Position effects and genetic disease.
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Animals↗
Biomedical subjects
P Fraser
Publications and source records attributed to P Fraser.
The Alzheimer's disease-associated presenilins are differentially phosphorylated proteins located predominantly within the endoplasmic reticulum.
BACKGROUND: Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the deposition of extracellular senile plaques composed of amyloid beta-peptide (A beta). Whereas most cases of AD occur sporadically, about 10% of AD cases are inherited as a fully penetrant autosomal dominant trait. Mutations in the recently cloned Presenilin genes (PS-1 and PS-2) are by far the most common cause of early onset familial AD. MATERIALS AND METHODS: Cellular expression of endogenous and overexpressed PS proteins was analyzed by immunocytochemistry and metabolic labeling followed by immunoprecipitation. In vivo phosphorylation sites of PS proteins were analyzed by extensive mutagenesis. RESULTS: PS-1 as well as PS-2 proteins were localized predominantly within the endoplasmic reticulum (ER). However, small amounts of the PS proteins were detected within the Golgi compartment, where they colocalize with the beta-amyloid precursor protein (beta APP). The PS-2 protein was found to be highly phosphorylated, whereas very little phosphorylation was observed for PS-1. The selective phosphorylation of PS-2 occurs exclusively on serine residues. In vivo phosphorylation of PS-2 was mapped to serine residues 7, 9, and 19 within an acidic stretch at the N terminus, which is absent in PS-1. casein kinase (CK)-1 and CK-2 were shown to phosphorylate the N terminus of PS-2 in vitro. CONCLUSIONS: The majority of PS proteins were detected in the ER where little if any proteolytic processing of beta APP was reported. ER retention of PS proteins might occur by intramolecular aggregation. Small amounts of PS proteins were also detected in the Golgi where they colocalized with beta APP. This might suggest that potential interactions between PS proteins and beta APP could occur within the Golgi. Selective phosphorylation of PS-2 proteins within the acidic domain missing in PS-1 indicates differences in the biological functions and regulation of the two highly homologous proteins.
Alzheimer Disease↗
Transcription complex stability and chromatin dynamics in vivo.
Distant regulatory sequences affect transcription through long-range chromatin interactions. Visualization of transcriptional activity of genes that compete for distant elements, using the globin locus as a model, has revealed the dynamics of chromatin interactions in vivo. Multiple genes appear to be transcribed alternately rather than at the same time to generate several messenger RNAs in one cell. The regulator may stably complex with one gene at a time and switch back and forth between genes in a flip-flop mechanism.
Animals↗
The chicken beta/epsilon-globin enhancer directs autonomously regulated, high-level expression of the chicken epsilon-globin gene in transgenic mice.
In transiently transfected chicken erythroid cells, beta-like globin gene switching is mediated through differential activation of the cis-linked embryonic epsilon- and adult beta-globin genes by a shared enhancer. Two underlying mechanisms have been proposed: (i) tissue- and stage-specific factors activate the beta-globin promoter in adult erythroid cells (autonomous regulation); and (ii) the epsilon-globin promoter, although transcriptionally competent in both embryonic and adult cells, is suppressed at the adult stage through competition with the beta-globin promoter for interaction with the enhancer (competitive regulation). Analyses of transgenic mice carrying the chicken beta/epsilon-globin locus demonstrated that both genes depended on the enhancer for erythroid expression, but only the epsilon-globin gene exhibited developmentally appropriate transcription at levels comparable to the endogenous mouse globin genes. Surprisingly, the chicken epsilon-globin gene also appeared to be autonomously regulated, as has been observed for human embryonic and fetal beta-like globin genes in transgenic mice. These results suggest that the chicken beta/epsilon-globin enhancer possesses either embryonic stage or epsilon-globin gene specificity when incorporated into the murine germ line.
Animals↗
An important role of heparan sulfate proteoglycan (Perlecan) in a model system for the deposition and persistence of fibrillar A beta-amyloid in rat brain.
A consistent rat model for the study of the consequences of congophilic and fibrillar A beta-amyloid in brain has been developed. One hundred percent of animals receiving infusions of synthetic beta-amyloid protein (A beta 1-40) plus a specific heparan sulfate proteoglycan (HSPG) for 1 week or 7 weeks (following 2 week infusions) demonstrated Congo red and thioflavin S-positive deposits adjacent to the infusion site. Extracellular amyloid fibrils were identified by electron microscopy and were immunogold decorated with A beta antibody. Significant increases in Congo red staining were observed in animals infused with A beta plus HSPG versus those infused with only A beta. Infusion of A beta alone was variable with respect to congophilic amyloid persistence, which occurred in 50% of animals and only when endogenous HSPGs accumulated at A beta deposition sites. By 7 weeks, only animals infused with A beta plus HSPG demonstrated compaction of the Congo red material from amorphous, wispy deposits (at 1 week) to stellate deposits resembling a Maltese cross. These spherical amyloid deposits were very similar to Congo red-stained amyloid plaques in human Alzheimer's disease brain, and in vitro data suggest that they were probably formed in vivo following interactions with endogenous brain components.
Amyloid beta-Peptides↗
Combined analysis of mortality in three United Kingdom nuclear industry workforces, 1946-1988.
Mortality during 1946-1988 has been analyzed in 75,006 employees of the United Kingdom Atomic Energy Authority, the Atomic Weapons Establishment and the Sellafield plant of British Nuclear Fuels. All-cause mortality was 19% lower than national rates among workers monitored for external radiation exposure and 18% lower among nonmonitored workers. Cancer mortality was also lower than national rates and was similar in the two groups of workers [rate ratio (RR) = 0.96]. Of 29 specific cancer sites examined, only for cancers of the pleura and uterus were there statistically significant excesses of mortality in monitored workers relative to nonmonitored workers [RR = 7.08, two-sided P (2P) = 0.008 and RR = 3.02, 2P = 0.003, respectively]. There was little association between cumulative external radiation and risk of death from all cancers combined 10 or more years after exposure [z for trend = +0.11, one-sided P (1P) = 0.5]. A positive association was observed for leukemia (assuming a 2-year lag between external radiation and increasing risk of death) (1P = 0.009) but not for other cancers associated with external radiation in previous analyses (lung, uterus, prostate and multiple myeloma, all 1P > or = 0.1). Positive associations (1P < or = 0.05) were also observed for melanoma and other skin cancers (1P = 0.03) and ill-defined and secondary cancers (1P = 0.04), but these results are difficult to interpret and, given the number of associations examined, may be chance findings. Estimates of excess relative risk per sievert were -0.02 (95% CI = -0.5-+0.6) for all cancers except leukemia and +4.18 for leukemia (95% CI = +0.4-+13.4). The positive estimates for leukemia contrast with negative values found for workers in the United States, although the confidence intervals obtained in the two studies overlap. While our estimates of risk are compatible with those derived from studies of A-bomb survivors, the statistical uncertainty associated with them is such that the data are consistent with risks ranging from no additional risk to twice the risk for cancers other than leukemia and, for leukemia, from one-fifth to three times the risk in A-bomb survivors.
Cause of Death↗
Case-control study of prostatic cancer in employees of the United Kingdom Atomic Energy Authority.
OBJECTIVE: To investigate the relation between risk of prostatic cancer and occupational exposures, especially to radionuclides, in employees of the United Kingdom Atomic Energy Authority. DESIGN: Case-control study of men with prostatic cancer and matched controls. Information about sociodemographic factors and exposures to radionuclides and other substances was abstracted and classified for each subject from United Kingdom Atomic Energy Authority records without knowledge of who had cancer. SUBJECTS: 136 men with prostatic cancer diagnosed between 1946 and 1986 and 404 matched controls, all employees of United Kingdom Atomic Energy Authority. MAIN OUTCOME MEASURES: Documented or possible contamination with specific radionuclides. RESULTS: Risk of prostatic cancer was significantly increased in men who were internally contaminated with or who worked in environments potentially contaminated by tritium, chromium-51, iron-59, cobalt-60, or zinc-65. Internal contamination with at least one of the five radionuclides was detected in 14 men with prostatic cancer (10%) and 12 controls (3%) (relative risk 5.32 (95% confidence interval 1.87 to 17.24). Altogether 28 men with prostatic cancer (21%) and 46 controls (11%) worked in environments potentially contaminated by at least one of the five radionuclides (relative risk 2.36 (1.26 to 4.43)); about two thirds worked at heavy water reactors (19 men with prostatic cancer and 32 controls (relative risk 2.13 (1.00 to 4.52)). Relative risk of prostatic cancer increased with increasing duration of work in places potentially contaminated by these radionuclides and with increasing level of probable contamination. Prostatic cancer was not associated with exposure to plutonium, uranium, cadmium, boron, beryllium, or organic or inorganic chemicals. CONCLUSIONS: Risk of prostatic cancer risk was increased in United Kingdom Atomic Energy Authority workers who were occupationally exposed to tritium, 51Cr, 59Fe, 60Co, or 65Zn. Exposure to these radionuclides was infrequent, and their separate effects could not be evaluated.
Adult↗
Estrogen-inducible and liver-specific expression of the chicken Very Low Density Apolipoprotein II gene locus in transgenic mice.
We have examined the chicken Very Low Density Apolipoprotein II (apoVLDL II) gene locus in transgenic mice. A DNA fragment composed of the transcribed region, 16 kb of 5' flanking and 400 bp of 3' flanking sequences contained all the information sufficient for estrogen-inducible, liver-specific expression of the apoVLDL II gene. The far-upstream region contains a Negative Regulating Element coinciding with a DNaseI-hypersensitive site at -11 kb. In transgenic mice, the NRE at -11 kb is used for downregulating the expression to a lower maximum level. The NRE might be used for modulating apoVLDL II gene expression, and may be involved in the rapid shut-down of the expression after hormone removal.
Animals↗
The regulation of human globin gene switching.
This paper describes the mechanism of regulation of the human beta-globin on the basis of a number of natural mutations and experiments in transgenic mice. From these data we conclude that this multigene locus is regulated at a number of different levels involving specific interactions between the Locus Control Region (LCR) and the individual genes. Most important is the action of stage specific transcription factors acting on sequences immediately flanking the genes. In addition, specificity is obtained through specific interaction of the genes with the LCR and through competition of the genes for interaction with the LCR.
Animals↗
Functional analysis of the human neurofilament light chain gene promoter.
We have carried out a structural and functional analysis on the human NF-L (H-NF-L) gene. It contains a methylation-free island, spanning the 5' flanking sequences and the first exon and a number of neuronal-specific DNase I hypersensitive sites have been identified in the upstream region as well as within the body of the gene. Analysis in cell lines and transgenic mice using a combination of these sites has revealed the presence of a conserved element(s) between -300bp and -190bp which is required for neuronal-specific expression.
Animals↗
Cancer mortality and morbidity in employees of the United Kingdom Atomic Energy Authority, 1946-86.
In further analyses of a cohort of 39,718 United Kingdom Atomic Energy Authority employees after 7 more years follow-up, cancer mortality, based on 1,506 deaths in 1946-86, was 20% below the national average. Prostatic cancer mortality showed a statistically significant association with external radiation exposure, largely confined to men who were also monitored for internal contamination by radionuclides other than plutonium. Prostatic cancer mortality was highest in radiation workers at Winfrith. In women monitored for radiation exposure, mortality from cancer of the uterus (including the cervix uteri) was increased relative to other employees, and, showed a statistically significant association with external radiation exposure. While there were some other statistically significant results, as would be expected by chance alone when multiple comparisons are made, there were no other cancer sites with consistently exceptional findings. Point estimates for risk associated with increasing exposure to radiation suggest a decrease of four deaths per 10(4) person-years per Sv for leukaemia and an increase of 20 deaths for all cancers except leukaemia, but confidence intervals indicate that a wide range of values are compatible with the data. Cancer morbidity based on 1,699 registrations in 1971-84 was 12% below the national average. Findings from site-specific analyses largely replicated those of the mortality analyses.
Cause of Death↗
Thy-1 tk transgenic mice with a conditional lymphocyte deficiency.
Thy-1 has been used as a cell surface marker for identification of mature T cells, T lymphoid precursors and the hematopoietic stem cell. The developmental program of these cells during hemato/lymphopoiesis is complex because of heterogeneity of the populations and subsequent migration. To study the differentiation of Thy-1 positive cells at precise periods of in vivo development we have used a strategy based on cell specific toxicity. In the transgenic mouse studies presented here, Thy-1 positive cells are ablated by targeting the expression of the conditional toxin Herpes simplex virus 1 thymidine kinase (tk) with Thy-1 transcriptional control elements. We demonstrate the controlled expression of HSV1 tk in Thy-1 expressing cells of adult transgenic mice and the conditional ablation of > 90% of maturing thymocytes. We describe the distinct subpopulations of cells remaining within individual ablated thymuses and show by phenotypic analyses that Thy-1 tk induced ablation enriches for CD4 low and double negative thymocytes. Furthermore, we demonstrate a differential effect of thymus directed ablation on the maturing peripheral T cell compartment at various times in mouse development. This strategy is successful for production of a conditional T lymphocyte deficiency and could be useful in the study of T lineage development and direct in vivo isolation of enriched T precursor cell populations.
Animals↗
Each hypersensitive site of the human beta-globin locus control region confers a different developmental pattern of expression on the globin genes.
We have tested the effect of the individual DNase I hypersensitive site (HS) regions of the globin locus control region (LCR) on the developmental expression pattern of the human gamma and beta genes in transgenic mice. The results show that HS3 is the most active site during the embryonic period. It is also the only site capable of high level expression of the gamma genes during fetal hematopoiesis, in a population of cells that are capable of expressing both the gamma and beta genes. Region HS4 shows the highest activity during the adult stage and expresses the gamma genes only at low levels during the embryonic period. HS2 drives equivalent levels of gamma or beta transgene expression throughout development. HS1 has a similar pattern to HS2, although the activity of HS1 is very low. From these results we conclude that the HS regions have distinct developmental specificities and suggest that in the complete LCR they interact with each other to form a larger complex which, in turn, interacts with the globin genes.
Animals↗
Regulation of human globin gene switching.
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Animals↗
Chronic microsporidian infection of the nasal mucosae, sinuses and conjunctivae in HIV disease.
A case of chronic infection of the nasal mucosae, sinuses and conjunctivae with a microsporidian parasite in association with HIV infection and immune deficiency is reported. This microsporidian resembles both Encephalitozoon cuniculi and the newly described Encephalitozoon hellem by electron microscopy. This occurred in an adult male resident in the UK with no history of foreign travel. Although there are previous descriptions of conjunctival infections from the USA, this is the first description of infection of the nasal epithelium. Further studies are underway to classify this protozoan.
Adult↗
I-123 iofetamine SPECT scan in systemic lupus erythematosus patients with cognitive and other minor neuropsychiatric symptoms: a pilot study.
Accurate diagnosis of central nervous system (CNS) lupus remains difficult, especially when the manifestations are of subtle cognitive and affective changes. This pilot study reports on the use of I-123 iofetamine single photon emission computerized tomography (SPECT) scans in 18 such patients with documented systemic lupus erythematosus. Eight of the 18 scans were abnormal (44%), four in a diffuse bi-temporo-parietal pattern previously noted only in Alzheimer's disease, and four with large focal deficits. Neither the existence of the abnormal scan nor the particular pattern of abnormality correlated with the results of other diagnostic tests. These preliminary results raise the possibility that SPECT scans may offer an additional valuable diagnostic instrument in CNS lupus, although further studies are necessary to delineate their precise role.
Adolescent↗
Prevalence of idiopathic vertebral sclerosis, Zöetermeer, Rotterdam, 1975-1978.
In order better to define the prevalence and characteristics of idiopathic vertebral sclerosis, we evaluated the roentgenograms of 1,391 individuals greater than or equal to 35 years of age) for the presence or absence of idiopathic vertebral sclerosis. One hundred two radiographs showed evidence of idiopathic vertebral sclerosis, a prevalence rate of 5% in this population. For the first time, a roentgenographic classification is offered. These "cases" were then classified into Types I-IV, based on the pattern and location of the sclerosis. The radiologic and demographic characteristics of Type I correlate most closely with previous studies that have investigated the association of vertebral sclerosis with chronic back pain. Women predominated in age-specific classifications; the female-to-male ratio in Type I was 4:1, a reproducible finding in previous studies. The large sample available for study supports the conclusion that this is an accurate estimate of the prevalence rate of idiopathic vertebral sclerosis.
Adult↗
Importance of globin gene order for correct developmental expression.
We have used transgenic mice to study the influence of position of the human globin genes relative to the locus control region (LCR) on their expression pattern during development. The LCR, which is located 5' of the globin gene cluster, is normally required for the activation of all the genes. When the human beta-globin gene is linked as a single gene to the LCR it is activated prematurely in the embryonic yolk sac. We show that the correct timing of beta gene activation is restored when it is placed farther from the LCR than a competing human gamma- or alpha-globin gene. Correct timing is not restored when beta is the globin gene closest to the LCR. Similarly, the human gamma-globin gene is silenced earlier when present farthest from the LCR. On the basis of this result, we propose a model of developmental gene control based on stage-specific elements immediately flanking the genes and on polarity in the locus. We suggest that the difference in relative distance to the LCR, which is a consequence of the ordered arrangement of the genes, results in nonreciprocal competition between the genes for activation by the LCR.
Aging↗