Neocentric small supernumerary marker chromosomes (sSMC)--three more cases and review of the literature

Here we report on three new patients with neocentric small supernumerary marker chromosomes (sSMC) derived from chromosome 2, 13 and 15, respectively. The sSMC(13) and sSMC(15) had inverted duplicated shapes and the sSMC(2) a ring chromosome shape. All three cases were clinically severely abnormal. A review of the available sSMC literature revealed that up to the present 73 neocentric sSMC cases including these three new cases have been reported. Seven of these cases were not characterized morphologically; in the remainder, 80% had an inverted duplication, 17% a ring and 3% a minute shape. 81% of the reported neocentric sSMC carriers showed severe, 12% moderate and 8% no clinical abnormalities. In summary, we report three more neocentric sSMC cases, provide a review on all up to now published cases, highlight their special characteristics and compare them to centric sSMC.

Molecular karyotyping using an SNP array for genomewide genotyping

BACKGROUND

Chromosomal imbalances are a major cause of developmental defects as well as cancer and often constitute the key in identification of novel disease related genes. Classical cytogenetic methods are limited in resolution and dependent on highly skilled labour, while methods with higher resolution, based on molecular cytogenetics approaches such as matrix CGH, are not widely available.

METHODS

We have developed and evaluated a method we term "molecular karyotyping", using readily available and easy to handle oligonucleotide arrays originally designed for parallel genomewide analysis of over 10,000 SNPs. We show that we can easily and reliably detect unbalanced chromosomal aberrations of various sizes from as little as 250 ng of DNA on a single microarray, based on fluorescence intensity information from clusters of SNPs.

RESULTS

We determined the resolution of this method through analysis of 20 trios with 21 previously confirmed subtle aberrations sizing between 0.2 and 13 Mb. Duplications and deletions of at least 5 Mb in size were reliably detectable, but detection of smaller aberrations was dependent on the number of SNPs they contained, thus seven of 10 different deletions analysed, with sizes ranging from 0.2 to 3.7 Mb, were not detectable due to insufficient SNP densitiy in the respective region.

CONCLUSIONS

Deduction of reliable cut off levels for array peaks in our series of well characterised patients allows the use of the GeneChip Mapping 10K SNP array for performing rapid molecular karyotyping from small amounts of DNA for the detection of even subtle deletions and duplications with high sensitivity and specificity.

Glutaric aciduria type III: a distinctive non-disease?

Glutaric aciduria type III is a rare metabolic abnormality leading to persistent isolated glutaric acid excretion. We report the clinical and biochemical phenotypes of three affected children. The first patient is a boy with dysmorphic features and a chromosomal deletion (monosomy 6q26-qter) in whom a persistent glutaric aciduria (500 mmol/mol creatinine, normal <10) was detected during a routine metabolic investigation. The second boy suffered from acute gastroenteritis and hyperthyroidism, when an excessively high urinary glutaric acid excretion was identified (1460 mmol/mol creatinine). The third patient is a girl with constantly elevated glutaric acid in her urine (290 mmol/mol creatinine) but no symptoms of significant disease. In all our patients, glutaric aciduria type I (glutaryl-CoA dehydrogenase deficiency), glutaric aciduria type II (multiple acyl-CoA dehydrogenation defect), and secondary forms of glutaric aciduria (for example due to intestinal infections or mitochondrial dysfunction) could be excluded. Loading with the precursor amino acid lysine in all patients as well as with pipecolic acid in the third case led to an increase in urinary glutaric acid excretion, proving the endogenous origin of glutarate. Glutaric aciduria type III (a defect reported to be caused by peroxisomal glutaryl-CoA oxidase deficiency) is our presumptive diagnosis. However, peroxisomal glutaryl-CoA oxidase is not well characterized and no reliable approach for the direct determination of this enzyme is available to us. To our knowledge, in the English language literature only a single patient with glutaric aciduria type III has been described. Our cases reported here confirm the earlier assumption that glutaric aciduria type III is not related to a distinctive phenotype. Glutaric aciduria type III appears to be a rare metabolic abnormality, presumably of peroxisomal metabolism. However, its pathophysiological impact still needs further investigation.

Monosomy 1p36--a recently delineated, clinically recognizable syndrome

Monosomy 1p36 is a recently delineated contiguous gene syndrome, which is now considered to be one of the most common subtelomeric microdeletion syndromes. We report four unrelated patients with subtle deletions within 1p36 confirmed by high resolution karyotyping and FISH. All exhibited severe psychomotor retardation. Microcephaly, seizures, and visual impairment occurred in three subjects. Results of a first routine karyotyping were unrevealing in three probands. The diagnosis was primarily suggested on the basis of a distinct pattern of facial anomalies in all except the first case. This report illustrates that monosomy 1p36 may be recognized clinically, at least in some patients, whereas the diagnosis is easily missed on routine karyotype.

FISH monitoring of 100 courses of human leukemias: the cytogenetic viewpoint

Interphase fluorescence in situ hybridization (I-FISH) analyses were performed from 2 up to 13 times along the course of 100 human leukemias (36 chronic myeloid leukemias, 38 acute myeloblastic leukemias, 17 acute lymphoblastic leukemias, and 9 additional hematopoietic neoplasias) in order to control clonality, evolution, and disappearance of the basic cytogenetic changes. The relevance of these data to confirm clinical remission or to detect minimal residual disease and/or relapse was evaluated. Fifty-four patients were monitored following hematopoietic stem cell transplantation, and 46 cases after chemotherapy. Various chromosome or aberration specific DNA probes were applied for follow-up in the time frame of 1 month up to 13 years. From the cytogenetic point of view, the aim was to determine the power of resolution of the I-FISH technique in the detection of clinically significant changes in the course of disease and its usefulness in daily routine cyto-genetics as compared with classical cytogenetics. In addition, reliability standards of the various DNA probes should be established. In 75 patients with remissions during the entire period of I-FISH monitoring no conspicuous signal constitution was detected. Of 25 relapses or progresses of disease, which were clinically confirmed, 22 were reliably detected by I-FISH, in only 1 case I-FISH monitoring failed to detect the aberrant clone. In 2 patients conventional karyotype analysis confirmed the relapse by detecting complex chromosomal aberrations, but specific probes for I-FISH confirmation were not available. These data suggest that I-FISH analyses in the follow-up of leukemias is a simple and in most cases sufficiently sensitive and highly reliable way of monitoring the outcome of therapy. It may well serve to close the gap between conventional karyotyping and the highly sensitive molecular techniques.

Deletion 15q24-26 in prenatally detected diaphragmatic hernia: increasing evidence of a candidate region for diaphragmatic development

Survival of children with congenital diaphragmatic hernia (CDH) is mainly dependent on the extent of lung hypoplasia and the presence of additional congenital anomalies or chromosomal aberrations. A chromosomal deletion 15q25-q26.2 in a fetus with prenatally diagnosed CDH and growth retardation is reported. Despite optimal pre- and neonatal management the baby died shortly after birth. There is increasing evidence that the long arm of chromosome 15, and especially the region 15q24 to 15q26, plays a crucial role in the development of the diaphragm. The finding of a deletion within 15q24-26 in a fetus with CDH has to be considered a predictor of poor prognosis. It is of utmost interest for proper parental counselling to search in fetuses with CDH for subtle chromosomal lesions paying special attention to chromosome 15q.

First known microdeletion within the Wolf-Hirschhorn syndrome critical region refines genotype-phenotype correlation

Deletions within HSA band 4p16.3 cause Wolf-Hirschhorn syndrome (WHS), which comprises mental retardation and developmental defects. A WHS critical region (WHSCR) of approximately 165 kb has been defined on the basis of 2 atypical interstitial deletions; however, genotype-phenotype correlation remains controversial, due to the large size of deletion usually involving several megabases. We report on the first known patient with a small de novo interstitial deletion restricted to the WHSCR who presented with a partial WHS phenotype consisting only of low body weight for height, speech delay, and minor facial anomalies; shortness of stature, microcephaly, seizures and mental retardation were absent. The deletion was initially demonstrated by FISH analysis, and breakpoints were narrowed with a "mini-FISH" technique using 3-5 kb amplicons. A breakpoint-spanning PCR assay defined the distal breakpoint as disrupting the WHSC1 gene within intron 5, exactly after an AluJb repeat. The proximal breakpoint was not found to be associated with a repeated sequence or a known gene. The deletion encompasses 191.5 kb and includes WHSC2, but not LETM1. Thus, manifestations attributable to this deletion are reduced weight for height, minor facial anomalies, ADHD and some learning and fine motor deficiencies, while seizures may be associated with deletions of LETM1.

The cytogenetic view of standard comparative genomic hybridization (CGH): deletions of 20q in human leukemia as a measure of the sensitivity of the technique

BACKGROUND

The limits of the resolving power of comparative genomic hybridization (CGH) have been given as 10-20 Mbp if at least 50% of the studied neoplastic cell population carried the corresponding aberration.

MATERIAL AND METHODS

Genomic DNA of five cases of hematologic neoplasias, in all of which--among other anomalies--deletions of different size of chromosome 20q were found by GTG banding and confirmed by FISH analyses, was subjected to CGH.

RESULTS

CGH revealed four types of del(20q), and, in addition, detected a tiny terminal del(3p) in one of the cases. The size of the smallest deleted segment, clearly visible by eye on the CGH metaphase image, was estimated to range between 5 and 7 Mbp.

CONCLUSION

Visual determination was shown to have a stronger resolving power in CGH than software used for the analysis in one case, while in another one, the results obtained from the ratio profiles would have been considered insignificant without the knowledge of the hybridization pattern on the corresponding CGH metaphase images. The potential of the standard CGH technique not only to detect, but visualize small segmental aneusomies as well, suggests that its resolution actually mirrors the resolution of banding techniques.

Comparative genomic hybridization-aided unraveling of complex karyotypes in human hematopoietic neoplasias

The information obtained by conventional cytogenetics (CC) in human leukemias is sometimes limited, in particular by complex karyotypes with many marker chromosomes. While CC is restricted to metaphases with a good quality, interphase fluorescence in situ hybridization (I-FISH) is also capable of analyzing specific anomalies in the interphase nuclei. Comparative genomic hybridization (CGH) gives additional information about the imbalanced karyotype changes in the whole genome. The aim of this study was to assess the contribution of CGH to the unraveling of complex GTG karyotypes, which are difficult to evaluate by banding analysis, and to compare these results with those by CC and FISH. Thirteen bone marrow samples and one sample obtained from peripheral blood of 13 leukemia patients were examined by CC, FISH and CGH. The GTG banding analysis showed complex karyotypes with many marker chromosomes. The most frequent abnormalities were numerical and structural aberrations on chromosomes 5 and 7. In 12 of the 14 samples, the CGH analysis was able to detect chromosomal imbalances with losses of material on chromosome 5 and 7 as the most frequent aberrations. In all 14 samples, additional FISH analyses were performed. For most of the studied neoplasias, a close correlation between CC, FISH and CGH data was observed. CGH was considerably helpful in adding additional information to classical karyotyping, if the low quality or number of metaphases was insufficient for a reliable CC analysis. Even in cases where whole chromosome painting could be applied, it added information on the breakpoints of the observed rearrangements. In only 2 of the studied 14 samples, neither CGH nor I-FISH could improve the result of karyotyping. CGH, nevertheless, can be regarded as a powerful additional technique in leukemias with unsuccessful CC, incomplete, or complex karyotypes with many marker chromosomes. A systematic analysis by three techniques such as CC, FISH and CGH guarantees an optimal genetic characterization of the neoplasias.

Prenatal diagnosis of heterokaryotypic mosaic twins discordant for fetal sex

The presence of a monozygotic twin gestation with discordant sex of the twins is a very rare constellation, which is referred to as heterokaryotypic monozygotic pregnancy. This constellation can develop either due to a chromosomal aberration after twinning or is - as in the following case - due to a mitotic error before twinning and an unequal distribution of mosaicism in both embryos. So far the diagnosis of heterokaryotypic monozygotic pregnancy has always been made postnatally, with only one exception (Gonsoulin et al., 1990). In this case we suspected the presence of monozygotic twins ultrasonically because of the chorionic and amniotic membrane characteristics. Surprisingly the sex of the fetuses was discrepant. As one of them had hydrops and a structural heart defect, we carried out an amniocentesis, which revealed mosaicism [45,X/46,X,i(Y)(p10)] of both fetuses. The female fetus with a predominant 45,X set of chromosomes and the typical intrauterine signs of the Ullrich-Turner syndrome (massive hygroma colli, hydrops fetalis and multiple cardiac defects) died during the 25th week of gestation due to cardiac decompensation. The other fetus appeared to be male with a predominance of a 46,X,i(Y)(p10) set of chromosomes and was born a few days after the intrauterine death of the hydropic fetus. In conclusion, our observation shows that ultrasonic evidence of discordant fetal sex in twins does not necessarily exclude monozygosity.

Delimiting the use of comparative genomic hybridization in human myeloid neoplastic disorders

Hematopoietic disorders can be used as a suitable tool of additional information on the actual resolving power of comparative genomic hybridization (CGH). Therefore, CGH examination was performed of DNA extracted from 23 acute and 15 chronic myeloproliferative disorders which had just been analyzed using classical cytogenetic techniques. In nearly all cases CGH analysis was repeated with reversely labeled probes. A Zeiss axioplan microscope was equipped with the ISIS 3 system for photometric evaluation of the CGH data. A main group was selected of 34 cases showing karyotypic mosaics when routinely diagnosed by classical cytogenetics. The grade of mosaicism was basically determined from the classical cytogenetic analysis and was additionally defined examining target anomalies by I-FISH analysis in 28 of the cases. The second group included 23 cases with deletions, and in 1 case another informative genomic imbalance could be analyzed. Every target anomaly irrespective of its type could be detected in all cases with an affected cell population equalling or exceeding about 25%, but in none was it below 23%. This value was the lowest and was found in a case, with CGH-detected 20q deletion. The smallest deletions of two bands on 20q which could visually be detected by CGH were estimated in the range of 5-7 Mb. CGH was also suitable to detect imbalances which were not clearly detected by routine cytogenetics. Reverse labelling, performed in nearly all cases, confirmed the result of the original CGH analysis. These data not only document the readiness and reliability of CGH studies on human leukemia, but also further contribute to a clearer definition of the limits of the resolving power of this technique.

FISH mapping of the sex-reversal region on human chromosome 9p in two XY females and in primates

Accumulating evidence suggests that haploinsufficiency of a dosage-sensitive gene(s) in human chromosome 9p24.3 is responsible for the failure of testicular development and feminisation in XY patients with monosomy for 9p. We have used molecular cytogenetic methods to characterise the sex-reversing 9p deletions in two XY females. Fluorescence in situ hybridisation (FISH) with YACs from the critical 9p region containing an evolutionarily conserved sex-determining gene, DMRT1, is a very fast and reliable assay for patient screening. Comparative YAC mapping on great ape and Old and New World monkey chromosomes demonstrated that the critical region was moved from an interstitial position on the ancestral primate chromosome to a very subtelomeric position in chimpanzee and humans by a pericentric inversion(s). Pathological 9p rearrangements may be the consequence of an evolutionary chromosome breakpoint in close proximity to the sex-reversal region.

Defective sexual development in an infant with 46, XY, der(9)t(8;9)(q23.1;p23)mat

We report on a male infant with ambiguous genitalia (scrotal hypospadias, sinus urogenitalis) trisomic for 8q23-ter and monosomic for 9p23-ter, who shared craniofacial and other abnormalities with either phenotype. Gonadal histology was nearly normal for age. Normal endocrinological findings and exclusion of mutations in SRY, androgen receptor and alpha-reductase genes point to supplementary gene(s) located in 9p2305-ter, haplo-insufficiency (by deletion) of which is expected to cause defective male morphogenesis.

CONCLUSION

This observation lends further support to the hypothesis that genetic factors are located at 9p23-ter which are involved in normal sex determination.

Further observations of true mosaic trisomy 17 ascertained in amniotic fluid cell cultures

Three new cases of true mosaic trisomy 17 (MT17) were diagnosed in amniotic fluid cells. Postnatal chromosome analysis from lymphocytes did not confirm the trisomic cell line, and follow-up studies showed normal psycho-motor development of the children, in one case up to the age of 4 1/2 years. We suggest that there are similarities between MT17 and MT20, in which the majority of pregnancies result in deliveries of healthy babies.

Incidence and significance of 22q11.2 hemizygosity in patients with interrupted aortic arch

Interruption of the aortic arch (IAA) is a severe malformation of the heart with known association to DiGeorge syndrome (DGS) and 22q11.2 hemizygosity. The aim of this study was to establish incidence and significance of 22q11.2 hemizygosity in an unbiased sample of patients with IAA. All 15 children with IAA who were referred to our hospital in a 3-year period were tested by chromosome and fluorescence in situ hybridization (FISH) analysis with the probes D22S75, Tuplel, and cHKAD26 and by a set of 10 simple tandem repeat polymorphic (STRP) markers. In nine of 11 children with IAA type B, 22q11.2 hemizygosity was demonstrated by FISH and STRP analysis, but in none of the four children with type A. In all but one child, deletion size was approximately 3 Mb. The girl with the smaller deletion of approximately 1.5 Mb differed because of an Ullrich-Turner syndrome-like phenotype and severe T-cell defect. Additionally, in one patient with phenotypic signs of DGS, a small deletion distal to the known DGS region containing the marker D22S308 was suspected by STRP analysis. One deletion was shown to be inherited from a healthy father and one IAA type A recurred in a sib. T-cell anomalies were evident in eight of the nine children with classical deletion, five of whom suffered also from hypoparathyroidism. With respect to cause and clinical course, IAA type A and B were shown to represent different entities. This study showed that variable symptoms of 22q11.2 hemizygosity may cluster.

Interstitial deletion del(3)(p12p21) in a malformed child subsequent to paternal paracentric insertion (or intraarm shift) 46,XY, ins(3)(p24.1p12.1p21.31)

We report on a malformed stillborn with deletion 3p subsequent to direct paracentric insertion (intraarm shift) in the normal father which had been first mistaken for paracentric inversion. The corrected diagnosis was supported by FISH of mapped markers on metaphase chromosomes. In addition we looked for recombinants in sperm. This observation reminds similar cases that had been considered exceptions to the expected meiotic recombination of paracentric inversions and points to a cytogenetic pitfall. Published deletions and paracentric inversions in 3p are briefly quoted.

Monozygotic twins concordant for Cayler syndrome

Deletions within chromosome band 22q11.2 are associated with a variety of conditions, although a simple genotype-phenotype correlation has not been established so far. Environmental factors, chance events, or a second hit theory were supported by two observations of monozygotic twins with 22q11.2 deletions and discordant phenotypes [Goodship et al., J Med Genet 1995;32:746-748; Fryer, J Med Genet 1996;33:173]. We present monozygotic twins concordant for 22q11.2 deletion and Cayler syndrome, favoring the view that there exists a predominant genetic determination of the del 22q11.2 phenotype. As these twins are diamniotic and dichorionic, they may offer a more reliable insight in genetic phenotype determination than the other published, probably monochorionic, twins who may have a discordant malformation by twinning itself.

True fetal mosaicism of an isochromosome of the long arm of a chromosome 20: the dilemma persists

We report the prenatal findings of mos 46,XY/46,XY,i(20q) after amniocentesis. The propositus presented with two epidermal scalp scars, retrobulbar orbital cysts, and dyssegmentation of the thoracic spine. The abnormal cell line was discovered in cells cultured from the proximal umbilical cord and--by fluorescence in situ hybridization (FISH)--in interphase nuclei from buccal epithelium and urinary sediment but not from the placenta, lymphocytes, or skin fibroblasts.

Brachydactyly in a child with duplication-deficiency subsequent to t(15;20)(q25.2;p12.2)mat. Candidate regions on one or both chromosomes?

We report a child with a duplication-deficiency subsequent to t(15;20)(q25.2;p12.2), transmitted in at least 5 generations, who showed features of 15q- syndrome. We speculate that brachydactyly--most likely because of brachymesophalangism--is a feature of the phenotype of this chromosomal aberration and points to candidate gene(s) in this region. A similar brachydactyly was, however, reported with dup(20p1-pter).

Prenatal detection of double aneuploidy trisomy 10/monosomy X in a liveborn twin with exclusively monosomy X in blood

Both double aneuploidy and trisomy 10 are rare chromosome findings. All five published cases of trisomy 10 in liveborns were found to be mosaic with an euploid cell line. In a liveborn female twin, double aneuploidy mosaicism 47,XX, + 10/45,X was detected prenatally by amniocentesis performed because of severe intrauterine growth retardation and malformations. Chromosome analysis from neonatal lymphocyte cultures revealed exclusively the 45,X cell line. Double aneuploidy mosaicism trisomy 10/monosomy X was confirmed from skin fibroblasts. The child died at the age of 7 weeks. This is the first reported case of double aneuploidy involving trisomy 10, and the first case of trisomy 10 without a normal cell line in a liveborn. Prenatal diagnosis of trisomy 10 in a liveborn has not been published so far. The case illustrates that in specific cases amniotic fluid cells may reflect the karyotype of the fetus better than blood.

Multiple (up to seven) different accessory small marker chromosomes: prenatal diagnosis and follow-up

We report on the prenatal discovery of 3 up to 7 accessory small marker chromosomes per cell with postnatal confirmation in various tissues. By FISH it could be shown that every marker had a different origin.

Deletion or triplication of the alpha 3 (VI) collagen gene in three patients with 2q37 chromosome aberrations and symptoms of collagen-related disorders

Two new cases of del(2)(q37.1) and one case of partial trp(2)(q37) are studied by FISH with cosmid probes from the COL6A3 and PAX3 genes mapped in 2q37.3 and 2q36, respectively. While the PAX3 gene dosage appeared unaffected, the COL6A3 gene was found to be deleted and triplicated, respectively. This finding could explain features of connective tissue disorders such as joint laxity and hypotonia or joint stiffness and epiphyseal dysplasia, particularly documented by congenital dislocation of the radial head. Karyotype-phenotype correlations with reference to published cases are discussed.

Clinical and molecular cytogenetic observations in three cases of "trisomy 12p syndrome"

Two unpublished cases with partial tandem duplication of 12p and one previously published case were studied by fluorescence in situ hybridization using 11 cosmid DNA probes from 12p. We propose that the smallest duplications of 12(p13.2pter) and 12(p13.1p13.33) produce the "trisomy 12p syndrome" which is characterized by heavy birth weight, macrocephaly, muscular hypotonia, short neck, flat face, high forehead, prominent cheeks, large philtrum, short nose with anteverted nostrils, and broad everted lower lip. From a review of the published cases we conclude that gross malformations are lacking in "pure" trisomy 12p, and mental retardation is severe in complete and moderate in partial trisomy 12p. Polydactyly and accessory nipples were found only with almost complete trisomy 12p. Abnormalities of hair growth may be related to a gene at 12p. The sub-band 12p11.21 may be critical for acrocallosal syndrome. Macrocephaly may be due to a metabolic disorder.

LW/SO cell line: a tool for studying the phenotypical characterization and commitment of hematopoietic stem cells

We report our observations with the cell line LW/SO, which was recently derived from the bone marrow of a patient with acute myeloid leukemia. Based on the morphological and histochemical examination, the leukemic cells were classified primarily as FAB type M4. However, 2 years later, in relapse, the cells changed their morphology and were hence specified as FAB type M2 (slightly positive for acid phosphatase and Sudan black). The cells established have now been in culture for approximately 11 months and display nearly 100% CD4/5/7/15/25/71/120a,b at varying densities. Some of them spontaneously and reversibly become either CD34 + /38- or CD34 - /38+, yet the majority of the cells remain negative for both. All attempts to separate the cells with a distinct phenotype by limiting dilution or sorting through a flow cytometer failed repeatedly. The subsets, enriched up to 98% (regardless of their primary immunophenotype CD34 - / 38-, CD34 + /38-, or CD34 - /38+), soon displayed a phenotypical constellation similar to that before sorting. The ratio of CD34- to CD34+ seems to be influenced by the cell density: The greater the cell-to-cell contact, the lower the percentage of CD34-expressing cells. Some of the cells apparently differentiate into T-cell phenotype and acquire CD3 and T-cell receptor (TCR) alpha/beta molecules. While the quantity of CD34-expressing cells significantly increased in the presence of dexamethasone (10(-7) M), and some of them additionally acquired CD33 antigen, the percentage of CD3-positive cells was enhanced by adding 1% DMSO in medium. In contrast, cytokines such as IL-1, IL-2, IL-3, IL-4, IL-6, G-CSF, GM-CSF, or SCF (c-kit ligand) altered neither the proliferation capacity nor the phenotypical constellation of LW/SO cells (each tested alone). Although normal karyotype was obtained from the bone marrow cells, the LW/SO cells revealed a homogeneous chromosomal composition of 45, X, -X, der(9) inv(9) (p12q13) del(9) (p22?). These data suggested that LW/SO cells might be the leukemic counterpart of putative pre-CD34-positive progenitors. In order to substantiate this assumption, we analyzed the expression of other so-called T-cell markers on CD34+ cells from peripheral blood stem cell aphereses of five patients who later underwent high-dose chemotherapy and subsequent stem cell retransfusion. These data clearly revealed that a considerable amount of CD34+ hematopoietic progenitors co-express CD2/4/(5)/(7)/25 at an early stage of differentiation, and support the notion that CD34-negative LW/SO cells with the surface markers CD4/5/7/25 are probably phenotypical representatives of pluripotent stem cell. Hence, not all CD34-negative populations with so-called T-cell surface markers should be considered T-cells; some may constitute the ancestor of CD34 antigen-expressing progenitors.

Familial reciprocal translocation t(17;19) (q11.2;q13.2) associated with neurofibromatosis type 1, including one patient with non-Hodgkin lymphoma and an additional t(14;20) in B lymphocytes

The cosegregation of a reciprocal translocation t(17;19) (q11.2;13.2) with neurofibromatosis type 1 in three generations suggested that the breakpoint on chromosome 17 involved the NF1 gene. In order to map the breakpoint, we analysed DNAs of patients using parts of the NF1 gene as probes. Southern analysis revealed that the chromosome 17 breakpoint lies within intron 23 of the NF1 gene. One of the patients of the family developed a non-Hodgkin lymphoma. An additional translocation t(14;20) (q32;13.1) in his B lymphocytes points to a gene on chromosome 20 that is juxtaposed to the IGH locus on 14q32, and that may be of relevance for the development of this tumor type.

Determination by interphase-FISH of the clonality of aberrant karyotypes in human hematopoietic neoplasias

Interphase-FISH (fluorescence in situ hybridization) studies have been devoted to the determination of clonality of aberrant karyotypes in human leukemia. Various levels of its extent have been examined, including the meaning of a single aberrant karyotype as representing a microclone, the use of FISH to confirm clonality in bi- or multiclonal leukemia, the estimation of the residual (aberrant) clone after contrasexual bone marrow transplantation, and the redetectability in interphase of the abl/bcr rearrangement. The quantitative findings of all these lines of interphase FISH analyses were based on the comparison with data from a large-scale "control" study on normal cells using the same DNA probes which have been chosen for the determination of clonality, i.e. centromeric DNA probes for chromosomes #1, #3, from #6 to #12, from #15 to #18, #20, X and Y, and a specific probe for the abl/bcr rearrangement. In addition, the validity of interphase-FISH analysis on classical bone marrow smears was examined. As a common outcome it was concluded that interphase-FISH technique is a valuable tool for defining clonality of karyotypic changes and, as a consequence, yields additional prognostic information in many human leukemias. It is recommended to perform interphase FISH in routine cytogenetics of leukemia, whenever reasonable.

Therapy with OKT3 monoclonal antibody in refractory T cell acute lymphoblastic leukemia induces interleukin-2 responsiveness

Administration of cytokines to patients with leukemia or lymphoma may recruit dormant malignant cells into cell cycle and thus make them more susceptible to chemotherapy. We treated a patient with refractory T cell acute lymphoblastic leukemia (ALL) with OKT3 monoclonal antibody and observed a dramatic but transient decrease of lymphoblasts. The T ALL cells were rather mature by morphology and immunophenotyping, expressing CD7, CD4, CD8 and CD3 surface antigens and nuclear TdT. Cytogenetic analysis revealed inversion of chromosome 14(q11q32.1). A total of 500 mg OKT3 (maximum dose 50 mg/day) was given. A decrease of lymphoblasts in the blood and a reduction of spleen size was observed. Complement levels dropped remarkably. Despite increasing serum levels of tumor necrosis factor, treatment was well tolerated overall. CD3 therapy induced strong IL-2 responsiveness of the lymphoblasts. Thus, OKT3 antibody treatment not only significantly decreased CD3-positive tumor cells, but also induced IL-2-mediated proliferation. This may also allow sequential application of CD3 and IL-2 to render certain T cell tumors more susceptible to chemotherapy.

Tetrasomy 8 as a clonal anomaly in myeloid neoplasias

Tetrasomy of chromosome 8 as a sole anomaly is apparently extremely rare in acute non-lymphocytic leukemia (ANLL): Only two cases have been reported, one of ANLL (M5b) with this karyotype. Very recently, another case was reported of a myelodysplastic syndrome (MDS) with isolated tetrasomy 8. We report tetrasomy 8 in four cases of ANLL, two of them with M5 and one with M1 subtype. Although in the latter case, tetrasomy 8 was evident in all karyotypes analyzed, in all other cases it constituted a subpopulation of cells other than those with trisomy 8 and those with a normal karyotype (in only one case another change was evident in the karyotype). Using fluorescence in situ hybridization (FISH), the proportion of tetrasomic cells was determined in interphase nuclei. By this technique, small cell populations (3-9%) were detected in three additional trisomy cases. An additional "control" group of five trisomy cases did not show a significant population of tetrasomic interphase nuclei. The data show that tetrasomy 8, if present as a sole anomaly in ANLL, may play a rather specific role for the subtype, and probably for the progression of myeloid neoplasia as well.

The acute lymphoblastic leukaemia cell line SEM with t(4;11) chromosomal rearrangement is biphenotypic and responsive to interleukin-7

A cell line, designated SEM, was established from the peripheral blood of a 5-year-old girl in relapse with acute lymphoblastic leukaemia (ALL). Both the lymphoblasts of the patient and the cells of the cell line SEM showed the t(4;11) chromosomal rearrangement. The analysis of the immunophenotype of the SEM cell line revealed the B-cell differentiation antigens CD19, CD22 and CDw75 in the absence of CD20, CD24 and immunoglobulin expression. Besides B-lineage antigens, SEM cells were positive for the myeloid antigens CD13, CD15, CD33 and CDw65. Immunogenotypic analysis of SEM cells showed a monoclonal rearrangement of immunoglobulin heavy-chain (IgH). T-cell receptor (TCR) gamma and delta genes. Addition of interleukin (IL)-7 promoted the growth of the patient's lymphoblasts in culture and enhanced the proliferation of SEM cells. The SEM cells also express messenger RNA (mRNA) for the IL-7 receptor (IL-7R), but no evidence for autocrine production of IL-7 by the cell line was found. Addition of IL-4, tumour necrosis factor (TNF)-alpha, interferon (IFN)-alpha, or IFN-gamma resulted in a profound inhibition of SEM growth. Thus, these cytokines may have important growth regulatory activities for biphenotypic leukaemic ALL cells.

Chromosomal heterogeneity of aneuploid leukemic cell populations detected by conventional karyotyping and by fluorescence in situ hybridization (FISH)

Beside the frequent aneusomies of chromosomes # 7 and # 8 gains or losses of several other chromosomes are found in bone marrow cells of leukemia patients. Chromosomal heterogeneity of interphase cell populations was studied by fluorescence in situ hybridization (FISH) with centromeric DNA probes for chromosomes #2, #3, #4, #6, #9, #11, #12, #15, #16, #17, #18, #20, as well as X and Y which were found to be aberrant by routine karyotyping of 28 cases of various malignant hematopoietic diseases. Particularly, the data obtained by both routes of analysis were compared quantitatively. As the most prominent result, all aberrations found by classical karyotyping were redetected by interphase cytogenetics, but additional aberrant clones could be observed among the interphase cell populations. The frequencies of the cell clones with hypersomies were in general higher in metaphase than in interphase, and, vice versa, monosomic cells were found more frequently in interphase than in metaphase. Single aberrant karyotypes in all cases were redetected as microclones of interphase cells. Interphase cytogenetics using FISH, therefore, was shown not only to be a reliable measure of the genomic heterogeneity of leukemic cell populations but, in addition, to be a valuable and informative supplement to routine leukemia cytogenetics with regard to the detection of microclones which, later on, could dominate the progression of the malignant disease.

Use of fluorescence in-situ hybridization (fish) for the estimation of the aberrant cell clone in leukemias with trisomy-8 or monosomy-7 detected by karyotyping

The sizes of leukemic cell clones with hypersomies of the chromosome #8 or monosomy #7, which primarily were detected by classical karyotyping, were estimated by fluorescence in situ hybridization (FISH) with centromeric DNA probes in interphase cell populations of the bone marrow of 31 leukemia patients. Particularly, the data obtained by both routes of analysis were compared quantitatively. As most prominent result, all aberrations found by classical karyotyping were redetected by interphase cytogenetics, but additional aberrant clones could be observed among the interphase cell populations. The frequencies of the cell clones with hypersomies #8, in general, were higher in metaphase than' in interphase, and, vice versa, cells monosomic for #7, in the majority of cases, were found to be more frequent in interphase than in metaphase. These data support the idea that metaphase data per se may not sufficiently reflect the actual portions of aneuploid cell clones in the whole leukemic cell population. This may be of practical importance in diagnostic and prognostic respects but also for the choice of specific therapies.

Simultaneous de novo interstitial deletion of 16q21 and intercalary duplication of 19q in a retarded infant with minor dysmorphic features

We report on a retarded infant with minor dysmorphic features in whom deletion 16 and duplication 19q were discovered. The karyotype is 46,XX,del(16) (q13.08-21.05),dup(19)(q13.13-13.2). The origin and significance of the aberrant chromosomes are unknown.

Multiple minute marker chromosomes derived from Y identified by FISH in an intersexual infant

Chromosomal analysis in a child with ambiguous sex showed mosaicism of at least two cell lines with one or more marker chromosomes or none at all. They were shown to be derived from the Y chromosome by fluorescent in situ hybridisation (FISH) using different DNA probes that cover parts of the long and the short arm.

Typical and partial cat eye syndrome: identification of the marker chromosome by FISH

Three children are reported with typical cat eye syndrome (CES) and three more children with partial CES because of absence of coloboma, in which the supernumerary marker chromosome was studied by FISH. Using a genomic library, and also a centromeric and particularly a cosmid probe of 22q11, partial tetrasomy was shown in all cases.

A study of ten small supernumerary (marker) chromosomes identified by fluorescence in situ hybridization (FISH)

In seven cases additional minute chromosomes studied by FISH were identified as no. 3, 11, 15, 18, 21 and X. Findings were unexpected except for partial trisomy 21 in an adolescent with minor features of Down's syndrome. Moreover, an i(18p) in a mentally retarded dysmorphic child and an idic(15) in a child with Fallot tetralogy was confirmed. In a child with r(21), a supernumerary marker was shown to be derived from no. 21, while in the mother an additional marker idic(22) was noted.

Multiple chromosomal changes and karyotypic evolution in a patient with myelofibrosis

Several subclones were identified in unstimulated peripheral blood cells from a patient with chronic myeloproliferative disease, which was classified as myelofibrosis by morphologic terms. These subclones were characterized by an unusual number of different karyotype anomalies. Some of the more complex chromosomal rearrangements could be clearly defined by fluorescence in situ hybridization. Chromosome arms involved in clonal aberrations were 1q, 3p, 6p, 7q, 11q, 13q, 15q, 17q, 18p, and 20q. Reconstruction of karyotype evolution was attempted by karyotypic analysis of 100 metaphase spreads each in two separate investigations.

Characterization and mapping of microdissected genomic clones from the adenomatous polyposis coli (APC) region

The gene associated with adenomatous polyposis coli (APC) has been mapped to the long arm of chromosome 5. To saturate the APC region with DNA markers, two independent microdissection libraries with an emphasis on 5q21.2-21.3 and 5q22 have been constructed from GTG-banded human metaphase chromosomes. PCR-amplified insert DNA of the primary amplificate used as a probe in chromosomal in situ suppression (CISS) hybridization of human metaphase spreads revealed region-specific signals at the chromosomal site that was excised for cloning. One hundred forty-two inserts, derived from both libraries, have been characterized in more detail. Deletion mapping analysis was performed with 17 single-copy clones on a hamster-human hybrid cell panel. Seven of these clones were located within two interstitial deletions of 6-8 Mb from APC-affected individuals around chromosome bands 5q21-22. The identification of new microclones mapping into these deletions and their use in isolating YAC clones should contribute to the construction of a contiguous physical map of the APC region.

Detection of APC region-specific signals by nonisotopic chromosomal in situ suppression (CISS)-hybridization using a microdissection library as a probe

The chromosome region 5q22 harbouring the putative gene associated with adenomatous polyposis coli (APC) was microdissected and microcloned from GTG-banded human metaphase chromosomes. In order to determine the precise regional localization of the microdissected material, we used polymerase chain reaction amplified microclones as a bulk-probe in nonradioactive chromosomal in situ suppression hybridization of human metaphase spreads. Specific in situ hybridization signals were obtained on the long arm of chromosome 5 in accordance with the chromosomal region excised for the cloning procedure. The application of this detection system should provide a rapid and powerful tool for analyzing patients with translocations or microdeletions of a given chromosome region.

[13q syndrome--partial monosomy of the long arm of chromosome 13]

Examination of spontaneous abortions often reveals deletion 13q-. The authors report on a case of de novo deletion in a female newborn with karyotype 46,XX,del (13) (q33) and discuss the problems of the mapping of clinical syndromes. The critical part of the 13q- syndrome is presumably the band 13q33 and/or 13q34. In clinically suspicious cases chromosome visualization should be done with reliable methods (R-banding) in order to detect even very small defects. The gene localisation of esterase D is obviously proximal of the terminal part of chromosome 13.

[The analysis of chromosomes today: aspects of the technic with indications and importance of the method]

0.5 to 1% of all newborn possess a chromosomal aberration. In a growing number of neoplasias chromosomal disturbances become known. 10 years after the introduction of the band technique into cytogenetics this method must be regarded as most essential progress in the description of chromosomes. Apart from the exact identification of each individual chromosome the band technique allows the exact establishment of fraction points and gives the possibility of new progress in the gene tabulation. With the help of instances some of these possibilities are demonstrated. Prerequisite for the effective use of the analysis of chromosomes is a strong indication. An indication catalogue concerning the clinical application of the method summarizes the essential problems from paediatrics, gynaecology and internal medicine.