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At the moment, cataract, which is the opacification of the eye’s lens, can only be treated by surgery. In order to develop and test new pharmacological treatment strategies for the disease, there is a need for an appropriate in vitro model using ex vivo animal lenses. In this study, porcine lenses were incubated in either culture medium, glucose, triamcinolone acetonide, sodium chloride, hydrogen peroxide, sodium selenite, neutral buffered formalin, or were exposed to microwave heating to experimentally induce lens opacification. Changes in the lens morphology, weight, size, and elasticity were monitored 7 days after treatment. The fastest induction of dense opacification was seen in lenses exposed to sodium chloride, neutral buffered formalin, and microwave heating. No change in the size and weight of the lenses were detected, whereas loss in elasticity could be detected in lenses treated with formalin solution or microwave heating. Thus, neutral buffered formalin- and microwave-treated ex vivo porcine lenses seem to be a suitable model for mature cataracts, whereas hypertonic sodium chloride may be useful for studies on osmolarity-induced lens opacification.

The premature aging disease Hutchinson-Gilford Progeria Syndrome (HGPS) is caused by a mutant lamin A (LA∆50). Nuclei in cells expressing LA∆50 are abnormally shaped and display a loss of heterochromatin. To determine the mechanisms responsible for the loss of heterochromatin, epigenetic marks regulating either facultative or constitutive heterochromatin were examined. In cells from a female HGPS patient, histone H3 trimethylated on lysine 27 (H3K27me3), a mark for facultative heterochromatin, is lost on the inactive X chromosome (Xi). The methyltransferase responsible for this mark, EZH2, is also down-regulated. These alterations are detectable before the changes in nuclear shape that are considered to be the pathological hallmarks of HGPS cells. The results also show a down-regulation of the pericentric constitutive heterochromatin mark, histone H3 trimethylated on lysine 9, and an altered association of this mark with heterochromatin protein la (Hpla) and the CREST antigen. This loss of constitutive heterochromatin is accompanied by an up-regulation of pericentric satellite III repeat transcripts. In contrast to these decreases in histone H3 methylation states, there is an increase in the trimethylation of histone H4K20, an epigenetic mark for constitutive heterochromatin. Expression of LA∆50 in normal cells induces changes in histone methylation patterns similar to those seen in HGPS cells. The epigenetic changes described most likely represent molecular mechanisms responsible for the rapid progression of premature aging in HGPS patients.

Lamins form stable filaments at the nuclear periphery in metazoans. Unlike B-type lamins, lamins A and C localize also in the nuclear interior, where they interact with lamin-associated polypeptide 2 alpha (LAP2α). Using antibody labeling, we previously observed a depletion of nucleoplasmic A-type lamins in mouse cells lacking LAP2α. Here, we show that loss of LAP2α actually causes formation of larger, biochemically stable lamin A/C structures in the nuclear interior that are inaccessible to lamin A/C antibodies. While nucleoplasmic lamin A forms from newly expressed pre-lamin A during processing and from soluble mitotic lamins in a LAP2α-independent manner, binding of LAP2α to lamin A/C during interphase inhibits formation of higher order structures, keeping nucleoplasmic lamin A/C in a mobile state independent of lamin A/C S22 phosphorylation. We propose that LAP2α is essential to maintain a mobile lamin A/C pool in the nuclear interior, which is required for proper nuclear functions.

Mutations in the gene encoding nuclear lamin A (LA) cause the premature aging disease Hutchinson-Gilford Progeria Syndrome. The most common of these mutations results in the expression of a mutant LA, with a 50-aa deletion within its C terminus. In this study, we demonstrate that this deletion leads to a stable farnesylation and carboxymethylation of the mutant LA (LAΔ50/progerin). These modifications cause an abnormal association of LAΔ50/progerin with membranes during mitosis, which delays the onset and progression of cytokinesis. Furthermore, we demonstrate that the targeting of nuclear envelope/lamina components into daughter cell nuclei in early G₁ is impaired in cells expressing LAΔ50/progerin. The mutant LA also appears to be responsible for defects in the retinoblastoma protein-mediated transition into S-phase, most likely by inhibiting the hyperphosphorylation of retinoblastoma protein by cyclin D1/cdk4. These results provide insights into the mechanisms responsible for premature aging and also shed light on the role of lamins in the normal process of human aging.

It took more than 100 years before it was established that the proteins that form intermediate filaments (IFs) comprise a unified protein family, the members of which are ubiquitous in virtually all differentiated cells and present both in the cytoplasm and in the nucleus. However, during the past 2 decades, knowledge regarding the functions of these structures has been expanding rapidly. Many disease-related roles of IFs have been revealed. In some cases, the molecular mechanisms underlying these diseases reflect disturbances in the functions traditionally assigned to IFs, i.e., maintenance of structural and mechanical integrity of cells and tissues. However, many disease conditions seem to link to the nonmechanical functions of IFs, many of which have been defined only in the past few years.

X-linked hypophosphatemia (XLH) is a rare genetic disorder characterized by renal phosphate wasting, leading to rickets in children and osteomalacia in adults. An underrecognized symptom in adults with XLH is enthesopathy, leading to pain and reduced quality of life. Although enthesopathies primarily affect tendon insertions, they are closely linked to the underlying bone pathology of XLH, reflecting mineralization defects characteristic of osteomalacia. This study aimed to determine the prevalence of enthesopathies in XLH patients using ultrasound and assess their association with pain and physical function. This cross-sectional study included 26 XLH patients (mean age: 37.9 ± 17.1 yr, 76.9% female). Ultrasound examinations assessed 6 tendons of the upper and 10 tendons of the lower extremity in adolescents and adults with XLH. Laboratory tests included phosphate, alkaline phosphatase, and i-FGF23 levels. Physical performance was evaluated using the 6-min walk test (6MWT) and the chair rising test. Pain was assessed using the brief pain inventory. Enthesopathies were detected by ultrasound in 84.6% of patients, affecting predominantly the lower extremities (80.8%) but also the upper extremities (50%). The quadriceps and achilles tendons were the most frequently affected sites. Enthesopathy prevalence increased with age (r = 0.61, p < .05) and negatively correlated with 6MWT performance (r = −0.4, p = .04). No significant association was found between enthesopathies and BMI or pain scores. Based on the worst pain scale, 73.1% of patients reported mild pain. Inter-rater agreement for ultrasound assessment was good to very good/excellent. Enthesopathies of the lower, but also upper extremities are common features of XLH. Their presence correlates with reduced mobility, emphasizing the need for targeted interventions. The exact pathophysiological mechanisms remain unclear, but age appears to be a key factor.

Abstract Little is known about the contribution of 3D surface geometry to the development of multilayered tissues containing fibrous extracellular matrix components, such as those found in bone. In this study, we elucidate the role of curvature in the formation of chiral, twisted-plywood-like structures. Tissues consisting of murine preosteoblast cells (MC3T3-E1) were grown on 3D scaffolds with constant-mean curvature and negative Gaussian curvature for up to 32 days. Using 3D fluorescence microscopy, the influence of surface curvature on actin stress-fiber alignment and chirality was investigated. To gain mechanistic insights, we did experiments with MC3T3-E1 cells deficient in nuclear A-type lamins or treated with drugs targeting cytoskeleton proteins. We find that wild-type cells form a thick tissue with fibers predominantly aligned along directions of negative curvature, but exhibiting a twist in orientation with respect to older tissues. Fiber orientation is conserved below the tissue surface, thus creating a twisted-plywood-like material. We further show that this alignment pattern strongly depends on the structural components of the cells (A-type lamins, actin, and myosin), showing a role of mechanosensing on tissue organization. Our data indicate the importance of substrate curvature in the formation of 3D tissues and provide insights into the emergence of chirality.

The Haplobank contains over 100,000 individually reversibly mutagenized, barcoded, mouse embryonic cell lines; proof-of-principle experiments were used to search for genes that are required for rhinovirus infection and angiogenesis using forward and reverse genetic screens, respectively. A biobank of genomic proportions Heterogeneity among clones of mouse embryonic stem cells, as well as the presence of two copies of the genomes in such cells, can impede genomic screens. Josef Penninger and colleagues have prepared a biobank of more than 100,000 clones that target nearly 17,000 genes in a conditional and reversible fashion. They showcase the power and versatility of the 'Haplobank' for studying the role of essential genes in mouse embryonic stem cells, to uncover genes that mediate the rhinovirus-induced inflammatory response and to identify novel genes that control angiogenesis and the specification of blood vessel lineage. The ability to directly uncover the contributions of genes to a given phenotype is fundamental for biology research. However, ostensibly homogeneous cell populations exhibit large clonal variance 1 , 2 that can confound analyses and undermine reproducibility 3 . Here we used genome-saturated mutagenesis to create a biobank of over 100,000 individual haploid mouse embryonic stem (mES) cell lines targeting 16,970 genes with genetically barcoded, conditional and reversible mutations. This Haplobank is, to our knowledge, the largest resource of hemi/homozygous mutant mES cells to date and is available to all researchers. Reversible mutagenesis overcomes clonal variance by permitting functional annotation of the genome directly in sister cells. We use the Haplobank in reverse genetic screens to investigate the temporal resolution of essential genes in mES cells, and to identify novel genes that control sprouting angiogenesis and lineage specification of blood vessels. Furthermore, a genome-wide forward screen with Haplobank identified PLA2G16 as a host factor that is required for cytotoxicity by rhinoviruses, which cause the common cold. Therefore, clones from the Haplobank combined with the use of reversible technologies enable high-throughput, reproducible, functional annotation of the genome.

The ability to directly uncover the contributions of genes to a given phenotype is fundamental for biology research. However, ostensibly homogeneous cell populations exhibit large clonal variance1,2 that can confound analyses and undermine reproducibility3. Here, we used genome-saturated mutagenesis to create a biobank of over 100,000 individual haploid murine embryonic stem cell (mESC) lines targeting 16,950 genes with genetically bar-coded, conditional and reversible mutations. This Haplobank is the largest resource of hemi-/homozygous mutant mESCs to date and is available to all researchers. Reversible mutagenesis overcomes clonal variance by permitting functional annotation of the genome directly in sister cells. We utilize Haplobank in reverse genetic screens to investigate the temporal resolution of essential genes in mESCs, and to identify novel genes that control sprouting angiogenesis and blood vessel lineage specification. Further, a genome-wide forward screen with Haplobank identified PLA2G16 as a host factor required for cytotoxicity by rhinoviruses, which cause the common cold. Thus, Haplobank clones and revertible technologies enable high-throughput, reproducible functional annotation of the genome.

It is not well established to what extent previous immunizations offer protection against infections with the SARS-CoV-2 Omicron variant in dialysis patients. We aimed to define the relevant humoral response in dialysis patients using a SARS-CoV-2 IgG chemiluminescence microparticle immunoassay (CMIA) compared to the activity of neutralizing antibodies assessed by a virus neutralization test. Next, we aimed to determine differences in humoral and cellular response levels over time among patients infected or not infected by the Omicron variant of SARS-CoV-2. Immunological parameters of cellular and humoral response to SARS-CoV-2 were analyzed at baseline and after 3 (T3), 6 (T6) and 14 months (T14). In this monocentric cohort study, we followed 110 dialysis patients (mean age 68.4 ± 13.7 years, 60.9% male) for a median of 545 days. We determined an anti-SARS-CoV-2 IgG level of 56.7 BAU/mL as an ideal cut-off value with a J-index of 90.7. Patients infected during the Omicron era had significantly lower (p < 0.001) mean antibody levels at T0 (3.5 vs. 111.2 BAU/mL), T3 (269.8 vs. 699.8 BAU/mL) and T6 (260.2 vs. 513.9 BAU/mL) than patients without Omicron infection. Patients who developed higher antibody levels at the time of the basic immunizations were less likely to become infected with SARS-CoV-2 during the Omicron era. There is a need to adjust the cut-off values for anti-SARS-CoV-2 IgG levels in dialysis patients.