Out of the North Sea: the Zeeland Ridges Neandertal

In 2001, a portion of human frontal bone was discovered in sediments extracted from the bottom of the North Sea, 15 km off the coast of the Netherlands. The extraction zone is located in the so-called Zeeland Ridges area located at 51°40′ northern latitude and 3°20′ eastern longitude. The specimen was dredged up from sediments containing Late Pleistocene faunal remains and Middle Palaeolithic artefacts, including well-finished small handaxes and Levallois flakes. The details of the supraorbital morphology, as well as the quantitative assessment of the shape of the external surface of the squama using traditional and 3D geometric morphometrics, unambiguously assign the Zeeland Ridges frontal bone to Homo neanderthalensis. Carbon and nitrogen isotopic analysis indicate that the Zeeland Ridges hominin, like other Neandertals, was highly carnivorous and does not show evidence for the consumption of aquatic foods. A lesion on the outer table and diploic layer of the bone in the area of the supratoral sulcus can be interpreted as the result of an intradiploic epidermoid cyst, a type of neoplasm diagnosed for the first time in Neandertal remains. So far, the Zeeland Ridges Neandertal is the first Pleistocene fossil hominin found under seawater and the first recorded in the Netherlands.     

The Monothiol Single-Domain Glutaredoxin Is Conserved in the Highly Reduced Mitochondria of Giardia intestinalis

The highly reduced mitochondria (mitosomes) of Giardia intestinalis are recently discovered organelles for which, it was suggested, iron-sulfur cluster assembly was their only conserved function. However, only an incomplete set of the components required for FeS cluster biogenesis was localized to the mitosomes. Via proteomic analysis of a mitosome-rich cellular fraction together with immunofluorescence microscopy, we identified a novel mitosomal protein homologous to monothiol glutaredoxins containing a CGFS motif at the active site. Sequence analysis revealed the presence of long nonconserved N-terminal extension of 77 amino acids, which was absent in the mature protein. Expression of the complete and N-terminally truncated forms of the glutaredoxin indicated that the extension is involved in glutaredoxin import into mitosomes. However, the mechanism of preprotein processing is unclear, as the mitosomal processing peptidase is unable to cleave this type of extension. The recombinant mature protein was shown to form a homodimeric structure, which binds a labile FeS cluster. The cluster is stabilized by glutathione and dithiothreitol. Phylogenetic analysis showed that giardial glutaredoxin is related to the mitochondrial monothiol glutaredoxins involved in FeS cluster assembly. The identification of a mitochondrial-type monothiol glutaredoxin in the mitosomes of G. intestinalis thus completes the mitosomal FeS cluster biosynthetic pathway and provides further evidence for the mitochondrial origin of these organelles.Giardia intestinalis is a parasitic protist that was considered amitochondrial until recently (7). Although typical ATP-producing mitochondria are not present, related organelles, named mitosomes, were discovered in this organism (29). Mitosomes and mitochondria have a number of similarities; most notably, both are surrounded by a double membrane (29), they have a common mode of protein import and maturation (6, 24), and both harbor key components of the FeS cluster assembly machinery (29). These similarities indicate that mitosomes are highly reduced forms of mitochondria (7, 30), even though alternative evolutionary scenarios are still being discussed (17).FeS clusters are cofactors of a number of FeS proteins involved mainly in electron transport, energetic metabolism, synthetic pathways, and biological sensing (12). Most importantly, the FeS protein Rli1 is indispensable for rRNA processing and ribosome biogenesis (15, 31). Consequently, the biogenesis of FeS clusters is an essential process for all cells from bacteria to human cells (15). In most nonplant eukaryotes, the crucial part of this biosynthetic pathway occurs in the mitochondrion or mitochondrion-related organelles (14, 24, 28). Studies of Saccharomyces cerevisiae mitochondria showed that the FeS cluster assembly is centered on IscU, a metallochaperone that serves as a scaffold for a new FeS cluster. The cysteine desulfurase IscS (in S. cerevisiae named Nfs1) forms a heterodimer with Isd11. This heterodimer catalyzes the mobilization of sulfur for the FeS cluster. The delivery of iron is most likely regulated by frataxin (1). Reducing equivalents, which are required during FeS cluster biogenesis, are provided by a short electron transport chain, including the mitochondrial [2Fe2S] ferredoxin and ferredoxin:NADH reductase. Finally, a transient FeS cluster is transferred from IscU (Isu1/2) to apoproteins by the action of the Hsp70 (Ssq1) and Hsp40 (Jac1) chaperones and the proteins IscA (Isa1/2) and Iba57 (15). This last step also requires a monothiol class glutaredoxin (Grx5) with a characteristic CGFS active site motif (20). This class of glutaredoxins catalyzes the reduction of disulfide bonds in proteins converting glutathione (GSH) to GSH disulfide. It has been recently demonstrated that dimeric monothiol glutaredoxins can coordinate a [2Fe2S] cluster via the cysteine residue of the active site of each monomer and the cysteines of two GSH molecules (20). Although the exact role of Grx5 remains to be elucidated, it was hypothesized that, in the final step of iron sulfur cluster biogenesis, the FeS cluster that is transiently formed on an IscU scaffold protein is transferred to a Grx5 dimer in a GSH-dependent manner and is subsequently passed on to the target apoproteins (20).The ability of Giardia mitosomes to assemble FeS clusters on apoferredoxin has been demonstrated (29), indicating that all necessary components of the FeS cluster assembly machinery are present in these organelles. However, only three components known from S. cerevisiae mitochondria have been shown to be localized to mitosomes so far (IscS, IscU, and [2Fe2S] ferredoxin), while some others, including Isd11, frataxin, and GSH, were reported to be absent in Giardia (4, 5, 21). In this study we identified monothiol glutaredoxin in a mitosome-enriched fraction of G. intestinalis (Gigrx) using a proteomic approach. The mitosomal localization of Gigrx was confirmed by expression of the tagged protein in Giardia cells. The protein contains an unusually long N-terminal extension, which is involved in targeting the protein to the organelle, while the C-terminal part contains conserved residues required for the coordination of an FeS cluster. Phylogenetic analysis showed the close relationship between Gigrx and its mitochondrial homologues, which is consistent with the proposed mitochondrial origin of the iron-sulfur cluster assembly machinery in G. intestinalis.     

The Warburg Effect Is Genetically Determined in Inherited Pheochromocytomas

The Warburg effect describes how cancer cells down-regulate their aerobic respiration and preferentially use glycolysis to generate energy. To evaluate the link between hypoxia and Warburg effect, we studied mitochondrial electron transport, angiogenesis and glycolysis in pheochromocytomas induced by germ-line mutations in VHL, RET, NF1 and SDH genes. SDH and VHL gene mutations have been shown to lead to the activation of hypoxic response, even in normoxic conditions, a process now referred to as pseudohypoxia. We observed a decrease in electron transport protein expression and activity, associated with increased angiogenesis in SDH- and VHL-related, pseudohypoxic tumors, while stimulation of glycolysis was solely observed in VHL tumors. Moreover, microarray analyses revealed that expression of genes involved in these metabolic pathways is an efficient tool for classification of pheochromocytomas in accordance with the predisposition gene mutated. Our data suggest an unexpected association between pseudohypoxia and loss of p53, which leads to a distinct Warburg effect in VHL-related pheochromocytomas.     

Persisting Mixed Cryoglobulinemia in Chikungunya Infection

Background

Chikungunya virus (CHIKV), an arbovirus, is responsible for a two-stage disabling disease, consisting of an acute febrile polyarthritis for the first 10 days, frequently followed by chronic rheumatisms, sometimes lasting for years. Up to now, the pathophysiology of the chronic stage has been elusive. Considering the existence of occasional peripheral vascular disorders and some unexpected seronegativity during the chronic stage of the disease, we hypothesized the role of cryoglobulins.

Methods

From April 2005 to May 2007, all travelers with suspected CHIKV infection were prospectively recorded in our hospital department. Demographic, clinical and laboratory findings (anti-CHIKV IgM and IgG, cryoglobulin) were registered at the first consultation or hospitalization and during follow-up.

Results

Among the 66 travelers with clinical suspicion of CHIKV infection, 51 presented anti-CHIKV IgM. There were 45 positive with the serological assay tested at room temperature, and six more, which first tested negative when sera were kept at 4°C until analysis, became positive after a 2-hour incubation of the sera at 37°C. Forty-eight of the 51 CHIKV-seropositive patients were screened for cryoglobulinemia; 94% were positive at least once during their follow-up. Over 90% of the CHIKV-infected patients had concomitant arthralgias and cryoglobulinemia. Cryoglobulin prevalence and level drop with time as patients recover, spontaneously or after short-term corticotherapy. In some patients cryoglobulins remained positive after 1 year.

Conclusion

Prevalence of mixed cryoglobulinemia was high in CHIKV-infected travelers with long-lasting symptoms. No significant association between cryoglobulinemia and clinical manifestations could be evidenced. The exact prognostic value of cryoglobulin levels has yet to be determined. Responsibility of cryoglobulinemia was suspected in unexpected false negativity of serological assays at room temperature, leading us to recommend performing serology on pre-warmed sera.     

Neandertals paleoenvironment in Western Provence: The contribution of Les Auzières 2 (Méthamis,Vaucluse, France)

The site of Les Auzières 2 (Méthamis, Vaucluse) was excavated from 2001 to 2005. It yielded an original and diverse fauna, unique in southeastern France (Provence). The spectrum of large mammals comprises 14 species including hyena, horse, ibex, woolly rhinoceros, giant deer and mammoth. Lithic artifacts are rare but testify to the presence of a Mousterian industry. All of these remains derive from layers that have been dated to 60 ± 10 ka by ESR/U-series method. Les Auzières 2 is of special importance for examining the issue of human/carnivore interaction in the Pleistocene since it has yielded a large assemblage of carnivore remains, and probably represents a hyena den. The diverse fauna offers a more comprehensive picture of Upper Pleistocene biodiversity in southeastern France than that usually provided by sites with a stronger anthropogenic signal.     

An unusual acenaphthylene-type sesquiterpene hydrocarbon from Siam and Sumatra benzoin gum

A new sesquiterpene was isolated from extracts of Sumatra benzoin gum. Its structure was elucidated by means of mass spectrometry and two-dimensional NMR. This new compound presented an acenaphthylene-type skeleton unpreviously described among the family of sesquiterpene hydrocarbons.     

Gene expression changes in the host response between resistant and susceptible inbred mouse strains after influenza A infection

Inbred mouse strains exhibit differences in susceptibility to influenza A infections. However, the molecular mechanisms underlying these differences are unknown. Therefore, we infected a highly susceptible mouse strain (DBA/2J) and a resistant strain (C57BL/6J) with influenza A H1N1 (PR8) and performed genome-wide expression analysis. We found genes expressed in lung epithelium that were specifically down-regulated in DBA/2J mice, whereas a cluster of genes on chromosome 3 was only down-regulated in C57BL/6J. In both mouse strains, chemokines, cytokines and interferon-response genes were up-regulated, indicating that the main innate immune defense pathways were activated. However, many immune response genes were up-regulated in DBA/2J much stronger than in C57BL/6J, and several immune response genes were exclusively regulated in DBA/2J. Thus, susceptible DBA/2J mice showed a hyper-inflammatory response. This response is similar to infections with highly pathogenic influenza virus and may serve as a paradigm for a hyper-inflammatory host response to influenza A virus.     

Challenges in experimental data integration within genome-scale metabolic models

A report of the meeting "Challenges in experimental data integration within genome-scale metabolic models", Institut Henri Poincaré, Paris, October 10-11 2009, organized by the CNRS-MPG joint program in Systems Biology.