Trans-seeding of Alzheimer-related tau protein by a yeast prion

Abnormal tau protein aggregates constitute a hallmark of Alzheimer's disease. The mechanisms underlying the initiation of tau aggregation in sporadic neurodegeneration remain unclear. Here we investigate whether a non-human prion can seed tau aggregation. Due to their structural similarity with tau aggregates, we chose Sup35NM yeast prion domain fibrils for explorative tau seedings. Upon in vitro incubation with tau monomers, Sup35NM fibrils promoted the formation of morphologically distinct tau fibril strains. In vivo, intrahippocampal inoculation of Sup35NM fibrils accentuated tau pathology in P301S tau transgenic mice. Thus, our results provide first in vivo evidence for heterotypic cross-species seeding of a neurodegenerative human prion-like protein by a yeast prion. This opens up the conceptual perspective that non-mammalian prions present in the human microbiome could be involved in the initiation of protein misfolding in neurodegenerative disorders, a mechanism for which we propose the term "trans-seeding."

P909Echocardiographic Assessment of Left Ventricular Function in Patients with Aortic Stenosis and the short-term effects after intervention

Introduction

Aortic stenosis (AS) is the most prevalent form of acquired valvular heart disease, it affects ∼2% of people aged over 75. Series of compensatory mechanisms occur, in order for LV to adapt to high pressure overload. Aortic valve replacement has been the mainstay AS treatment either surgically or percutaneously. The evaluation of myocardial strains after Transcatheter Aortic Valve Implantation (TAVI) and Surgical Aortic Valve Replacement (SAVR) is still underexplored and there is no single study to date scouting the difference between TAVI and SAVR.

Aim

To assess the impact of unloading LV after TAVI and SAVR on LV remodelling.

Methods

In this prospective study, we have recruited 111 patients (75±11 years, 63% were females) with varying degrees of aortic stenosis. Of the 111 patients, 43 patients and 11 patients underwent TAVI and SAVR respectively between November 2017 and May 2018. Demographics, clinical and echocardiographic measurements along with speckle tracking parameters were recorded for all participants and again 4±2 weeks after intervention.

Results

Pre-TAVI LV-GLS mean was −10.8±3.5% and after implantation of aortic prosthesis immediate improvement of the myocardial deformation to −13.98±2.9% was observed after one month of the intervention, mean difference of −3.16% following procedure. There was an evidence of significant improvement in LV-GRS after TAVI (44.86±12.9% to 49.77±10.8%, P value= 0.047). Per contra, when comparing pre and post TAVI LV-GCS, no statistical evidence was noted. However, a difference of −2.4% in GCS following the intervention might be clinically important, but no previous evidence can support this. This is attributed to the poor reproducibility and yet not available standardisation.

Table 1 Variables TAVI (n=43) SAVR (n=11) P value† Pre Post P* value Pre Post P* value GLS (%) −10.82±3.5 −13.98±2.9 <0.001 −12.75±4.3 −16.1±2 0.021 0.152 GCS (%) −30.1±8.1 −32.49±9.2 0.134 −27±9.8 −33.9±4.69 0.063 0.062 GRS (%) 44.86±12.9 49.77±10.8 0.047 36.6±13.3 44.97±4.9 0.074 0.058 Data are expressed as mean ± SD. Comparisons were performed using paired Student's t tests. *Pre and post intervention. †Post TAVI vs. post SAVR. Comparison done using unpaired t test of the differences.

Conclusion

Significant improvement was evident in myocardial deformation parameters – in particular GLS – after weeks of the intervention demonstrating a strong evidence of reversed remodelling following SAVR and TAVI.

GLUT1 mutations are a rare cause of familial idiopathic generalized epilepsy

OBJECTIVE

The idiopathic generalized epilepsies (IGE) are the most common genetically determined epilepsies. However, the underlying genes are largely unknown. We screened the SLC2A1 gene, encoding the glucose transporter type 1 (GLUT1), for mutations in a group of 95 European patients with familial IGE.

METHODS

The affected individuals were examined clinically by EEG and brain imaging. The coding regions of SLC2A1 were sequenced in the index cases of all families. Wild-type and mutant transporters were expressed and functionally characterized in Xenopus laevis oocytes.

RESULTS

We detected a novel nonsynonymous SLC2A1 mutation (c.694C>T, p.R232C) in one IGE family. Nine family members were affected mainly by absence epilepsies with a variable age at onset, from early childhood to adulthood. Childhood absence epilepsy in one individual evolved into juvenile myoclonic epilepsy. Eight affected and 4 unaffected individuals carried the mutation, revealing a reduced penetrance of 67%. The detected mutation was not found in 846 normal control subjects. Functional analysis revealed a reduced maximum uptake velocity for glucose, whereas the affinity to glucose and the protein expression were not different in wild-type and mutant transporters.

CONCLUSION

Our study shows that GLUT1 defects are a rare cause of classic IGE. SLC2A1 screening should be considered in IGE featuring absence epilepsies with onset from early childhood to adult life, because this diagnosis may have important implications for treatment and genetic counseling.

Whole-genome linkage scan for epilepsy-related photosensitivity: a mega-analysis

Photoparoxysmal response (PPR) is considered to be a risk factor for idiopathic generalised epilepsy (IGE) and it has a strong genetic basis. Two genome-wide linkage studies have been published before and they identified loci for PPR at 6p21, 7q32, 13q13, 13q31 and 16p13. Here we combine these studies, augmented with additional families, in a mega-analysis of 100 families. Non-parametric linkage analysis identified three suggestive peaks for photosensitivity, two of which are novel (5q35.3 and 8q21.13) and one has been found before (16p13.3). We found no evidence for linkage at four previously detected loci (6p21, 7q32, 13q13 and 13q31). Our results suggest that the different family data sets are not linked to a shared locus. Detailed analysis showed that the peak at 16p13 was mainly supported by a single subset of families, while the peaks at 5q35 and 8q21 had weak support from multiple subsets. Family studies clearly support the role of PPR as a risk factor for IGE. This mega-analysis shows that distinct loci seem to be linked to subsets of PPR-positive families that may differ in subtle clinical phenotypes or geographic origin. Further linkage studies of PPR should therefore include in-depth phenotyping to make appropriate subsets and increase genetic homogeneity.

Partial agonist/antagonist properties of androstenedione and 4-androsten-3beta,17beta-diol

Androgens play important endocrine roles in development and physiology. Here, we characterize activities of two "Andro" prohormones, androstenedione (A-dione) and 4-androsten-3beta,17beta-diol (A-diol) in MDA-MB-453 (MDA) and LNCaP cells. A-dione and A-diol, like cyproterone acetate, were partial agonists of transfected mouse mammary tumor virus (MMTV) and endogenous prostate-specific antigen (PSA) promoters. Different from bicalutamide but similar to CPA, both are inducers of LNCaP cell proliferation with only mild suppression of 5alpha-dihydrotestosterone (DHT)-enhanced cell growth. Like bicalutamide and cyproterone acetate, A-dione and A-diol significantly antagonized DHT/R1881-induced PSA expression by up to 30% in LNCaP cells. Meanwhile, in MDA cells, EC(50)s for the MMTV promoter were between 10 and 100nM. Co-factor studies showed GRIP1 as most active for endogenous androgen receptor (AR), increasing MMTV transcription by up to five-fold, without substantially altering EC(50)s of DHT, A-dione or A-diol. Consistent with their transcriptional activities, A-dione and A-diol bound full-length endogenous AR from MDA or LNCaP cells with affinities of 30-70nM, although binding to expressed ligand-binding domain (LBD) was >20-fold weaker. In contrast, DHT, R1881, and bicalutamide bound similarly to LBD or aporeceptor. Together, these data suggest that A-dione and A-diol are ligands for AR with partial agonist/antagonist activities in cell-based transcription assays. Binding affinities for both are most accurately assessed by AR aporeceptor complex. In addition to being testosterone precursors in vivo, either may impart its own transcriptional regulation of AR.

Phosphorylation of the membrane proximal region of tumor necrosis factor receptor CD120a (p55) at ERK consensus sites

The interaction of tumor necrosis factor-alpha with its receptor CD120a (p55) initiates downstream signaling cascades that include the activation of the mitogen-activated protein kinase (MAPK), p42(mapk/erk2). The membrane proximal region of CD120a (p55) is Ser-, Thr-, and Pro-rich and contains four mitogen-activated protein kinase consensus phosphorylation sites. In recent work, we showed that CD120a (p55) itself is a target of phosphorylation by p42(mapk/erk2), and after phosphorylation, the receptor is redistributed from the cell surface and Golgi complex to intracellular tubular structures associated with elements of the endoplasmic reticulum. The goal of this study was to define the specific amino acid residues that are phosphorylated. Deletional mutagenesis of the cytoplasmic domain of CD120a (p55) indicated that two sites located between residues 207-254 and 250-300 were phosphorylated predominantly on Thr and Ser residues, respectively. Site-directed mutagenesis of Ser and Thr residues contained within the extracellular signal-regulated kinase (ERK) consensus sequences indicated that the preferred residues were Thr-236 and Ser-270. Primary phosphorylation at these sites appeared to enable subsequent phosphorylation at Ser-240 and Ser-244, although the level of phosphorylation of these latter two sites was less than the preferred sites. Through the use of specific ligation of CD120a (p55) alone and mice deficient in CD120a (p55), CD120b (p75), or both receptors, CD120a (p55) was shown to be necessary and sufficient for the induction of kinase activity. These findings thus suggest that the phosphorylation of Thr-236 and Ser-270 within the membrane proximal region of CD120a (p55) are the preferred sites of phosphorylation by p42(mapk/erk2) and may set in motion phosphorylation at other sites.