De novo apparently balanced complex chromosome rearrangement (CCR) involving chromosomes 4, 18, and 21 in a girl with mental retardation: report and review.

We describe a complex and unique, de novo apparently balanced translocation involving chromosomes 4, 18, and 21 with 4 breakpoints, in a patient who was referred for an evaluation of possible fragile-X syndrome. Fluorescence in situ hybridization (FISH) confirmed the complexity of the rearrangement and showed the derivative 21 to be composed of 3 distinct segments derived from chromosomes 21, 18, and 4. The derivative chromosome 18 had undergone a double translocation, the first such event to be described in constitutional complex chromosomal rearrangements (CCRs) involving chromosome 18. A review of these CCRs suggests the existence of a breakpoint "hot spot" on 18q21.

Familial complex chromosome rearrangement giving rise to balanced and unbalanced recombination products.

We report on a family ascertained through a 14-month-old girl with a terminal deletion of chromosome 8p23.1. Analysis of the karyotype of other relatives showed that the mother is the carrier of a balanced complex 4-break chromosome rearrangement, which she and her brother inherited from their father following recombination. This complex chromosome rearrangement (CCR) was confirmed by fluorescence in-situ hybridization (FISH) using libraries for chromosomes 1, 8, and 9, and telomeric probes for the long arm of chromosome 9. The karyotype of the maternal grandfather was 46,XY,t(1;8) (p31;q21.1),t(8;9) (p23.1;q34). The karyotype of his daughter is 46,XX,rec(8)t(1;8) (p31;q21.1)t(8;9)(p23.1;q34)pat. The karyotype of the proposita is 46,XX,rec(8)t(8;9) (p23.1;q34)mat, and that of her abnormal elder sister is 46,XX,t(1;8)(p31;q21.1)rec(8) t(8;9) (p23.1;q34)mat,der(9)t(8;9) (p23.1;q34) mat. Unbalanced segregation and/or recombination during maternal meiosis gave rise to the two abnormal sisters, one effectively with 8p trisomy and the other with monosomy for that same 8p segment. To our knowledge, this is the first case of a familial CCR giving rise to unbalanced recombination products.

Preferential involvement of the short arm in chromosome 8-derived supernumerary markers and ring as identified by chromosome arm painting.

We report on the use of fluorescence in situ hybridization (FISH) with specific chromosome 8 arm painting to characterize further small supernumerary chromosome 8-derived markers/rings (SMC/SRC) identified in three patients. Two patients (patients 1 and 2) who carried the marker (SMC) were evaluated because of mental retardation and minor facial anomalies. The patient (patient 3) who carried the ring (SRC) had ventriculomegaly. Parental blood chromosomes of patients 2 and 3 were normal and unavailable on patient 1. The identification of the SMC/SRC was first characterized by FISH specific alpha-repeat centromeric probes, second by FISH whole chromosome painting (WCP), and finally by FISH chromosome arm painting (CAP). The latter showed involvement of only the short arm of chromosome 8 in all three SMC/SRC cases, suggesting a U-type exchange mechanism.

Biphenotypic hematological malignancy with T-lymphoid and myeloid differentiation: association with t(3;12)(p25;q24.3). Case report and review of the literature.

Biphenotypic hematological malignancies of T-lymphoid and myeloid differentiation are relatively rare and have most commonly been associated with t(8;13). However, this entity is invariably associated with eosinophilia and generally progresses to acute leukemia within a year of diagnosis. We describe a case of a biphenotypic hematological malignancy with T-lymphoid and myeloid differentiation without associated eosinophilia; however, there was an association with t(3;12)(p25;q24.3) as a sole abnormality and progression to acute leukemia within 10 months of presentation. This association with such a malignancy has not previously been described. Additional cases need to be accrued to determine the prognostic significance and clinical implications of such an association.

A clinically aggressive, polymorphic, polyclonal posttransplantation lymphoproliferative disorder.

Posttransplantation lymphoproliferative disorders (PTLD) have been divided, based on morphology, into polymorphic and monomorphic types, since findings in the literature reveal that polymorphic PTLD more likely responds to reduced immunosuppression. We report a clinically aggressive, polymorphic (and polyclonal) PTLD despite reduced immunosuppression and discuss possible therapeutic options. In addition, our case suggests that cytogenetic studies may be useful in determining prognosis when DNA molecular techniques do not detect monoclonality.

Deletion of 3'-CBFB gene in association with an inversion (16)(p13q22) and a loss of the Y chromosome in a 2-year-Old child with acute myelogenous leukemia-M4.

Inversion 16(p13q22) is most commonly associated with acute myelomonocytic leukemia with abnormal eosinophils (M4). In association with this inversion, a proximal deletion at the 16p13 primary arm breakpoint occurs in 20% of cases. We report on a first case of inversion 16 with a distal deletion at the primary arm breakpoint 16q22, detected by using the fluorescent-labeled dual-color probe CBFB.

Jumping translocations of 3q in acute promyelocytic leukemia.

Jumping translocation is a rare phenomenon, seldom reported to occur in cancer. A complex four-way translocation involving chromosomes 3, 9, 15, and 17 was identified in the chromosome study on a patient with a history of an acute promyelocytic leukemia (APL). In the follow-up studies, the same complex rearrangement exhibited a jumping translocation between chromosomes 3 and 9 in one clone and 3 and 6 in another clone. This is the first reported case of jumping translocation in APL.

Is t(6;14) a non-random translocation in childhood acute mixed lineage leukemia?

We report a case of childhood acute mixed lineage leukemia (AMLL) with a translocation t(6;14)(q25;q32) as the main clonal abnormality. A comparison of this case with another one with similar cytogenetics and clinical findings may suggest that t(6;14)(q25;q32) is a non-random occurrence in childhood AMLL.

Co-existence of alternative forms of 8q gain in cytogenetic clones of three patients with acute myeloid leukemia, pointing to 8q22 approximately 8qter as a region of biologic significance.

Clonal trisomy 8 chromosome abnormalities can be detected in 15% of patients with acute myeloid leukemia (AML). The most common form of change is complete gain of the whole chromosome 8, followed by partial gains in unbalanced forms. The biologic consequences of trisomy 8 remain unclear, but a gene dosage effect is suspected. We report on three patients with AML who had alternative forms of chromosome 8 gain in their bone marrow cells. The partial gains resulted from a breakpoint in the chromosome band 8q22. This indicates that the region 8q22 to 8qter may be of particular pathogenetic importance.

Case of lipoblastoma with two derivative chromosomes 8 containing homogeneously staining-like regions and a review of the literature: lipoblastoma and chromosome 8.

We report a case of a lipoblastoma in a 10-month-old girl in which the cytogenetic aberration showed a homogeneously staining-like region (hsr) within two derivative chromosomes 8. There was a loss of one normal copy of chromosome 8 and gain of two identical derivative chromosomes 8 with the karyotype designation 47,XX,psu idic(8)(pter-->q12 approximately 13::hsr::q12 approximately 13-->pter),+psu idic (8)(pter-->q12 approximately 13::hsr::q12 approximately 13-->pter). This is the first report of a chromosomal aberration of this type seen in lipoblastoma.

Simultaneous presence of t(2;8)(p12;q24) and t(14;18)(q32;q21) in a B-cell lymphoproliferative disorder with features suggestive of an aggressive variant of splenic marginal-zone lymphoma.

We report a case of an aggressive variant of splenic marginal-zone lymphona (SMZL) with circulating villous lymphocytes. The karyotype of all examined cells had multiple structural and numerical abnormalities, including two lymphoma characteristic translocations, t(2;8)(p12;q24) and t(14;18)(q32;q21). Based on a literature review of cytogenetic aberrations of splenic lymphoma with villous lymphocytes (SLVL) and SMZL, this is apparently the first documentation of these two translocations in a case of SMZL, and could reflect the heterogeneity of the disorder.

Trisomy 15 is frequently observed as a minor clone in patients with Anemia/MDS/NHL and as a major clone in patients with AML.

Trisomy 15 as the sole karyotypic aberration is an uncommon clonal cytogenetic aberration in hematological malignancies, making its significance unclear. Previous studies have reported relations of trisomy 15 with low-grade myelodysplasia or a benign age-related phenomenon associated with loss of the Y chromosome. To define the significance of trisomy 15, we conducted a retrospective study of all examples of trisomy 15 accessed in our laboratories. Trisomy 15 was observed as a clonal abnormality (> or =2 cells) in 17 cases and nonclonal (single cell) in 9 cases. The majority of cases (14/17 clonal cases) had a minor clone (5-35% of metaphase cells) of trisomy 15. The minority of cases (3/17) had a major clone (80-95% of metaphase cells) of trisomy 15. Two of these 3 cases were diagnosed as having acute myelocytic leukemia. Fluorescence in-situ hybridization (FISH) with the use of a chromosome 15-specific alpha-satellite probe was performed on 3 of 17 clonal cases and on 3 of 9 nonclonal cases. FISH results revealed the presence of a minor clone (from 3 to 5 of 700 interphase cells) in 5 of them, 2 of which had trisomy 15 in 20% of metaphase cells. These results may indicate that the 20% of trisomy 15 are very likely an overrepresentation of a very minor clone that could be transitory. In summary, the analysis of our cytogenetic and FISH results revealed the presence of two types of trisomy 15 clones: a minor clone that could be transitory or indolent and a major clone that could be of a neoplastic nature.

A simple VNTR-PCR method for detecting maternal cell contamination in prenatal diagnosis.

The effectiveness of variable number tandem repeats (VNTRs) was evaluated in the detection of maternal cell contamination. Nonradioactive PCRs were performed on 30 sets of prenatal tissue using VNTRs as primers. The combination of two VNTRs (YNZ22 and APOB) provided information on all 30 cases, distinguishing maternal-fetal genotype patterns and detecting maternal cell contamination in 5 of 30 prenatal cases. The amplification of these two VNTRs does not require radioactive or fluorescence labeling, and a small gel electrophoresis is sufficient to see the maternal-fetal genotype pattern. By this method, detection of maternal cell contamination in prenatal tissues can be obtained in 1 day, without the use of expensive instruments, thus providing DNA laboratories a very sensitive, rapid, and simple proof pretest on all prenatal tissues before performing the final genetic diagnostic testing.

Successful umbilical cord blood stem cell transplantation in a patient with Rothmund-Thomson syndrome and combined immunodeficiency.

The ATP-dependent DNA helicase Q4 (RECQL4) belongs to a family of conserved RECQ helicases that are felt to be important in maintaining chromosomal integrity (Kitao et al., 1998, Genomics: 54 (3): 443-452). Deletions in the RECQL4 gene located on chromosome 8 region q24.3 have been associated with Rothmund-Thomson syndrome (RTS, OMIM 268400), a condition characterized by poikiloderma, sparse hair, small stature, skeletal abnormalities, cataracts and an increased risk of malignancy. We present a patient with a molecularly confirmed diagnosis of RTS with two unique genetic alterations in RECQL4 (IVS16-2A>T and IVS2+27_51del25), who at the age of 7 months nearly succumbed to Pneumocystis carinii pneumonia. Evaluation of his immune system demonstrated a T- B+ NK- phenotype with agammaglobulinemia consistent with combined immunodeficiency (CID). Studies to evaluate for known genetic causes of CID were not revealing. The patient received an umbilical cord blood (UCB) transplant with complete immune reconstitution. This report represents the first description of a CID phenotype and UCB transplantation in a patient with RTS.

DELETION MAPPING OF CRITICAL REGION FOR HYPOSPADIAS, PENOSCROTAL TRANSPOSITION AND IMPERFORATE ANUS ON HUMAN CHROMOSOME 13.

BACKGROUND: The 13q-deletion syndrome causes human congenital birth defects due to the loss of regions of one long arm of human chromosome 13. A distal critical region for severe genitourinary and anorectal birth defects in the region of 13q32.2-34 has been suggested; we sought to narrow this critical region. METHODS: From patients with karyotypes revealing haploinsufficiency for distal chromosome 13q and their parents, peripheral blood was obtained and lymphocytes were immortalized for DNA isolation. Genetic and molecular cytogenetic methods were used to map deletions. Patient and parental samples were genotyped with a panel of 20 microsatellite markers spanning 13q31.3 qter and deletions identified by loss of heterozygosity. Deletions were also mapped using a panel of 35 BAC clones from the same region as probes for fluorescence in-situ hybridization on patient lymphoblastoid metaphase preparations. The data were synthesized and a deletion map defining the critical region was generated. RESULTS: Eight patients with known deletions around 13q32qter and their parents were analyzed, and categorized into three groups: three patients with anorectal and genitourinary anomalies (hypospadias, penoscrotal transposition), four male patients without anorectal and genitourinary anomalies, and one XY patient with ambiguous genitalia without anorectal anomalies. We mapped the critical region for anorectal and genitourinary anomalies to a approximately 9.5-Mb interval of 13q33.3-q34 delineated by markers D13S280-D13S285; this spans approximately 8% of the chromosome and contains 20 annotated genes CONCLUSION: The critical region of chromosome 13q mediating genitourinary/anorectal anomalies has been mapped, and will be narrowed by additional patients and further mapping. Identification of the gene(s) mediating these syndromic genitourinary defects should further our knowledge of molecular mediators of non-syndromic hypospadias, penoscrotal transposition and anorectal malformations.

An unbalanced half-cryptic translocation involving the 6q subtelomeric region and 2p25.3 in a child with mental retardation: uses and limitations of fluorescence in situ hybridization.

We report on a 5-year-old boy with minor anomalies, growth retardation, and developmental delay carrying an extra chromatin material on the terminal band of the long arm of chromosome 6. To determine the origin of this extra material, whole chromosome fluorescence in situ hybridization (FISH) was used initially. Results showed fully painted 6qs, excluding the possibility of a derivative. However, maternal cytogenetic investigation suggested the presence of a possible half-cryptic balanced translocation that was further assessed using specific subtelomeric FISH probes of chromosome 6. Results showed that the 6q subtelomeric region was translocated on an A-group chromosome that was ultimately characterized, using FISH, as chromosome 2. This illustrates the use of specific subtelomeric regions and the limitations of whole chromosome FISH to identify the origin of a subtle chromosomal abnormality.

Genomic organization and localization of gene for human carbonic anhydrase IV to chromosome 17q.

Carbonic anhydrase IV (CA IV) is a glycosylphosphatidylinositol-anchored membrane isozyme expressed on the luminal surfaces of pulmonary (and certain other) capillaries and on the luminal surface of proximal renal tubules. It is of interest for its functional importance in CO2 and HCO3- transport, its ancient evolutionary status among CA isozymes, and its possible role in inherited renal abnormalities of HCO3- transport. To determine the localization of the CA IV gene and define its genomic structure, we isolated and characterized a full-length genomic clone. The 9.5-kb gene contains eight exons and seven introns. The first exon (exon 1a) encodes the signal sequence. Exons 1b through 7 encode the remaining coding sequence. Exon 7 encodes the C terminus of the enzyme precursor, the C terminus of the mature protein and also contains the 120-bp sequence corresponding to the 3' untranslated region of the cDNA. The positions of introns 3, 4, 5, and 6 are identical with the corresponding positions of introns in the genes for the soluble CA isozymes (CA I, II, III, and VII). However, intron 1a is not found in these genes, and the positions of introns 1b and 2 in CA IV differ from the positions of the corresponding introns in genes for the soluble isozymes. The 5' upstream region of the gene (-500 to -1) is GC rich and contains 30 CpG dinucleotides. A TATA box sequence and a potential Sp1 binding site are identified upstream of the first exon. By using PCR on DNA from human/rodent somatic cell hybrids, the CA IV gene was assigned to chromosome 17.(ABSTRACT TRUNCATED AT 250 WORDS)

Homologous telomere association of 19q in a female with premature ovarian failure.

Premature ovarian failure (POF) may be due to a variety of genetic mechanisms. We report here, for the first time, telomere association of the long arms of chromosome 19, identified at low frequency (1%) in the peripheral blood cultures of a 30-year-old female with POF. Repeat cultures identified, in addition, the presence of 16q and 22q associations at a lower frequency (0.5%). These consistent observations are suggestive of a non-random event. Their association with POF may just be coincidental or may hypothetically explain it by an abnormal mechanism of chromosome separation, a constitutional telomere anomaly or an unidentified chromosome instability disorder.

Genomic organization of the human gene (CA5) and pseudogene for mitochondrial carbonic anhydrase V and their localization to chromosomes 16q and 16p.

Carbonic anhydrase V (CA V) is expressed in mitochondrial matrix in liver and several other tissues. It is of interest for its putative roles in providing bicarbonate to carbamoyl phosphate synthetase for ureagenesis and to pyruvate carboxylase for gluconeogenesis and its possible importance in explaining certain inherited metabolic disorders with hyperammonemia and hypoglycemia. Following the recent characterization of the cDNA for human CA V, we report the isolation of the human gene from two lambda genomic libraries and its characterization. The CA V gene (CA5) is approximately 50 kb long and contains 7 exons and 6 introns. The exon-intron boundaries are found in positions identical to those determined for the previously described CA II, CA III, and CA VII genes. Like the CA VII gene, CA5 does not contain typical TATA and CAAT promoter elements in the 5' flanking region but does contain a TTTAA sequence 147 nucleotides upstream of the initiation codon. CA5 also contains a 12-bp GT-rich segment beginning 13 bp downstream of the polyadenylation signal in the 3' untranslated region of exon 7. FISH analysis allowed CA5 to be assigned to chromosome 16q24.3. An unprocessed pseudogene containing sequence homologous to exons 3-7 and introns 3-6 was also isolated and was assigned by FISH analysis to chromosome 16p11.2-p12.

Two unbalanced translocations involving a common 6p25 region in two XY female patients.

We report two 46,XY female patients with two different de novo unbalanced translocations, each involving the chromosomal region 6p25. The patient with a 46,XY,der(6)t(X;6)(p21.2;p25) karyotype had a sex reversal phenotype. The patient with a 46,XY,der(13)t(6;13)(p25;q33) karyotype had a male pseudohermaphrodite phenotype. Multi-paint fluorescent in situ hybridization was performed to determine the origin of the derivative material on 6p and 13q. The association of abnormalities of the 6p25 region with either an Xp duplication or a 13q deletion is reported here for the first time.