The Chromosomal Passenger Protein Birc5b Organizes Microfilaments and Germ Plasm in the Zebrafish Embryo

Microtubule-microfilament interactions are important for cytokinesis and subcellular localization of proteins and mRNAs. In the early zebrafish embryo, astral microtubule-microfilament interactions also facilitate a stereotypic segregation pattern of germ plasm ribonucleoparticles (GP RNPs), which is critical for their eventual selective inheritance by germ cells. The precise mechanisms and molecular mediators for both cytoskeletal interactions and GP RNPs segregation are the focus of intense research. Here, we report the molecular identification of a zebrafish maternal-effect mutation motley as Birc5b, a homolog of the mammalian Chromosomal Passenger Complex (CPC) component Survivin. The meiosis and mitosis defects in motley/birc5b mutant embryos are consistent with failed CPC function, and additional defects in astral microtubule remodeling contribute to failures in the initiation of cytokinesis furrow ingression. Unexpectedly, the motley/birc5b mutation also disrupts cortical microfilaments and GP RNP aggregation during early cell divisions. Birc5b localizes to the tips of astral microtubules along with polymerizing cortical F-actin and the GP RNPs. Mutant Birc5b co-localizes with cortical F-actin and GP RNPs, but fails to associate with astral microtubule tips, leading to disorganized microfilaments and GP RNP aggregation defects. Thus, maternal Birc5b localizes to astral microtubule tips and associates with cortical F-actin and GP RNPs, potentially linking the two cytoskeletons to mediate microtubule-microfilament reorganization and GP RNP aggregation during early embryonic cell cycles in zebrafish. In addition to the known mitotic function of CPC components, our analyses reveal a non-canonical role for an evolutionarily conserved CPC protein in microfilament reorganization and germ plasm aggregation.     

Steered Molecular Dynamics Simulations of a Type IV Pilus Probe Initial Stages of a Force-Induced Conformational Transition

Type IV pili are long, protein filaments built from a repeating subunit that protrudes from the surface of a wide variety of infectious bacteria. They are implicated in a vast array of functions, ranging from bacterial motility to microcolony formation to infection. One of the most well-studied type IV filaments is the gonococcal type IV pilus (GC-T4P) from Neisseria gonorrhoeae, the causative agent of gonorrhea. Cryo-electron microscopy has been used to construct a model of this filament, offering insights into the structure of type IV pili. In addition, experiments have demonstrated that GC-T4P can withstand very large tension forces, and transition to a force-induced conformation. However, the details of force-generation, and the atomic-level characteristics of the force-induced conformation, are unknown. Here, steered molecular dynamics (SMD) simulation was used to exert a force in silico on an 18 subunit segment of GC-T4P to address questions regarding the nature of the interactions that lead to the extraordinary strength of bacterial pili. SMD simulations revealed that the buried pilin α1 domains maintain hydrophobic contacts with one another within the core of the filament, leading to GC-T4P''s structural stability. At the filament surface, gaps between pilin globular head domains in both the native and pulled states provide water accessible routes between the external environment and the interior of the filament, allowing water to access the pilin α1 domains as reported for VC-T4P in deuterium exchange experiments. Results were also compared to the experimentally observed force-induced conformation. In particular, an exposed amino acid sequence in the experimentally stretched filament was also found to become exposed during the SMD simulations, suggesting that initial stages of the force induced transition are well captured. Furthermore, a second sequence was shown to be initially hidden in the native filament and became exposed upon stretching.     

The Integrator Complex Subunit 6 (Ints6) Confines the Dorsal Organizer in Vertebrate Embryogenesis

Dorsoventral patterning of the embryonic axis relies upon the mutual antagonism of competing signaling pathways to establish a balance between ventralizing BMP signaling and dorsal cell fate specification mediated by the organizer. In zebrafish, the initial embryo-wide domain of BMP signaling is refined into a morphogenetic gradient following activation dorsally of a maternal Wnt pathway. The accumulation of β-catenin in nuclei on the dorsal side of the embryo then leads to repression of BMP signaling dorsally and the induction of dorsal cell fates mediated by Nodal and FGF signaling. A separate Wnt pathway operates zygotically via Wnt8a to limit dorsal cell fate specification and maintain the expression of ventralizing genes in ventrolateral domains. We have isolated a recessive dorsalizing maternal-effect mutation disrupting the gene encoding Integrator Complex Subunit 6 (Ints6). Due to widespread de-repression of dorsal organizer genes, embryos from mutant mothers fail to maintain expression of BMP ligands, fail to fully express vox and ved, two mediators of Wnt8a, display delayed cell movements during gastrulation, and severe dorsalization. Consistent with radial dorsalization, affected embryos display multiple independent axial domains along with ectopic dorsal forerunner cells. Limiting Nodal signaling or restoring BMP signaling restores wild-type patterning to affected embryos. Our results are consistent with a novel role for Ints6 in restricting the vertebrate organizer to a dorsal domain in embryonic patterning.     

Clinical symptoms of ADHD and psychopathy in perpetrators

ADHD and psychopathy are both associated with poor social adaptation and antisocial behavior. Previous studies have also suggested that ADHD and psychopathy share some symptomatology. The current study attempted to further uncover the relationship between ADHD and psychopathy in perpetrators by investigating the possibility of underlying common factors of ADHD and psychopathy using standardized instruments. Correlation analyses and principal component analyses were performed on ADHD-SB self-rating questionnaires and the PCL-SV from a population of 314 offenders. Further, subjects without ADHD, full ADHD and partially remitted ADHD according to DSM-IV were compared regarding psychopathic traits. ADHD and psychopathy rating scores were found to be correlated. Only psychopathic features related to unstable and antisocial lifestyle, but not related to affective features of psychopathy accounted to this association. Findings on the principal component analysis suggest that ADHD and psychopathy are unrelated on a symptomatic level, with the exception of impulsivity, which is a common feature that seems to combine both constructs.     

Higher Risk Perception of HIV than of Chlamydia and HPV among Secondary School Students in Two German Cities

Background

Chlamydia and genital human papillomavirus (HPV) are the two most common sexually transmitted infections (STIs) among teens and young adults in industrialised countries. The majority of adolescents, however, have limited or no knowledge of these infections. Within the context of a cross-sectional survey on awareness and knowledge of sexually transmitted infections, secondary school students attending the 8th grade and above in Bremen and Bremerhaven, two cities in northern Germany, were asked to rate the risk of peers to get infected with HIV, HPV or chlamydia.

Methods

Between October and December 2011, students aged 12–20 years completed an anonymous, self-administered questionnaire at their school. In addition to answering questions on awareness and knowledge of sexually transmitted infections, all students were also asked to rate the risk of peers to get infected with HIV, HPV or chlamydia. Furthermore, those reporting ever having sexual intercourse were asked to rate their own risk of getting infected with each of the three infections.

Results

1,148 students, 55% female, completed the questionnaire. 27% of the students reported having had sexual intercourse. 68% of all students rated the risk of same-aged students to get infected with HIV/AIDS as high/medium. The corresponding proportions for HPV and chlamydia were 19 and 25% respectively. Those reporting ever having sexual intercourse generally perceived their own risk of getting infected with HIV, chlamydia or HPV as lower than that of their peers.

Conclusion

Generally, the risk of getting infected with HIV was perceived as being higher than that of getting infected with HPV or chlamydia, most likely due to the fact that the students were more aware of HIV than of the other two infections. Efforts should be made to improve awareness and knowledge of HPV and chlamydia among school going adolescents, and to make them realize that these are common infections that are preventable.     

High Levels of Asymmetric Dimethylarginine Are Strongly Associated with Low HDL in Patients with Acute Myocardial Infarction

Objectives

Low levels of high-density lipoprotein (HDL) cholesterol are associated with an increased risk of acute myocardial infarction possibly through impaired endothelial atheroprotection and decreased nitric oxide (NO) bioavailability. Asymmetric dimethylarginine (ADMA) mediates endothelial function by inhibiting nitric oxide synthase activity. In patients with acute myocardial infarction, we investigated the relationship between serum levels of HDL and ADMA.

Approach and Results

Blood samples from 612 consecutive patients hospitalized for acute MI <24 hours after symptom onset were taken on admission. Serum levels of ADMA, its stereoisomer, symmetric dimethylarginine (SDMA) and L-arginine were determined using high-performance liquid chromatography. Patients with low HDL (<40 mg/dL for men and <50 mg/dL for women) were compared with patients with higher HDL. Most patients (59%) had low HDL levels. Median ADMA levels were markedly higher in the low HDL group (0.69 vs. 0.50 µmole/L, p<0.001). In contrast, SDMA and L-arginine levels were similar for the two groups (p = 0.120 and p = 0.064). Notably, ADMA, but not SDMA or L-arginine, was inversely correlated with HDL (r = −0.311, p<0.001). In stratified analysis, this relationship was only found for low HDL levels (r = −0.265, p<0.001), but not when HDL levels were higher (r = −0.077, p = 0.225). By multivariate logistic regression analysis, ADMA level was strongly associated with low HDL levels (OR(95%CI):6.06(3.48–10.53), p<0.001), beyond traditional confounding factors.

Conclusions

Our large population-based study showed for the first time a strong inverse relationship between HDL and ADMA in myocardial infarction patients, suggesting a functional interaction between HDL and endothelium, beyond metabolic conditions associated with low HDL levels.     

Age‐Related Effects on the Biological Clock and its Behavioral Output in a Primate

In humans, activity rhythms become fragmented and attenuated in the elderly. This suggests an alteration of the circadian system per se that could in turn affect the expression of biological rhythms. In primates, very few studies have analyzed the effect of aging on the circadian system. The mouse lemur provides a unique model of aging in non‐human primates. To assess the effect of aging on the circadian system of this primate, we recorded the circadian and daily rhythms of locomotor activity of mouse lemurs of various ages. We also examined age‐related changes in the daily rhythm of immunoreactivities for vasoactive intestinal polypeptide (VIP) and arginine‐vasopressin (AVP) in suprachiasmatic nucleus neurons (SCN), two major peptides of the biological clock. Compared to adult animals, aged mouse lemurs showed a significant increase in daytime activity and an advanced activity onset. Moreover, when maintained in constant dim red light, aged animals exhibited a shortening of the free‐running period compared to adult animals. In adults, AVP immunoreactivity (ir) peaked during the second part of the day, and VIP ir peaked during the night. In aged mouse lemurs, the peaks of AVP ir and VIP ir were significantly shifted with no change in amplitude. AVP ir was most intense at the beginning of the night; whereas, VIP ir peaked at the beginning of the daytime. A weakened oscillator could account for the rhythmic disorders often observed in the elderly. Changes in the daily rhythms of AVP ir and VIP ir may affect the ability of the SCN to transmit rhythmic information to other neural target sites, and thereby modify the expression of some biological rhythms.     

Unique gene alterations are induced in FACS‐purified Fos‐positive neurons activated during cue‐induced relapse to heroin seeking

Cue‐induced heroin seeking after prolonged withdrawal is associated with neuronal activation and altered gene expression in prefrontal cortex (PFC). However, these previous studies assessed gene expression in all neurons regardless of their activity state during heroin seeking. Using Fos as a marker of neural activity, we describe distinct molecular alterations induced in activated versus non‐activated neurons during cue‐induced heroin seeking after prolonged withdrawal. We trained rats to self‐administer heroin for 10 days (6 h/day) and assessed cue‐induced heroin seeking in extinction tests after 14 or 30 days. We used fluorescent‐activated cell sorting (FACS) to purify Fos‐positive and Fos‐negative neurons from PFC 90 min after extinction testing. Flow cytometry showed that Fos‐immunoreactivity was increased in less than 10% of sparsely distributed PFC neurons. mRNA levels of the immediate early genes fosB, arc, egr1, and egr2, as well as npy and map2k6, were increased in Fos‐positive, but not Fos‐negative, neurons. In support of these findings, double‐label immunohistochemistry indicated substantial coexpression of neuropeptide Y (NPY)‐ and Arc‐immunoreactivity in Fos‐positive neurons. Our data indicate that cue‐induced relapse to heroin seeking after prolonged withdrawal induces unique molecular alterations within activated PFC neurons that are distinct from those observed in the surrounding majority of non‐activated neurons.     

Species Diversity,Phylogeny and Large Scale Biogeographic Patterns of the Genus Padina (Phaeophyceae,Dictyotales)

The brown algal genus Padina (Dictyotales, Phaeophyceae) is distributed worldwide in tropical and temperate seas. Global species diversity and distribution ranges, however, remain largely unknown. Species‐level diversity was reassessed using DNA‐based, algorithmic species delineation techniques based on cox3 and rbcL sequence data from 221 specimens collected worldwide. This resulted in estimates ranging from 39 to 61 putative species (ESUs), depending on the technique as well as the locus. We discuss the merits, potential pitfalls, and evolutionary and biogeographic significance of algorithmic species delineation. We unveil patterns whereby ESUs are in all but one case restricted to either the Atlantic or Indo‐Pacific Ocean. Within ocean basins we find evidence for the vast majority of ESUs to be confined to a single marine realm. Exceptions, whereby ESUs span up to three realms, are located in the Indo‐Pacific Ocean. Patterns of range‐restricted species likely arise by repeated founder events and subsequent peripatric speciation, hypothesized to dominate speciation mechanisms for coastal marine organisms in the Indo‐Pacific. Using a three‐gene (cox3, psaA and rbcL), relaxed molecular clock phylogenetic analysis we estimated divergence times, providing a historical framework to interpret biogeographic patterns.     

Soluble Melanoma Cell Adhesion Molecule (sMCAM/sCD146) Promotes Angiogenic Effects on Endothelial Progenitor Cells through Angiomotin

The melanoma cell adhesion molecule (CD146) contains a circulating proteolytic variant (sCD146), which is involved in inflammation and angiogenesis. Its circulating level is modulated in different pathologies, but its intracellular transduction pathways are still largely unknown. Using peptide pulldown and mass spectrometry, we identified angiomotin as a sCD146-associated protein in endothelial progenitor cells (EPC). Interaction between angiomotin and sCD146 was confirmed by enzyme-linked immunosorbent assay (ELISA), homogeneous time-resolved fluorescence, and binding of sCD146 on both immobilized recombinant angiomotin and angiomotin-transfected cells. Silencing angiomotin in EPC inhibited sCD146 angiogenic effects, i.e. EPC migration, proliferation, and capacity to form capillary-like structures in Matrigel. In addition, sCD146 effects were inhibited by the angiomotin inhibitor angiostatin and competition with recombinant angiomotin. Finally, binding of sCD146 on angiomotin triggered the activation of several transduction pathways that were identified by antibody array. These results delineate a novel signaling pathway where sCD146 binds to angiomotin to stimulate a proangiogenic response. This result is important to find novel target cells of sCD146 and for the development of therapeutic strategies based on EPC in the treatment of ischemic diseases.