1,720,970 research outputs found
Pelota mediates gonocyte maturation and maintenance of spermatogonial stem cells in mouse testes
No full textPelota (Pelo) is an evolutionarily conserved gene, and its deficiency in Drosophila affects both male and female fertility. In mice, genetic ablation of Pelo leads to embryonic lethality at the early implantation stage as a result of the impaired development of extra-embryonic endoderm (ExEn). To define the consequences of Pelo deletion on male germ cells, we temporally induced deletion of the gene at both embryonic and postnatal stages. Deletion of Pelo in adult mice resulted in a complete loss of whole-germ cell lineages after 45 days of deletion. The absence of newly emerging spermatogenic cycles in mutants confirmed that spermatogonial stem cells (SSCs) were unable to maintain spermatogenesis in the absence of PELO protein. However, germ cells beyond the undifferentiated SSC stage were capable of completing spermatogenesis and producing spermatozoa, even in the absence of PELO. Following the deletion of Pelo during embryonic development, we found that although PELO is dispensable for maintaining gonocytes, it is necessary for the transition of gonocytes to SSCs. Immunohistological and protein analyses revealed the attenuation of FOXO1 transcriptional activity, which induces the expression of many SSC self-renewal genes. The decreased transcriptional activity of FOXO1 in mutant testes was due to enhanced activity of the PI3K/AKT signaling pathway, which led to phosphorylation and cytoplasmic sequestration of FOXO1. These results suggest that PELO negatively regulates the PI3K/AKT pathway and that the enhanced activity of PI3K/AKT and subsequent FOXO1 inhibition are responsible for the impaired development of SSCs in mutant testes
Respiratory Distress and Early Neonatal Lethality in Hspa4l/Hspa4 Double-Mutant Mice
No full textHeat shock proteins HSPA4L and HSPA4 are closely related members of the HSP110 family and act as cochaperones. We generated Hspa4l(-1-) Hspa4(-1-) mice to investigate a functional complementarity between HSPA4L and HSPA4 during embryonic development. Hspa4l(-1-) Hspa4(-1-) 2 embryos exhibited marked pulmonary hypoplasia and neonatal death. Compared with lungs of wild- type, Hspa4l(-1-) , and Hspa4(-1-) embryos, Hspa4l(-1-) Hspa4(-1-) lungs were characterized by diminished saccular spaces and increased mesenchymal septa. Mesenchymal hypercellularity was determined to be due to an increased cell proliferation index and decreased cell death. A significant increase in expression levels of prosurvival protein B cell leukemia/ lymphoma 2 may be the cause for inhibition of apoptotic process in lungs of Hspa4(-1-) Hspa4l(-1-) embryos. Accumulation of glycogen and diminished expression of surfactant protein B, prosurfactant protein C, and aquaporin 5 in saccular epithelium suggested impaired maturation of type II and type I pneumocytes in the Hspa4l(-1-) Hspa4(-1-) lungs. Further experiments showed a significant accumulation of ubiquitinated proteins in the lungs of Hspa4l(-1-) Hspa4(-1-) embryos, indicating an impaired chaperone activity. Our study demonstrates that HSPA4L and HSPA4 collaborate in embryonic lung maturation, which is necessary for adaptation to air breathing at birth
Genetic deletion of calcium/calmodulin-dependent protein kinase type II delta does not mitigate adverse myocardial remodeling in volume-overloaded hearts
No full textCalcium/calmodulin-dependent protein kinase type II delta (CaMKIIδ), the predominant CaMKII isoform expressed in the heart, has been implicated in the progression of myocardial infarction- and pressure overload-induced pathological remodeling. However, the role of CaMKIIδ in volume overload (VO) has not been explored. We have previously reported an activation of CaMKII during transition to HF in long-term VO. Here, we address whether CaMKIIδ is critically involved in the mortality, myocardial remodeling, and heart failure (HF) progression in response to VO. CaMKIIδ knockout (δ-KO) and wild-type (WT) littermates were exposed to aortocaval shunt-induced VO, and the progression of adverse myocardial remodeling was assessed by serial echocardiography, histological and molecular analyses. The mortality rates during 10 weeks of VO were similar in δ-KO and WT mice. Both genotypes displayed comparable eccentric myocardial hypertrophy, altered left ventricle geometry, perturbed systolic and diastolic functions after shunt. Additionally, cardiomyocytes hypertrophy, augmented myocyte apoptosis, and up-regulation of hypertrophic genes were also not significantly different in δ-KO versus WT hearts after shunt. Therefore, CaMKIIδ signaling seems to be dispensable for the progression of VO-induced maladaptive cardiac remodeling. Accordingly, we hypothesize that CaMKIIδ-inhibition as a therapeutic approach might not be helpful in the context of VO-triggered HF
Heat shock protein A4 ablation leads to skeletal muscle myopathy associated with dysregulated autophagy and induced apoptosis
No full textBACKGROUND: Molecular chaperones assist protein folding, facilitate degradation of misfolded polypeptides, and thereby maintain protein homeostasis. Impaired chaperone activity leads to defective protein quality control that is implicated in multiple skeletal muscle diseases. The heat shock protein A4 (HSPA4) acts as a co-chaperone for HSP70. Previously, we showed that Hspa4 deletion causes impaired protein homeostasis in the heart. However, its functional role in skeletal muscle has not been explored. METHODS: We performed a comparative phenotypic and biochemical analyses of Hspa4 knockout (KO) mice with wild-type (WT) littermates. RESULTS: HSPA4 is markedly upregulated in regenerating WT muscle in vivo, and in differentiated myoblasts in vitro. Hspa4-KO mice are marked by growth retardation and increased variability in body weight, accompanied by 35% mortality rates during the peri-weaning period. The surviving Hspa4-KO mice experienced progressive skeletal muscle myopathy, characterized by increased number of muscle fibers with centralized nuclei, heterogeneous myofiber size distribution, inflammatory cell infiltrates and upregulation of embryonic and perinatal myosin heavy chain transcripts. Hspa4-KO muscles demonstrated an accumulation of autophagosome-associated proteins including microtubule associated protein1 light chain 3-II (LC3-II) and p62/sequestosome accompanied by increased number of TUNEL-positive nuclei. CONCLUSIONS: Our findings underscore the indispensable role of HSPA4 in maintenance of muscle integrity through contribution in skeletal muscle autophagy and apoptosis, which might provide a novel therapeutic strategy for skeletal muscle morbidities. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12967-022-03418-3
In vivo [U-13C]glucose labeling to assess heart metabolism in murine models of pressure and volume overload
No full textAlterations in the metabolism of substrates such as glucose are integrally linked to the structural and functional changes that occur in the remodeling heart. Assessment of such metabolic changes under in vivo conditions would provide important insights into this interrelationship. We aimed to investigate glucose carbon metabolism in pressure-overload and volume-overload cardiac hypertrophy by using an in vivo [U-13C]glucose labeling strategy to enable analyses of the metabolic fates of glucose carbons in the mouse heart. Therefore, [U-13C]glucose was administered in anesthetized mice by tail vein infusion, and the optimal duration of infusion was established. Hearts were then excised for 13C metabolite isotopomer analysis by NMR spectroscopy. [U-13C]glucose infusions were performed in mice 2 wk following transverse aortic constriction (TAC) or aortocaval fistula (Shunt) surgery. At this time point, there were similar increases in left ventricular (LV) mass in both groups, but TAC resulted in concentric hypertrophy with impaired LV function, whereas Shunt caused eccentric hypertrophy with preserved LV function. TAC was accompanied by significant changes in glycolysis, mitochondrial oxidative metabolism, glucose metabolism to anaplerotic substrates, and de novo glutamine synthesis. In contrast to TAC, hardly any metabolic changes could be observed in the Shunt group. Taken together, in vivo [U-13C]glucose labeling is a valuable method to investigate the fate of nutrients such as glucose in the remodeling heart. We find that concentric and eccentric cardiac remodeling are accompanied by distinct differences in glucose carbon metabolism.NEW & NOTEWORTHY This study implemented a method for assessing the fate of glucose carbons in the heart in vivo and used this to demonstrate that pressure and volume overload are associated with distinct changes. In contrast to volume overload, pressure overload-induced changes affect the tricarboxylic acid cycle, glycolytic pathways, and glutamine synthesis. A better understanding of cardiac glucose metabolism under pathological conditions in vivo may provide new therapeutic strategies specific for different types of hemodynamic overload.</p
Zfp819, a novel KRAB-zinc finger protein, interacts with KAP1 and functions in genomic integrity maintenance of mouse embryonic stem cells
No full textAbstractPluripotency is maintained by both known and unknown transcriptional regulatory networks. In the present study, we have identified Zfp819, a KRAB-zinc finger protein, as a novel pluripotency-related factor and characterized its role in pluripotent stem cells. We show that Zfp819 is expressed highly in various types of pluripotent stem cells but not in their differentiated counterparts. We identified the presence of non-canonical nuclear localization signals in particular zinc finger motifs and identified them as responsible for the nuclear localization of Zfp819. Analysis of the Zfp819 promoter region revealed the presence of a transcriptionally active chromatin signature. Moreover, we confirmed the binding of pluripotency-related factors, Oct4, Sox2, and Nanog to the distal promoter region of Zfp819, indicating that the expression of this gene is regulated by a pluripotency transcription factor network. We found that the expression of endogenous retroviral elements (ERVs) such as Intracisternal A Particle (IAP) retrotransposons, Long Interspersed Nuclear Elements (LINE1), and Short Interspersed Nuclear Elements (SINE B1) is significantly upregulated in Zfp819-knockdown (Zfp819_KD) cells. In line with the activation of ERVs, we observed the occurrence of spontaneous DNA damage in Zfp819_KD cells. Furthermore, we tested whether Zfp819 can interact with KAP1, a KRAB-associated protein with a transcriptional repression function, and found the interaction between these two proteins in both in vitro and in vivo experiments. The challenging of Zfp819_KD cells with DNA damaging agent revealed that these cells are inefficient in repairing the damaged DNA, as cells showed presence of γH2A.X foci for a prolonged time. Collectively, our study identified Zfp819 as a novel pluripotency-related factor and unveiled its function in genomic integrity maintenance mechanisms of mouse embryonic stem cells
Histological assessment of cardiac amyloidosis in patients undergoing transcatheter aortic valve replacement
No full textAbstract
Aims
Studies have reported a strongly varying co‐prevalence of aortic stenosis (AS) and cardiac amyloidosis (CA). We sought to histologically determine the co‐prevalence of AS and CA in patients undergoing transcatheter aortic valve replacement (TAVR). Consequently, we aimed to derive an algorithm to identify cases in which to suspect the co‐prevalence of AS and CA.
Methods and results
In this prospective, monocentric study, endomyocardial biopsies of 162 patients undergoing TAVR between January 2017 and March 2021 at the University Medical Centre Göttingen were analysed by one pathologist blinded to clinical data using haematoxylin–eosin staining, Elastica van Gieson staining, and Congo red staining of endomyocardial biopsies. CA was identified in only eight patients (4.9%). CA patients had significantly higher N‐terminal pro‐brain natriuretic peptide (NT‐proBNP) levels (4356.20 vs. 1938.00 ng/L,
P
= 0.034), a lower voltage‐to‐mass ratio (0.73 vs. 1.46 × 10
−2
mVm
2
/g,
P
= 0.022), and lower transaortic gradients (Pmean 17.5 vs. 38.0 mmHg,
P
= 0.004) than AS patients. Concomitant CA was associated with a higher prevalence of post‐procedural acute kidney injury (50.0% vs. 13.1%,
P
= 0.018) and sudden cardiac death [SCD;
P
(log‐rank test) = 0.017]. Following propensity score matching, 184 proteins were analysed to identify serum biomarkers of concomitant CA. CA patients expressed lower levels of chymotrypsin (
P
= 0.018) and carboxypeptidase 1 (
P
= 0.027). We propose an algorithm using commonly documented parameters—stroke volume index, ejection fraction, NT‐proBNP levels, posterior wall thickness, and QRS voltage‐to‐mass ratio—to screen for CA in AS patients, reaching a sensitivity of 66.6% with a specificity of 98.1%.
Conclusions
The co‐prevalence of AS and CA was lower than expected, at 4.9%. Despite excellent 1 year mortality, AS + CA patients died significantly more often from SCD. We propose a multimodal algorithm to facilitate more effective screening for CA containing parameters commonly documented during clinical routine. Proteomic biomarkers may yield additional information in the future.Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659Open-Access-Publikationsfonds 202
Single-nucleus transcriptomics reveals adrenergic and STAT3 signaling in paradoxical low-flow low-gradient -specific cardiomyocyte subclusters: implications for aortic stenosis pathogenesis and treatment
No full text- …
