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D L Van Dyke

Publications and source records attributed to D L Van Dyke.

At least 19 recordsLinked to original sources
PubMed2006

Redefining the risks of prenatally ascertained supernumerary marker chromosomes: a collaborative study.

BACKGROUND: A marker chromosome is defined as a structurally abnormal chromosome that cannot be identified by routine cytogenetics. The risk for phenotypic abnormalities associated with a marker chromosome depends on several factors, including inheritance, mode of ascertainment, chromosomal origin, and the morphology, content, and structure of the marker. METHODS: to understand the karyotype-phenotype relationship of prenatally ascertained supernumerary de novo marker chromosomes, we combined data from prenatal cases obtained from 12 laboratories with those from studies in the literature. We were able to obtain cytogenetic and phenotypic data from 108 prenatally ascertained supernumerary de novo marker chromosomes to refine the phenotypic risk associated with these markers. Because of the growing number of cases and because more techniques are available to delineate marker morphology, we have been able to group risk estimates into subcategories, such as by marker type and whether there are ultrasound abnormalities. RESULTS: If a de novo supernumerary marker chromosome is found prenatally, our data suggest there is a 26% risk for phenotypic abnormality when there is no other information defining the marker (such as chromosomal origin or information about the existing phenotype). However, if high resolution ultrasound studies are normal, this risk reduces to 18%. CONCLUSIONS: Our findings strongly support the value of additional genetic studies for more precisely defining the risk in individual cases involving marker chromosomes.

Chromosome Aberrations↗
PubMed2001

Significance of p53 mutations in patients with chronic lymphocytic leukemia: a sequential study of 30 patients.

BACKGROUND: In patients with B-cell chronic lymphocytic leukemia (CLL), considerable disease heterogeneity within clinical stages necessitates the search for relevant prognostic indicators, particularly those that may help to determine the need for early therapeutic intervention. In the current study, the authors investigated the role of p53 mutations and chromosomal abnormalities in 30 patients with CLL. METHODS: Thirty patients were screened for p53 mutations. Half of the group had aggressive disease characterized by leucocytosis, lymph node enlargement, organomegaly, and shortened tumor doubling time. Because 95% of p53 mutations reside in "hot-spot" regions of exons 5-9 of the p53 gene, the authors sequenced these exons completely for mutation detection. RESULTS: Sequence analysis identified p53 mutations in 14 of 30 patients that were distributed equally among patients with aggressive disease and nonaggressive disease. There were six mutations in exon 7, five mutations in exon 5, and one mutation each in exons 6 and 8. Five of 15 patients with clinically aggressive disease had mutations in exon 7. Only one patient with nonaggressive disease had an exon 7 mutation. Abnormal cytogenetics were present in 22 of 30 patients (73%). Most patients with the p53 mutation (13 of 14 patients; 93%) displayed abnormal cytogenetics. Twelve of 15 patients with aggressive disease and 9 of 15 patients with average disease exhibited abnormal karyotypes. CONCLUSIONS: The presence of p53 mutations did not predict clinical behavior or disease outcome, although the frequency of mutations appears to be higher than reported previously. In this study, mutations of exon 7 (5 of 6 patients) occurred in patients with clinically aggressive disease. The significance of this observation warrants further examination.

Exons↗
PubMed2001

Cytogenetic analysis and construction of a BAC contig across a common neocentromeric region from 9p.

Over 40 cases of neocentric marker chromosomes, without detectable alpha-satellite DNA, have been reported. Although these have originated from many different chromosomes, a few of these chromosomes have been involved in multiple cases of marker formation. In this study, two different markers originating from the short arm of chromosome 9 were analyzed, identifying a common neocentromeric region. A bacterial artificial chromosome (BAC) contig extending over more than 900 kb has been assembled across this neocentromeric region. Fluorescent in situ hybridization and immunofluorescence assays (CENP-C and CENP-E) have localized the neocentromere to a 500 kb region. Preliminary analysis of DNA sequences in this neocentromere revealed a highly AT-rich region, which also has an increase in the level of retroviral elements compared with the average levels in the genome.

Animals↗
PubMed2000

Analphoid 3qter markers.

Two cases of marker chromosomes derived from a non-centromeric location were studied to determine the characteristics of these markers with respect to the presence of functional centromeres and whether an associated phenotype could be described. The markers were characterized by fluorescence in situ hybridization and centromeric protein studies. Assessments were done to identify clinical features. Case 1 is a girl referred at age 1.5 years with swirly areas of hyperpigmentation, bilateral preauricular pits, hypotonia, developmental delay, and seizures. Case 2 is a male first evaluated as a newborn and then later during the first year of life. He had streaky hypopigmentation, right preauricular pit, accessory nipples, postaxial polydactyly, asymmetric cerebral ventricles, duplicated right kidney, a right pulmonary artery stenosis, and seizures. Mosaicism for an extra marker from the 3qter region was present in both cases. Both markers had a constriction near one end and were C-band negative. Centromeric protein studies indicated absence of CENP-B, presence of CENP-C (data for case 1 only), and presence of CENP-E. Marker chromosomes were thus identified with a chromosomal origin far from their usual centromeric region and yet appeared to have functional centromeres. These two cases did not permit a specific clinical phenotype to be ascribed to the presence of tetrasomy for 3q26.2 approximately 3q27.2-->3qter.

Autoantigens↗
PubMed2000

Trisomy 15, sex chromosome loss, and hematological malignancy.

We report 6 patients with myelodysplasia who, on routine cytogenetic studies, demonstrated trisomy 15. Four of these also had sex chromosome loss. A review of the literature revealed 6 other cases of trisomy 15 with sex chromosome loss and 22 cases of trisomy 15 as the sole chromosomal abnormality. All cases had hematologic malignancy or myelodysplasia. Trisomy 15 is uncommon but tends to be associated with myelodysplasia in older subjects, and with sex chromosome loss in about one third of cases.

Aged↗
PubMed2000

Clinical significance of Y chromosome loss in hematologic disease.

We have studied 215 male patients (aged 45-97 years) whose sole cytogenetic abnormality was clonal loss of the Y chromosome in metaphase cells from unstimulated cultures. The patients comprised a control group with no evidence of hematologic disease and four disease case groups: 1) myelodysplastic syndrome (MDS), refractory anemia, refractory anemia with excess blasts (RAEB), RAEB in transformation, and chronic myelomonocytic leukemia; 2) acute myelogenous leukemia; 3) myeloproliferative disorder (MPD), chronic granulocytic leukemia, and polycythemia vera; and 4) B-cell lymphoma/leukemia. The frequency of cells with Y loss increased with age and was significantly greater in cases than in controls, but it was not correlated with survival or with prior therapy. The frequency of cases with a -Y clone was 6.3% of male karyotypes and represented 16.4% of all abnormal male cytogenetic reports. Much of the difference between cases and controls appears to be accounted for by a greater frequency of cases with > 75% Y loss. A value of 81% chromosome Y loss maximized the combined sensitivity (28%) and specificity (100%) for predicting disease status, but a 75% cutoff provided the best estimate of disease risk. Even in older males, if > 75% of metaphase cells are 45,X,-Y, they probably represent a disease-associated clonal population, and it is possible that the critical genetic change is not visible through the microscope. This observation is true for MDS, MPD, B-cell disease, and especially acute myelogenous leukemia. The prognostic association of Y chromosome loss for survival appears to be neutral or favorable. Genes Chromosomes Cancer 27:11-16, 2000.

Aged↗
PubMed2000

Common trisomy mosaicism diagnosed in amniocytes involving chromosomes 13, 18, 20 and 21: karyotype-phenotype correlations.

Karyotype-phenotype correlations of common trisomy mosaicism prenatally diagnosed via amniocentesis was reviewed in 305 new cases from a collaboration of North American cytogenetic laboratories. Abnormal outcome was noted in 10/25 (40%) cases of 47,+13/46, 17/31 (54%) cases of 47,+18/46, 10/152 (6.5%) cases of 47,+20/46, and in 49/97 (50%) cases of 47,+21/46 mosaicism. Risk of abnormal outcome in pregnancies with less than 50% trisomic cells and greater than 50% trisomic cells were: 26% (4/15) versus 60% (6/10) for 47,+13/46, 52% (11/21) versus 75% (6/8) for 47,+18/46, 4.5% (6/132) versus 20% (4/20) 47,+20/46, and 45% (27/60) versus 59% (22/37) for 47,+21/46. Phenotypically normal liveborns were observed with mean trisomic cell lines of 9.3% for 47,+13/46, 8.6% for 47,+18/46, 27% for 47, +20/46, and 17% for 47,+21/46. Cytogenetic confirmation rates were 46% (6/13 cases) for 47,+13/46 mosaicism, 66% (8/12 cases) for 47, +18/46, 10% (10/97 cases) for 47,+20/46, and 44% (24/54 cases) for 47,+21/46. There were higher confirmation rates in pregnancies with abnormal versus normal outcome: 50% versus 44% for 47,+13/46 mosaicism, 100% versus 33% for 47,+18/46, 66% versus 7% for 47, +20/46, and 55% versus 40% for 47,+21/46. Repeat amniocentesis is not helpful in predicting clinical outcome. It may be considered when there is insufficient number of cells or cultures to establish a diagnosis. Fetal blood sampling may have a role in mosaic trisomy 13, 18, and 21 as the risk for abnormal outcome increases with positive confirmation: 1/5 (20%) normal cases versus 5/8 (62%) abnormal cases. High resolution ultrasound examination(s) is recommended for clinical correlation and to facilitate genetic counselling.

Abnormalities, Multiple↗
PubMed1999

Child with velocardiofacial syndrome and del (4)(q34.2): another critical region associated with a velocardiofacial syndrome-like phenotype.

We report on a child with congenital heart disease (atrial septal defect, ventricular septal defect, pulmonic stenosis), submucosal cleft palate, hypernasal speech, learning difficulties, and right fifth finger anomaly manifestations, consistent with velocardiofacial syndrome (VCFS); however, cytogenetic analysis demonstrated a small terminal deletion of the segment 4q34.2 to 4qter. Fluorescent in situ hybridization did not identify a deletion of the critical region associated with VCFS. In previously reported 4q deletions with a breakpoint distal to 4q34.2, no cardiac defects or cleft of palate were reported. Our patient has a deletion of 4q34.2 to 4qter and has palate and cardiac involvement and minor learning difficulties, which implies that genes involved in heart and palate development lie distal to 4q34.2, and that the critical region for more severe mental retardation on 4q may reside proximal to 4q34.2. These results suggest that a distal 4q deletion can lead to a phenotype similar to VCFS and emphasizes the importance of searching for other karyotype abnormalities when a VCFS-like phenotype is present and a 22q deletion is not identified.

Abnormalities, Multiple↗
PubMed1999

Investigation of two cases of paternal disomy 13 suggests timing of isochromosome formation and mechanisms leading to uniparental disomy.

Uniparental disomy (UPD) is the abnormal inheritance of two copies of a chromosome from the same parent. Possible mechanisms for UPD include trisomy rescue, monosomy rescue, gametic complementation, and somatic recombination. Most of these mechanisms can involve rearranged chromosomes, particularly isochromosomes and Robertsonian translocations. Both maternal and paternal UPD have been reported for most of the acrocentric chromosomes. However, only UPD for chromosomes 14 and 15 show an apparent imprinting effect. Herein, we present two cases of paternal UPD 13 involving isochromosomes. Both cases were referred for UPD studies due to the formation of a de novo rea(13q13q). Case 2 was complicated by the segregation of a familial rob(13q14q) of maternal origin. Both propositi were phenotypically normal at the time of examination. Polymorphic marker analysis in Case 1 showed the distribution of alleles of markers along chromosome 13 to be complete isodisomy, consistent with an isochromosome. This rearrangement could have occurred either meiotically, without recombination, or mitotically. A likely mechanism for UPD in this case is monosomy rescue, through postzygotic formation of the isochromosome. In Case 2 the distribution of proximal alleles indicated an isochromosome, but recombination was evident. Thus, this isochromosome must have formed prior to or during meiosis I. A likely mechanism for UPD in this case is gametic complementation, since the mother carries a rob(13q14q) and is at risk of producing aneuploid gametes. However, trisomy rescue of a trisomy 13 conceptus cannot be completely excluded. Given that both cases were phenotypically normal, these data further support that paternal UPD 13 does not have an adverse phenotypic outcome and, thus, does not show an apparent imprinting effect.

Alleles↗
PubMed1999

Chromosomal aberrations identified in culture of squamous carcinomas are confirmed by fluorescence in situ hybridisation.

AIMS: Chromosomal aberrations in tumour cells are often not discernable by direct analysis. Although cell culture allows qualitative analysis of the karyotype, potential selection and evolution during growth in vitro may yield misleading data. To determine whether aberrations observed in vitro are representative of the original lesion, chromosomal aberrations found after prolonged growth in vitro of two squamous cell carcinomas of the head and neck (SSCHN) were evaluated with fluorescence in situ hybridisation (FISH) on the original tumour nuclei. METHODS: Specific karyotypic aberrations identified in cultures of two squamous cell carcinomas were targets for FISH analysis on tumour sections. Chromosome painting mixtures were selected based on in vitro karyotypic data. FISH was performed on cultured interphase and metaphase cells, and on histological sections from the original tumours. RESULTS: The 9cen and 17cen probes yielded FISH signals consistent with the aneusomies predicted for the respective chromosomes from the culture karyotypes. Whole chromosome 9 paint confirmed the prior existence in the tumours of i(9p) and i(9q), although only the latter hybridised with the 9cen probe. FISH data also supported in vivo representation of the diploid and tetraploid tumour subclones observed in cultures. In tumour HFH-SCC-8a, FISH results were generally concordant between cultured interphase and metaphase cells and the histological sections, and improved the interpretation of marker chromosomes identified in culture. CONCLUSION: The karyotypes obtained in these cases after prolonged passage in culture were consistent with the genetic alterations in the original tumours.

Carcinoma, Squamous Cell↗
PubMed1998

Prader-Willi-like syndrome in a patient with an Xq23q25 duplication.

We report on a 24-year old woman with an Xq duplication and findings suggestive of Prader-Willi syndrome (PWS). Her birth weight was at the 3rd centile and her birth length was less than the 3rd centile. She was hypotonic and had a weak cry as an infant. There were no feeding difficulties, although her mother reports that as an infant, she was "small for her age." Excessive weight gain began between 3 and 4 years. The patient's development was delayed and she received special education. She has a history of hiding food. She has a sleep disturbance disorder and inappropriate social behavior. At the age of 24 years her height was below the 5th centile and weight >>95th centile. She has physical findings typical of PWS, skin picking, and speech articulation defects. Cytogenetic analysis showed a 46,X,dup(X)(q23q25) karyotype. Fluorescent in situ hybridization (FISH) studies using a chromosome X painting probe demonstrated that the rearrangement was intrachromosomal. The X-chromosome fold scoring technique was used to determine the X inactivation pattern and indicated that some cells expressed the abnormal X chromosome. Results of FISH studies using the SNRPN probe localized to 15q11q13 and DNA studies using the PW71B and SNRPN probes were normal. The duplicated X chromosome, random X inactivation pattern, and the negative molecular studies for PWS indicate that the abnormal X chromosome is the basis of this patient's phenotype. This patient emphasizes the importance of obtaining a karyotype even when a syndrome diagnosable by molecular methods is strongly suspected.

Adult↗
PubMed1998

Duplication 6q21q23 in two unrelated patients.

We report on two patients with rare 6q duplications. The karyotype of patient 1 is 46,XY,dup(6)(q21q23.3). The karyotype of patient 2 is 46,XX,dup(6)(q21.15q23.3). These two patients have some nonspecific physical findings in common including a depressed nasal bridge, epicanthal folds, mild heart defects, and developmental delay, but each had other congenital anomalies.

Abnormalities, Multiple↗
PubMed1998

Sequential G-banding and fluorescent in situ hybridization on peripheral blood, bone marrow, and amniotic fluid samples.

We describe a method for fluorescent in situ hybridization (FISH) on previously G-banded slides and mounted coverslip preparations. The technique is successful on previously G-banded slides from peripheral blood and bone marrow specimens and on amniotic fluid samples from in situ harvests. Satellite sequence probes, whole chromosome paints, and unique sequence probes have all produced reliable results.

Amniotic Fluid↗
PubMed1998

The spreading of X inactivation into autosomal material of an x;autosome translocation: evidence for a difference between autosomal and X-chromosomal DNA.

X inactivation involves initiation, propagation, and maintenance of genetic inactivation. Studies of replication timing in X;autosome translocations have suggested that X inactivation may spread into adjacent autosomal DNA. To examine the inactivation of autosomal material at the molecular level, we assessed the transcriptional activity of X-linked and autosomal loci spanning an inactive translocation in a phenotypically normal female with a karyotype of 46,X,der(X)t(X;4)(q22;q24). Since 4q duplications usually manifest dysmorphic features and severe growth and mental retardation, the normal phenotype of this individual suggested the spreading of X inactivation throughout the autosomal material. Consistent with this model, reverse transcription-PCR analysis of 20 transcribed sequences spanning 4q24-qter revealed that three known genes and 11 expressed sequence tags (ESTs) were not expressed in a somatic-cell hybrid that carries the translocation chromosome. However, three ESTs and three known genes were expressed from the t(X;4) chromosome and thus "escaped" X inactivation. This direct assay of expression demonstrated that the spreading of inactivation from the adjoining X chromosome was incomplete and noncontiguous. These findings are broadly consistent with the existence of genes known to escape inactivation on normal inactive X chromosomes. However, the fact that a high proportion (30%) of tested autosomal genes escaped inactivation may indicate that autosomal material lacks X chromosome-specific features that are associated with the spreading and/or maintenance of inactivation.

Adult↗
PubMed1998

Evidence for a Turner syndrome locus or loci at Xp11.2-p22.1.

Turner syndrome is the complex human phenotype associated with complete or partial monosomy X. Principle features of Turner syndrome include short stature, ovarian failure, and a variety of other anatomic and physiological abnormalities, such as webbed neck, lymphedema, cardiovascular and renal anomalies, hypertension, and autoimmune thyroid disease. We studied 28 apparently nonmosaic subjects with partial deletions of Xp, in order to map loci responsible for various components of the Turner syndrome phenotype. Subjects were carefully evaluated for the presence or absence of Turner syndrome features, and their deletions were mapped by FISH with a panel of Xp markers. Using a statistical method to examine genotype/phenotype correlations, we mapped one or more Turner syndrome traits to a critical region in Xp11.2-p22.1. These traits included short stature, ovarian failure, high-arched palate, and autoimmune thyroid disease. The results are useful for genetic counseling of individuals with partial monosomy X. Study of additional subjects should refine the localization of Turner syndrome loci and provide a rational basis for exploration of candidate genes.

Adolescent↗
PubMed1997

Cytogenetic and clinical findings in a patient with a deletion of 16q23.1: first report of bilateral cataracts and a 16q deletion.

The most commonly reported manifestations of 16q deletions are severe growth and developmental disorders and anomalies of the craniofacial, visceral, and musculoskeletal systems. We reviewed the findings of patients reported with 16q- syndrome and compared them to our patient, a 4 1/2-year-old boy with a deletion of 16q23.1. Findings include psychomotor retardation, hypotonia, high forehead, hypertelorism, upslanting palpebral fissures, low-set abnormally modeled ears, and talipes equinovarus. Anomalies present in our patient not reported in others with 16q- syndrome include bilateral cataracts, iris coloboma, and autistic-like behavior. It is of note that a locus for autosomal dominant congenital cataract, known as Marner cataract, was mapped previously to 16q22. Because our patient has bilateral cataracts and a unilateral iris coloboma, it seems likely that a gene involved in ocular development is located within 16q23.1. Our patient's deletion may also include the gene involved in Marner cataract and may further assist in the isolation of this gene.

Abnormalities, Multiple↗