Mechanisms of ring chromosome formation in 11 cases of human ring chromosome 21

We studied the mechanism of ring chromosome 21 (r(21)) formation in 13 patients (11 unique r(21)s), consisting of 7 from five families with familial r(21) and 6 with de novo r(21). The copy number of chromosome 21 sequences in the rings of these patients was determined by quantitative dosage analyses for 13 loci on 21q. Nine of 11 r(21)s, including the 5 familial r(21)s, showed no evidence for duplication of 21q sequences but did show molecular evidence of partial deletion of 21q. These data were consistent with the breakage and reunion of short- and long-arm regions to form the r(21), resulting in deletion of varying amounts of 21q22.1 to 21qter. The data from one individual who had a Down syndrome phenotype were consistent with asymmetric breakage and reunion of 21q sequences from an intermediate isochromosome or Robertsonian translocation chromosome as reported by Wong et al. Another patient, who also exhibited Down syndrome, showed evidence of a third mechanism of ring formation. The likely initial event was breakage and reunion of the short and long arms, resulting in a small r(21), followed by a sister-chromatid exchange resulting in a double-sized and symmetrically dicentric r(21). The phenotype of patients correlated well with the extent of deletion or duplication of chromosome 21 sequences. These data demonstrate three mechanisms of r(21) formation and show that the phenotype of r(21) patients varies with the extent of chromosome 21 monosomy or trisomy.     

Loss of heterozygosity on chromosome 11p13 in primary bladder carcinoma

Although the occurrence of bladder cancer is common, the molecular events underlying the pathogenesis of this cancer remain ill-defined. A loss of heterozygosity (LOH) at specific chromosomal loci may predispose individuals to the development of bladder cancer but this has not been examined in detail. Furthermore, the role that deletion or inactivation of putative tumour suppressor genes might play in the genesis of bladder cancer has not been established. In this study, allelic deletion analysis on the short arm of chromosome 17 of patients with primary bladder tumours failed to show deletion at 17p13 (0/7), a region known to contain the p53 tumour suppressor gene. Chromosome 11p15 showed allelic deletion at the IGF2 locus (2/7: 29%) and the PTH locus (1/11: 9%). However, no deletion was observed at the CALCA locus (0/6). LOH at 11p13, a region containing the Wilm's tumour suppressor gene (WT1), was also studied. Analysis of LOH at 11p13 showed deletion at the CAT locus (13/18: 72%), the J/D11S414 locus (5/15: 33%), the WT1 locus (7/14: 50%) and the FSHB locus (6/16: 38%). The significance of these findings is discussed.     

Recurrent chromosome alterations in transitional cell bladder carcinomas.

A karyotype study was performed in 42 cases of transitional cell bladder carcinoma. The results, confirmed by DNA content evaluation, showed a prevalence of near-diploid modes not related to the histologic grade of differentiation. Nonrandom alterations were represented by monosomy of chromosome 13 and 22, trisomy of chromosome 7 and deletion of chromosomes 6 and 11. These anomalies allow the identification of different sub-groups of tumors, each with its own biological characteristics of aggressiveness. Prognosis was particularly poor in cases with monosomy of chromosomes 13 and 22 but more favourable in poorly differentiated carcinomas with trisomy of chromosome 7.     

A case of ring Y chromosome

Summary Ring Y chromosome 45,X/46,X,r(Y) was identified by fluorescence in a child with ambiguous external genitalia, urogenital sinus, vagina, uterus, and Fallopian tubes. Testicular tissue was noted on gonadal biopsy.     

Maternal transmission of ring chromosome 21

Summary A psychomotor-retarded infant with minor dysmorphic signs and a karyotype 46.XY,r(21)mat in lymphocytes is reported. The mother is phenotypically normal but shows the same unstable r(21). This is another case demonstrating that a chromosomal aberration does not necessarily lead to infertility by meiotic failure. Nevertheless, segregation of ring chromosomes is problematic for two reasons: mitotic problems of the ring structure itself and synaptic difficulties during the pachytene stage.     

The persistence of chromosome translocations in a radiation worker accidentally exposed to tritium.

The chromosome translocation frequency in lymphocytes of an individual accidentally exposed to tritium six years previously was measured using chromosome painting. Comparisons with results from cytogenetic studies shortly after the accident indicate that the translocation frequency has remained unaltered in this individual for six years.     

Nucleolar persistence in embryonal carcinoma cells

A series of embryonal carcinoma (EC) lines were found to have nucleoli which persisted through metaphase and anaphase in 60–88% of cells. When these cells differentiated, either spontaneously or upon chemical induction with retinoic acid or dimethylacetamide, the level of nucleolar persistence dropped to under 20%. Mouse embryo fibroblasts and mouse bone marrow cells had few persistent nucleoli. Persistent nucleoli in EC cells contained DNA, labeled with tritiated uridine and stained with ammoniacal silver, all of which support the hypothesis that rRNA synthesis continues in persistent nucleoli.     

A case report of Turner's syndrome with ring X chromosome.

A case of Turner's syndrome with short stature and 45, XO/46, XXr mosaicism in chromosome study was presented. With special emphasis on endocrinological study, the size of the breasts was normal in contrast to the poor development of the breasts in most of types of Turner's syndrome. She showed normal thyroid function, slightly low level of urinary 17-OHCS, decreased 17-KS, poor response in metopirone test and poor response of HGH to insulin.     

Tandem duplication chromosome 21 in the offspring of a ring chromosome 21 carrier

A direct tandem duplication chromosome 21 was found in a boy with Down's syndrome. The proband's mother and grandmother both carried a ring chromosome 21. The observed duplication chromosome in the child may be explained either by recombination between the maternal ring and the mother's normal chromosome 21 or by break of a double-sized ring chromosome 21.     

CYFRA 21-1: A potential molecular marker for noninvasive differential diagnosis of urothelial carcinoma of bladder

Establishing CYFRA 21-1 detection for noninvasive differential diagnosis of urothelial carcinoma (UC) of bladder would help to improve assessment and follow-up of patients, as well as to improve screening of high-risk groups. The study group comprised of 147 subjects including 72 patients with UC of bladder, 75 controls and 17 follow-up cases. The levels of CYFRA 21-1 in serum, urine and urinary cell lysate were estimated by high sensitivity ELISA. Our results indicate that urinary CYFRA 21-1 provides a high value of overall sensitivity for UC of bladder and is also useful even for detection of low grade tumors that might indicate possible earlier detection and treatment administration.     

Unstable ring Y chromosome in an aspermic male

Summary A ring Y chromosome was found in a male showing growth retardation and aspermia but normally developed external genitalia. The ring does not display either the characteristic brilliant Y fluorescence or the typical latereplicating heterochromatin.