The genetic legacy of the expansion of Bantu-speaking peoples in Africa.

The expansion of people speaking Bantu languages is the most dramatic demographic event in Late Holocene Africa and fundamentally reshaped the linguistic, cultural and biological landscape of the continent1-7. With a comprehensive genomic dataset, including newly generated data of modern-day and ancient DNA from previously unsampled regions in Africa, we contribute insights into this expansion that started 6,000-4,000 years ago in western Africa. We genotyped 1,763 participants, including 1,526 Bantu speakers from 147 populations across 14 African countries, and generated whole-genome sequences from 12 Late Iron Age individuals8. We show that genetic diversity amongst Bantu-speaking populations declines with distance from western Africa, with current-day Zambia and the Democratic Republic of Congo as possible crossroads of interaction. Using spatially explicit methods9 and correlating genetic, linguistic and geographical data, we provide cross-disciplinary support for a serial-founder migration model. We further show that Bantu speakers received significant gene flow from local groups in regions they expanded into. Our genetic dataset provides an exhaustive modern-day African comparative dataset for ancient DNA studies10 and will be important to a wide range of disciplines from science and humanities, as well as to the medical sector studying human genetic variation and health in African and African-descendant populations.

Genetic Affinities among Southern Africa Hunter-Gatherers and the Impact of Admixing Farmer and Herder Populations.

Southern African indigenous groups, traditionally hunter-gatherers (San) and herders (Khoekhoe), are commonly referred to as "Khoe-San" populations and have a long history in southern Africa. Their ancestors were largely isolated up until ∼2,000 years ago before the arrival of pastoralists and farmers in southern Africa. Assessing relationships among regional Khoe-San groups has been challenging due to admixture with immigrant populations that obscure past population affinities and gene flow among these autochthonous communities. We re-evaluate a combined genome-wide data set of previously published southern Africa Khoe-San populations in conjunction with novel data from Khoe-San individuals collected in Xade (Central Kalahari Game Reserve, Botswana) prior to their resettlement outside the reserve. After excluding regions in the genome that trace their ancestry to recent migrant groups, the genetic diversity of 20 Khoe-San groups fitted an isolation-by-distance model. Even though isolation-by-distance explained most genetic affinities between the different autochthonous groups, additional signals of contact between Khoe-San groups could be detected. For instance, we found stronger genetic affinities, than what would be explained by isolation-by-distance gene flow, between the two geographically separated Khoe-San groups, who speak branches of the Kx'a-language family (ǂHoan and Ju). We also scanned the genome-wide data for signals of adaptive gene flow from farmers/herders into Khoe-San groups and identified a number of genomic regions potentially introduced by the arrival of the new groups. This study provides a comprehensive picture of affinities among Khoe-San groups, prior to the arrival of recent migrants, and found that these affinities are primarily determined by the geographic landscape.

Low-Dose-Rate Irradiation for 1 Hour Induces Protection Against Lethal Radiation Doses but Does Not Affect Life Span of DBA/2 Mice.

Prior findings showed that serum from DBA/2 mice that had been given whole-body irradiation for 1 hour at a low dose rate (LDR) of 30 cGy/h induced protection against radiation in reporter cells by a mechanism depending on transforming growth factor ß3 and inducible nitric oxide synthase activity. In the present study, the effect of the 1 hour of LDR irradiation on the response of the preirradiated mice to a subsequent lethal dose and on the life span is examined. These DBA/2 mice were prime irradiated for 1 hour at 30 cGy/h. Two experiments with 9 and 9.5 Gy challenge doses given 6 weeks after priming showed increased survival in primed mice compared to unprimed mice followed up to 225 and 81 days after challenge irradiation, respectively. There was no overall significant difference in life span between primed and unprimed mice when no challenge irradiation was given. The males seemed to have a slight increase in lifespan after priming while the opposite was seen for the females.

TGF-B3 Dependent Modification of Radiosensitivity in Reporter Cells Exposed to Serum From Whole-Body Low Dose-Rate Irradiated Mice.

Prior findings in vitro of a TGF-ß3 dependent mechanism induced by low dose-rate irradiation and resulting in increased radioresistance and removal of low dose hyper-radiosensitivity (HRS) was tested in an in vivo model. DBA/2 mice were given whole-body irradiation for 1 h at low dose-rates (LDR) of 0.3 or 0.03 Gy/h. Serum was harvested and added to RPMI (4% mouse serum and 6% bovine serum).This medium was transferred to reporter cells (T-47D breast cancer cells or T98G glioblastoma cells). The response to subsequent challenge irradiation of the reporter cells was measured by the colony assay. While serum from unirradiated control mice had no effect on the radiosensitivity in the reporter cells, serum from mice given 0.3 Gy/h or 0.03 Gy/h for 1 h removed HRS and also increased survival in response to doses up to 5 Gy. The effect lasted for at least 15 months after irradiation. TGF-ß3 neutralizer added to the medium containing mouse serum inhibited the effect. Serum from mice given irradiation of 0.3 Gy/h for 1 h and subsequently treated with iNOS inhibitor 1400W did not affect radiosensitivity in reporter cells; neither did serum from the unirradiated progeny of mice given 1h LDR whole-body irradiation.

Targeting tumour hypoxia to prevent cancer metastasis. From biology, biosensing and technology to drug development: the METOXIA consortium.

The hypoxic areas of solid cancers represent a negative prognostic factor irrespective of which treatment modality is chosen for the patient. Still, after almost 80 years of focus on the problems created by hypoxia in solid tumours, we still largely lack methods to deal efficiently with these treatment-resistant cells. The consequences of this lack may be serious for many patients: Not only is there a negative correlation between the hypoxic fraction in tumours and the outcome of radiotherapy as well as many types of chemotherapy, a correlation has been shown between the hypoxic fraction in tumours and cancer metastasis. Thus, on a fundamental basis the great variety of problems related to hypoxia in cancer treatment has to do with the broad range of functions oxygen (and lack of oxygen) have in cells and tissues. Therefore, activation-deactivation of oxygen-regulated cascades related to metabolism or external signalling are important areas for the identification of mechanisms as potential targets for hypoxia-specific treatment. Also the chemistry related to reactive oxygen radicals (ROS) and the biological handling of ROS are part of the problem complex. The problem is further complicated by the great variety in oxygen concentrations found in tissues. For tumour hypoxia to be used as a marker for individualisation of treatment there is a need for non-invasive methods to measure oxygen routinely in patient tumours. A large-scale collaborative EU-financed project 2009-2014 denoted METOXIA has studied all the mentioned aspects of hypoxia with the aim of selecting potential targets for new hypoxia-specific therapy and develop the first stage of tests for this therapy. A new non-invasive PET-imaging method based on the 2-nitroimidazole [(18)F]-HX4 was found to be promising in a clinical trial on NSCLC patients. New preclinical models for testing of the metastatic potential of cells were developed, both in vitro (2D as well as 3D models) and in mice (orthotopic grafting). Low density quantitative real-time polymerase chain reaction (qPCR)-based assays were developed measuring multiple hypoxia-responsive markers in parallel to identify tumour hypoxia-related patterns of gene expression. As possible targets for new therapy two main regulatory cascades were prioritised: The hypoxia-inducible-factor (HIF)-regulated cascades operating at moderate to weak hypoxia (<1% O(2)), and the unfolded protein response (UPR) activated by endoplasmatic reticulum (ER) stress and operating at more severe hypoxia (<0.2%). The prioritised targets were the HIF-regulated proteins carbonic anhydrase IX (CAIX), the lactate transporter MCT4 and the PERK/eIF2α/ATF4-arm of the UPR. The METOXIA project has developed patented compounds targeting CAIX with a preclinical documented effect. Since hypoxia-specific treatments alone are not curative they will have to be combined with traditional anti-cancer therapy to eradicate the aerobic cancer cell population as well.

Signatures of the preagricultural peopling processes in sub-Saharan Africa as revealed by the phylogeography of early Y chromosome lineages.

The study of Y chromosome variation has helped reconstruct demographic events associated with the spread of languages, agriculture, and pastoralism in sub-Saharan Africa, but little attention has been given to the early history of the continent. In order to overcome this lack of knowledge, we carried out a phylogeographic analysis of haplogroups A and B in a broad data set of sub-Saharan populations. These two lineages are particularly suitable for this objective because they are the two most deeply rooted branches of the Y chromosome genealogy. Their distribution is almost exclusively restricted to sub-Saharan Africa where their frequency peaks at 65% in groups of foragers. The combined high-resolution single nucleotide polymorphism analysis with short tandem repeats variation of their subclades reveals strong geographic and population structure for both haplogroups. This has allowed us to identify specific lineages related to regional preagricultural dynamics in different areas of sub-Saharan Africa. In addition, we observed signatures of relatively recent contact, both among Pygmies and between them and Khoisan speaker groups from southern Africa, thus contributing to the understanding of the complex evolutionary relationships among African hunter-gatherers. Finally, by revising the phylogeography of the very early human Y chromosome lineages, we have obtained support for the role of southern Africa as a sink, rather than a source, of the first migrations of modern humans from eastern and central parts of the continent. These results open new perspectives on the early history of Homo sapiens in Africa, with particular attention to areas of the continent where human fossil remains and archaeological data are scant.

Mechanisms of the elimination of low dose hyper-radiosensitivity in T-47D cells by low dose-rate priming.

PURPOSE: To investigate the mechanisms of elimination of low-dose hyper-radiosensitivity (HRS) in T-47D cells induced by 0.3 Gy low dose-rate (LDR) priming. MATERIALS AND METHODS: The mitotic ratio was measured using mitotic marker histone H3 phosphorylation in LDR primed as well as untreated T-47D cells. The HRS response in unprimed cells receiving medium which was irradiated after being harvested from unprimed cells was measured with or without serum present during cell conditioning. 4,6-benzylidene-D-glucose (BG) was used to inhibit protein synthesis during LDR priming. RESULTS: LDR primed T-47D cells were HRS-deficient and showed a decrease in mitotic ratio with increasing dose while unprimed, i.e., HRS-competent T-47D cells, showed no decrease in mitotic ratio for doses in the HRS-range. HRS was eliminated in LDR primed cells, in cells receiving medium transfer from LDR primed cells, and in cells receiving LDR irradiated medium harvested from unprimed cells. The efficacy of the transferred medium depended on the presence of serum during cell conditioning. LDR priming eliminated HRS even in the presence of protein synthesis inhibitor BG. CONCLUSIONS: LDR priming of T-47D cells as well as LDR priming of medium conditioned on T-47D cells induce a factor in the medium which cause the early G(2)-checkpoint to be activated in recipient cells by doses normally in the HRS dose-range.

Taking advantage of tumor cell adaptations to hypoxia for developing new tumor markers and treatment strategies.

Cancer cells in hypoxic areas of solid tumors are to a large extent protected against the action of radiation as well as many chemotherapeutic drugs. There are, however, two different aspects of the problem caused by tumor hypoxia when cancer therapy is concerned: One is due to the chemical reactions that molecular oxygen enters into therapeutically targeted cells. This results in a direct chemical protection against therapy by the hypoxic microenvironment, which has little to do with cellular biological regulatory processes. This part of the protective effect of hypoxia has been known for more than half a century and has been studied extensively. However, in recent years there has been more focus on the other aspect of hypoxia, namely the effect of this microenvironmental condition on selecting cells with certain genetic prerequisites that are negative with respect to patient prognosis. There are adaptive mechanisms, where hypoxia induces regulatory cascades in cells resulting in a changed metabolism or changes in extracellular signaling. These processes may lead to changes in cellular intrinsic sensitivity to treatment irrespective of oxygenation and, furthermore, may also have consequences for tissue organization. Thus, the adaptive mechanisms induced by hypoxia itself may have a selective effect on cells, with a fine-tuned protection against damage and stress of many kinds. It therefore could be that the adaptive mechanisms may take advantage of for new tumor labeling/imaging and treatment strategies. One of the Achilles' heels of hypoxia research has always been the exact measurements of tissue oxygenation as well as the control of oxygenation in biological tumor models. Thus, development of technology that can ease this control is vital in order to study mechanisms and perform drug development under relevant conditions. An integrated EU Framework project 2004-2009, termed EUROXY, demonstrates several pathways involved in transcription and translation control of the hypoxic cell phenotype and evidence of cross-talk with responses to pH and redox changes. The carbonic anhydrase isoenzyme CA IX was selected for further studies due to its expression on the surface of many types of hypoxic tumors. The effort has led to marketable culture flasks with sensors and incubation equipment, and the synthesis of new drug candidates against new molecular targets. New labeling/imaging methods for cancer diagnosing and imaging of hypoxic cancer tissue are now being tested in xenograft models and are also in early clinical testing, while new potential anti-cancer drugs are undergoing tests using xenografted tumor cancers. The present article describes the above results in individual consortium partner presentations.

Hypoxic treatment inhibits insulin-induced chondrogenesis of ATDC5 cells despite upregulation of DEC1.

Chondrogenesis occurs in vivo in a hypoxic environment, in which the hypoxia inducible factor 1, HIF-1, plays a regulatory role, possibly mediated through the transcription factor DEC1. We have analyzed the effect of hypoxia (1% oxygen) alone and in combination with insulin on the chondrogenic differentiation of the mouse embryonic stem cell line ATDC5. Hypoxic treatment alone induced early chondrogenesis as evidenced by enhanced expression of aggrecan and collagen II, whereas hypoxic incubation of insulin-treated cells delayed and suppressed insulin-mediated early chondrogenesis and almost completely blocked hypertrophic differentiation. Paradoxically, the transcriptional activation of DEC1 was invariably enhanced by the hypoxic exposure.

Evaluation of cell-penetrating peptides (CPPs) as vehicles for intracellular delivery of antisense peptide nucleic acid (PNA).

Cell-penetrating peptides (CPPs) are characterized by their ability to be internalized in mammalian cells. To investigate the relative potency of CPPs as carriers of medicinally relevant cargo, a positive read-out assay based on the ability of a peptide nucleic acid (PNA) oligomer to promote correct expression of a recombinant luciferase gene was employed. Seven different CPPs were included in the study: Transportan, oligo-arginine (R7-9), pTat, Penetratin, KFF, SynB3, and NLS. The CPP-PNA conjugates were synthesized by different conjugation chemistries: continuous synthesis, maleimide coupling, and ester or disulfide linkage. Under serum-free conditions PNA-SS-Transportan-amide (ortho)-PNA was found to be the most potent conjugate, resulting in maximum luciferase signal at a concentration of 1-2 microM. (D-Arg)9-PNA showed optimal efficacy at 5 microM but gave rise to only one-third of the luciferase signal obtained with the Transportan conjugate. The pTat- and KFF-PNA conjugates showed significantly lower efficacy. The penetratin-, SynB3-. and NLS-PNA conjugates showed only minimal or no activity. Serum was found to have a drastic negative impact on CPP-driven cellular uptake. PNA-SS-Transportan-acid (ortho) and (D-Arg)9-PNA were least sensitive to the presence of serum. Both the chemical nature and, in the case of Transportan, the position of the peptide PNA coupling were found to have a major impact on the transport capacity of the peptides. However, no simple relationship between linker type and antisense activity of the conjugates could be deduced from the data.

Evaluation of transfection protocols for unmodified and modified peptide nucleic acid (PNA) oligomers.

We have compared the efficacy of different transfection protocols reported for peptide nucleic acid (PNA) oligomers. A precise evaluation of uptake efficacy was achieved by using a positive readout assay based on the ability of a PNA oligomer to correct aberrant splicing of a recombinant luciferase gene. The study comprised transfection of PNA conjugated to acridine, adamantyl, decanoic acid, and porphyrine (acr-PNA, ada-PNA, deca-PNA, and por-RNA, respectively) and unmodified PNA partially hybridized to a DNA oligomer (PNA/DNA cotransfection). Furthermore, the effect of conjugation to a nuclear localization signal (NLS) was evaluated as part of the PNA/DNA cotransfection protocol. Transfection of the tested PNAs was systematically optimized. PNA/DNA cotransfection was found to produce the highest luciferase activity, but only after careful selection of the DNA oligonucleotide. Both a cationic lipid, Lipofectamine, and a nonliposomal cationic polymer, polyethylenimine (PEI, ExGen 500), were efficient transfection reagents for the PNA/DNA complex. However, Lipofectamine, in contrast to PEI, showed severe side effects, such as cytotoxicity. acr-PNA, ada-PNA, and por-PNA were transfectable with efficacies between 5 and 10 times lower than that seen with PNA/DNA cotransfection. Conjugation of PNA to NLS had no effect on PNA/DNA cotransfection efficacy. An important lesson from the study was the finding that because of uncontrollable biologic variations, even optimal transfection conditions differed to a certain extend from experiment to experiment in an unpredictable way.

Temporal transcriptome of mouse ATDC5 chondroprogenitors differentiating under hypoxic conditions.

The formation of cartilage takes place in vivo in an environment of reduced oxygen tension. To study the effect of hypoxia on the process of chondrogenesis, ATDC5 mouse chondroprogenitor cells were induced to differentiate by the addition of insulin and cultured under ambient and hypoxic conditions corresponding to 21% and 1% O2 in the gas phase, respectively. The production of extracellular proteoglycans as well as the transcriptional profile of 104 selected genes was determined by real-time RT-PCR. Hypoxia alone induced early chondrogenesis as evidenced by the synthesis of glycosaminoglycans and expression of aggrecan and collagen type II genes. Surprisingly, however, hypoxic incubation of insulin-treated cells delayed and suppressed the insulin-mediated early chondrogenesis and almost completely blocked hypertrophic differentiation. Analysis of the gene expression yielded several clues as to the mechanisms involved. In addition, a group of genes was identified that have not previously been associated with hypoxia, including Ak4, Akt3, Col X, Fmod, Ier3, IGFbp4, MafF, Mxi1, Rcor2, Rras, Sox6, Tnni2, Wnt5a, and Zfp313.

Optimized chondrogenesis of ATCD5 cells through sequential regulation of oxygen conditions.

The objective of this study was to determine the optimal oxygen conditions for chondrogenesis of ATDC5 mouse embryonic stem cells. Chondrogenesis was induced by addition of insulin and the cells were then cultured at different oxygen concentrations ranging from 1 to21%. At 2- to 3-day intervals, chondrocyte-specific extracellular matrix (ECM) production was monitored. Furthermore, the transcription of collagen II, an early-phase marker, and collagen X, a marker of hypertrophic conversion, was followed by real-time RT-PCR. Low oxygen concentrations between 1 and 9% inhibited chondrogenic conversion, as evidenced by reduced glycosaminoglycan deposition in the ECM in a manner proportional to the degree of hypoxia. Cells cultured at oxygen concentrations of 12 and 15% underwent a faster and higher degree of early-phase chondrogenesis when compared to control cells cultured at ambient air (21% O2). For the hypertrophic conversion of the ATDC5 cells, all degrees of hypoxia inhibited collagen X expression in a dose-dependent manner. Short-term culturing of the ATDC5 cells for 6 to 8 days at 12% oxygen with subsequent culturing at 21% for the remainder of the experiment resulted in maximal production of major ECM components, including collagen II and glycosaminoglycans. It is thus possible to modify in vitro chondrogenesis through modulation of the gas-phase composition.

Derivation and characterization of four new human embryonic stem cell lines: the Danish experience.

In September 2003, legislation approved in Denmark legalized work on surplus human embryos from IVF for clinical purposes to establish human embryonic stem (ES) cell cultures. The aim of this study was to establish such stem cell lines. Fresh surplus embryos were donated after informed consent from the donors. Embryos were cultured into blastocysts and using the immunosurgery procedure, inner cell masses were isolated and cultured on irradiated human foreskin fibroblasts in KnockOut D-MEM supplemented with KnockOut Serum Replacement, bFGF, and LIF. Within a period of 12 months, 198 embryos were donated. Four isolated inner cell masses developed into putative ES cell lines, CLS1, CLS2, CLS3, CLS4, which have now been continuously cultured for eight months, corresponding to 30 passages. These cells expressed markers for undifferentiated human ES cells: stage-specific embryonic antigen-4, tumour-related antigen (TRA)-1-60, TRA-1-81, OCT4, NANOG, SOX2, and FGF4. The cells expressed high levels of telomerase activity, had a normal karyotype, and have been successfully cryopreserved and thawed. Finally, the cells displayed the potential to differentiate in vitro into cell types originating from all three germ layers. It is thought that the cell lines described in this study are the first human ES cells established in Denmark.

Quantitative transcriptional profiling of ATDC5 mouse progenitor cells during chondrogenesis.

During the differentiation of a mouse chondroprogenitor cell line, ATDC5, an analysis of the transcription cartilage-related genes was carried out using real-time RT-PCR in a semiquantitative fashion. A total number of 104 genes both previously linked to chondrogenesis and hitherto not associated with the development of cartilage were analyzed. Parametric statistics, and unsupervised hierarchical and K-medians clustering approaches were used to analyze the gene expression during the sequential processes of proliferation, condensation, differentiation, maturation, and hypertrophic conversion of ATDC5 cells. The obtained data provided a robust determination of expression patterns that make possible an accurate assessment of the molecular events along the chondrogenic differentiation pathway. In addition, time-course expression profiles were described for eight highly regulated genes that have not been associated with chondrogenesis as yet. These included Cryab, Rcor2, Hig1, Bnip3, Mst4, Calml4, Gng2, and Islr.

Pericellular oxygen depletion during ordinary tissue culturing, measured with oxygen microsensors.

Recent research has found important differences in oxygen tension in proximity to certain mammalian cells when grown in culture. Oxygen has a low diffusion rate through cell culture media, thus, as a result of normal respiration, a decrease in oxygen tension develops close to the cells. Therefore, for the purpose of standardization and optimization, it is important to monitor pericellular oxygen tension and cell oxygen consumption. Here, we describe an integrated oxygen microsensor and recording system that allows measurement of oxygen concentration profiles in vertical transects through a 1.6-mm deep, stagnant, medium layer covering a cell culture. The measurement set-up reveals that, when confluent, a conventional culture of adherent cells, although exposed to the constant oxygen tension of ambient air, may experience pericellular oxygen tensions below the level required to sustain full oxidative metabolism. Depletions reported are even more prominent and potentially aggravating when the cell culture is incubated at reduced oxygen tensions (down to around 4% oxygen). Our results demonstrate that, if the pericellular oxygen tension is not measured, it is impossible to relate in vitro culture results (for example, gene expression to the oxygen tension experienced by the cell), as this concentration may deviate very substantially from the oxygen concentration recorded in the gas phase.

Transcriptional regulation of plasminogen activator inhibitor-1 expression by insulin-like growth factor-1 via MAP kinases and hypoxia-inducible factor-1 in HepG2 cells.

Insulin-like growth factor 1 (IGF-1) and plasminogen activator inhibitor-1 (PAI-1) appear to play a crucial role in a number of processes associated with growth and tissue remodelling. IGF-1 was shown to enhance PAI-1 expression in primary hepatocytes and HepG2 hepatoma cells, but the molecular mechanisms underlying this effect have not been fully elucidated. In this study, we investigated the transcriptional mechanism and the signaling pathway by which IGF-1 mediates induction of PAI-1 expression in HepG2 cells. By using human PAI-1 promoter reporter gene assays we found that mutation of the hypoxia responsive element (HRE), which could bind hypoxia-inducible factor-1 (HIF-1), nearly abolished the induction by IGF-1. We found that IGF-1-induced up-regulation of PAI-1 expression was associated with activation of HIF-1 alpha. Furthermore,IGF-1 enhanced HIF-1alpha protein levels and HIF-1 DNA-binding to each HRE,E4 and E5 as shown by EMSA. Mutation of the E-boxes, E4 and E5, did not affect the IGF-1-dependent induction of PAI-1 promoter constructs under normoxia but abolished the effect of IGF-1 under hypoxia. Inhibition of either the PI3K by LY294002 or ERK1/2 by U0126 reduced HIF-1alpha protein levels while both inhibitors together completely abolished the IGF-1 effect on HIF-1alpha. Remarkably, transfection of HepG2 cells with vectors expressing a dominant-negative PDK1 or the PKB inhibitor, TRB3, did not influence while dominant-negative Raf inhibited the IGF-1 effect on HIF-1alpha. Thus, IGF-1 activates human PAI-1 gene expression through activation of the PI3-kinase and ERK1/2 via HIF-1alpha.

Induction of adipocyte-like phenotype in human mesenchymal stem cells by hypoxia.

Human mesenchymal stem cells (hMSCs) have the capacity to differentiate along several pathways to form bone, cartilage, tendon, muscle, and adipose tissues. The adult hMSCs reside in vivo in the bone marrow in niches where oxygen concentration is far below the ambient air, which is the most commonly encountered laboratory condition. The study reported here was designed to determine whether oxygen has a role in the differentiation of hMSCs into adipocytes. Indeed, when exposed to atmosphere containing only 1% of oxygen, the formation of adipocyte-like phenotype with cytoplasmic lipid inclusions was observed. The effect of hypoxia on the expression of adipocyte-specific genes was determined by real-time reverse transcription polymerase chain reaction. Interestingly, neither of the two central regulators of adipogenesis--the transcription factors peroxisome proliferator-activated receptor gamma2 (PPAR-gamma2) and ADD1/SREBP1c-was induced. Furthermore, hypoxia did not have any effect on the transcription of early (lipoprotein lipase) or late (aP2) marker genes. By the same token, neither of the mature adipocyte-specific genes--leptin and adipophilin--was found responsive to the treatment. High level of induction, however, was observed with the PPAR-gamma-induced angiopoietin-related gene, PGAR. The lack of an adipocyte-specific transcription pattern thus indicates that despite accumulation of the lipid, true adipogenic differentiation did not take place. In conclusion, hypoxia appears to exert a potent lipogenic effect independent of PPAR-gamma2 maturation pathway.

Genotypic characterization of Kaposi's sarcoma-associated herpesvirus in asymptomatic infected subjects from isolated populations.

Molecular epidemiological studies of Kaposi's sarcoma-associated herpesvirus (KSHV) have concentrated on characterization of viral strains in tumour biopsy samples from Kaposi's sarcoma (KS) patients, mostly obtained in the United States and Europe. Tumour biopsies are a convenient source of viral DNA, as they have a high viral load compared to peripheral blood. However, sequences obtained from biopsies may not be representative of viral strains in asymptomatic subjects and information on ethnicity is often not available. Here, a population-based approach has been used to study the molecular and seroepidemiology of KSHV in isolated populations in Ecuador and Botswana. Amerindians in Ecuador had a variable prevalence of KSHV and all strains characterized were of subtype E, based on K1 sequencing. All Amerindian strains had predominant (P)-type K15 alleles and had sequences in both T0.7 and ORF 75 that appeared to be characteristic of these strains. The prevalence of KSHV in two ethnic groups in Botswana was extremely high. K1 sequences from both Bantu and San subjects were mostly of subtypes B and A5, which are typical of African KSHV strains, but the sequence from one San subject did not cluster with any known subtype. Considerable heterogeneity was seen in the T0.7 and ORF 75 genes in the San subjects and one had a minor (M)-type K15 allele. The heterogeneity of the KSHV strains found in these subjects from Botswana contrasts with the homogeneity of KSHV strains in Amerindians, reflecting differences in the evolutionary history of these populations.