An Interstitial 4q Deletion with a Mosaic Complementary Ring Chromosome in a Child with Dysmorphism, Linear Skin Pigmentation, and Hepatomegaly.

Interstitial deletions of 4q are rarely reported, vary in size, and have limited genotype-phenotype correlations. Here, genome-wide array CGH analysis identified a 21.6 Mb region of copy number loss at 4q12-q21.1 in a patient diagnosed with dysmorphism, linear skin pigmentation, and hepatomegaly. An additional small ring chromosome was detected in 5/30 cells examined via G-banding. Confirmation of the origin of the ring chromosome was obtained by FISH analysis which identified that the ring chromosome contained material from the deleted region of chromosome 4 and was therefore complementary to the 21.6 Mb deletion. Further microarray studies in the proband using a different microarray platform showed no evidence of mosaicism. This case highlights the importance of an integrated approach to cytogenetic analysis and demonstrates the value of G-banding for detecting mosaicism, as current microarray platforms are unable to detect low level mosaics.

Phenotypic effects of balanced X-autosome translocations in females: a retrospective survey of 104 cases reported from UK laboratories.

Females with balanced X-autosome translocations are a clinically heterogeneous group of patients in which X breakpoint position and replication behaviour may influence phenotypic outcome. This study reviewed all cases reported by UK cytogenetics laboratories over a 15-year period (1983-1997). Publication bias was avoided by reviewing all reported cases. One hundred and four female carriers were identified, 62 of who were probands. By reason for referral, these were: multiple congenital abnormalities and/or developmental delay (MCA/DD): 26 (42%); gonadal dysfunction: 22 (35%); phenotypically normal with or without recurrent miscarriage (NRM): 9 (15%); recognized X-linked syndrome: 5 (8%). The information obtained was compared with published data and with data from the authors' own laboratories of female patients with balanced autosome-autosome translocations (n=115). We concluded that: (1) MCA/DD cases were significantly over-represented compared to previous published data (P<0.005) and were more common than in female probands with balanced autosome-autosome translocations (P<0.05). (2) MCA/DD cases showed random breakpoint distribution along the X chromosome (P>0.05). MCA/DD cases with subtelomeric breakpoints at Xp22 or Xq28 were not always associated with deviation from the expected pattern of X-inactivation where this was known. De novo cases were significantly more likely to be assigned as MCA/DD than any other category (P<0.005). (3) Gonadal dysfunction (GD) was invariably associated with a 'critical region' breakpoint, Xq13-q26, (20/22 probands). However, 7/44 (16%) of patients surveyed had breakpoints within Xq13-Xq26 and proven fertility. (4) Recognized 'X-linked syndrome' cases were significantly under-represented (P<0.001) compared to previous published data.

Trends in cytogenetic prenatal diagnosis in the UK: results from UKNEQAS external audit, 1987-1998.

The aim of this audit was to evaluate trends in mean reporting time, culture success rate and abnormality rate for conventional cytogenetic prenatal diagnoses for amniotic fluid samples (AFS) and chorionic villus samples (CVS) in the UK. Anonymized data in the form of retrospective external audits were obtained from UKNEQAS in Clinical Cytogenetics annual reports, for AFS (1987-1997/98) and CVS (1988-1997/98). UK laboratories providing a prenatal service by referral criteria applicable at local level participated in the scheme. Over the period the number of AFS processed per annum increased from 28 639 to 36 817 (29 per cent) and for CVS from 2294 to 7918 (245 per cent). CVS made up 17.6 per cent of the total sample numbers in 1997/98 compared with 7.4 per cent in 1988. Reporting times and culture success rates have improved, notably overall reporting time means have fallen from 20.2 to 13.8 days for AFS and 21.3 to 14.5 days for CVS. Data submitted by individual laboratories suggest that further reductions in mean reporting times for both sample types are feasible. Such a potential improvement, if achieved by all laboratories, may question the value of a supplementary FISH or PCR-based 'rapid' aneuploidy screening test prior to karyotyping.

The sequential analysis of trisomy 12 in B-cell chronic lymphocytic leukaemia.

In this longitudinal study we evaluated the clinical significance of screening for trisomy 12 by fluorescence in situ hybridization (FISH) and correlated these findings with survival, disease progression and need for treatment. Interphase FISH was performed on 85 patients in 1993/94 and repeated on 41 patients in 1996/97. Over the 4-year period there was no significant change in the percentage of trisomic cells, even in patients with disease progression. Overall survival and requirement for treatment were similar for patients with and without FISH-defined trisomy 12.

Deletions at 11q identify a subset of patients with typical CLL who show consistent disease progression and reduced survival.

Eighty-four patients with typical chronic lymphocytic leukemia (CLL) (by morphological and immunophenotypic criteria) on whom karyotypes were available were studied. Binet stage at diagnosis and follow-up were defined. Survival was calculated from diagnosis. Fifty-one percent of patients had a karyotypic abnormality, the commonest being abnormalities at 13q14 (16%); these patients did not have significantly different survival from patients with normal karyotype. The second commonest abnormality was del(11q) (13%); these patients had significantly worse survival when compared both with patients with normal karyotype (P < 0.0001) and with other patients with karyotypic abnormality (P = 0.0012). All patients with del(11q) had progressed to stage C at follow-up while only 20% of the other patients had shown any disease progression (P < 0.0001). Del(11q) may identify a subset of patients with typical CLL who have worse survival and consistent disease progression and in future may help define a group of patients with CLL who could benefit from earlier or more intensive therapy.

Solid tissue culture for cytogenetic analysis: a collaborative survey for the Association of Clinical Cytogeneticists.

AIMS: To survey the diagnostic service provided by UK laboratories for the culture of solid tissue samples (excluding tumours) and in particular to examine the variation in culture success rates and the problems of maternal cell overgrowth. METHODS: Twenty seven laboratories took part in a collaborative survey during 1992. Each laboratory submitted data on up to a maximum of 60 consecutive specimens (n = 1361) over a six month period. RESULTS: Skin specimens, the largest category received (n = 520), were the most problematic (51% success rate). Culture success rates were significantly lower (43%) when skin specimens (n = 140) were transported dry to the laboratory. Success rates for skin specimens also varied, depending on the origin of the specimen, from 18% for intra-uterine deaths (IUD) (n = 94) to 85% for neonatal deaths (n = 33) and 83% for live patients (n = 54). Culture of selected extra-fetal tissues from IUD, stillbirths and following elective termination of pregnancy (TOP) gave comparable success rates to those achieved for skin samples from neonatal deaths and live births. Skewed sex ratios, female > male, were identified for products of conception (POC) (n = 298) and placental biopsy specimens (n = 97). CONCLUSIONS: By appropriate selection, transport and processing of tissues, and in particular by avoiding relying solely on skin samples from IUD, stillbirths and TOP, an increase in culture success rates for solid tissue samples submitted for cytogenetic analysis could be achieved. The high risk of maternal cell contamination from POC and placental biopsy specimens was also identified in this survey.

A DA/DAPI positive human 14p heteromorphism defined by fluorescence in-situ hybridisation using chromosome 15-specific probes D15Z1 (satellite III) and p-TRA-25 (alphoid).

We have investigated the use of the satellite III probe, D15Z1, as an alternative to DA/DAPI staining in the identification of chromosome 15-derived markers. The probe hybridises to the short arm of chromosome 15 under high stringency conditions. We have screened 100 randomly selected patients, by fluorescence in-situ hybridisation (FISH), using co-hybridisation experiments with D15Z1 and a whole chromosome library, pBS-15. 88 individuals showed the expected pattern of two D15Z1 signals on the p-arm of both homologues of chromosome 15, whereas 12 individuals showed an additional signal on a third acrocentric D-group chromosome. Sequential GTC banding and D15Z1 hybridisation revealed that in each case it was one homologue of chromosome 14 that was D15Z1 positive. This pattern always correlated with positive DA/DAPI staining. In contrast, the 15 centromere-specific alphoid probe, pTRA-25, gave the expected two signals on both homologues of chromosome 15 in every case. Thus, D15Z1 and DA/DAPI signals co-localize while pTRA-25 is 15 centromere-specific and should be applied for unequivocal identification of chromosome 15-derived markers in clinical studies. The chromosome 14 heteromorphism, as identified by D15Z1, and defined by pTRA-25, may have arisen by intrachromosomal amplification or interchromosomal exchange.

Chromosome in situ suppression hybridisation in clinical cytogenetics.

The use of chromosome in situ suppression hybridisation with whole chromosome libraries has previously been reported by various research laboratories to be an effective method of identifying specific human chromosomal material. As a clinical cytogenetic service laboratory we have used the technique as a complement to diagnosis by classical chromosome banding. In three examples of structural rearrangements the potential use of the 'chromosome painting' method is assessed for its ability to enhance the routine cytogenetic service currently available.

Transplants of mouse trisomy 16 hippocampus provide a model of Alzheimer's disease neuropathology.

Alzheimer's disease, which is characterized by amyloid plaques and neurofibrillary tangles, may be attributed to the abnormal expression of gene(s) located on human chromosome 21. Genetic linkage studies have narrowed the region of candidate genes to 21q11.2-21q22 of the long arm of this chromosome. Several single copy sequences within this region, including the amyloid precursor protein (APP), have been mapped to mouse chromosome 16. Reliable strategies exist for breeding Trisomy 16 mice. However, the consequences of developmental overexpression of genes on chromosome 16 have not been previously investigated, because of the lethal effects of this aneuploidy during gestation. In the present report, we employ neural transplantation to study long-term survival and pathogenesis in Trisomy 16 central nervous system tissues. Immunocytochemical staining with antiserum raised against the synthetic APP, beta-A4 and alpha 1-antichymotrypsin revealed numerous densely stained cells within hippocampal grafts of Trisomy 16 mice. Similarly, a population of grafted cells were positively stained following incubation with an antiserum raised against components of the pathological neurofibrillary tangle and with the monoclonal antibodies Tau 6.423 and ubiquitin.

Robertsonian translocation and an extra microchromosome: independent origin identified by in situ hybridization.

Robertsonian translocation may result in either a monocentric or a dicentric product involving the long arms of the participating chromosomes. In the former case a microchromosome involving the short arms of both acrocentrics would be expected to arise, but in practice is rarely observed. Where such small bisatellited markers are seen in association with Robertsonian translocations, they are assumed to represent such reciprocal products. We present a case, involving a t(14q21q) and a DA/DAPI positive microchromosome, where using in situ hybridization we show that this assumption is incorrect and that the microchromosome has arisen independently.

Prenatal diagnosis of a double bisatellited marker with an unusual copy number ratio.

Prenatal diagnosis, by amniocentesis, revealed mosaicism with respect to a bisatellited, apparently dicentric, DA/DAPI positive, de novo marker. The following cell lines were observed in decreasing order of frequency: 46,XX greater than 48,XX,+mar,+mar much greater than 47,XX,+mar. The pregnancy was terminated and post-mortem examination revealed an apparently normal fetus. Cytogenetic studies of fetal and placental tissues revealed approximately the same level of mosaicism together with the unusual copy number ratio seen in the amniotic fluid cultures. Non-disjunction at the first post-zygotic mitotic division giving rise to a mosaic: 46,XX/48,XX,+mar,+mar followed by subsequent mitotic instability of the marker could account for the unusual copy number ratio.

Trisomy 20q caused by der (X)t(X;20)(q28;q11.2).

A first case of "pure" trisomy 20q (q11.2-qter) is described in a female child with minor anomalies and developmental delay. This resulted from the inheritance, from a carrier mother, of an abnormal X chromosome: der (X)t(X;20)(q28;q11.2). Involvement of other autosomes has complicated the interpretation of the phenotypic effect of trisomy 20q in previously published case reports. Red cell gene dosage studies using adenosine deaminase (ADA) have confirmed that the proposita is trisomic for 20q. Taken together with RBG staining studies, these results suggest that there is incomplete inactivation, if any, of the autosomal portion of the consistently late-replicating abnormal X. Unexpectedly, ADA gene dosage results in the carrier mother showed a level of gene expression about half that of normal controls.

The mechanism of chromosomal translocation t(11;14) involving the T-cell receptor C delta locus on human chromosome 14q11 and a transcribed region of chromosome 11p15.

A chromosomal translocation t(11;14) (p15;q11) is described in a human acute T-cell leukaemia of immature phenotype (CD3-, CD4-, CD8-). The translocation occurs at a T-cell receptor joining J delta segment, 12 kb upstream of the constant C delta gene and 98 kb upstream of the C alpha gene at chromosome band 14q11. Nucleotide sequencing shows that both J delta and C delta are very conserved between mouse and man. The region of chromosome 11 involved in the translocation is transcriptionally active and produces a 4-kb mRNA. The DNA sequence at the chromosome 11 junction shows a perfect match to a recombinase signal sequence implying that this translocation occurred by recombinase error. The occurrence of the translocation breakpoint at the C delta locus, normally rearranged in immature T cells, and the structure of the translocation junctions suggests that the translocation occurred during an attempt at normal rearrangement of the J delta segment in an early thymocyte.

Cytogenetic abnormalities in human small cell lung carcinoma: cell lines characterized for myc gene amplification.

Nine cell lines established from various malignant tissues of patients with small cell lung carcinoma (SCLC) were examined for chromosomal abnormalities and myc gene amplification. Cytogenetic studies revealed that all cell lines were aneuploid, often with a bimodal distribution with modal concentrations in the hypodiploid and hypertriploid range. With respect to chromosome #3, deletions of 3p were confined to six of nine SCLC "classic" lines. The region of overlap of the observed 3p deletions lies within 3p21-3p24 which is in agreement with previous assignments. Six of the nine lines tested with c-, N-, and L-myc probes showed an increase of between ten- and 100 fold in myc gene copy number. Coamplification of two or more of these genes was not observed in any cell line. Five of the six lines with myc gene amplification had cytogenetic markers of gene amplification either in the form of homogeneously staining regions (HSR) or double minutes (DM). Our results confirm that cytogenetically visible deletions of 3p are often present in cell lines established from patients with SCLC, and that mutually exclusive c-, L-, or N-myc gene amplification is also a common event in SCLC cell lines.

Oncogene amplification and chromosomal abnormalities in small cell lung cancer.

Twelve cell lines isolated from patients with small cell lung cancer have been studied for amplification of the three characterised members of the myc proto-oncogene family (c-myc, N-myc, and L-myc) and for abnormalities of chromosome 3. Ten of these lines were being studied for the first time. Ten of the 12 small cell lung cancer cell lines had amplification of one member of the myc proto-oncogene family. Amplification of c-myc was observed in only one small cell lung line--a "morphological variant". One "classic" small cell lung cancer line expressed c-myc but had no obvious amplification of the gene. N-myc and L-myc were more commonly amplified than c-myc. Chromosomal abnormalities (mainly deletions) in chromosome 3 were observed in all small cell lung carcinoma cell lines examined. When the small cell lung carcinoma lines were grouped according to "classic" or "variant" characteristics, it was found that the "classics" had deletions of the short arm of chromosome 3, whereas the "biochemical variants" had deletions of the long arm of chromosome 3. The extent of the deletions varied between cell lines. For the deletion in the short arm of chromosome 3 the minimum common region of overlap was assigned to bands 3p23-3p24.