An antisense transcript to SMAD5 expressed in fetal and tumor tissues

SMAD5, a transducer of TGF-beta/BMP inhibitory signals and a tumor suppressor candidate, localizes to the region of invariant loss in human myeloid neoplasms, on chromosome 5q31.1. Recent evidence indicates a gene-dosage effect along the TGF-beta/BMP signaling pathways. We have identified a novel transcript designated DAMS, whose 3' exonic sequences contain in part an alternate 5' exon of SMAD5, in the antisense orientation. Expressed sequenced tags (ESTs) for DAMS are found in fetal tissues (heart, adrenal glands, and total fetus) and pancreatic tumor cDNA libraries. In contrast to SMAD5, DAMS expression is not readily detectable in adult and fetal tissues. Semiquantitative PCR suggests that the stoichiometry between SMAD5 and DAMS transcripts ranges between 15 and 120 in normal and malignant hematopoietic cells. The findings raise the possibility that DAMS may be a fail-safe mechanism for precise regulation of SMAD5 transcript levels that may be critical in maintaining normal homeostasis.

Seizure exacerbation and developmental regression with carbamazepine

BACKGROUND

Unexpected exacerbation of seizures may occur following initiation of treatment with carbamazepine (CBZ). We reviewed the occurrence of such reactions in our patient population at a tertiary care children's hospital.

METHODS

A retrospective analysis of our clinic database identified 129/691 (18.6%) patients with epilepsy treated with CBZ, as monotherapy. 38/129 children were later switched to another drug. In 11/38 (28.5%) clinical and/or EEG deterioration was observed. Two patients identified at another institution with similar exacerbation were also included in our analysis. We report on the findings in these 13 cases.

RESULTS

Two groups were identified: Group I--6 patients with normal neurological exam, normal EEG background, and a diagnosis of idiopathic generalized epilepsy. Group II--7 patients with an abnormal neurological exam and/or abnormal EEG background. Following introduction of CBZ therapy, worsening of preexisting seizures, appearance of new seizure types, behavioral regression, and accompanying EEG deterioration were reported in both groups. Dramatic improvement in seizure control occurred, following withdrawal of CBZ and substitution of another anticonvulsant.

CONCLUSION

Physicians treating epilepsy must be aware that CBZ can exacerbate seizures, and cause developmental regression in children. Careful patient selection, when choosing CBZ as treatment, and prompt recognition of clinical deterioration and intervention, may help avoid or reverse these paradoxical reactions.

5q- in a child with refractory anemia with excess blasts: similarities to 5q- syndrome in adults

A 19-month-old boy was referred to our institution because of chronic macrocytic anemia and severe thrombocytopenia. At age 17 months, he had developed petechiae. He had a leukocyte count of 4.4 x 10(9)/L, hemoglobin concentration of 7.9 g/dL, packed cell volume of 21%, mean corpuscular volume of 101 fL, and platelet count of 19 x 10(9)/L. At the time of referral, a bone marrow aspirate and biopsy revealed myelodysplastic changes that included megakaryocytic hyperplasia with hypolobated megakaryocytes, megaloblastoid erythropoiesis, 12% blast cells, and bone marrow fibrosis; the diagnosis was refractory anemia with excess blasts (RAEB). Cytogenetic analysis showed the following abnormalities: 47, XY, inv(3)(p21q25), del(5)(q22q31), +21/46, XY. By dinucleotide polymorphism analysis, the 5q22-q31 loci were normal in peripheral blood granulocytes. Because of severe thrombocytopenia that became refractory to platelet transfusions and because of possible progression to leukemia, the patient received an unrelated-donor bone marrow transplant. Recovery was complicated by a visceral fungal infection, but the patient now has normal, fully reconstituted bone marrow function. This patient is the youngest to be reported with RAEB and a 5q- anomaly accompanied by thrombocytopenia, megakaryocytic hyperplasia with hypolobated megakaryocytes, and macrocytic anemia with megaloblastoid erythropoiesis, similar to "5q- syndrome" in adults.

The unexplored 5q13 locus: a role in hematopoietic malignancies

Deletions and translocations at 5q13 point out a locus involved in the development of acute myeloblastic leukemia (AML) and myelodysplastic syndromes (MDS) as well as other neoplasms. The chromosomal rearrangements of 5q13 are well documented, but have not been a primary focus of research. In this report, we provide evidence for a novel critical locus at 5q13.3, encoding gene(s) which may be disrupted by chromosomal translocations or deletions. Rare cases of myeloid neoplasms with t(5q13) as the sole chromosomal anomaly argue for a gene which gives rise to fusion proteins. Our preliminary studies have localized one of the critical genes to a <3 Mb. interval between the polymorphic markers AFMB347yf9 and GATAP18104 at the band 5q13.3. Other results also suggest that the 5q 13.3 locus may span a fragile site which undergoes unbalanced translocations and interstitial deletions accompanied by loss of significant segments of chromosome 5. Molecular reagents generated by the human genome mapping and sequencing initiative will allow us to characterize the critical genes at 5q13.3 and facilitate genotypic analysis of AML and MDS.

Molecular anatomy of chromosome 7q deletions in myeloid neoplasms: evidence for multiple critical loci

Complete or partial deletions of the long arm of chromosome 7 (7q- and -7) are nonrandom abnormalities seen in primary and therapy-induced myelodysplasia (MDS) and acute myelogenous leukemia (AML). Monosomy 7, occurring as the sole cytogenetic anomaly in a small but significant number of cases, may denote a dominant mechanism involving critical tumor suppressor gene(s). We have determined the extent of allele loss in cytogenetically prescreened MDS and AML patients for microsatellite markers from chromosome 7q22 and 7q31. Whereas >80% of these cases revealed allele loss for the entire region, a rare case of the 7q- chromosome showed allele loss for only the proximal 7q31.1 loci flanked by the markers D7S486 and D7S2456, and a case of monosomy 7 revealed allele loss for loci at both 7q31 and 7q22 with retention of sequences between these sets of loci. Furthermore, a case of AML with no cytogenetic anomaly of chromosome 7 revealed a submicroscopic allelic imbalance for a third distal locus, D7S677. These findings suggest the presence of three distinct critical loci that may contribute alone or in combination to the evolution of MDS and AML. The data also provide molecular evidence for unbalanced translocation with noncontiguous deletions, as an alternate mechanism underlying monosomy 7.

Preferential expression of HMGI-C isoforms lacking the acidic carboxy terminal in human leukemia

The high mobility group HMGI chromosomal proteins are an important component of chromatin. The HMGI-C protein consists of three amino terminal DNA binding domains ("AT hooks"), a linker region and an acidic carboxy domain. In mesenchymal tumors, chromosomal translocations of 12q13-15 result in fusion proteins containing the AT hooks and novel carboxy terminals. We have investigated the status of the HMGI-C gene in two cases of leukemia with anomalies of chromosome 12q and identified three novel isoforms (designated alpha, beta and gamma) derived from alternate splicing. One of the patients expressed all three isoforms, whereas the second patient expressed only the gamma isoform; preferential expression of the HMGI-C gamma isoform was also detected in the leukemic cell lines ML3 and BV173. The results are consistent with a crucial role for truncation of the acidic carboxy domain of HMGI-C in abnormal growth.

Localization of SMAD5 and its evaluation as a candidate myeloid tumor suppressor

Acquired interstitial or complete losses of chromosome 5 are recurring anomalies associated with preleukemic myelodysplasia and acute myelogenous leukemia with a poor prognosis. Previous studies have delineated a potential myeloid tumor suppressor locus to a <2.4-Mb interval between the genes for IL9 and EGR1 on 5q31. In this report, we have localized the SMAD5 gene, a homologue of the tumor suppressor genes SMAD4/DPC-4 and SMAD2/JV18.1, to the minimal myeloid tumor suppressor locus and characterized its open reading frame and genomic organization. SMAD5 transcripts are readily detectable in hematolymphoid tissues and leukemic blasts. Absence of intragenic mutations in the remaining SMAD5 allele of leukemic patients and multiple solid tumor cell lines prescreened for loss of heterozygosity suggests that SMAD5 may not be a common target of somatic inactivation in malignancy.

Effects of nitrous oxide on electrocorticography during epilepsy surgery

Interictal spikes on intraoperative electrocorticography during epilepsy are used to tailor resections. There have been a few systematic quantitative studies of anesthetic effects on these interictal discharges, and none on the effects of nitrous oxide (N2O). We calculated spike rates on ECoG on and off N2O in 18 epilepsy surgery patients with subdural strips and grids, analyzing the most active recording contract. In a blinded analyses ten patients had fewer spikes on N2O, while eight patients had more spikes on N2O. The mean spike rates did not differ (41/min on N2O and 40/min off N2O). Spike rate on and off N2O were compared using the non-parametric Wilcoxon matched pairs test. These rates were not significantly different. Our study indicates that N2O in doses employed dose not effect interictal spikes and this agent may be used during epilepsy surgery without concerns about suppression of epileptiform activity.

Molecular characterization of GCV3, the Saccharomyces cerevisiae gene coding for the glycine cleavage system hydrogen carrier protein

YAL044, a gene on the left arm of Saccharomyces cerevisiae chromosome one, is shown to code for the H-protein subunit of the multienzyme glycine cleavage system. The gene designation has therefore been changed to GCV3, reflecting its role in the glycine cleavage system. GCV3 encodes a 177-residue protein with a putative mitochondrial targeting signal at its amino terminus. Targeted gene replacement shows that GCV3 is not required for growth on minimal medium; however, it is essential when glycine serves as the sole nitrogen source. Studies of GCV3 expression revealed that it is highly regulated. Supplementation of minimal medium with glycine, the glycine cleavage system's substrate, induced expression at least 30-fold. In contrast, and consistent with the cleavage of glycine providing activated single-carbon units, the addition of the metabolic end products that require activated single-carbon units repressed expression about 10-fold. Finally, like many amino acid biosynthetic genes, GCV3 is subject to regulation by the general amino acid control system.

Translocations and deletions of 5q13.1 in myelodysplasia and acute myelogenous leukemia: evidence for a novel critical locus

Acquired partial and complete deletions of chromosome 5 (5q-, -5) are common cytogenetic anomalies associated with myelodysplasia (MDS) and acute myeloid leukemia (AML). A critical region of consistent loss at 5q31.1 (in > 90% of cases) has led us and others to postulate the presence of a key negative regulator(s) of leukemogenesis. Although the interstitial deletion limits vary among patients, del(5) (q13q33) and del(5)(q13q35) constitute major subsets. Furthermore, it is not rare to encounter deletions, translocations, or paracentric inversions involving 5q11 to 5q13, which indicates inactivation or disruption of important gene(s) at that locus. In this report, we have localized a novel locus at 5q13.1 to a 2.0-Mb interval between the anonymous markers D5S672 and GATA-P1804. This locus resided within the region of loss in 12 of 27 patients with anomalies of chromosome 5; one of these cases had apparent retention of both alleles of all the telomeric loci. Fluorescence in situ hybridization (FISH) studies demonstrate that the AML cell line ML3 is disrupted at 5q13.1 by a translocation involving chromosome 3, with apparent retention of the entire chromosome 5 sequence. Our results suggest that this novel proximal locus encodes a critical gene that may be deleted or disrupted in a subset of MDS/AML patients with chromosome 5 anomalies.

Ubiquitous expression and cell cycle regulation of the protein kinase PIM-1

The murine pim-1 gene, isolated as a locus frequently activated by proviral integration in T cell lymphomas, encodes a protein serine kinase. Although genetic evidence suggests a crucial role for this protooncogene in cell growth and transformation, very little is known about its protein product. The murine pim-1 mRNA provides alternate translational starts at a CUG codon +87-89 and an AUG codon at +339-341, in the same open reading frame (ORF), resulting in 44-kDa (397 amino acids) and 34-kDa (313 amino acids) isoforms. In this report, we demonstrate that the human PIM-1 mRNA is translated only from the single initiation methionine codon at +339-341 under cell-free conditions. Immunoblotting analyses of several human solid tumor cell lines, with highly specific antisera reveal two ubiquitously expressed isoforms (35 and 34 kDa). The estimated half-life of these proteins is shorter in the normal peripheral blood leukocytes (<5 min) than in the chronic myelogenous leukemia cells K562 (<20 min). Immunoblotting analyses of centrifugally elutriated fractions of the chronic myelogenous leukemia BV173 cells demonstrate that the levels of PIM-1 increase during the progression from early to late GI, remain high at the G1/S boundary and G2 phases of the cell cycle. The results presented here suggest a ubiquitous role for PIM-1 in progression through cell cycle.

Contralateral temporal hypometabolism on positron emission tomography in temporal lobe epilepsy

INTRODUCTION

No detailed case studies report lateralised hypometabolism on positron emission tomography (PET) contralateral to the epileptogenic focus in temporal lobe epilepsy (TLE).

MATERIAL AND METHODS

We performed 18F fluorodeoxyglucose (FDG) PET in two intractable TLE patients.

RESULTS

One had right temporal interictal spikes on electroencephalography (EEG) and a right medial temporal lobe lesion on magnetic resonance imaging (MRI). FDG-PET showed decreased uptake in the left temporal lobe. Right temporal ictal onset, with bilateral interictal epileptiform activity, occurred on intracranial EEG. He is seizure free after right temporal lobectomy and ganglioglioma resection. The second had right temporal lobe interictal and ictal EEG activity. MRI demonstrated right anteriomedial temporal increased T2 signal. Neuropsychology revealed bilateral cognitive dysfunction. FDG-PET showed left anterior temporal and lateral frontal hypometabolism. He is seizure free after right temporal lobectomy.

CONCLUSION

These findings suggest that regional uptake asymmetry on FDG-PET may be give misleading lateralising information in TLE.

Physical mapping of the minimal region of loss in 5q- chromosome

Acquired interstitial loss of all or part of the long arm of human chromosome 5 (5q-) is an anomaly that is seen frequently in patients with preleukemic myelodysplasia and acute myelogenous leukemia. Loss of a critical region of overlap at band 5q31.1 in all of these cases, with various cytogenetic breaks, signifies the existence of a key negative regulator of leukemogenesis. Previous studies have defined the proximal and distal ends of the critical region to reside between the genes for IL9 and EGR1, respectively. In this report, we describe a yeast artificial chromosome contig spanning this myeloid tumor suppressor locus. The combined order of the polymorphic loci is centromere-IL9-(D5S525-D5S558-D5S89-D5S526 -D5S393)-D5S399-D5S396-D5S414-EGR1 and telomere. The physical distance between the IL9 and EGR1 genes is estimated to be < 2.4 Mb. Here we report the utility of these polymorphic loci by detecting a submicroscopic deletion of 5q31; an acute myelogenous leukemia patient with a three-way translocation, t(5;18;17)(q31;p11;q11), as the sole anomaly revealed allele loss of the D5S399 and D5S396 loci.

Molecular analysis of the 5q- chromosome

Acquired interstitial deletions of the long arm of chromosome 5, are seen in anomalies of the myeloid cells. The refractory anemia (RA) or 5q- syndrome, in which the erythroid and megakaryocytic lineages are predominantly affected, is a relatively indolent clinical entity distinguishable, from the constellation of preneoplastic myelodysplastic syndrome (MDS) and acute myelogenous leukemia (AML) with trilineage involvement. Recent molecular evidence suggests that the critical region of 5q deletion in MDS/AML resides in the D5S89 locus, which is proximal (centromeric) to the minimal region of loss in the 5q- syndrome RA. The invariable loss of the D5S89 locus in MDS/AML qualifies it for the MDS/AML tumor suppressor locus. The telomeric 5q31 gene governs erythroid and megakaryocytic differentiation and can be termed the RA locus. Isolation and characterization of these genes will lead to an understanding of molecular mechanisms underlying normal hematopoiesis and leukemic transformation.

Development of a sensitive PCR to detect allele loss in a model hematopoietic neoplasm

Loss or gain of an entire chromosome and interstitial deletions or amplifications are hallmarks of several hematopoietic neoplasms. These chromosomal anomalies can be identified by conventional cytogenetic analysis of bone marrow aspirates. We have developed a PCR-based assay to detect loss of chromosome 5q31 loci, in the model system of myeloid disorders with the 5q- chromosome (interstitial deletion of 5q), by taking advantage of a highly polymorphic dinucleotide repeat within the interleukin-9 (IL9) gene on 5q31. In a given sample, quantitation of amplification of individual alleles in a Phosphorimager allowed the representation of alleles to be expressed as a ratio of the larger to the smaller allele. Comparison of these ratios in paired DNA samples from Ficoll buoyant and pelletted fractions provides evidence for allele loss. Results presented here demonstrate that this technique of comparison of ratios of isotope incorporation could be expanded to Investigate any deletion or numerical abnormality in hematopoietic tumors.

5q- chromosome. Evidence for complex interstitial breaks in a case of refractory anemia with excess blasts

Interstitial loss of the long arm of chromosome 5 (5q-) is an anomaly frequently seen in myelodysplasia (MDS) and acute myelogenous leukemia (AML). Although the limits of the interstitial deletions vary among patients, there is a critical region of overlap at 5q31 that is consistently deleted in most cases. The order of genes in the critical 5q31 region is centromere, interleukin gene cluster, an anonymous polymorphic locus D5S89, early growth response factor, CSF1 receptor, telomere. Fluorescence in situ hybridization of specific 5q31 probes to metaphases with del(5) (q11q31) from a patient with secondary refractory anemia with excess blasts in transformation demonstrates that the interstitial deletion is not contiguous. The 5q- chromosome has lost the D5S89 and CSF1R loci while retaining some of the sequences in between. A probe derived from a 300-kbp yeast artificial chromosome containing the D5S89 locus is interrupted on the normal chromosome 5 of this patient. Data presented in this report are consistent with (i) presence of a critical gene within the YAC and (ii) more than a single interstitial break within the 5q- chromosome. These results, while pinpointing one of the critical 5q31 loci, also provide evidence for a second telomeric locus.

Consistent loss of the D5S89 locus mapping telomeric to the interleukin gene cluster and centromeric to EGR-1 in patients with 5q- chromosome

Interstitial deletions of the long arm of chromosome 5 are common in a number of disorders of leukemic and preleukemic myeloid disorders. Although the limits of these deletions vary among patients, a region of cytogenetic overlap that includes band 5q31 is deleted consistently, suggesting loss of 5q31 loci critical for normal myeloid differentiation and leukemogenesis. An anonymous genomic DNA segment D5S89, previously mapped to 5q21-31, detects consistent loss of alleles in cases showing the 5q- chromosome at presentation or relapse. Analysis of a panel of natural-deletion somatic-cell hybrids in conjunction with irradiation hybrids containing fragments of human chromosome 5q shows that the D5S89 locus is telomeric to the interleukin (IL) genes (IL-3, IL-4, IL-5, IL-9, and granulocyte-macrophage colony-stimulating factor [GM-CSF]) and interferon response factor-1 (IRF-1) gene and centromeric to the early response transcription factor (early growth response gene-1 [EGR-1]) on 5q31. To further define the principal region of loss, we have isolated and characterized yeast artificial chromosomes (YACs) spanning D5S89. The presence of several CpG islands within the 300-kb YAC is suggestive of multiple transcription units. However, IL-4, IL-5, IRF-1, IL-3, GM-CSF, and EGR-1 genes were not detected in the YAC clone spanning D5S89, implying that none of these genes are in the vicinity of the D5S89 marker. Further characterization of these YACs should facilitate the isolation of novel candidate genes that may play a role in the evolution of the abnormal phenotype associated with 5q- chromosome.

Transcriptional attenuation of PIM-1 gene

Levels of the mRNA for PIM-1, a protooncogene encoding a cytoplasmic serine threonine kinase show a wide variation among tissues and cell lines, although this gene is transcribed from a GC- rich housekeeping promoter. Previous studies have failed to identify tissue specific elements in the PIM-1 promoter raising the possibility that these elements might reside within the gene. Transient transfections of Luciferase reporter gene constructs into the chronic myelogenous leukemia cell line K562 (which expresses high levels of PIM-1 mRNA) demonstrate that the 1.7kbp PIM-1 promoter sequences alone were three times more efficient than constructs driven by the promoter+PIM-1 genomic sequences. Nuclear run on assays of nascent RNA from K562 cells revealed premature transcriptional termination within the PIM-1 gene. Thus, PIM-1 gene may be constitutively transcribed in all tissues and transcriptional attenuation could be one of the mechanisms regulating the observed differences in steady state levels of mRNA.

A mouse c-ros genomic clone: identification of a highly conserved 22-amino acid segment in the juxta-membrane domain

The mouse c-ros protooncogene genomic sequences have been cloned; an analysis of the partial genomic clone revealed a high conservation of the exons encoding the juxta-membrane (JM) and the 5' most protein tyrosine kinase domains. We have identified a segment of 22 amino acids conserved between the human and mouse JM domains; this segment may have a critical role in the function of the c-ros-encoded protein tyrosine kinase receptor.