Escherichia coli: high resistance or dependence on streptomycin produced by the same allele.

Mutations to streptomycin resistance in Escherichia coli K12, when transferred to a C strain, can confer dependence on streptomycin. These alternatives in expression of the allele are probably a result of interaction between two ribosomal proteins.

Glucose-6-phosphate dehydrogenase deficient red cells: resistance to infection by malarial parasites.

Erythrocyte mosaicism occurs in females heterozygous for glucose-6-phosphate dehydrogenase deficiency. In blood from female children with acute Plasmodium falciparum malaria the parasite rate was 2 to 80 times higher in normal than in deficient erythrocytes. This may be the mechanism whereby the gene for glucose-6-phosphate dehydrogenase deficiency confers selective advantage against malaria to heterozygous females, and thus may have attained the polymorphic frequency occurring in populations living in areas with endemic malaria.

Imbalance in X-chromosome expression: evidence for a human X-linked gene affecting growth of hemopoietic cells.

In each of six family members who were heterozygous at the X-linked locus for glucose-6-phosphate dehydrogenase, only one or the other of the two alleles at that locus was almost exclusively expressed. The data are consistent with evidence that X-chromosome inactivation is a random process that may be followed by selection for one of the two resulting cell types on the basis of an unknown gene, which is located on the X chromosome and which can affect the rate of proliferation of hemopoietic cells in humans.

Persistence of expression of the TMPRSS2:ERG fusion gene after pre-surgery androgen ablation may be associated with early prostate specific antigen relapse of prostate cancer: preliminary results.

BACKGROUND: The recently identified TMPRSS2: ERG fusion gene is a candidate oncogene for prostate cancer (PCa). SUBJECTS AND METHODS: We have tested for the presence of this gene in tumor samples from 84 patients who had radical prostatectomy in 1998-2000. Sixty patients (group A) had surgery only; 24 patients (group B) received androgen ablation therapy for 3 months before surgery. The occurrence of the rearrangement was evaluated by RT-PCR and by fluorescent in situ hybridization analysis. RESULTS: A TMPRSS2:ERG fusion gene was present and expressed, as demonstrated by RT-PCR, in 84% of patients in group A and in 54% of patients in group B (p=0.01). The presence of TMPRSS2:ERG transcripts and the levels of ERG RNA, measured by quantitative Real Time-PCR, did not correlate significantly with clinical and pathologic characteristics of the tumors. In patients of group A, but not in those of group B, ERG expression showed a negative correlation with the Gleason score (p=0.0001). Histochemical analysis showed that ERG expression is limited to tumor cells, and in group A patients (but not in group B patients) it is limited to those glands that express TMPRSS2:ERG. CONCLUSION: The lower proportion of patients expressing TMPRSS2: ERG in group B suggests that androgen ablation inhibits the expression of TMPRSS2:ERG. Moreover, in group B, but not in group A, patients with expression of the fusion gene had earlier prostate specific antigen recurrence (p=0.007). Although preliminary, the data indicate that tumors in which pre-surgery androgen ablation fails to suppress expression of the fusion gene have a higher risk of recurrence.

The molecular basis of glucose-6-phosphate dehydrogenase deficiency.

With more than 300 different variants reported, the human enzyme glucose-6-phosphate dehydrogenase (G6PD; EC 1.1.1.49) is one of the most polymorphic proteins known. An estimated 400 million people throughout the world are deficient in G6PD; numerous lines of evidence indicate that this is because female heterozygotes have a selective advantage in malaria infections. The cloning of the G6PD gene has made it possible to clarify the molecular basis underlying this enzyme deficiency and polymorphism.

Anomalous rearrangements of the immunoglobulin heavy chain genes in human leukemias support the loop-out mechanism of class switch.

Discrete rearrangements of immunoglobulin genes are characteristic of lymphoproliferative diseases of B cells and provide direct evidence of their clonal nature. In addition, because leukemic transformation and growth may amplify B cell clones regardless of selection by antigen, analysis of rearranged Ig genes in leukemic clones may give insight into molecular events taking place during the ontogenesis of normal B cells. We have tested DNA samples from patients with chronic B cell leukemias in search for abnormal rearrangements of the Ig heavy chain gene region. By Southern blot analysis we found an unexpected break in the JH-C mu region in 7 out of 118 cases. Two of these cases were investigated in detail by constructing from each a phage genomic library and isolating the phage clones containing the break points. In both cases the JH-C mu separation was confirmed. Further analysis demonstrated that in both cases the abnormality was an inversion of the Ig heavy chain gene between C mu and one of the C gamma segments. This inversion structure strongly suggests that, as has been demonstrated in murine cell lines and in splenocytes stimulated in vitro, class switching in human B lymphocytes occurs in vivo via a loop-out deletion mechanism. The frequency of abnormal events may be as high as 15%. Our data indicate that a proportion of cases of chronic B cell leukemia arise from a cell which has attempted an Ig class switch.

Enzymic properties of different types of human erythrocyte glucose-6-phosphate dehydrogenase, with characterization of two new genetic variants.

Enzymic properties have been compared in the following five genetic variants of glucose-6-phosphate dehydrogenase from human erythrocytes: the two common variants with normal activity, A and B; the common variant associated with enzyme deficiency, A-; and two new rare variants, "Ijebu-Ode" and "Ita-Bale."The maximal velocity of the enzyme reaction (V(max)) increases steadily with pH over the entire range explored (from pH 5.5 to 9.5) for all enzyme variants when buffers are used that show no specific ion effects on enzyme activity. Small differences are found among the variants in the pH range 7.5-8.2, where A and B show a "peak and trough," while A-, "Ijebu-Ode," and "Ita-Bale" exhibit a plateau. When the effects of reagents that bind to sulphydryl groups are compared, iodoacetate, bromoacetate, and iodoacetamide are weak inhibitors, while N-ethylmaleimide (NEM) and hydroxymercuribenzoate (HMB) are potent inhibitors. The last two reagents have differential inhibitory action on different variants; one of these, "Ijebu-Ode," is strikingly resistant to HMB and totally resistant to NEM (up to 3 mmoles/liter). The enzyme inactivation as a function of temperature exhibits distinctive profiles for all variants examined. BOTH OF THE NEW VARIANTS DESCRIBED DIFFER SIGNIFICANTLY FROM THE NORMAL B TYPE IN SEVERAL RESPECTS: "Ijebu-Ode" in electrophoretic mobility, thermostability, dependence of V(max) on pH, and resistance to sulphydryl group reagents; "Ita-Bale" in electrophoretic mobility, Michaelis constant (K(m)) for glucose-6-phosphate, and dependence of V(max) on pH. When these data are compared with those available in the literature, both variants are different from all those previously described. The estimated frequencies of the corresponding genes in western Nigeria are between 0.0005 and 0.0025 for "Ijebu-Ode" and less than 0.0005 for "Ita-Bale". The A- variant, compared to A, has a distinctly higher K(m) for 2-deoxyglucose-6-phosphate and is more inhibited by very low concentrations of HMB. These are the first observed differences in kinetic properties between A and A-.

Murine embryonic stem cells without pig-a gene activity are competent for hematopoiesis with the PNH phenotype but not for clonal expansion.

Paroxysmal nocturnal hemoglobinuria (PNH) develops in patients who have had a somatic mutation in the X-linked PIG-A gene in a hematopoietic stem cell; as a result, a proportion of blood cells are deficient in all glycosyl phosphatidylinositol (GPI)-anchored proteins. Although the PIG-A mutation explains the phenotype of PNH cells, the mechanism enabling the PNH stem cell to expand is not clear. To examine this growth behavior, and to investigate the role of GPI-linked proteins in hematopoietic differentiation, we have inactivated the pig-a gene by homologous recombination in mouse embryonic stem (ES) cells. In mouse chimeras, pig-a- ES cells were able to contribute to hematopoiesis and to differentiate into mature red cells, granulocytes, and lymphocytes with the PNH phenotype. The proportion of PNH red cells was substantial in the fetus, but decreased rapidly after birth. Likewise, PNH granulocytes could only be demonstrated in the young mouse. In contrast, the percentage of lymphocytes deficient in GPI-linked proteins was more stable. In vitro, pig-a- ES cells were able to form pig-a- embryoid bodies and to undergo hematopoietic (erythroid and myeloid) differentiation. The number and the percentage of pig-a- embryoid bodies with hematopoietic differentiation, however, were significantly lower when compared with wild-type embryoid bodies. Our findings demonstrate that murine ES cells with a nonfunctional pig-a gene are competent for hematopoiesis, and give rise to blood cells with the PNH phenotype. pig-a inactivation on its own, however, does not confer a proliferative advantage to the hematopoietic stem cell. This provides direct evidence for the notion that some additional factor(s) are needed for the expansion of the mutant clone in patients with PNH.

Defects in DNA and globin messenger RNA in homozygotes for hemoglobin Lepore.

Globin messenger RNA (mRNA) isolated from three patients homozygous for hemoglobin Lepore is shown to have a marked reduction of the amount of beta-like globin mRNA (Lepore-globin mRNA sequences) compared with alpha-globin mRNA by molecular hybridization. The relative amounts of alpha- and Lepore mRNA are similar to the amounts of alpha- and Lepore globin synthesized in intact cells and by isolated mRNA in a cell-free system. It is also demonstrated that Lepore-globin mRNA can completely hybridize to full-length or nearly full-length beta-globin specific complementary DNA and protect it from nuclease digestion, indicating close homology between the delta-mRNA sequences present in Lepore mRNA and the beta-complementary-DNA probe. We have also quantitated the numbers of beta-like globin gene sequences in genomic Lepore DNA by molecular hybridization and demonstrated a reduction in their number consistent with the Lepore gene being a delta beta-gene fusion product.

Type I transforming growth factor beta receptor maps to 9q22 and exhibits a polymorphism and a rare variant within a polyalanine tract.

In a search for mutations of the type I transforming growth factor beta receptor (TbetaR-I), we mapped the gene to 9q22 and found a common polymorphism [TbetaR-I(6A)] and a rare variant [TbetaR-I(10A)] of TbetaR-I, causing an in-frame deletion of three alanines and an in-frame insertion of one alanine, respectively, in the receptor's extracellular domain. The biological relevance of the polymorphism TbetaR-I(6A) was investigated. When TbetaR-I(6A) was transiently transfected into TbetaR-I-deficient cells, the growth-inhibitory effects of transforming growth factor beta were restored. TbetaR-I(6A) and TbetaR-I(10A) frequency were assessed in 108 tumor samples and 80 nontumor samples from patients with a diagnosis of cancer, as well as in 118 normal blood donors of comparable ethnic composition. The frequency of TbetaR-I(6A) heterozygotes was fairly similar in normal blood donors (8%), in nontumor DNA of patients with a diagnosis of cancer (10%), and in tumor samples (14%). However, the frequency of TbetaR-I(6A) homozygotes among nontumor (4%) and tumor (8%) samples obtained from patients with a diagnosis of cancer was higher than that predicted by the Hardy-Weinberg law. The clinical and biological significance of TbetaR-I(6A) homozygosity needs to be further investigated.

TbetaR-I(6A) is a candidate tumor susceptibility allele.

We have previously described a type I transforming growth factor (TGF)-beta receptor (TbetaR-I) polymorphic allele, TbetaR-I(6A), that has a deletion of three alanines from a nine-alanine stretch. We observed a higher than expected number of TbetaR-I(6A) homozygotes among tumor and nontumor DNA from patients with a diagnosis of cancer. To test the hypothesis that TbetaR-I(6A) homozygosity is associated with cancer, we performed a case-control study in patients with a diagnosis of cancer and matched healthy individuals with no history of cancer and who were identical in their gender and their geographical and ethnic background to determine the relative germ-line frequencies of this allele. We found nine TbetaR-I(6A) homozygotes among 851 patients with cancer. In comparison, there were no TbetaR-I(6A) homozygotes among 735 healthy volunteers (P < 0.01). We also observed an excess of TbetaR-I(6A) heterozygotes in cancer cases compared to controls (14.6% versus 10.6%; P = 0.02, Fisher's exact test). A subset analysis revealed that 4 of 112 patients with colorectal cancer were TbetaR-I(6A) homozygotes (P < 0.01). Using mink lung epithelial cell lines devoid of TbetaR-I, we established stably transfected TbetaR-I and TbetaR-I(6A) cell lines. We found that, compared to TbetaR-I, TbetaR-I(6A) was impaired as a mediator of TGF-beta antiproliferative signals. We conclude that TbetaR-I(6A) acts as a tumor susceptibility allele that may contribute to the development of cancer, especially colon cancer, by means of reduced TGF-beta-mediated growth inhibition.

Purification and properties of human glucose-6-phosphate dehydrogenase made in E. coli.

The cDNA for the X-chromosome encoded human glucose-6-phosphate dehydrogenase (G6PD) has been expressed in E. coli and the enzyme purified to homogeneity, using a simple one-step fractionation on 2'5'-ADP-Sepharose. By selecting one of several different expression vectors and by optimizing culture conditions a yield of more than 10 mg of pure enzyme per liter of culture is obtained reproducibly. When the recombinant enzyme and authentic G6PD purified from normal human red cells were compared, they proved to be indistinguishable by the following criteria: electrophoretic mobility in both native and denaturing conditions, the Km values for glucose 6-phosphate and NADP and the Ki value for NADPH. The recombinant enzyme, unlike the red cell enzyme, retained 100% activity when stored at 4 degrees C for over 1 year.

The cellular pathogenesis of paroxysmal nocturnal haemoglobinuria.

Paroxysmal nocturnal haemoglobinuria (PNH) is a unique disorder characterised by the triad of intravascular haemolysis, thrombosis and bone marrow failure. In the early seventies it was shown that PNH is a clonal disease; and in the nineties the molecular basis of the PNH abnormality was elucidated. However, what makes a PNH clone expand is still not known. Here, we suggest that this is due to somatic cell selection, resulting from the presence in the patient of autoreactive T cells that target glycosylphosphatidylinositol (GPI) in the context of an MHC-like molecule on the surface of haemopoietic stem cells. PNH cells would escape damage precisely because they have lost most or all of their ability to produce GPI.

Immunoglobulin gene rearrangements in hairy cell leukemia and other chronic B cell lymphoproliferative disorders.

Immunoglobulin gene rearrangements have been investigated in 11 patients with hairy cell leukemia (HCL), 11 with prolymphocytic Leukemia (PLL), and 34 with chronic lymphocytic leukemia (CLL). Heavy and Light Ig chain gene probes have been used, and Ig genes were found in a rearranged configuration in all cases. Production of kappa and lambda light chains correlated with the respective gene rearrangements. With respect to the heavy chain locus, we found that in 6 of 21 cases of kappa-producing CLL only one allele was rearranged, whereas both alleles were rearranged in nearly all cases of lambda-producing CLL and either kappa- or lambda-producing HCL and PLL. Our data confirm the B cell nature of HCL and lead us to suggest that HCL derives from the clonal expansion of a cell at a later developmental stage than in CLL and PLL.

Prospective analysis of minimal bone marrow infiltration in pediatric Burkitt's lymphomas by long-distance polymerase chain reaction for t(8;14)(q24;q32).

The chromosomal translocation t(8;14)(q24;q32) represents a characteristic marker for Burkitt's lymphoma (BL). This translocation involves the MYC oncogene on chromosome 8 and the immunoglobulin heavy-chain (IgH) locus on chromosome 14. Since the translocation does not produce a fusion gene, we established a long-distance polymerase chain reaction (LD-PCR) assay that can detect the t(8;14) at the genomic level. The sensitivity of the LD-PCR was 10(-4). We used the LD-PCR assay to prospectively study 78 BL patients and found a specific PCR product in 52 of them. Among the 52 positive patients, we could test both the tumor and the bone marrow (BM) at diagnosis in 33 and determined the prevalence of minimal disseminated disease (MDD) at diagnosis. In 12/33 patients, BM was positive by LD-PCR and in 10 of them we conducted a study of minimal residual disease (MRD). Eight out of 10 children showed a clearance of MRD after one cycle of chemotherapy. The only two patients who did not achieve a negative MRD status died of disease progression. The comparative analysis of sensitivity of BM aspirate, BM biopsy and LD-PCR in t(8;14)-positive patients demonstrated a superiority of the molecular method in the assessment of MDD. The LD-PCR for t(8;14) is an important tool to study minimal BM infiltration at diagnosis and to determine its response kinetics in BL.

Dynamics of hematopoiesis in paroxysmal nocturnal hemoglobinuria (PNH): no evidence for intrinsic growth advantage of PNH clones.

PNH is characterized by expansion of one or more stem cell clones with a PIG-A mutation, which causes a severe deficiency in the expression of glycosylphosphatidylinositol (GPI)-anchored proteins. There is evidence that the expansion of PIG-A mutant clones is concomitant with negative selection against PIG-A wild-type stem cells by an aplastic marrow environment. We studied 36 patients longitudinally by serial flow cytometry, and we determined the proportion of PNH red cells and granulocytes over a period of 1-6 years. We observed expansion of the PNH blood cell population(s) (at a rate of over 5% per year) in 12 out of 36 patients; in all other patients the PNH cell population either regressed or remained stable. The dynamics of the PNH cell population could not be predicted by clinical or hematologic parameters at presentation. These data indicate that in most cases the PNH cell expansion has already run its course by the time of diagnosis. In addition, since in most cases no further expansion takes place, we can infer that the tendency to overgrow normal cells is not an intrinsic property of the PNH clone.

Retroviral-mediated gene transfer of a mutant H-ras gene into normal human bone marrow alters myeloid cell proliferation and differentiation.

To investigate the effects of mutant ras expression on the growth and differentiation of normal human bone marrow, we used retrovirus-mediated gene transfer. A retrovirus (HR-1) containing a mutant ras gene (H12-ras) in addition to the selectable neo gene was transferred by cocultivation of a packaging cell line with long-term cultures of normal human bone marrow. Controls were established by cocultivating aliquots of the same bone marrow with a retrovirus (VSN-2) containing only neo. The efficiency of gene transfer, as determined by the percentage of G418-resistant colony-forming units-granulocyte/macrophage (CFU-GM) immediately after termination of cocultivation, was similar: 8 +/- 4% with HR-1 and 5 +/- 3% with VSN-2. After a further week in long-term culture, there was an increase in the number and percentage of G418-resistant CFU-GM in both the HR-1-infected and VSN-2-infected marrows. Thereafter, the numbers of G418-resistant CFU-GM declined, becoming undetectable at 4 weeks. The time course of the production of G418-resistant colonies was not significantly different in HR-1- and VSN-2-infected marrows, indicating that H12-ras did not alter the proliferation of normal CFU-GM. However, the total cellularity of HR-1-infected marrow cultures was significantly greater than that of VSN-2-infected marrow cultures. This was due to increased cellular proliferation of HR-1-infected cultured cells, since differential counts showed a significant increase in myeloid blast cells together with a slight reduction in mature myeloid cells in HR-1-infected marrow compared to baseline and to VSN-2-infected marrow. No leukemic blast cell colonies were grown from HR-1-infected marrows or control marrows, and HR-1 infection did not confer serum independence. These data show successful retroviral infection of normal bone marrow progenitor cells and suggest that expression of mutant H12-ras in such cells results in enhanced proliferation of early myeloid cells at the expense of differentiation.

Analysis of beta, gamma, and delta T-cell receptor genes in lymphomatoid papulosis: cellular basis of two distinct histologic subsets.

To investigate the histogenesis of lymphomatoid papulosis (LYP), we have analyzed the configuration of the beta, gamma, and delta T-cell receptor (TCR) and Ig genes in DNA from 31 biopsies of 18 patients with this condition and also from peripheral blood mononuclear cells of eight of these patients. Immunoglobulin genes were in a germ-line configuration in all patients, and TCR genes were in a germ-line configuration in six patients. In nine patients, one or two rearranged bands (RB) were detected with both beta and gamma TCR probes and in one patient with beta, gamma, and delta TCR probes. Two patients, in whom beta and delta TCR genes were in a germline configuration, had evidence of multiple discrete rearrangements of gamma TCR genes, consistent with a polyclonal T-cell population. Analysis of multiple biopsies revealed that RB, when present, were identical in different lesions from individual patients. All but one of the peripheral blood samples showed a germ-line configuration. The exception had evidence of a rearrangement of gamma and delta in peripheral blood and a beta and gamma rearrangement within tissue. This study has established that only a proportion of patients with LYP have a monoclonal T-cell proliferation. Correlation with the clinicopathologic and immunophenotypic data revealed that a T-cell clone was limited to patients with Willemze type B LYP or "mixed type" LYP, whereas patients with type A LYP consistently showed a germline configuration of TCR genes. This study indicates that in LYP the atypical hyperchromatic cerebriform mononuclear cells of type B invariably constitute a monoclonal T-cell population whereas the atypical CD30 positive type A cells represent a proliferation of cells of non-B, non-T-cell lineage.