scholarly journals Plastin 3 in X-Linked Osteoporosis: Imbalance of Ca2+-Dependent Regulation Is Equivalent to Protein Loss

2021 ◽  
Vol 8 ◽  
Author(s):  
Christopher L. Schwebach ◽  
Elena Kudryashova ◽  
Dmitri S. Kudryashov
Keyword(s):  
Osteogenesis Imperfecta ◽  
Actin Cytoskeleton ◽  
Bone Development ◽  
Genetic Disorder ◽  
Cellular Structures ◽  
Protein Loss ◽  
Pathogenic Variants ◽  
Recent Advances ◽  
Intracellular Ca

Osteogenesis imperfecta is a genetic disorder disrupting bone development and remodeling. The primary causes of osteogenesis imperfecta are pathogenic variants of collagen and collagen processing genes. However, recently variants of the actin bundling protein plastin 3 have been identified as another source of osteogenesis imperfecta. Plastin 3 is a highly conserved protein involved in several important cellular structures and processes and is controlled by intracellular Ca2+ which potently inhibits its actin-bundling activity. The precise mechanisms by which plastin 3 causes osteogenesis imperfecta remain unclear, but recent advances have contributed to our understanding of bone development and the actin cytoskeleton. Here, we review the link between plastin 3 and osteogenesis imperfecta highlighting in vitro studies and emphasizing the importance of Ca2+ regulation in the localization and functionality of plastin 3.

scholarly journals Serotonin modifies cytoskeleton and brush-border membrane architecture in human intestinal epithelial cells

2008 ◽  
Vol 295 (4) ◽  
pp. G700-G708 ◽  
Author(s):  
Ravinder K. Gill ◽  
Le Shen ◽  
Jerrold R. Turner ◽  
Seema Saksena ◽  
Waddah A. Alrefai ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Brush Border ◽  
Brush Border Membrane ◽  
In Vitro Assays ◽  
Receptor Subtypes ◽  
Ion Transporters ◽  
Cortical Actin ◽  
Intracellular Ca ◽  
Membrane Architecture

Serotonin or 5-hydroxytryptamine (5-HT) influences numerous functions in the gastrointestinal tract. We previously demonstrated that 5-HT treatment of Caco-2 cells inhibited Na+/H+ exchangers (NHE) and Cl−/OH− exchange activities via distinct signaling mechanisms. Since regulation of several ion transporters such as NHE3 is influenced by intact cytoskeleton, we hypothesized that 5-HT modifies actin cytoskeleton and/or brush-border membrane architecture via involvement of signaling pathways. Ultrastructural analysis showed that 5-HT (0.1 μM, 1 h) treatment of Caco-2 cells caused the apical membrane to assume a convex dome shape that was associated with shortening of microvilli. To examine whether these cellular architecture changes are cytoskeleton driven, we analyzed actin cytoskeleton by fluorescence microscopy. 5-HT induced basal stress fibers with prominent cortical actin filaments via 5-HT3 and 5-HT4 receptor subtypes. This induction was partially attenuated by chelation of intracellular Ca2+ and PKCα inhibition (Go6976). In vitro assays revealed that PKCα interacted with actin and this association was increased by 5-HT. Our data provide novel evidence that 5-HT-induced signaling via 5-HT3/4 receptor subtypes to cause Ca2+ and PKCα-dependent regulation of actin cytoskeleton may play an important role in modulation of ion transporters that contribute to pathophysiology of diarrheal conditions associated with elevated levels of 5-HT.

scholarly journals Skeletal cell YAP and TAZ redundantly promote bone development by regulation of collagen I expression and organization

2017 ◽  
Author(s):  
Christopher D. Kegelman ◽  
Devon E. Mason ◽  
James H. Dawahare ◽  
Genevieve D. Vigil ◽  
Scott S. Howard ◽  
...  
Keyword(s):  
Osteogenesis Imperfecta ◽  
Target Genes ◽  
Bone Development ◽  
Bone Matrix ◽  
Cell Lineage ◽  
Binding Domains ◽  
Conditional Deletion ◽  
Neonatal Lethality ◽  
Allele Dosage

ABSTRACTThe functions of the transcriptional co-activators YAP and TAZ in bone are controversial. Each has been observed to either promote or inhibit osteogenesis in vitro, while their roles in bone development are unknown. Here we report that combinatorial YAP/TAZ deletion from skeletal cells in mice caused osteogenesis imperfecta with severity dependent on targeted cell lineage and allele dosage. Osteocyte-conditional deletion impaired bone accrual and matrix collagen, while allele dosage-dependent deletion from all osteogenic lineage cells caused spontaneous fractures, with neonatal lethality only in dual homozygous knockouts. We identified putative target genes whose mutation in humans causes osteogenesis imperfecta and which contain promoter-proximate binding domains for the YAP/TAZ co-effector, TEAD4. Two candidates, Col1a1 and SerpinH1, exhibited reduced expression upon either YAP/TAZ deletion or YAP/TAZ-TEAD inhibition by verteporfin. Together, these data demonstrate that YAP and TAZ redundantly promote bone matrix development and implicate YAP/TAZ-mediated transcriptional regulation of collagen in osteogenesis imperfecta.

scholarly journals A Founder Pathogenic Variant of PPIB Unique to Chinese Population Causes Osteogenesis Imperfecta IX

2021 ◽  
Vol 12 ◽  
Author(s):  
Wenting Zhu ◽  
Kai Yan ◽  
Xijing Chen ◽  
Wei Zhao ◽  
Yiqing Wu ◽  
...  
Keyword(s):  
Osteogenesis Imperfecta ◽  
Founder Effect ◽  
Chinese Population ◽  
Disease Incidence ◽  
Genetic Disorder ◽  
Missense Variant ◽  
Bone Fragility ◽  
Pathogenic Variant ◽  
Pathogenic Variants ◽  
Specific Allele

Background: Osteogenesis imperfecta (OI) is a heterogeneous genetic disorder characterized by bone fragility. PPIB pathogenic variants cause a perinatal lethal form of OI type IX. A limited number of pathogenic variants have been reported so far worldwide.Methods: We identified a rare pedigree whose phenotype was highly consistent with OI-IX. Exome sequencing was performed to uncover the causal variants. The variant pathogenicity was classified following the ACMG/AMP guidelines. The founder effect and the age of the variant were assessed.Results: We identified a homozygous missense variant c.509G > A/p.G170D in PPIB in an affected fetus. This variant is a Chinese-specific allele and can now be classified as pathogenic. We estimated the allele frequency (AF) of this variant to be 0.0000427 in a Chinese cohort involving 128,781 individuals. All patients and carriers shared a common haplotype, indicative of a founder effect. The estimated age of variant was 65,160 years. We further identified pathogenic variants of PPIB in gnomAD and ClinVar databases, the conserved estimation of OI type IX incidence to be 1/1,000,000 in Chinese population.Conclusion: We reported a founder pathogenic variant in PPIB specific to the Chinese population. We further provided our initial estimation of OI-IX disease incidence in China.

scholarly journals Omics Profiling of S2P Mutant Fibroblasts as a Mean to Unravel the Pathomechanism and Molecular Signatures of X-Linked MBTPS2 Osteogenesis Imperfecta

2021 ◽  
Vol 12 ◽  
Author(s):  
Pei Jin Lim ◽  
Severin Marfurt ◽  
Uschi Lindert ◽  
Lennart Opitz ◽  
Timothée Ndarugendamwo ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Osteogenesis Imperfecta ◽  
Er Stress ◽  
Bone Development ◽  
Differentially Expressed ◽  
Single Amino Acid ◽  
Missense Mutations ◽  
Cartilage Development ◽  
Molecular Features

Osteogenesis imperfecta (OI) is an inherited skeletal dysplasia characterized by low bone density, bone fragility and recurrent fractures. The characterization of its heterogeneous genetic basis has allowed the identification of novel players in bone development. In 2016, we described the first X-linked recessive form of OI caused by hemizygous MBTPS2 missense variants resulting in moderate to severe phenotypes. MBTPS2 encodes site-2 protease (S2P), which activates transcription factors involved in bone (OASIS) and cartilage development (BBF2H7), ER stress response (ATF6) and lipid metabolism (SREBP) via regulated intramembrane proteolysis. In times of ER stress or sterol deficiency, the aforementioned transcription factors are sequentially cleaved by site-1 protease (S1P) and S2P. Their N-terminal fragments shuttle to the nucleus to activate gene transcription. Intriguingly, missense mutations at other positions of MBTPS2 cause the dermatological spectrum condition Ichthyosis Follicularis, Atrichia and Photophobia (IFAP) and Keratosis Follicularis Spinulosa Decalvans (KFSD) without clinical overlap with OI despite the proximity of some of the pathogenic variants. To understand how single amino acid substitutions in S2P can lead to non-overlapping phenotypes, we aimed to compare the molecular features of MBTPS2-OI and MBTPS2-IFAP/KFSD, with the ultimate goal to unravel the pathomechanisms underlying MBTPS2-OI. RNA-sequencing-based transcriptome profiling of primary skin fibroblasts from healthy controls (n = 4), MBTPS2-OI (n = 3), and MBTPS2-IFAP/KFSD (n = 2) patients was performed to identify genes that are differentially expressed in MBTPS2-OI and MBTPS2-IFAP/KFSD individuals compared to controls. We observed that SREBP-dependent genes are more downregulated in OI than in IFAP/KFSD. This is coupled to alterations in the relative abundance of fatty acids in MBTPS2-OI fibroblasts in vitro, while no consistent alterations in the sterol profile were observed. Few OASIS-dependent genes are suppressed in MBTPS2-OI, while BBF2H7- and ATF6-dependent genes are comparable between OI and IFAP/KFSD patients and control fibroblasts. Importantly, we identified genes involved in cartilage physiology that are differentially expressed in MBTPS2-OI but not in MBTPS2-IFAP/KFSD fibroblasts. In conclusion, our data provide clues to how pathogenic MBTPS2 mutations cause skeletal deformities via altered fatty acid metabolism or cartilage development that may affect bone development, mineralization and endochondral ossification.

scholarly journals An epilepsy-causing mutation leads to co-translational misfolding of the Kv7.2 channel

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Janire Urrutia ◽  
Alejandra Aguado ◽  
Carolina Gomis-Perez ◽  
Arantza Muguruza-Montero ◽  
Oscar R. Ballesteros ◽  
...  
Keyword(s):  
Structural Instability ◽  
Binding Assays ◽  
Iq Motif ◽  
Channel Function ◽  
Human Epilepsy ◽  
Pathogenic Variants ◽  
In Silico Studies ◽  
Nascent Chain

Abstract Background The amino acid sequence of proteins generally carries all the necessary information for acquisition of native conformations, but the vectorial nature of translation can additionally determine the folding outcome. Such consideration is particularly relevant in human diseases associated to inherited mutations leading to structural instability, aggregation, and degradation. Mutations in the KCNQ2 gene associated with human epilepsy have been suggested to cause misfolding of the encoded Kv7.2 channel. Although the effect on folding of mutations in some domains has been studied, little is known of the way pathogenic variants located in the calcium responsive domain (CRD) affect folding. Here, we explore how a Kv7.2 mutation (W344R) located in helix A of the CRD and associated with hereditary epilepsy interferes with channel function. Results We report that the epilepsy W344R mutation within the IQ motif of CRD decreases channel function, but contrary to other mutations at this site, it does not impair the interaction with Calmodulin (CaM) in vitro, as monitored by multiple in vitro binding assays. We find negligible impact of the mutation on the structure of the complex by molecular dynamic computations. In silico studies revealed two orientations of the side chain, which are differentially populated by WT and W344R variants. Binding to CaM is impaired when the mutated protein is produced in cellulo but not in vitro, suggesting that this mutation impedes proper folding during translation within the cell by forcing the nascent chain to follow a folding route that leads to a non-native configuration, and thereby generating non-functional ion channels that fail to traffic to proper neuronal compartments. Conclusions Our data suggest that the key pathogenic mechanism of Kv7.2 W344R mutation involves the failure to adopt a configuration that can be recognized by CaM in vivo but not in vitro.

scholarly journals Restoration of Osteogenesis by CRISPR/Cas9 Genome Editing of the Mutated COL1A1 Gene in Osteogenesis Imperfecta

2021 ◽  
Vol 10 (14) ◽  
pp. 3141
Author(s):  
Hyerin Jung ◽  
Yeri Alice Rim ◽  
Narae Park ◽  
Yoojun Nam ◽  
Ji Hyeon Ju
Keyword(s):  
Osteogenesis Imperfecta ◽  
Type I Collagen ◽  
Disease Modeling ◽  
Bone Fragility ◽  
Osteogenic Potential ◽  
Type I ◽  
Gene Correction ◽  
Col1a1 Gene ◽  
Collagen Formation

Osteogenesis imperfecta (OI) is a genetic disease characterized by bone fragility and repeated fractures. The bone fragility associated with OI is caused by a defect in collagen formation due to mutation of COL1A1 or COL1A2. Current strategies for treating OI are not curative. In this study, we generated induced pluripotent stem cells (iPSCs) from OI patient-derived blood cells harboring a mutation in the COL1A1 gene. Osteoblast (OB) differentiated from OI-iPSCs showed abnormally decreased levels of type I collagen and osteogenic differentiation ability. Gene correction of the COL1A1 gene using CRISPR/Cas9 recovered the decreased type I collagen expression in OBs differentiated from OI-iPSCs. The osteogenic potential of OI-iPSCs was also recovered by the gene correction. This study suggests a new possibility of treatment and in vitro disease modeling using patient-derived iPSCs and gene editing with CRISPR/Cas9.

scholarly journals Protein Analysis of Pollen Tubes after the Treatments of Membrane Trafficking Inhibitors Gains Insights on Molecular Mechanism Underlying Pollen Tube Polar Growth

2021 ◽  
Vol 40 (2) ◽  
pp. 205-222
Author(s):  
Monica Scali ◽  
Alessandra Moscatelli ◽  
Luca Bini ◽  
Elisabetta Onelli ◽  
Rita Vignani ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Actin Cytoskeleton ◽  
Membrane Trafficking ◽  
Tip Growth ◽  
Male Gametophyte ◽  
Pollen Tubes ◽  
Structural Features ◽  
Two Dimensional Gel Electrophoresis ◽  
Depth Analysis

AbstractPollen tube elongation is characterized by a highly-polarized tip growth process dependent on an efficient vesicular transport system and largely mobilized by actin cytoskeleton. Pollen tubes are an ideal model system to study exocytosis, endocytosis, membrane recycling, and signaling network coordinating cellular processes, structural organization and vesicular trafficking activities required for tip growth. Proteomic analysis was applied to identifyNicotiana tabacumDifferentially Abundant Proteins (DAPs) after in vitro pollen tube treatment with membrane trafficking inhibitors Brefeldin A, Ikarugamycin and Wortmannin. Among roughly 360 proteins separated in two-dimensional gel electrophoresis, a total of 40 spots visibly changing between treated and control samples were identified by MALDI-TOF MS and LC–ESI–MS/MS analysis. The identified proteins were classified according to biological processes, and most proteins were related to pollen tube energy metabolism, including ammino acid synthesis and lipid metabolism, structural features of pollen tube growth as well modification and actin cytoskeleton organization, stress response, and protein degradation. In-depth analysis of proteins corresponding to energy-related pathways revealed the male gametophyte to be a reliable model of energy reservoir and dynamics.

scholarly journals Effect of memantine, an anti-Alzheimer’s drug, on rodent microglial cells in vitro

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Toru Murakawa-Hirachi ◽  
Yoshito Mizoguchi ◽  
Masahiro Ohgidani ◽  
Yoshinori Haraguchi ◽  
Akira Monji
Keyword(s):  
Neuronal Death ◽  
Phagocytic Activity ◽  
Microglial Cell ◽  
Cell Function ◽  
Microglial Cells ◽  
Phagocytosis Assay ◽  
Intracellular Ca ◽  
Β Amyloid ◽  
The Brain

AbstractThe pathophysiology of Alzheimer’s disease (AD) is related to neuroinflammatory responses mediated by microglia. Memantine, an antagonist of N-methyl-d-aspartate (NMDA) receptors used as an anti-Alzheimer’s drug, protects from neuronal death accompanied by suppression of proliferation and activation of microglial cells in animal models of AD. However, it remains to be tested whether memantine can directly affect microglial cell function. In this study, we examined whether pretreatment with memantine affects intracellular NO and Ca2+ mobilization using DAF-2 and Fura-2 imaging, respectively, and tested the effects of memantine on phagocytic activity by human β-Amyloid (1–42) phagocytosis assay in rodent microglial cells. Pretreatment with memantine did not affect production of NO or intracellular Ca2+ elevation induced by TNF in rodent microglial cells. Pretreatment with memantine also did not affect the mRNA expression of pro-inflammatory (TNF, IL-1β, IL-6 and CD45) or anti-inflammatory (IL-10, TGF-β and arginase) phenotypes in rodent microglial cells. In addition, pretreatment with memantine did not affect the amount of human β-Amyloid (1–42) phagocytosed by rodent microglial cells. Moreover, we observed that pretreatment with memantine did not affect 11 major proteins, which mainly function in the phagocytosis and degradation of β-Amyloid (1–42), including TREM2, DAP12 and neprilysin in rodent microglial cells. To the best of our knowledge, this is the first report to suggest that memantine does not directly modulate intracellular NO and Ca2+ mobilization or phagocytic activity in rodent microglial cells. Considering the neuroinflammation hypothesis of AD, the results might be important to understand the effect of memantine in the brain.

scholarly journals Loss-of-function and missense variants in NSD2 cause decreased methylation activity and are associated with a distinct developmental phenotype

2021 ◽  
Author(s):  
Paolo Zanoni ◽  
Katharina Steindl ◽  
Deepanwita Sengupta ◽  
Pascal Joset ◽  
Angela Bahr ◽  
...  
Keyword(s):  
Loss Of Function ◽  
Mild Phenotype ◽  
Psychological Issues ◽  
Missense Variants ◽  
Mild Developmental Delay ◽  
Pathogenic Variants ◽  
In Silico Modeling ◽  
And Function ◽  
Methylation Activity

Abstract Purpose Despite a few recent reports of patients harboring truncating variants in NSD2, a gene considered critical for the Wolf–Hirschhorn syndrome (WHS) phenotype, the clinical spectrum associated with NSD2 pathogenic variants remains poorly understood. Methods We collected a comprehensive series of 18 unpublished patients carrying heterozygous missense, elongating, or truncating NSD2 variants; compared their clinical data to the typical WHS phenotype after pooling them with ten previously described patients; and assessed the underlying molecular mechanism by structural modeling and measuring methylation activity in vitro. Results The core NSD2-associated phenotype includes mostly mild developmental delay, prenatal-onset growth retardation, low body mass index, and characteristic facial features distinct from WHS. Patients carrying missense variants were significantly taller and had more frequent behavioral/psychological issues compared with those harboring truncating variants. Structural in silico modeling suggested interference with NSD2’s folding and function for all missense variants in known structures. In vitro testing showed reduced methylation activity and failure to reconstitute H3K36me2 in NSD2 knockout cells for most missense variants. Conclusion NSD2 loss-of-function variants lead to a distinct, rather mild phenotype partially overlapping with WHS. To avoid confusion for patients, NSD2 deficiency may be named Rauch–Steindl syndrome after the delineators of this phenotype.

scholarly journals Inborn errors of immunity—recent advances in research on the pathogenesis

2021 ◽  
Vol 41 (1) ◽  
Author(s):  
Motoi Yamashita ◽  
Kento Inoue ◽  
Tsubasa Okano ◽  
Tomohiro Morio
Keyword(s):  
Immune System ◽  
Hematopoietic Cell Transplantation ◽  
Epigenetic Modification ◽  
Genetic Disorder ◽  
Loss Of Function ◽  
Inborn Errors ◽  
Whole Genome Analysis ◽  
Curative Therapy ◽  
Inborn Errors Of Immunity ◽  
Recent Advances

AbstractPrimary immunodeficiency (PID) is a genetic disorder with a defect of one of the important components of our immune system. Classical PID has been recognized as a disorder with loss of function of the immune system. Recent studies have unveiled disorders with immune dysfunction with autoimmunity, autoinflammation, allergy, or predisposition to malignancy. Some of them were caused by an augmented immune function or a defect in immune regulation. With this background, the term inborn errors of immunity (IEI) is now used to refer to PID in the International Union of Immunological Societies (IUIS) classification. More than 400 responsible genes have been identified in patients with IEI so far, and importantly, many of them identified lately were caused by a heterologous mutation. Moreover, the onset is not necessarily in childhood, and we started seeing more and more IEI patients diagnosed in adulthood in the clinical settings. Recent advances in genetic analysis, including whole-exome analysis, whole-genome analysis, and RNA-seq have contributed to the identification of the disease-causing gene mutation. We also started to find heterogeneity of phenotype even in the patients with the same mutation in the same family, leading us to wonder if modifier gene or epigenetic modification is involved in the pathogenesis. In contrast, we accumulated many cases suggesting genetic heterogeneity is associated with phenotypic homogeneity. It has thus become difficult to deduce a responsible gene only from the phenotype in a certain type of IEI. Current curative therapy for IEI includes hematopoietic cell transplantation and gene therapy. Other curative therapeutic modalities have been long waited and are to be introduced in the future. These include a small molecule that inhibits the gain-of-function of the molecule- and genome-editing technology. Research on IEI will surely lead to a better understanding of other immune-related disorders including rheumatic diseases and atopic disorders.

Sign in / Sign up

Export Citation Format

Share Document