The importance of seasonal environmental factors in the foraging habitat selection of Alpine Ring Ouzels Turdus torquatus alpestris

Species inhabiting mountain ecosystems are expected to be particularly vulnerable to environmental change, yet information on their basic ecology is often lacking. Knowledge from field-based empirical studies remains essential to refine our understanding of the impact of current habitat alterations and for the consequential development of meaningful conservation management strategies. This study focuses on a poorly investigated and vulnerable mountain bird species in Europe, the Ring Ouzel Turdus torquatus. Our aim was to identify the species’ key ecological requirements during the crucial period of nestling provisioning in the context of environmental change. We radiotracked and observed Alpine Ring Ouzels in a high-density population, investigating their pattern of foraging habitat selection in 2015 and 2017, and evaluated the transferability of these results over a wider geographical range across the SW Swiss Alps. Foraging birds selected, consistently in space and time, short grass swards (< 10 cm) with interspersed patches of accessible and penetrable soils, at intermediate moisture levels (around 40–65% volumetric water content). In Alpine ecosystems, this microhabitat configuration is typically widespread during the spring snowmelt, but extremely seasonal, with a rapid decrease in its availability over the course of the breeding season. This underlines the high vulnerability of the Ring Ouzel to environmental change: an earlier snowmelt could generate a temporal mismatch between the peak of the breeding effort and optimal foraging conditions; however, abandoning grazing activities on semi-wooded Alpine pastures may further decrease foraging habitat suitability through taller and denser grass swards, and subsequent woody vegetation encroachment. This study provides a mechanistic appraisal of the challenges Ring Ouzels will face in the future, as well as initial guidelines for targeted habitat management within timberline ecotones.     

Pyramidal Neurons Derived from Human Pluripotent Stem Cells Integrate Efficiently into Mouse Brain Circuits In Vivo

Download : Download video (68MB)     

Bone morphogenetic protein-9 activates Smad and ERK pathways and supports human osteoclast function and survival in vitro

BMP-9 is a potent osteogenic factor; however, its effects on osteoclasts, the bone-resorbing cells, remain unknown. To determine the effects of BMP-9 on osteoclast formation, activity and survival, we used human cord blood monocytes as osteoclast precursors that form multinucleated osteoclasts in the presence of RANKL and M-CSF in long-term cultures. BMP-9 did not affect osteoclast formation, but adding BMP-9 at the end of the culture period significantly increased bone resorption compared to untreated cultures, and reduced both the rate of apoptosis and caspase-9 activity. BMP-9 also significantly downregulated the expression of pro-apoptotic Bid, but only after RANKL and M-CSF, which are both osteoclast survival factors, had been eliminated from the culture medium. To investigate the mechanisms involved in the effects of BMP-9, we first showed that osteoclasts expressed some BMP receptors, including BMPR-IA, BMPR-IB, ALK1, and BMPR-II. We also found that BMP-9 was able to induce the phosphorylation of Smad-1/5/8 and ERK 1/2 proteins, but did not induce p38 phosphorylation. Finally, knocking down the BMPR-II receptor abrogated the BMP-9-induced ERK-signaling, as well as the increase in bone resorption. In conclusion, these results show for the first time that BMP-9 directly affects human osteoclasts, enhancing bone resorption and protecting osteoclasts against apoptosis. BMP-9 signaling in human osteoclasts involves the canonical Smad-1/5/8 pathway, and the ERK pathway.     

Structures of Oligonucleotides Containing 5-(methoxymethyl)-2′-deoxyuridine Determined by NMR Spectroscopy

Abstract

Base pairing of 5-(methoxymethyl)-2′-deoxyuridine (MMdU) opposite either adenine or guanine in a seven base pair oligonucleotide duplex has been studied by NMR spectroscopy. When paired with A, we observe that the MMdU. Abase pair adopts Watson-Crick geometry. The methoxymethyl substituent is not held in a fixed conformation and may rotate around the C5-CH₂ and CH₂?O bonds. Examination of the potential energy as a function of rotation around these bonds indicates the presence of four low energy conformations. No hydrogen bonding is indicated for the methoxymethyl substituent, and the four potential minima result from reduced steric clash. For the MMdU. G base pair, the two bases adopt a wobble geometry which does not change with increasing solvent pH. Similarly, we find four low energy conformations for the methoxymethyl substituent in the major groove of the DNA helix.     

The Golgi Protein ACBD3, an Interactor for Poliovirus Protein 3A,Modulates Poliovirus Replication

We have shown that the circulating vaccine-derived polioviruses responsible for poliomyelitis outbreaks in Madagascar have recombinant genomes composed of sequences encoding capsid proteins derived from poliovaccine Sabin, mostly type 2 (PVS2), and sequences encoding nonstructural proteins derived from other human enteroviruses. Interestingly, almost all of these recombinant genomes encode a nonstructural 3A protein related to that of field coxsackievirus A17 (CV-A17) strains. Here, we investigated the repercussions of this exchange, by assessing the role of the 3A proteins of PVS2 and CV-A17 and their putative cellular partners in viral replication. We found that the Golgi protein acyl-coenzyme A binding domain-containing 3 (ACBD3), recently identified as an interactor for the 3A proteins of several picornaviruses, interacts with the 3A proteins of PVS2 and CV-A17 at viral RNA replication sites, in human neuroblastoma cells infected with either PVS2 or a PVS2 recombinant encoding a 3A protein from CV-A17 [PVS2-3A(CV-A17)]. The small interfering RNA-mediated downregulation of ACBD3 significantly increased the growth of both viruses, suggesting that ACBD3 slowed viral replication. This was confirmed with replicons. Furthermore, PVS2-3A(CV-A17) was more resistant to the replication-inhibiting effect of ACBD3 than the PVS2 strain, and the amino acid in position 12 of 3A was involved in modulating the sensitivity of viral replication to ACBD3. Overall, our results indicate that exchanges of nonstructural proteins can modify the relationships between enterovirus recombinants and cellular interactors and may thus be one of the factors favoring their emergence.     

A new molecular evolution model for limited insertion independent of substitution

We recently introduced a new molecular evolution model called the IDIS model for Insertion Deletion Independent of Substitution  and . In the IDIS model, the three independent processes of substitution, insertion and deletion of residues have constant rates. In order to control the genome expansion during evolution, we generalize here the IDIS   model by introducing an insertion rate which decreases when the sequence grows and tends to 0 for a maximum sequence length _nmax$n_{\max }$.     

Effect of weight loss,independent of change in diet composition,on apolipoprotein AI kinetic in men with metabolic syndrome

We investigated the effect of weight loss, independent of change in diet composition, on HDL and apoAI metabolism in men with metabolic syndrome (MetS). Subjects (19 men with MetS [NCEP-ATPIII]) were fed an isoenergetic Mediterranean-style diet for 5 weeks (all foods provided). Participants then underwent a 20-week free-living period during which they were counseled to restrict energy intake, after which they were again fed an isoenergetic Mediterranean-style diet for 5 weeks. At the end of the two controlled diets, participants received a single bolus of [5,5,5-²H₃] _L-leucine, and fasting blood samples were collected over a 96 h period. ApoAI kinetic was assessed using multicompartmental modeling of the tracer enrichment data. Participants achieved a 9.1 ± 2.8% reduction in body weight (P < 0.001). Weight loss resulted in an increase in plasma HDL-cholesterol (HDL-C) concentrations of 6.0% (P = 0.059) and HDL₃-C of 7.9% (P = 0.045), attributable to a reduction in apoAI fractional catabolic rate (−7.8%; P = 0.046) with no change in apoAI production rate (2.2%; P = 0.58). These data indicate that weight loss, independent of variation in diet composition, increases plasma HDL primarily by delaying the catabolism of apoAI.     

Conjugative Transfer and cis-Mobilization of a Genomic Island by an Integrative and Conjugative Element of Streptococcus agalactiae

Putative integrative and conjugative elements (ICEs), i.e., genomic islands which could excise, self-transfer by conjugation, and integrate into the chromosome of the bacterial host strain, were previously identified by in silico analysis in the sequenced genomes of Streptococcus agalactiae (M. Brochet et al., J. Bacteriol. 190:6913–6917, 2008). We investigated here the mobility of the elements integrated into the 3′ end of a tRNA^Lys gene. Three of the four putative ICEs tested were found to excise but only one (ICE_515_tRNA^Lys) was found to transfer by conjugation not only to S. agalactiae strains but also to a Streptococcus pyogenes strain. Transfer was observed even if recipient cell already carries a related resident ICE or a genomic island flanked by attL and attR recombination sites but devoid of conjugation or recombination genes (CIs-Mobilizable Element [CIME]). The incoming ICE preferentially integrates into the 3′ end of the tRNA^Lys gene (i.e., the attR site of the resident element), leading to a CIME-ICE structure. Transfer of the whole composite element CIME-ICE was obtained, showing that the CIME is mobilizable in cis by the ICE. Therefore, genomic islands carrying putative virulence genes but lacking the mobility gene can be mobilized by a related ICE after site-specific accretion.