Disease relevance of Isochromosomes

• Because p53 abnormalities correlate with progressive and refractory disease in cancer and isochromosome 17q has been described in SLVL, a low-grade lymphoma that behaves aggressively in a minority of patients, this study investigated p53 changes by molecular and immunophenotypic methods in samples from 59 patients [1].
• A new dicentric X isochromosome i(X)(pter to q2102 to pter) of similar size to a normal X is described in a girl with gonadal dysgenesis [2].
• We confirmed that an isochromosome for 12p, i(12p), is the only consistent structural chromosomal abnormality in TGCT, present in about 70% of our cases [3].
• This is the first report of an isochromosome X patient to develop endometrial cancer without receiving estrogen replacement [4].
• The appearance of the face and digits is very similar to that observed in Pallister-Killian syndrome (mosaic isochromosome 12p), although the incidence of cleft palate, diaphragmatic hernia, and neonatal death is much lower in the latter condition [5].

High impact information on Isochromosomes

• Isochromosome 9q in an infant exposed to ethanol prenatally [6].
• These cells frequently become resistant to PALA through a mechanism that increases the aspartate transcarbamylase activity with no increase in CAD copy number, or they obtain one extra copy of CAD by forming an isochromosome 2p or by retaining an extra copy of chromosome 2 [7].
• To test the centromere misdivision model of isochromosome formation, we have defined the breakpoints of cytogenetically monocentric and dicentric Xq isochromosomes (i(Xq)) from Turner syndrome probands, using FISH with cosmids and YACs derived from a contig spanning proximal Xp [8].
• Isochromosomes for the long arm of chromosome 5 of the wheat B genome (5BL) were microdissected from first meiotic metaphase spreads of a monoisosomic 5BL line of the common wheat Triticum aestivum cv. Chinese Spring. The dissected isochromosomes were amplified by degenerate oligonucleotide-primed PCR in a single tube reaction [9].
• A molecular study of X isochromosomes: parental origin, centromeric structure, and mechanisms of formation [10].

Biological context of Isochromosomes

• These factors may be localised within the Y chromosome through the study of structural anomalies of the Y. A thorough review of seven different structural anomalies of the Y is presented: dicentric Y chromosomes, Y isochromosomes, ring Y chromosomes, Y; autosome, Y;X, and Y;Y translocations, and Y deletions [11].
• To determine which segments of a chromosome arm are responsible for the initiation of chiasmate pairing in meiosis, a series of novel isochromosomes was developed in hexaploid wheat (Triticum aestivum L.). These isochromosomes are deficient for different terminal segments in the two arms [12].
• C-banding, quinacrine- and DA/DAPI-staining indicated inactivation of one of the centromeres in almost all Yq isochromosomes [13].
• Cytogenetic studies of a patient with mosaicism of isochromosome 13q and a dicentric (Y;13) translocation showing differential centromeric activity [14].
• Tetrasomy for the short arm of chromosome 12 with accessory isochromosome (+i(12p] and a marked LDH-B gene dosage effect [15].

Anatomical context of Isochromosomes

• Genetic alterations such as isochromosome 12p, 13q loss and CDKN2A/p16 are therefore not common in intracranial germ cell tumors [16].
• Apparently neither the X monosomy nor the Xq isochromosome influences the 'in vitro' X-ray-induced chromosomal damage in Turner syndrome lymphocytes [17].
• Molecular cytogenetic analysis using fluorescence in situ hybridization was used retrospectively to confirm the presence of the isochromosome 12p in various formalin-fixed fetal tissues [18].
• Karyotypes in the peripheral blood and bone marrow cells were mosaic 45,X and 46,X,i(Xq): isochromosome Xq, which were consistent with infertile Turner syndrome [19].

Associations of Isochromosomes with chemical compounds

• Isochromosome for derivative 17q in acute promyelocytic leukemia: evidence for two copies of PML-RARA and favorable response to all-trans-retinoic acid therapy [20].
• OBJECTIVE: Advance knowledge about the mechanism of isochromosome formation [21].
• For 4 months after transformation, isochromosome 21 persisted while the patient was receiving treatment with zidovudine [22].
• A malignant triton tumor with an unbalanced translocation (1;13)(q10;q10) and an isochromosome (8)(q10) as the sole karyotypic abnormalities [23].

Gene context of Isochromosomes

• Several molecular alterations appear to be involved, including isochromosome 17q and the p53, PTCH, and beta-catenin gene mutations [24].
• Isochromosome 12p is a specific aberration frequently observed in MGCT [25].
• Using this approach, we identified medulloblastoma-characteristic alterations, e.g., isochromosome for 17q, MYC amplification and losses on chromosomes 10, 11, and 16, alongside novel regions of genetic loss (e.g., 10q21.1-26.3, 11q24.1-qter) [26].
• SBDS mutations and isochromosome 7q in a patient with Shwachman-Diamond syndrome: no predisposition to malignant transformation [27]?
• Cytogenetic abnormalities that have been described in childhood medulloblastoma include loss of 17p, amplification of MYCC (c-myc), amplification of MYCN (N-myc), and isochromosome 17q [28].

Analytical, diagnostic and therapeutic context of Isochromosomes

• CONCLUSION: Because diaphragmatic hernia is a common component of mosaic isochromosome 12p syndrome and this chromosome abnormality is predominantly found in fibroblasts but not lymphocytes, an amniocentesis may be more accurate than fetal blood sampling in defining the true fetal chromosome status when diaphragmatic hernia is detected prenatally [29].
• Prenatal diagnosis of de novo isochromosome 13q associated with microcephaly, alobar holoprosencephaly and cebocephaly in a fetus [30].
• Analysis of 12 Y-chromosome loci by fluorescent in situ hybridization (FISH) and polymerase chain reaction (PCR) demonstrated that the marker chromosome is of Y origin and corresponds to an authentic isochromosome for the short arm of the Y chromosome, i(Yp) [31].
• Microdissection of the marker followed by reverse painting and array CGH analysis showed that the isochromosome contains approximately 6 Mb of 12pter-12p13.31 derived sequence [32].

References