Ring syndrome: still true?

Rossi, Elena; Messa, Jole; Zuffardi, Orsetta

doi:10.1136/jmg.2008.060442

Cited by 19 publications

(21 citation statements)

References 26 publications

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“…More recently, the growth failure associated with ‘ring syndrome’ has been suggested to be related to haploinsufficiency due to specific deletions within ring chromosomes, rather than a general mechanism due to ring chromosome formation 31. Our data do not support this, since the majority of the 28 patients we studied do not have any detectable deletions of chromosome 20, and the seven patients with deletions have heterogeneous deletions, with no genes that were uniformly deleted in all patients.…”

Section: Discussioncontrasting

confidence: 84%

Molecular analysis of ring chromosome 20 syndrome reveals two distinct groups of patients

Conlin

Kramer

Hutchinson

et al. 2010

Journal of Medical Genetics

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Section: Discussioncontrasting

confidence: 84%

Molecular analysis of ring chromosome 20 syndrome reveals two distinct groups of patients

Conlin

Kramer

Hutchinson

et al. 2010

Journal of Medical Genetics

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“…However the FISH results on our series revealed only about 1% of monosomic cells in each patient, different to the significantly higher percentage (8%) detected by Elghezal et al [13] but in agreement with the recently reported conclusions weakening the hypothesis of the "ring syndrome" phenotype caused by ring instability [23]. Ring (20) chromosome mosaicism generally represents a de novo event.…”

Section: Discussionsupporting

confidence: 76%

Genetic investigations on 8 patients affected by ring 20 chromosome syndrome

et al. 2010

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BackgroundMosaic Chromosome 20 ring [r(20)] is a chromosomal disorder associated with a rare syndrome characterized by a typical seizure phenotype, a particular electroclinical pattern, cognitive impairment, behavioural problems and absence of a consistent pattern of dysmorphology. The pathogenic mechanism underlying seizures disorders in r(20) syndrome is still unknown. We performed a detailed clinical and genetic study on 8 patients with r(20) chromosome, aimed at detecting the genetic mechanism underlying r(20) syndrome.MethodsWe submitted 8 subjects with a previous diagnosis of ring 20 chromosome mosaicism to a clinical re-evaluation, followed by cytogenetic, FISH, array-CGH and molecular analyses. The genetic study was also extended to their available parents.ResultsFISH and array-CGH experiments indicate that cryptic deletions on chromosome 20 are not the cause of the r(20) chromosome associated disease. Moreover, no evidence of chromosome 20 uniparental disomy was found. Analysis of FISH signals given by variant in size alphoid tandem repeats probes on the normal chromosome 20 and the r(20) chromosome in the mosaic carriers suggests that the r(20) chromosome is the same chromosome not circularized in the "normal" cell line.ConclusionsHigher percentages of r(20) chromosome cells were observed to be related with precocious age at seizure onset and with resistance to antiepileptic drug treatment. Behavioural problems also seem to be associated with higher percentages of r(20) chromosome cells. Our results suggest that an epigenetic mechanism perturbing the expression of genes close to the telomeric regions, rather than deletion of genes located at the distal 20p and/or 20q regions, may underlie the manifestation of r(20) syndrome.

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“…Because these four cases show similar phenotypic features to other MDCR positive patients without monosomy, we propose that the pathological traits are not correlated with the monosomy. Indeed, the concept of the ring chromosome syndrome phenotype due to the mosaic state of the ring chromosome has weakened by emerging an array of comparative genomic hybridization (CGH) data and we cannot exclude the possibility that the ring mosaicism is an artifact of the culture state (11).…”

Section: Discussionmentioning

confidence: 99%

Mild ring 17 syndrome shares common phenotypic features irrespective of the chromosomal breakpoints location

et al. 2009

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Ring 17 syndrome is a rare disorder with clinical features influenced by the presence or deletion of the Miller-Dieker critical region (MDCR). Presence of the MDCR is associated with a mild phenotype, including growth delay (GD), mental retardation (MR), seizures, cafè au lait skin (CALS) spots and minor facial dysmorphisms. Previous studies have been mainly focused on this locus providing poor information about the role of other genes located on the p- and q-arms. Here, we used bacterial artificial chromosome (BAC)/P1 artificial chromosome (PAC) and fosmid clones as fluorescence in situ hybridization (FISH) probes to perform a cyto-molecular analysis of a ring 17 case and found that the breakpoints were close to the telomeric ends. METRNL is the sole gene located on the q-arm terminal end, whereas two open reading frames and the RPH3AL gene are located on the terminal p-arm. To detect possibly unrevealed small deletions involving the transcription units, we used subcloned FISH probes obtained by long-range polymerase chain reaction (PCR), which showed that the investigated regions were preserved. Comparing our findings with other reports, it emerges that different breakpoints, involving (or not) large genomic deletions, present overlapping clinical aspects. In conclusion, our data suggest that a mechanism based on gene expression control besides haploinsufficiency should be considered to explain the common phenotypic features found in the mild ring 17 syndrome.

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Ring syndrome: still true?

Cited by 19 publications

References 26 publications

Molecular analysis of ring chromosome 20 syndrome reveals two distinct groups of patients

Molecular analysis of ring chromosome 20 syndrome reveals two distinct groups of patients

Genetic investigations on 8 patients affected by ring 20 chromosome syndrome

Mild ring 17 syndrome shares common phenotypic features irrespective of the chromosomal breakpoints location

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