Genetic separation of Brca1 functions reveal mutation-dependent Polθ vulnerabilities.

Homologous recombination (HR)-deficiency induces a dependency on DNA polymerase theta (Polθ/Polq)-mediated end joining, and Polθ inhibitors (Polθi) are in development for cancer therapy. BRCA1 and BRCA2 deficient cells are thought to be synthetic lethal with Polθ, but whether distinct HR gene mutations give rise to equivalent Polθ-dependence, and the events that drive lethality, are unclear. In this study, we utilized mouse models with separate Brca1 functional defects to mechanistically define Brca1-Polθ synthetic lethality.

Immense random colocalization, revealed by automated high content image cytometry, seriously questions FISH as gold standard for detecting EML4-ALK fusion.

EML4-ALK gene fusion (inv2(p21p23)) of non-small cell lung cancer (NSCLC) predisposes to tyrosine kinase inhibitor treatment. One of the gold standard diagnostics is the dual color (DC) break-apart (BA) FISH technique, however, the unusual closeness of the involved genes has been suggested to raise likelihood of random co-localization (RCL) of signals. Although this is suspected to decrease sensitivity (often to as low as 40-70%), the exact level and effect of RCL has not been revealed thus far.

Losses of both products of the Cdkn2a/Arf locus contribute to asbestos-induced mesothelioma development and cooperate to accelerate tumorigenesis.

The CDKN2A/ARF locus encompasses overlapping tumor suppressor genes p16(INK4A) and p14(ARF), which are frequently co-deleted in human malignant mesothelioma (MM). The importance of p16(INK4A) loss in human cancer is well established, but the relative significance of p14(ARF) loss has been debated. The tumor predisposition of mice singly deficient for either Ink4a or Arf, due to targeting of exons 1α or 1β, respectively, supports the idea that both play significant and nonredundant roles in suppressing spontaneous tumors.

The use of M-FISH and M-BAND to define chromosome abnormalities.

Multicolour fluorescence in situ hybridisation (M-FISH) and multicolour banding (M-BAND) are advanced chromosome painting techniques combining multiple chromosome- or region-specific paints in one step. M-FISH identifies all chromosomes or chromosome arms at once, whereas M-BAND identifies the different regions of a single chromosome. The use of either or both can improve the accuracy of karyotyping and help identify cryptic chromosome rearrangements.

Molecular cytogenetic investigation of two patients with Y chromosome rearrangements and intellectual disability.

We describe two males with intellectual disability (ID) and facial dysmorphism, both of whom have non-mosaic Y chromosome rearrangements resulting in deletions of large portions of the Y chromosome. Patient A, with ID, mild dysmorphism, speech delay, Duane anomaly of the eye, hypermetropia and conductive hearing loss, had two structurally rearranged Y chromosomes resulting in both p and q arm deletions in addition to a Yp duplication. Patient B, also with speech and language delay, developmental delay and short stature, had an interstitial deletion of Yq11.

Detailed characterization of 7q deletions by multicolor banding (mBAND) in marginal zone cell lymphoma.

High-resolution multicolor banding (mBAND) analysis was applied to precisely fine-map the genomic extent of 7q deletions in a series of 26 marginal zone lymphoma patients displaying the abnormality on conventional karyotypes. Using this approach, the breakpoints and the extent of deletions revealed by conventional banding techniques had to be re-defined in 70% of cases. Although no common minimal region of deletion was delineated, mBAND demonstrated the involvement of the 7q32 region in more than 90% of cases.

Maternally inherited duplication of chromosome 7, dup(7)(p11.2p12), associated with mild cognitive deficit without features of Silver-Russell syndrome.

We report on a familial duplication in the short arm of chromosome 7, dup(7)(p11.2p12), present in three generations. The duplication was identified by GTG-banding and fluorescence in situ hybridization (FISH) with a whole chromosome 7 DNA painting probe that verified that the duplicated material originated from chromosome 7.

Intrachromosomal amplification of chromosome 21 (iAMP21) may arise from a breakage-fusion-bridge cycle.

Intrachromosomal amplification of chromosome 21 (iAMP21), involving amplification of the RUNX1 gene and duplication of chromosome 21, dup(21q), defines a new cytogenetic subgroup in B-lineage acute lymphoblastic leukemia (ALL) with a poor prognosis. Characterization of this abnormality has become vital to ensure that the most accurate detection method is used. We have previously defined common regions of amplification and deletion of chromosome 21 in these patients, although the level and extent of amplification within the amplicon was highly variable.

A FISH comparison of variant derivatives of the recurrent dic(17;20) of myelodysplastic syndromes and acute myeloid leukemia: Obligatory retention of genes on 17p and 20q may explain the formation of dicentric chromosomes.

The dic(17;20) is a recurrent unbalanced translocation occurring rarely in myelodysplastic syndromes and acute myeloid leukemia. We have studied eleven cases with the dic(17;20) or a more complex derivative, all of which showed deletion of 17p and 20q material. The tumor suppressor gene TP53 was not always lost, supporting a more distal gene as the target of these 17p deletions.

[Characterization of marker chromosomes using molecular cytogenetic methods in patients with mental retardation and congenital malformations].

Introduction: Until recently, great variety of marker chromosomes and difficulties with their identification have presented a problem for cytogenetic and clinical interpretation of the karyotype. At present, molecular cytogenetic methods of chromosome analysis enable precise characterization of such abnormalities providing knowledge necessary for estimation of their genetic risk.

Aim: The aim of the study was molecular cytogenetic characterization of marker chromosomes recognized in three patients, an analysis of clinical features in relation to the abnormality and estimation of genetic risk of identified markers.

Constitutional tetrasomy 18p.

We present here the first case of constitutional tetrasomy 18p from India. A 3 year old female with developmental delay and dysmorphic features revealed 47,XX,+mar karyotype. The small meta-centric marker chromosome was identified as i(18p) with m-FISH followed by m-BAND.

FISH studies on the telomeric regions of the T-cell acute lymphoblastic leukemia cell line CCRF-CEM.

So far, the problem of an influence of translocations on the telomeres of the involved chromosomes has not been addressed yet in human cells. Therefore, the telomeres of a karyotypically rather well characterized T-cell acute lymphoblastic leukemia (T-ALL) cell line (CCRF-CEM) with several marker chromosomes were examined using peptide nucleic acid (PNA) telomere FISH probes to compare the telomere length of these markers with that of the chromosome arms of their origin. In addition, chromosome libraries, centromeric probes, and subtelomeric DNA probes were used to further define the marker chromosomes.

Rearrangements of the telomeric region of mouse chromosome 11 in Pre-B ABL/MYC cells revealed by mBANDing, spectral karyotyping, and fluorescence in-situ hybridization with a subtelomeric probe.

Previous work has demonstrated that chromosome 11 is trisomic or shows a duplicated region encompassing the E1/E2 band of chromosome 11 in 90% of v-abl/myc-induced plasmacytomas (Wiener et al. 1995). In the present report, we have studied BALB/c PreB lymphocytes that were immortalized by v-abl and stably transfected with a conditional MycER vector (Mai et al.

A de novo complex karyotype with two independent balanced translocations and a double inversion of chromosome 6 presenting with multiple congenital anomalies.

We report a 4-year-old female with a de novo complex karyotype with multiple chromosomal rearrangements and a distinctive phenotype. Her medical history is significant for having been a twin born at 35 weeks gestation, breech presentation, with feeding problems and poor growth as an infant, gastroesophageal reflux disease, peripheral pulmonic stenosis, omphalocele, high myopia, and severe mental retardation. She is small for her age with microcephaly, posteriorly sloping forehead, shallow orbits, long palpebral fissures, prominent nose, wide mouth, absent uvula, kyphosis, brachydactyly, bridged palmar crease, and hypertonia.

mBAND: a high resolution multicolor banding technique for the detection of complex intrachromosomal aberrations.

Precise breakpoint definition of chromosomal rearrangements using conventional banding techniques often fails, especially when more than two breakpoints are involved. The classic banding procedure results in a pattern of alternating light and dark bands. Hence, in banded chromosomes a specific chromosomal band is rather identified by the surrounding banding pattern than by its own specific morphology.

Chromosome intrachanges and interchanges detected by multicolor banding in lymphocytes: searching for clastogen signatures in the human genome.

Genomic fingerprints of mutagenic agents would have wide applications in the field of cancer biology, epidemiology and prevention. The differential spectra of chromosomal aberrations induced by different clastogens suggest that ratios of specific aberrations can be exploited as biomarkers of carcinogen exposure. We have tested this hypothesis using the novel technique of multicolor banding in situ hybridization (mBAND) in human peripheral blood lymphocytes exposed in vitro to X rays, neutrons, heavy ions, or the restriction endonuclease AluI.

A multiple translocation event in a patient with hexadactyly, facial dysmorphism, mental retardation and behaviour disorder characterised comprehensively by molecular cytogenetics. Case report and review of the literature.

Unlabelled: We report a 13-year-old female patient with multiple congenital abnormalities (microcephaly, facial dysmorphism, anteverted dysplastic ears and postaxial hexadactyly), mental retardation, and adipose-gigantism. Ultrasonography revealed no signs of a heart defect or renal abnormalities. She showed no speech development and suffered from a behavioural disorder.

Cytogenetic evolution of human ovarian cell lines associated with chemoresistance and loss of tumorigenicity.

In order to identify genomic changes associated with a resistant phenotype acquisition, we used comparative genomic hybridization (CGH) to compare a human ovarian cell line, Igrov1, and four derived subcell lines, resistant to vincristine and presenting a reversion of malignant properties. Multicolor FISH (Multiplex-FISH and Spectral Karyotype) and conventional FISH are also used to elucidate the karyotype of parental cell line. The drug-resistant subcell lines displayed many chromosomal abnormalities suggesting the implication of different pathways leading to a multidrug resistance phenotype.

Cryptic t(X;18), ins(6;18), and SYT-SSX2 gene fusion in a case of intraneural monophasic synovial sarcoma.

A 54-year-old male presented with a spontaneous peroneal nerve palsy and a diagnosis of monophasic synovial sarcoma (SS) was rendered by histologic examination. Cytogenetic analysis revealed a complex abnormal karyotype without evidence of the typical t(X;18)(p11;q11) associated with SS. Subsequent reverse transcriptase polymerase chain reaction analysis showed the presence of an SYT/SSX2 fusion transcript, confirming the presence of a cyptic t(X;18).

The DNA-based structure of human chromosome 5 in interphase.

In contrast to those of metaphase chromosomes, the shape, length, and architecture of human interphase chromosomes are not well understood. This is mainly due to technical problems in the visualization of interphase chromosomes in total and of their substructures. We analyzed the structure of chromosomes in interphase nuclei through use of high-resolution multicolor banding (MCB), which paints the total shape of chromosomes and creates a DNA-mediated, chromosome-region-specific, pseudocolored banding pattern at high resolution.

Multicolor-FICTION: expanding the possibilities of combined morphologic, immunophenotypic, and genetic single cell analyses.

Phenotypic and genotypic analyses of cells are increasingly essential for understanding pathogenetic mechanisms as well as for diagnosing and classifying malignancies and other diseases. We report a novel multicolor approach based on the FICTION (fluorescence immunophenotyping and interphase cytogenetics as a tool for the investigation of neoplasms) technique, which enables the simultaneous detection of morphological, immunophenotypic, and genetic characteristics of single cells. As prerequisite, multicolor interphase fluorescence in situ hybridization assays for B-cell non-Hodgkin's lymphoma and anaplastic large-cell lymphoma have been developed.

Identification of a dup(5)(p15.3) by multicolor banding.

A 7-year-old female was referred to the Genetics Clinic because of developmental delay and attentional difficulty. The patient was adopted and there was a nonspecific prenatal history of drug and alcohol abuse. The patient had clinical signs that were not compatible with typical fetal alcohol syndrome (FAS), although there was a history of alcohol exposure in utero, neurodevelopmental difficulties with learning and behavioral problems, and mild dysmorphisms.