Disease relevance of Ring Chromosomes

• In contrast, in the two stably dedifferentiated hepatoma cell lines, amplified dihydrofolate reductase genes are found on large chromosomes of variable size, on ring chromosomes, and on chromosomes containing terminal, median, or multiple centromeres [1].
• Genetics of dermatofibrosarcoma protuberans family of tumors: from ring chromosomes to tyrosine kinase inhibitor treatment [2].
• A ring chromosome 6 has been identified by GTG-banding in a male with microcephaly, growth retardation, seizures, epicanthus, hypertelorism, micrognathia, and other congenital anomalies [3].
• Comparison of the phenotype of five other patients with a ring chromosome 10 with the present case showed the following common manifestations: growth retardation, microcephaly, undescended testes, hydronephrosis, and, in males, posterior urethral valves [4].
• A ring chromosome 7 was found in a 19-month-old girl with microcephaly, growth and developmental delay, multiple angiomas, and partial sacral agenesis [5].

Psychiatry related information on Ring Chromosomes

• Despite the fact that mental retardation, microcephaly, seizures, and hyperactivity are common in patients with ring chromosome 4, little has been written about the underlying neuropathology [6].

High impact information on Ring Chromosomes

• The phenotypically normal father and grandfather of the patient each had a small supernumerary ring chromosome and demonstrated three copies for the loci D22S9, D22S43, and ATP6E [7].
• Studies of the ring chromosome that has XIST DNA but does not transcribe it show that its AR allele is transcribed along with the one on the normal X allele.(ABSTRACT TRUNCATED AT 250 WORDS)[8]
• Telomeric sequences also were observed within a ring chromosome [9].
• We found that a MAR had been deleted from one of the two rabbit immunoglobulin kappa-chain genes and that MARs reside next to a long interspersed repetitive element within the recombination junction of a human ring chromosome 21 [10].
• Six cases of epilepsy associated with ring chromosome 20 are presented [11].

Chemical compound and disease context of Ring Chromosomes

• Polyhydramnios associated with a ring chromosome and low maternal serum alpha-fetoprotein levels managed with indomethacin [12].

Biological context of Ring Chromosomes

• In contrast, three highly polymorphic anonymous probes, YNZ22.1 (D17S5), YNH37.3 (D17S28), and 144-D6 (D17S34), were deleted in each of four patients with visible deletions, including one with a ring chromosome 17 that is deleted for a portion of the single telomeric prometaphase subband p13 [13].
• It is suggested that the clinical features associated with this ring chromosome are more likely to be the result of the effects of a diploid/monosomy 4/polysomy 4 mosaicism than to the deficiency of the telomeric regions of the chromosome [14].
• MDM2 gene amplification correlates with ring chromosome in soft tissue tumors [15].
• It is characterized by the presence of ring chromosomes or chromosomal translocations fusing the promoter of the collagen gene COL1A1 to the platelet-derived growth factor beta-chain gene PDGFB, increasing the production of PDGF locally and promoting autocrine or paracrine tumor growth [16].
• Cytogenetic and molecular characterization of a small ring chromosome in the complex karyotype of a girl with Turner syndrome [17].

Anatomical context of Ring Chromosomes

• A male child with features of the Russell-Silver syndrome, including pre- and postnatal growth delay, triangular facies, bilateral fifth finger clinodactyly, and disproportionate lower extremities, was found to have a ring chromosome 15 in all peripheral leucocytes examined [18].
• The son with bilateral WT had a ring chromosome (R) both in the lymphocytes as well as in the kidney tissue [19].
• In addition to the 14q+ anomaly, a 6q- and a ring chromosome were seen in a blood sample stimulated with lipopolysaccharide, a B-cell mitogen [20].
• PET evidence for a role of the basal ganglia in patients with ring chromosome 20 epilepsy [21].

Associations of Ring Chromosomes with chemical compounds

• PET with 6-18F-L-3,4-fluorodihydroxyphenylalanine (18F-fluoro-L-DOPA) has recently demonstrated a reduction of striatal dopamine uptake in drug-resistant epileptic patients with ring chromosome 20 (r20) using a multiple-time graphical analysis [22].
• The results indicate that DS cells exposed to bleomycin are hypersensitive to the production of dicentric and ring chromosomes compared to normal cells [23].
• The induction of 2-break chromosome aberrations (dicentrics and ring chromosomes) in human lymphocytes by the antitumor agents bleomycin and peplomycin is strongly enhanced when those agents are applied together with the heart drug verapamil (isoptin) [24].

Gene context of Ring Chromosomes

• In addition, a cell line with a ring chromosome 21 containing a breakpoint which excluded the distal part of the q22.3 band was negative for expression of PFKL [25].
• Carriers of the XRCC1 codon 280His variant allele had a two-fold increase (frequency ratio [FR] = 2.01, 95% confidence interval [CI] = 1.01-3.98; P = 0.046) in unstable exchanges (dicentrics and ring chromosomes) [26].
• Meiotic recombination between this ring chromosome and a linear homolog produces new molecules of sizes distinguishable on gels from either parental molecule [27].
• A 61-kb ring chromosome shows an ARS-dependent increase in its mitotic stability in the mcm2 mutant of yeast [28].
• A possible explanation is haploinsufficiency of the COL6A1, COL6A2, and/or COL18A genes located on the distal portion of chromosome 21q, which are lost when the ring chromosome is formed [29].

Analytical, diagnostic and therapeutic context of Ring Chromosomes

• The genetic and EEG finding from this patient strongly suggest that epilepsy associated with 20 ring chromosome syndrome is a distinct new entity, although the clinical manifestations may be broader than previously recognized [30].
• In situ hybridization studies, gene dosage, and DNA polymorphism analysis showed that the ring chromosome carries a duplicated region which extends from D21S406 on the centromeric side and includes marker D21S3 on the telomeric side [31].

References