deletion from 8q11.1→q12.1. FISH with a chromosome 8 alpha-satellite probe demonstrated that the deletion removed a significant portion of the pericentromeric alpha-satellite repeat sequences and proximal q arm. The deleted chromosome 8 appeared to have a constriction at 8p22, suggesting the formation of a neocentromere, even though alpha-satellite sequences still appeared at the normal location. Chromosome analysis of the phenotypically normal father revealed the same deleted chromosome 8, as well as an apparently balancing mosaic marker chromosome 8. FISH studies revealed that the majority of the chromosome 8 alpha-satellite DNA resided in the marker chromosome. Immunofluorescence studies with antibodies to CENP-C, a kinetochore protein, proved the presence of a neocentromere at 8p22. The excision of the marker from the deleted chromosome 8 likely necessitated the formation of a new kinetochore at the 8p22 neocentromere to stabilize the chromosome during mitosis.
  
  
  CONCLUSIONS
  This case clearly illustrates the utilization of classic cytogenetics, FISH, and array technologies to better characterize chromosomal abnormalities and provide information on recurrence risks. It also represents a rare case where a neocentromere can form even in the presence of existing alpha-satellite DNA.
authors.affiliation: Laboratory Corporation of America, Research Triangle Park, NC 27709, USA. burnsir@labcorp.com
authors.forename: R D
authors.initials: RD
authors.lastname: Burnside
authors.forename: J
authors.initials: J
authors.lastname: Ibrahim
authors.forename: C
authors.initials: C
authors.lastname: Flora
authors.forename: S
authors.initials: S
authors.lastname: Schwartz
authors.forename: J H
authors.initials: JH
authors.lastname: Tepperberg
authors.forename: P R
authors.initials: PR
authors.lastname: Papenhausen
authors.forename: P E
authors.initials: PE
authors.lastname: Warburton
mesh_terms: D002503:Centromere / Q000235:genetics*; D002648:Child; D002869:Chromosome Aberrations; D002871:Chromosome Banding; D002872:Chromosome Deletion; D020090:Chromosome Segregation / Q000235:genetics*; D002898:Chromosomes, Human, Pair 8 / Q000235:genetics*; D000013:Congenital Abnormalities / Q000235:genetics; D004276:DNA, Satellite / Q000235:genetics; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D018386:Kinetochores; D008297:Male; D010641:Phenotype
chemical_list: D004276:DNA, Satellite