Parallel evolution and phenotypic divergence in lichenized fungi: a case study in the lichen-forming fungal family Graphidaceae (Ascomycota: Lecanoromycetes: Ostropales)

A molecular phylogeny of combined mtSSU, nuLSU, and RPB2 data revealed previously unrecognized levels of parallel evolution and phenotypic divergence in the lichen family Graphidaceae. Five clades were supported within the family: the Fissurina, Ocellularia, Graphis, Topeliopsis, and Thelotrema clades, containing 33 of the 42 currently accepted genera within the family. The results for the first time provide a fully resolved phylogeny of this family and confirm the synonymy of Graphidaceae and Thelotremataceae. Ancestral character state reconstruction using likelihood, Bayesian, and parsimony approaches indicate that lirellate ascomata evolved independently in each of the five clades. Carbonized ascomata evolved independently in at least four of the five clades. An unexpected result was the independent evolution of columella structures in the Fissurina and Ocellularia clades. Besides these more general findings, we document several cases in which evolution of several traits in parallel resulted in striking look-alikes within unrelated lineages, such as Topeliopsismuscigena and Chapsameridensis in the Topeliopsis and Thelotrema clades, Leptotremawightii, Myriotremalaeviusculum, and Leucodectonphaeosporum in the Ocellularia and Thelotrema clades, Ocellulariastylothecia and Melanotremameiosporum in the Fissurina and Ocellularia clades, and Myriotremapycnoporellum, Myriotremaclandestinum and Wirthiotremaglaucopallens in the Fissurina, Ocellularia, and Topeliopsis clades. Pagel's test of independent character evolution suggested that at least for some of the traits involved in these cases, ecological constraints may have caused their evolution in parallel. The most intriguing find is the correlation between gall-forming thalli and vertical columns of calcium oxalate crystals, suggesting that these crystals do not function as light distributors, as previously assumed, but instead stabilize the thalli which are usually hollow beneath, similar to a dome-shaped structure. Ancestral character state reconstruction together with an approach to visualize the phenotype of putative ancestral lineages suggested the alpha-Graphidaceae to resemble some of the extant species currently classified in Myriotrema s.lat., with pore-like ascomata, and non-amyloid ascospores with lens-shaped lumina.     

Structure and dynamics of the mammalian ribosomal pretranslocation complex

Although the structural core of the ribosome is conserved in all kingdoms of life, eukaryotic ribosomes are significantly larger and more complex than their bacterial counterparts. The extent to which these differences influence the molecular mechanism of translation remains elusive. Multiparticle cryo-electron microscopy and single-molecule FRET investigations of the mammalian pretranslocation complex reveal spontaneous, large-scale conformational changes, including an intersubunit rotation of the ribosomal subunits. Through structurally related processes, tRNA substrates oscillate between classical and at least two distinct hybrid configurations facilitated by localized changes in their L-shaped fold. Hybrid states are favored within the mammalian complex. However, classical tRNA positions can be restored by tRNA binding to the E site or by the eukaryotic-specific antibiotic and translocation inhibitor cycloheximide. These findings reveal critical distinctions in the structural and energetic features of bacterial and mammalian ribosomes, providing a mechanistic basis for divergent translation regulation strategies and species-specific antibiotic action.     

Statistical inference for stochastic simulation models--theory and application

Statistical models are the traditional choice to test scientific theories when observations, processes or boundary conditions are subject to stochasticity. Many important systems in ecology and biology, however, are difficult to capture with statistical models. Stochastic simulation models offer an alternative, but they were hitherto associated with a major disadvantage: their likelihood functions can usually not be calculated explicitly, and thus it is difficult to couple them to well-established statistical theory such as maximum likelihood and Bayesian statistics. A number of new methods, among them Approximate Bayesian Computing and Pattern-Oriented Modelling, bypass this limitation. These methods share three main principles: aggregation of simulated and observed data via summary statistics, likelihood approximation based on the summary statistics, and efficient sampling. We discuss principles as well as advantages and caveats of these methods, and demonstrate their potential for integrating stochastic simulation models into a unified framework for statistical modelling.     

Sulindac sulfide reverses aberrant self-renewal of progenitor cells induced by the AML-associated fusion proteins PML/RARα and PLZF/RARα

Chromosomal translocations can lead to the formation of chimeric genes encoding fusion proteins such as PML/RARα, PLZF/RARα, and AML-1/ETO, which are able to induce and maintain acute myeloid leukemia (AML). One key mechanism in leukemogenesis is increased self renewal of leukemic stem cells via aberrant activation of the Wnt signaling pathway. Either X-RAR, PML/RARα and PLZF/RARα or AML-1/ETO activate Wnt signaling by upregulating γ-catenin and β-catenin. In a prospective study, a lower risk of leukemia was observed with aspirin use, which is consistent with numerous studies reporting an inverse association of aspirin with other cancers. Furthermore, a reduction in leukemia risk was associated with use of non-steroidal anti-inflammatory drug (NSAID), where the effects on AML risk was FAB subtype-specific. To better investigate whether NSAID treatment is effective, we used Sulindac Sulfide in X-RARα-positive progenitor cell models. Sulindac Sulfide (SSi) is a derivative of Sulindac, a NSAID known to inactivate Wnt signaling. We found that SSi downregulated both β-catenin and γ-catenin in X-RARα-expressing cells and reversed the leukemic phenotype by reducing stem cell capacity and increasing differentiation potential in X-RARα-positive HSCs. The data presented herein show that SSi inhibits the leukemic cell growth as well as hematopoietic progenitors cells (HPCs) expressing PML/RARα, and it indicates that Sulindac is a valid molecular therapeutic approach that should be further validated using in vivo leukemia models and in clinical settings.     

Mobilisation of hematopoietic CD34+ precursor cells in patients with acute stroke is safe--results of an open-labeled non randomized phase I/II trial

Background

Regenerative strategies in the treatment of acute stroke may have great potential. Hematopoietic growth factors mobilize hematopoietic stem cells and may convey neuroprotective effects. We examined the safety, potential functional and structural changes, and CD34⁺ cell–mobilization characteristics of G-CSF treatment in patients with acute ischemic stroke.

Methods and Results

Three cohorts of patients (8, 6, and 6 patients per cohort) were treated subcutaneously with 2.5, 5, or 10 µg/kg body weight rhG-CSF for 5 consecutive days within 12 hrs of onset of acute stroke. Standard treatment included IV thrombolysis. Safety monitoring consisted of obtaining standardized clinical assessment scores, monitoring of CD34⁺ stem cells, blood chemistry, serial neuroradiology, and neuropsychology. Voxel-guided morphometry (VGM) enabled an assessment of changes in the patients'' structural parenchyma. 20 patients (mean age 55 yrs) were enrolled in this study, 5 of whom received routine thrombolytic therapy with r-tPA. G-CSF treatment was discontinued in 4 patients because of unrelated adverse events. Mobilization of CD34⁺ cells was observed with no concomitant changes in blood chemistry, except for an increase in the leukocyte count up to 75,500/µl. Neuroradiological and neuropsychological follow-up studies did not disclose any specific G-CSF toxicity. VGM findings indicated substantial atrophy of related hemispheres, a substantial increase in the CSF space, and a localized increase in parenchyma within the ischemic area in 2 patients.

Conclusions

We demonstrate a good safety profile for daily administration of G-CSF when begun within 12 hours after onset of ischemic stroke and, in part in combination with routine IV thrombolysis. Additional analyses using VGM and a battery of neuropsychological tests indicated a positive functional and potentially structural effect of G-CSF treatment in some of our patients.

Trial Registration

German Clinical Trial Register DRKS 00000723