Intricate evolutionary histories in montane species: a phylogenetic window into craniodental discrimination in the Peromyscus mexicanus species group (Mammalia: Rodentia: Cricetidae)

Mountain‐associated species, which exhibit allopatric distributions associated with elevation, endemisms and complex evolutionary histories, pose challenging evolutionary scenarios in which to discern the diversification of species. The Peromyscus mexicanus mice group, distributed along mountains in southern Mexico and Central America, is morphometrically variable, a key rationale for the ongoing controversy regarding its species delimitation. Based on the recognized 15 mitochondrial lineages for the group, we analysed external and craniodental morphometric variables to test whether lineages can be differentiated morphometrically and allow for the delimitation of species. We also aimed to test the prediction that the phylogenetic structure of the morphometric data is concordant with that of the molecular information. Based on 19 craniodental measurements from 521 specimens, multivariate and discriminant analyses showed that lineages are morphometrically discernible, representing distinct phenotypes, and that overall size and mandible measurements are significant features that discriminate lineages, supporting hypotheses about differences in feeding habits between species. Also, a pattern of increasing size with elevation was observed, further supported by specific morphological differences exhibited between highland and lowland lineages inhabiting the same mountain. Our results demonstrate that P. mexicanus is both genetically and morphometrically variable, where most highland montane species are differentiated from lowland species; also, a significant correlation between mitochondrial and morphometric information is indicative of phenetic concordance, altogether in agreement with a recent taxonomic proposal for the group. We suggest that the group's intricate diversification responds to ecological diversification and adaptation to a variety of mountain habitats and Pleistocene biogeographic climatic dynamics.     

Mitochondrial fragmentation in neurodegeneration

Mitochondria are remarkably dynamic organelles that migrate, divide and fuse. Cycles of mitochondrial fission and fusion ensure metabolite and mitochondrial DNA mixing and dictate organelle shape, number and bioenergetic functionality. There is mounting evidence that mitochondrial dysfunction is an early and causal event in neurodegeneration. Mutations in the mitochondrial fusion GTPases mitofusin 2 and optic atrophy 1, neurotoxins and oxidative stress all disrupt the cable-like morphology of functional mitochondria. This results in impaired bioenergetics and mitochondrial migration, and can trigger neurodegeneration. These findings suggest potential new treatment avenues for neurodegenerative diseases.     

The N-terminal Amphipathic ��-Helix of Viperin Mediates Localization to the Cytosolic Face of the Endoplasmic Reticulum and Inhibits Protein Secretion

Viperin is an evolutionarily conserved interferon-inducible protein that localizes to the endoplasmic reticulum (ER) and inhibits a number of DNA and RNA viruses. In this study, we report that viperin specifically localizes to the cytoplasmic face of the ER and that an amphipathic α-helix at its N terminus is necessary for the ER localization of viperin and sufficient to promote ER localization of a reporter protein, dsRed. Overexpression of intact viperin but not the amphipathic α-helix fused to dsRed induced crystalloid ER. Consistent with other proteins that induce crystalloid ER, viperin self-associates, and it does so independently of the amphipathic α-helix. Viperin expression also affected the transport of soluble but not membrane-associated proteins. Expression of intact viperin or an N-terminal α-helix-dsRed fusion protein significantly reduced secretion of soluble alkaline phosphatase and reduced its rate of ER-to-Golgi trafficking. Similarly, viperin expression inhibited bulk protein secretion and secretion of endogenous α₁-antitrypsin and serum albumin from HepG2 cells. Converting hydrophobic residues in the N-terminal α-helix to acidic residues partially or completely restored normal transport of soluble alkaline phosphatase, suggesting that the extended amphipathic nature of the N-terminal α-helical domain is essential for inhibiting protein secretion.Type I interferons are the first line of defense against viral infections. The significance of the interferon pathway is illustrated by the susceptibility of interferon signaling mutants to infection and by viral mechanisms that counteract this pathway (1, 2). Although many genes are induced upon interferon stimulation, very few of these genes have been functionally characterized. Viperin is highly induced by both Type I and II interferons and has a broad range of antiviral activity, inhibiting DNA viruses, notably human cytomegalovirus (3); RNA viruses such as influenza, hepatitis C virus (HCV),² and alphaviruses (4-6); and retroviruses such as human immunodeficiency virus (7). Upon expression, viperin localizes to the endoplasmic reticulum (ER), where it interacts with farnesyl-diphosphate synthase, an enzyme involved in lipid biosynthesis. This interaction appears to result in the disruption of lipid raft microdomains and prevention of influenza virus from budding from the plasma membrane (4).Although recent studies have explored the antiviral functions of viperin, the general biochemical properties of this protein remain largely undefined. Viperin is highly conserved across both mammals and lower vertebrates and shares homology with the MoaA family of “radical S-adenosylmethionine” enzymes that bind Fe-S clusters (3, 8). In addition to a putative Fe-S cluster-binding domain, viperin has a 42-amino acid residue N-terminal amphipathic α-helix, and similar domains in other proteins have been shown to bind membranes and induce membrane curvature (9, 10).In this study, we examined the role of the viperin N-terminal α-helical domain in both cellular localization and ER membrane morphology and analyzed the biochemical properties of viperin. We discovered that viperin forms dimers and induces a tightly ordered, visually striking array of ER membranes, known as crystalloid ER(11-13), upon overexpression. In addition, viperin expression impedes the secretion of a variety of soluble proteins. Although the N-terminal amphipathic α-helix is not sufficient to induce crystalloid ER formation, it is both necessary and sufficient to mediate ER localization and to inhibit protein secretion.     

Can Playing the Computer Game “Tetris” Reduce the Build-Up of Flashbacks for Trauma? A Proposal from Cognitive Science

Background

Flashbacks are the hallmark symptom of Posttraumatic Stress Disorder (PTSD). Although we have successful treatments for full-blown PTSD, early interventions are lacking. We propose the utility of developing a ‘cognitive vaccine’ to prevent PTSD flashback development following exposure to trauma. Our theory is based on two key findings: 1) Cognitive science suggests that the brain has selective resources with limited capacity; 2) The neurobiology of memory suggests a 6-hr window to disrupt memory consolidation. The rationale for a ‘cognitive vaccine’ approach is as follows: Trauma flashbacks are sensory-perceptual, visuospatial mental images. Visuospatial cognitive tasks selectively compete for resources required to generate mental images. Thus, a visuospatial computer game (e.g. “Tetris”) will interfere with flashbacks. Visuospatial tasks post-trauma, performed within the time window for memory consolidation, will reduce subsequent flashbacks. We predicted that playing “Tetris” half an hour after viewing trauma would reduce flashback frequency over 1-week.

Methodology/Principal Findings

The Trauma Film paradigm was used as a well-established experimental analog for Post-traumatic Stress. All participants viewed a traumatic film consisting of scenes of real injury and death followed by a 30-min structured break. Participants were then randomly allocated to either a no-task or visuospatial (“Tetris”) condition which they undertook for 10-min. Flashbacks were monitored for 1-week. Results indicated that compared to the no-task condition, the “Tetris” condition produced a significant reduction in flashback frequency over 1-week. Convergent results were found on a clinical measure of PTSD symptomatology at 1-week. Recognition memory between groups did not differ significantly.

Conclusions/Significance

Playing “Tetris” after viewing traumatic material reduces unwanted, involuntary memory flashbacks to that traumatic film, leaving deliberate memory recall of the event intact. Pathological aspects of human memory in the aftermath of trauma may be malleable using non-invasive, cognitive interventions. This has implications for a novel avenue of preventative treatment development, much-needed as a crisis intervention for the aftermath of traumatic events.     

Different HLA-DRB1 allele distributions in distinct clinical subgroups of sarcoidosis patients

Background

A strong genetic influence by the MHC class II region has been reported in sarcoidosis, however in many studies with different results. This may possibly be caused by actual differences between distinct ethnic groups, too small sample sizes, or because of lack of accurate clinical subgrouping.

Subjects and methods

In this study we HLA typed a large patient population (n = 754) recruited from one single centre. Patients were sub-grouped into those with Löfgren''s syndrome (LS) (n = 302) and those without (non-Löfgren''s) (n = 452), and the majority of them were clinically classified into those with recovery within two years (resolving) and those with signs of disease for more than two years (non-resolving). PCR was used for determination of HLA-DRB1 alleles. Swedish healthy blood donors (n = 1366) served as controls.

Results

There was a dramatic difference in the distribution of HLA alleles in LS compared to non-LS patients (p = 4 × 10^-36). Most notably, DRB1*01, DRB1*03 and DRB1*14, clearly differed in LS and non-LS patients. In relation to disease course, DRB1*07, DRB1*14 and DRB1*15 generally associated with, while DRB1*01 and DRB1*03 protected against, a non-resolving disease. Interestingly, the clinical influence of DRB1*03 (good prognosis) dominated over that of DRB1*15 (bad prognosis).

Conclusions

We found several significant differences between LS and non-LS patients and we therefore suggest that genetic association studies in sarcoidosis should include a careful clinical characterisation and sub-grouping of patients, in order to reveal true genetic associations. This may be particularly accurate to do in the heterogeneous non-LS group of patients.     

Subcellular distribution and relative expression of fibrocyte markers in the CD/1 mouse cochlea assessed by semiquantitative immunogold electron microscopy

Spiral ligament fibrocytes function in cochlear homeostasis, maintaining the endocochlear potential by participating in potassium recycling, and fibrocyte degeneration contributes to hearing loss. Their superficial location makes them amenable to replacement by cellular transplantation. Fibrocyte cultures offer one source of transplantable cells, but determining what fibrocyte types they contain and what phenotype transplanted cells may adopt is problematic. Here, we use immunogold electron microscopy to assess the relative expression of markers in native fibrocytes of the CD/1 mouse spiral ligament. Caldesmon and aquaporin 1 are expressed more in type III fibrocytes than any other type. S-100 is strongly expressed in types I, II, and V fibrocytes, and α1Na,K-ATPase is expressed strongly only in types II and V. By combining caldesmon or aquaporin 1 with S-100 and α1Na,K-ATPase, a ratiometric analysis of immunogold density distinguishes all except type II and type V fibrocytes. Other putative markers (creatine kinase BB and connective tissue growth factor) did not provide additional useful analytical attributes. By labeling serial sections or by double or triple labeling with combinations of three antibodies, this technique could be used to distinguish all except type II and type V fibrocytes in culture or after cellular transplantation into the lateral wall.