Naturally occurring autoantibodies against beta-amyloid: investigating their role in transgenic animal and in vitro models of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder primarily affecting regions of the brain responsible for higher cognitive functions. Immunization against β-amyloid (Aβ) in animal models of AD has been shown to be effective on the molecular level but also on the behavioral level. Recently, we reported naturally occurring autoantibodies against Aβ (NAbs-Aβ) being reduced in Alzheimer's disease patients. Here, we further investigated their physiological role: in epitope mapping studies, NAbs-Aβ recognized the mid-/C-terminal end of Aβ and preferentially bound to oligomers but failed to bind to monomers/fibrils. NAbs-Aβ were able to interfere with Aβ peptide toxicity, but NAbs-Aβ did not readily clear senile plaques although early fleecy-like plaques were reduced. Administration of NAbs-Aβ in transgenic mice improved the object location memory significantly, almost reaching performance levels of wild-type control mice. These findings suggest a novel physiological mechanism involving NAbs-Aβ to dispose of proteins or peptides that are prone to forming toxic aggregates

Loss of Roquin induces early death and immune deregulation but not autoimmunity

Deletion of Roquin in T or B cells, or in the entire hematopoietic system of mice, alters immune homeostasis but does not result in autoimmunity

Roquin Paralogs 1 and 2 Redundantly Repress the Icos and Ox40 Costimulator mRNAs and Control Follicular Helper T Cell Differentiation

SummaryThe Roquin-1 protein binds to messenger RNAs (mRNAs) and regulates gene expression posttranscriptionally. A single point mutation in Roquin-1, but not gene ablation, increases follicular helper T (Tfh) cell numbers and causes lupus-like autoimmune disease in mice. In T cells, we did not identify a unique role for the much lower expressed paralog Roquin-2. However, combined ablation of both genes induced accumulation of T cells with an effector and follicular helper phenotype. We showed that Roquin-1 and Roquin-2 proteins redundantly repressed the mRNA of inducible costimulator (Icos) and identified the Ox40 costimulatory receptor as another shared mRNA target. Combined acute deletion increased Ox40 signaling, as well as Irf4 expression, and imposed Tfh differentiation on CD4+ T cells. These data imply that both proteins maintain tolerance by preventing inappropriate T cell activation and Tfh cell differentiation, and that Roquin-2 compensates in the absence of Roquin-1, but not in the presence of its mutated form

Standardized, systemic phenotypic analysis reveals kidney dysfunction as main alteration of Kctd1 I27N mutant mice

Background: Increased levels of blood plasma urea were used as phenotypic parameter for establishing novel mouse models for kidney diseases on the genetic background of C3H inbred mice in the phenotype-driven Munich ENU mouse mutagenesis project. The phenotypically dominant mutant line HST014 was established and further analyzed. Methods: Analysis of the causative mutation as well as the standardized, systemic phenotypic analysis of the mutant line was carried out. Results: The causative mutation was detected in the potassium channel tetramerization domain containing 1 (Kctd1) gene which leads to the amino acid exchange Kctd1 I27N thereby affecting the functional BTB domain of the protein. This line is the first mouse model harboring a Kctd1 mutation. Kctd1 I27N homozygous mutant mice die perinatally. Standardized, systemic phenotypic analysis of Kctd1 I27N heterozygous mutants was carried out in the German Mouse Clinic (GMC). Systematic morphological investigation of the external physical appearance did not detect the specific alterations that are described in KCTD1 mutant human patients affected by the scalp-ear-nipple (SEN) syndrome. The main pathological phenotype of the Kctd1 I27N heterozygous mutant mice consists of kidney dysfunction and secondary effects thereof, without gross additional primary alterations in the other phenotypic parameters analyzed. Genome-wide transcriptome profiling analysis at the age of 4 months revealed about 100 differentially expressed genes (DEGs) in kidneys of Kctd1 I27N heterozygous mutants as compared to wild-type controls. Conclusions: In summary, the main alteration of the Kctd1 I27N heterozygous mutants consists in kidney dysfunction. Additional analyses in 9–21 week-old heterozygous mutants revealed only few minor effects

Claudin-12 is not required for blood-brain barrier tight junction function

Background The blood-brain barrier (BBB) ensures central nervous system (CNS) homeostasis by strictly controlling the passage of molecules and solutes from the bloodstream into the CNS. Complex and continuous tight junctions (TJs) between brain endothelial cells block uncontrolled paracellular diffusion of molecules across the BBB, with claudin-5 being its dominant TJs protein. However, claudin-5 deficient mice still display ultrastructurally normal TJs, suggesting the contribution of other claudins or tight-junction associated proteins in establishing BBB junctional complexes. Expression of claudin-12 at the BBB has been reported, however the exact function and subcellular localization of this atypical claudin remains unknown. Methods We created claudin-12-lacZ-knock-in C57BL/6J mice to explore expression of claudin-12 and its role in establishing BBB TJs function during health and neuroinflammation. We furthermore performed a broad standardized phenotypic check-up of the mouse mutant. Results Making use of the lacZ reporter allele, we found claudin-12 to be broadly expressed in numerous organs. In the CNS, expression of claudin-12 was detected in many cell types with very low expression in brain endothelium. Claudin-12(lacZ/lacZ) C57BL/6J mice lacking claudin-12 expression displayed an intact BBB and did not show any signs of BBB dysfunction or aggravated neuroinflammation in an animal model for multiple sclerosis. Determining the precise localization of claudin-12 at the BBB was prohibited by the fact that available anti-claudin-12 antibodies showed comparable detection and staining patterns in tissues from wild-type and claudin-12(lacZ/lacZ) C57BL/6J mice. Conclusions Our present study thus shows that claudin-12 is not essential in establishing or maintaining BBB TJs integrity. Claudin-12 is rather expressed in cells that typically lack TJs suggesting that claudin-12 plays a role other than forming classical TJs. At the same time, in depth phenotypic screening of clinically relevant organ functions of claudin-12(lacZ/lacZ) C57BL/6J mice suggested the involvement of claudin-12 in some neurological but, more prominently, in cardiovascular functions

Epigallocatechin gallate (EGCG) reduces the intensity of pancreatic amyloid fibrils in human islet amyloid polypeptide (hIAPP) transgenic mice

The formation of amyloid fibrils by human islet amyloid polypeptide protein (hIAPP) has been implicated in pancreas dysfunction and diabetes. However, efficient treatment options to reduce amyloid fibrils in vivo are still lacking. Therefore, we tested the effect of epigallocatechin gallate (EGCG) on fibril formation in vitro and in vivo. To determine the binding of hIAPP and EGCG, in vitro interaction studies were performed. To inhibit amyloid plaque formation in vivo, homozygous (tg/tg), hemizygous (wt/tg), and control mice (wt/wt) were treated with EGCG. EGCG bound to hIAPP in vitro and induced formation of amorphous aggregates instead of amyloid fibrils. Amyloid fibrils were detected in the pancreatic islets of tg/tg mice, which was associated with disrupted islet structure and diabetes. Although pancreatic amyloid fibrils could be detected in wt/tg mice, these animals were non-diabetic. EGCG application decreased amyloid fibril intensity in wt/tg mice, however it was ineffective in tg/tg animals. Our data indicate that EGCG inhibits amyloid fibril formation in vitro and reduces fibril intensity in non-diabetic wt/tg mice. These results demonstrate a possible in vivo effectiveness of EGCG on amyloid formation and suggest an early therapeutical application

A large scale hearing loss screen reveals an extensive unexplored genetic landscape for auditory dysfunction

The developmental and physiological complexity of the auditory system is likely reflected in the underlying set of genes involved in auditory function. In humans, over 150 non-syndromic loci have been identified, and there are more than 400 human genetic syndromes with a hearing loss component. Over 100 non-syndromic hearing loss genes have been identified in mouse and human, but we remain ignorant of the full extent of the genetic landscape involved in auditory dysfunction. As part of the International Mouse Phenotyping Consortium, we undertook a hearing loss screen in a cohort of 3006 mouse knockout strains. In total, we identify 67 candidate hearing loss genes. We detect known hearing loss genes, but the vast majority, 52, of the candidate genes were novel. Our analysis reveals a large and unexplored genetic landscape involved with auditory function

A comprehensive and comparative phenotypic analysis of the collaborative founder strains identifies new and known phenotypes.

The collaborative cross (CC) is a large panel of mouse-inbred lines derived from eight founder strains (NOD/ShiLtJ, NZO/HILtJ, A/J, C57BL/6J, 129S1/SvImJ, CAST/EiJ, PWK/PhJ, and WSB/EiJ). Here, we performed a comprehensive and comparative phenotyping screening to identify phenotypic differences and similarities between the eight founder strains. In total, more than 300 parameters including allergy, behavior, cardiovascular, clinical blood chemistry, dysmorphology, bone and cartilage, energy metabolism, eye and vision, immunology, lung function, neurology, nociception, and pathology were analyzed; in most traits from sixteen females and sixteen males. We identified over 270 parameters that were significantly different between strains. This study highlights the value of the founder and CC strains for phenotype-genotype associations of many genetic traits that are highly relevant to human diseases. All data described here are publicly available from the mouse phenome database for analyses and downloads

CIP2A Promotes T-Cell Activation and Immune Response to Listeria monocytogenes Infection

The oncoprotein Cancerous Inhibitor of Protein Phosphatase 2A ( CIP2A) is overexpressed in most malignancies and is an obvious candidate target protein for future cancer therapies. However, the physiological importance of CIP2A-mediated PP2A inhibition is largely unknown. As PP2A regulates immune responses, we investigated the role of CIP2A in normal immune system development and during immune response in vivo. We show that CIP2A-deficient mice (CIP2A(HOZ)) present a normal immune system development and function in unchallenged conditions. However when challenged with Listeria monocytogenes, CIP2A(HOZ) mice display an impaired adaptive immune response that is combined with decreased frequency of both CD4(+) T-cells and CD8(+) effector T-cells. Importantly, the cell autonomous effect of CIP2A deficiency for T-cell activation was confirmed. Induction of CIP2A expression during T-cell activation was dependent on Zap70 activity. Thus, we reveal CIP2A as a hitherto unrecognized mediator of T-cell activation during adaptive immune response. These results also reveal CIP2A(HOZ) as a possible novel mouse model for studying the role of PP2A activity in immune regulation. On the other hand, the results also indicate that CIP2A targeting cancer therapies would not cause serious immunological side-effects.Peer reviewe