Localization of the gene (OGDH) coding for the E1k component of the alpha-ketoglutarate dehydrogenase complex to chromosome 7p13-p11.2

alpha-Ketoglutarate dehydrogenase (E1k), also designated oxoglutarate dehydrogenase (OGDH; EC 1.2.4.2), is a component of the enzyme complex that catalyzes the conversion of alpha-ketogluterate to succinyl coenzyme A, a critical step in the Krebs tricarboxylic acid cycle. Deficiencies in the activity of this enzyme complex have been observed in brain and peripheral cells of patients with Alzheimer's disease. This finding led us to localize the genes for the polypeptides that compose the alpha-ketoglutarate dehydrogenase complex (KDGHC). The E1k locus was mapped to chromosome 7p13-p11.2 using a pair of human/rodent somatic cell hybrid panels. A second related sequence, possibly a pseudogene, was identified and mapped to chromosome 10.

T-cell receptor J beta I/J beta II locus rearrangements concurring with a complex chromosomal aberration in an HTLV-1 positive T-cell lymphoma

Human T-lymphotropic virus type I (HTLV-1) integration has been associated with the development of adult T-cell leukemia/lymphoma (ATL). Recently, a correlation between T-cell receptor (TCR) gene rearrangements and chromosomal aberrations has been implicated in this leukemia. We present a case of HTLV-1 infected adult T-cell lymphoma that initially presented with a normal karyotype and germline J beta I/J beta II loci. As the disease evolved to the aggressive stage, a complex chromosomal rearrangement with a duplication of chromosome 6p23-->pter translocated to a derivative chromosome 16, was identified by molecular cytogenetic techniques. The nature of this complex abnormality would have been difficult to determine if only conventional banding techniques were performed. Rearrangement involving one J beta allele was also detected at that time. After initiation of chemotherapy, no germline J beta loci were detected, suggesting a possible second rearrangement involving this locus that was homologous. Although no known immune response genes are located at the breakpoints involved in this abnormality, the chromosomal aberration concurred with the initial J beta rearrangement.

Isolation, characterization, and mapping of gene encoding dihydrolipoyl succinyltransferase (E2k) of human alpha-ketoglutarate dehydrogenase complex

We have isolated and sequenced cDNAs representing the full-length (2987-bp) gene for dihydrolipoyl succinyltransferase (E2k component) of the human alpha-ketoglutarate dehydrogenase complex (KGDHC) from a human fetal brain cDNA library. The E2k cDNA was mapped to human chromosome 14 using a somatic cell hybrid panel, and more precisely to band 14q24.3 by in situ hybridization. This cDNA also cross-hybridized to an apparent E2k pseudogene on chromosome 1p31. Northern analysis revealed the E2k gene to be ubiquitously expressed in peripheral tissues and brain. Interestingly, chromosome 14q24.3 has recently been reported to contain gene defects for an early-onset form of familial Alzheimer's disease and for Machado-Joseph disease. Future studies will be necessary to determine whether the E2k gene plays a role in either of these two disorders.

Contralateral suppression of non-linear click-evoked otoacoustic emissions

Click-evoked otoacoustic emissions from nominal 80 dB pSP (peak sound pressure) 80-microseconds pulses presented at 50 pulses per second were collected from the right ears of eleven normal hearing subjects using an ILO88 Otodynamic Analyzer in the non-linear mode. Clicks, pure tones, and narrow bands of noise were then presented to their left ears through insert earphones. The 80-microseconds contralateral clicks ranged in intensity from 80 dB pSP in 5 dB steps down to 60 dB pSP but data on only 10 of the subjects were collected successfully. The pure tones and narrow bands of noise centered at 250, 500, 1000, 2000, and 4000 Hz were also presented through insert phones at 20, 40, 60 and 80 dB HL (Hearing Level) to all 11 subjects. The mean overall 'echo amplitude' without contralateral stimuli was 11 dB SPL and underwent more than 3 dB of overall suppression in response to the noises which were the most effective of the contralateral suppressors. When we analyzed the echo suppression to noise in 2-ms segments, we found consistent contralateral suppression of 3-4 dB concentrated in the time zones after 8 ms. Time shifts of more than 200 microseconds between the control and experimental traces were also observed in the same zones. The clicks were the next most effective suppressors, but showed their amplitude and time effects in somewhat earlier time zones. The tones were the least effective suppressors suggesting that efferent effects we measured in the human system are not strongly tonotopic. Because 'non-linear' mode high intensity clicks were deliberately selected as stimuli to evoke the TEOAE's, the emissions and their suppression can represent neither the 'true' TEOAE nor all of the efferent system's suppression abilities.

Direct visualization of the transposed ABL gene in a duplicated masked Ph chromosome

In a small percentage of cases of chronic myelogenous leukemia (CML), where the Ph chromosome is masked because of highly complex translocations and sub-microscopic rearrangements, precise identification of chromosomal aberrations by routine banding techniques has been difficult. We report on a new case of CML in which a single copy of a masked Ph chromosome was duplicated during blast crisis, i.e., the karyotype was 47,XY,dir ins(22;9)(q11;q34.1q34.2),t(1;22) (q21;q11), + der (22)t(1;22)(q21;q11). The chromosome in situ suppression hybridization (CISS) technique with whole chromosome 1 and 22 specific painting probes demonstrated that 22q11-qter had been translocated to 1q21, whereas 22q11 was the recipient of 1q21-qter. Furthermore, a cosmid probe identified the location of the ABL gene on only one chromosome 9 (band q34). The other ABL gene could be detected on both derivative chromosomes 22 at band q11 which was flanked by the translocated part of the long arm of chromosome 1, thus providing direct visualization of the ABL insertion in a double masked Ph chromosome. A breakpoint within the 5.8 kb major breakpoint cluster [M-BCR] region was shown by Southern blotting.

Effect of age on the expressed B cell repertoire: role of B cell subsets

Aged humans and experimental animals are impaired in their responses to most foreign antigens although they produce greater amounts of autoantibodies. We have examined the effect of age on the production of antibodies to a prototypic foreign antigen, sheep erythrocytes (SRBC), and to a prototypic autoantigen, bromelain-treated mouse erythrocytes (BrMRBC), in young and old mice before and after immunization with SRBC. Old mice express more anti-BrMRBC plaque-forming cell (PFC) antibodies before and an even greater number after immunization with SRBC than young mice. Conversely, old mice produce far fewer anti-SRBC PFC than young mice following immunization with SRBC. We hypothesized that the differences in the responses of old mice to BrMRBC and SRBC reflects differences in the activity of CD5+ and CD5- B cells. To test this hypothesis we immunized young and old mice with foreign antigens reported (and confirmed in our studies) to stimulate CD5+ B cells [TNP-ficoll and phosphorylcholine-keyhole limpet hemocyanin (KLH)] or CD5- B cells (SRBC and TNP-KLH). We found that the PFC response of old mice to antigens mediated by CD5+ B cells was equal to or greater than that of young mice. In contrast the PFC response of old mice induced by antigens mediated by CD5- B cells was only 10% that of young mice. Thus it appears that the immune response of old mice is well maintained for antigens which elicit a CD5+ B cell response but not for those which elicit a CD5- B cell response.(ABSTRACT TRUNCATED AT 250 WORDS)

Prothymosin alpha gene expression correlates with proliferation, not differentiation, of HL-60 cells

Accumulating evidence suggests that prothymosin alpha has an as yet undefined intracellular, perhaps intranuclear, function related to cell proliferation. Prothymosin alpha mRNA and/or peptide levels increase when cells are stimulated to proliferate. Because proliferation and differentiation events are often inversely correlated, we examined prothymosin alpha gene expression during proliferation and differentiation of HL-60 myeloid leukemia cells. Steady-state levels of prothymosin alpha mRNA, which are high in exponentially growing HL-60, decrease within hours after induction of HL-60 to differentiate along the neutrophil pathway with dimethylsulfoxide (DMSO) or along the macrophage lineage with either tetradecanoylphorbol acetate (TPA) or bryostatin 1. The decline in prothymosin alpha mRNA in response to these differentiation signals parallels that of c-myc mRNA under the same conditions. We then determined whether the downregulation of prothymosin alpha and c-myc mRNA were due to differentiation or cessation or proliferation. Recombinant human gamma-interferon induces monocytic differentiation of HL-60, but permits continued proliferation, and, under these conditions, expression of prothymosin alpha, as well as of c-myc, mRNA remains elevated. We conclude that prothymosin alpha and c-myc expression are coregulated in differentiating HL-60 and that their expression correlates with the proliferative state of HL-60 cells, rather than with the differentiated state.

Does type I afferent neuron dysfunction reveal itself through lack of efferent suppression?

We present here two patients and three control subjects to demonstrate the clinical utility of studying evoked otoacoustic emissions and their contralateral suppression, as an aid to the delineation of afferent neuron dysfunction and possible lack of efferent suppression. The key patients here who fail to show contralateral suppression of their very robust otoacoustic emissions, concomitantly show paradoxically absent auditory brainstem responses (ABRs) and absence of middle ear muscle reflexes despite normal audiograms in the 2 kHz region and normal tympanograms. One of these patients has nearly normal pure tone sensitivity up to 3 kHz. The other has normal sensitivity in the 2 kHz region, but poor sensitivity on either side of that frequency. In addition, the two patients of interest show absent masking level differences and inordinately poor speech discrimination. Three 'foils' are presented: one patient with poor hearing on either side of 2 kHz, one with Bell's Palsy, and the third with bilateral temporal lobe disease. These patients show respectively that (1) isolated normal hearing at 2 kHz, (2) absence of middle ear muscle reflexes and (3) conscious cortical awareness of sound do not contribute directly to this intriguing clinical state. We propose that these patients with absent ABRs suffer from an auditory nervous system dysfunction which disrupts access to the efferent system. This condition also disables whatever systems contribute to the neural synchrony inherent in recording compound far-field action potentials such as the ABR. There are a number of hypotheses to be considered here. One suggests that the key patients are deficient in synchronous activation of Type I afferent fibers to the degree that they cannot activate efferent feedback, or they may be able to use only so-called Type II afferent neurons to support their normal zones of pure tone sensitivity. A less likely consideration focuses on the notion that discharge of primary neurons might be in some way synchronized by an efferent system which in these patients is the primary source of deficit.

The age-dependent proliferation of rat aortic smooth muscle cells is independent of differential splicing of PDGF A-chain mRNA

Arterial smooth muscle cells (SMC) from old rats proliferate in vivo (after injury) and in vitro more rapidly than smooth muscle cells from young rats. We previously observed that SMC from old rats contained more PDGF-like growth factor activity than did young SMC. We therefore tested the hypothesis that age-related differences in type of PDGF A-chain gene expression might be responsible for the difference in growth factor activity, since PDGF B-chain gene is minimally expressed both in young and old SMC. Specifically we tested if the old SMC predominantly expressed the long form of the A-chain mRNA, leading to autocrine stimulation by cell-associated PDGF AA-homodimers. A partial cDNA for the rat PDGF A-chain was cloned and sequenced; it is highly conserved compared to the human PDGF-A chain and similarly has two forms, a long form containing all exons, which tends to remain cell-associated and a short form lacking exon 6, which tends to be secreted. Different tissues of both young and old animals express different ratios of these two forms of PDGF-A. However, the relative expression of the different mRNA forms does not change with age, suggesting that differential splicing of PDGF-A and accumulation of cell-associated PDGF A-chain does not determine the enhanced growth potential of old rat SMC.

Prothymosin alpha gene in humans: organization of its promoter region and localization to chromosome 2

A genomic clone encoding prothymosin alpha (gene symbol: PTMA), a nuclear-targeted protein associated with cell proliferation, was isolated and the 5'-regulatory region subcloned and sequenced. Because of previously reported discrepancies between several cDNA clones and a genomic clone for prothymosin alpha, we determined the sequence of the first exon and of a 1.7-kb region 5' to the first exon. The sequence of the genomic clone reported here corresponds to the published cDNA sequences, suggesting that the previously noted discrepancies may be due to genetic polymorphism in this region. In addition, our sequence data extend the known 5'-upstream sequence by an additional 1.5 kb allowing the identification of numerous, potential cis-acting regulatory sites. This 5'-flanking cloned probe permitted us to localize the prothymosin gene to chromosome 2 in humans.

Human Tcrb-V6.10 is a pseudogene with Alu repetitive sequences in the promoter region

Tcrb-V6.10 represents an abnormal human V gene with an Alu insertion in the promoter, a point mutation of a conserved Cys at position 23, and a missing nonamer within the usually conserved recombinase signal sequence. Here it is shown that b-V6.10 is found in the genome of most individuals, is normally located in the Tcrb-V locus on chromosome 7, but is not rearranged or transcribed. Thus, it is likely that the abnormal signal sequence precludes recombination and that the Alu insertion results in a disabled promoter, indicating the functional importance of the affected regions. Tcrb-V6.10 probably evolved by duplication of an ancestral Tcrb V13-V6-V5 cassette, like other members of the large b-V6 subfamily, and more recently became inactivated into a pseudogene.

Prenatal exclusion of choroideremia

We performed prenatal testing to predict the inheritance of choroideremia (CHM) using a linked polymorphic DNA marker, DXS95. DNA analysis of chorionic villi at the 12th week of pregnancy indicated that the allele at risk had not been passed from the heterozygous mother to the fetus. This prenatal exclusion of choroideremia was confirmed by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis.

Chromosomal localization of HTLV-1 viral integration sites using in situ hybridization: detection of a novel IL2R fragment

The presence of human T-cell leukemia virus (HTLV-1) in patients with adult T-cell leukemia (ATL) was investigated by Southern blotting and in situ hybridization. In all seven patients, HTLV-1 provirus was detected. A large and variable number of labeled restriction fragments were observed, indicating multiple integrations. Two of the patients analyzed by in situ hybridization had two, while the third patient had three, sites of viral integration on six different chromosomes, suggesting random integration. A single site of integration was shared by two patients, which was on chromosome 10 at bands p11-->p15. One of these sites was on an apparently normal chromosome 10 and the other was on a derivative chromosome 10,t(10;14)(p12;q32). The interleukin 2 receptor (IL2R) has previously been localized to this region (10p14-->p15). The alpha-chain of the IL2R is continuously expressed on affected T-cells in this disease. Southern blotting with pIL2R showed the presence of a novel 3.5 kb fragment in five out of the seven patients. This novel fragment has not been previously reported. No direct correlation was found between the novel 3.5 kb fragment, present in patients both cytogenetically normal and abnormal, and viral integration in the 10p11-->p15 region in two patients. Therefore, it is suggested that the presence of the 3.5 kb fragment and the numerous chromosomal breaks associated with this disease may not be direct results of viral integration.

IL-1, IL-6, and PDGF mRNA expression in alveolar cells following stimulation with a tobacco-derived antigen

To test the hypothesis that inflammatory cytokine production might be an early event in the development of the disease associated with smoking, we used alveolar cells from healthy nonsmokers stimulated with TGP as a model system. TGP, a phenol-rich glycoprotein which is present in tobacco leaves and cigarette smoke condensate, activates the immune system. It stimulates polyclonal B cell differentiation, induces primarily an IgE response, and activates human leukocytes to produce IL-1. Using in situ nucleic acid hybridization we show that the steady-state levels of IL-1 alpha, IL-1 beta, IL-6, platelet-derived growth factor (PDGF)-A, and PDGF-B mRNAs are consistently elevated in the alveolar cells of all donors following TGP stimulation. The kinetics of mRNA expression suggest that IL-1 alpha and IL-1 beta mRNAs are independently regulated in alveolar cells, while the regulation of PDGF-A and PDGF-B mRNA seems to be similar. The activated cells also synthesize elevated levels of IL-1 and IL-6. These findings lend support to the suggestion that some clinical consequences of smoking might be initiated and enhanced by the production of inflammatory cytokines. Moreover, IL-6 could also activate a polyclonal B cell response, which could lead to the synthesis of autoantibodies and thus cause immune-mediated tissue injury.

Localization of the gene coding for ventricular myosin regulatory light chain (MYL2) to human chromosome 12q23-q24.3

Human myosin light chain-2 (MYL2) is an important protein involved in the regulation of myosin ATPase activity in smooth muscle. In cardiac muscle, the precise role of MYL2 is not well understood; however, an increase in ventricular MYL2 is observed during myocardial hypertrophy in cardiac patients with valve stenosis. The chromosomal location of the gene coding for MYL2 was identified using a cloned cDNA for human MYL2. Southern blot analysis of DNA from a human/rodent somatic cell hybrid mapping panel showed that the BamHI fragment that hybridized with this cDNA probe was concordant with chromosome 12. The 768-bp cDNA was hybridized to human metaphase chromosomes. The results revealed a significant clustering of silver grains over chromosome 12 bands q23-q24.3, indicating that the gene coding for MYL2 is located in this region.

Prothymosin alpha expression occurs during G1 in proliferating B or T lymphocytes

To gain insight into possible functions for prothymosin alpha in the proliferative cycle of lymphocytes, we examined the kinetics of prothymosin alpha mRNA expression in mitogen stimulated murine lymphocytes. This mRNA increases after mitogen stimulation, peaking in mid G1. This kinetics is compatible with induction of the prothymosin alpha gene by the c-myc protein (Eilers, M., Schirm, S. and Bishop, J.M. (1991) EMBO J., 10, 133-141). Thus, although prothymosin alpha mRNA is found throughout the cell cycle, the elevated expression in G1 may be associated with an increased requirement for prothymosin alpha during the G1/S transition or the S phase of the cell cycle.

The genomic structure of human V beta 6 T cell antigen receptor genes

Six genomic clones were characterized containing members of the human V beta 6 subfamily of T cell antigen receptor genes. There were four major findings. (a) New V beta genes were discovered, including V beta 6.10, V beta 13.4, V beta 13.5, and V beta 5.5. (b) Members of the V beta 13, V beta 6, and V beta 5 subfamilies cluster together in the V beta locus and may have evolved through multiple duplication events of an ancestral cassette containing V beta 13-V beta 6-V beta 5 genes. These V beta subfamilies are used by an estimated one-third of T cells in humans and probably represent a highly useful component of the V beta repertoire. (c) The promoters of V beta 13, V beta 6, and V beta 5 genes contain conserved decamer motifs, but discrete differences were observed between promoters of different V beta subfamilies, raising the question of different transcriptional control depending on V beta subfamily usage. (d) The new V beta 6.10 gene is probably a pseudogene, which may have been inactivated due to retrotransposition of Alu elements into its promoter region, a mutation affecting a highly conserved cysteine residue or mutations of the 3' recombinase signal sequence.

Cellular control of IgE induction by a polyphenol-rich compound. Preferential activation of Th2 cells

The polyphenol group rutin (R) appears to influence isotype expression, because R-BSA conjugates induce anti-BSA responses in mice that show a significant decrease in hemagglutinating antibodies (HA) to BSA, as compared to mice immunized with BSA. However, the level of IgE antibodies to BSA is unaltered. To determine if suppressor cells for isotypes other than IgE are induced by R-BSA, cell transfers were performed. The results were consistent with the view that the decrease in HA titer to BSA in R-BSA immunized mice is not due to the activation of suppressor cells for isotypes other than IgE. Inasmuch as the IgE response in mice is associated with the production of IL-4 by Th2 cells, we analyzed the factors produced by spleen cells cultured with R-BSA. We found that supernatant from spleen cells cultured with R-BSA contained IL-4 as determined by the enhanced expression of Fc epsilon R (CD23) on B cells. This enhancement was inhibited by 11B11, the anti-IL-4 mAb. IL-2, a product of Th1 cells, was not detected in these supernatants. Moreover, IL-4 mRNA, but not IL-2 mRNA, was detected by Northern blot analysis of RNA from spleen cells cultured with R-BSA. Taken together the data suggest that the polyphenol containing compounds preferentially activate Th2 cells, thereby favoring IgE production.

Cellular control of IgE induction by a polyphenol-rich compound. Preferential activation of Th2 cells

The polyphenol group rutin (R) appears to influence isotype expression, because R-BSA conjugates induce anti-BSA responses in mice that show a significant decrease in hemagglutinating antibodies (HA) to BSA, as compared to mice immunized with BSA. However, the level of IgE antibodies to BSA is unaltered. To determine if suppressor cells for isotypes other than IgE are induced by R-BSA, cell transfers were performed. The results were consistent with the view that the decrease in HA titer to BSA in R-BSA immunized mice is not due to the activation of suppressor cells for isotypes other than IgE. Inasmuch as the IgE response in mice is associated with the production of IL-4 by Th2 cells, we analyzed the factors produced by spleen cells cultured with R-BSA. We found that supernatant from spleen cells cultured with R-BSA contained IL-4 as determined by the enhanced expression of Fc epsilon R (CD23) on B cells. This enhancement was inhibited by 11B11, the anti-IL-4 mAb. IL-2, a product of Th1 cells, was not detected in these supernatants. Moreover, IL-4 mRNA, but not IL-2 mRNA, was detected by Northern blot analysis of RNA from spleen cells cultured with R-BSA. Taken together the data suggest that the polyphenol containing compounds preferentially activate Th2 cells, thereby favoring IgE production.

Genetic mapping of X-linked albinism-deafness syndrome (ADFN) to Xq26.3-q27.I

X-linked albinism-deafness syndrome (ADFN) was described in one Israeli Jewish family and is characterized by congenital nerve deafness and piebaldness. The ADFN mutation probably affects the migration of neural crest-derived precursors of the melanocytes. As a first step toward identifying the ADFN gene, a linkage study was performed to localize the disease locus on the X chromosome. The family was found to be informative for 11 of 107 RFLPs along the X, and two-point analysis showed four of them--factor 9 (F9), DXS91, DXS37, and DNF1--to have definite or suggestive linkage with ADFN. Multipoint linkage analysis indicated two possible orders within this cluster of loci, neither of which was preferable. In both orders F9 was the most distal, and the best estimate for the location of ADFN was between F9 and the next proximal marker (8.6 cM from F9 [Z = 8.1] or 8.3 cM from F9 [Z = 7.9]). These results suggest that the ADFN is at Xq26.3-q27.1. Disagreement between our data and previous localization of DXS91 at Xq11-q13 was resolved by hybridization of the probe pXG-17, which detects the DXS91 locus, to a panel of somatic cell hybrids containing different portions of the X chromosome. This experiment showed that this locus is definitely at Xq24-q26. Together with the linkage data, our results place DXS91 at Xq26 and underscore the importance of using more than one mapping method for the localization of molecular probes.