Presence of telomeric and subtelomeric sequences at the fusion points of ring chromosomes indicates that the ring syndrome is caused by ring instability

Annalisa Pezzolo, Giorgio Gimelli, Amnon Cohen, Antonella Lavaggetto, Cesare Romano, Giuseppina Fogu, Orsetta Zuffardi

Research output: Contribution to journalArticle


In situ hybridization of a telomeric (TTA-GGG)n sequence to metaphases from three cases of ring chromosome, involving respectively chromosomes 4, 16, and 20, showed the presence of the cognate sequences in all three rings. To investigate whether these ring chromosomes originated by telomere-telomere fusion, we determined, by in situ hybridization, whether telomere-associated sequences and/or specific distal sequences were still present in the ring chromosomes. The finding that these sequences were preserved in all the ring chromosomes strongly indicates that they originated by telomere-telomere fusion. All three subjects carrying the ring chromosomes are affected by the so-called ring syndrome, with failure to thrive, minor dysmorphic signs and no major anomalies. The r(4) patient has the ring in mosaic form with a normal cell line and has normal intelligence. The r(16) and the r(20) patients have moderate mental retardation and suffer from seizures. We conclude that the ring syndrome, even in its more severe manifestation, is caused by ring chromosome instability.

Original languageEnglish
Pages (from-to)23-27
Number of pages5
JournalHuman Genetics
Issue number1
Publication statusPublished - Aug 1993


ASJC Scopus subject areas

  • Genetics(clinical)
  • Genetics

Cite this