Functional Characterization of a Novel Truncating Mutation in Lamin A/C Gene in a Family with a Severe Cardiomyopathy with Conduction Defects

Background/Aims: Truncating LMNA gene mutations occur in many inherited cardiomyopathy cases, but the molecular mechanisms involved in the disease they cause have not yet been systematically investigated. Here, we studied a novel frameshift LMNA variant (p.D243Gfs*4) identified in three members of an Italian family co-segregating with a severe form of cardiomyopathy with conduction defects. Methods: HEK293 cells and HL-1 cardiomyocytes were transiently transfected with either Lamin A or D243Gfs*4 tagged with GFP (or mCherry). D243Gfs*4 expression, cellular localization and its effects on diverse cellular mechanisms were evaluated with western blotting, laser-scanning confocal microscopy and video-imaging analysis in single cells. Results: When expressed in HEK293 cells, GFP- (or mCherry)-tagged LMNA D243Gfs*4 colocalized with calnexin within the ER. ER mislocalization of LMNA D243Gfs*4 did not significantly induce ER stress response, abnormal Ca2+ handling and apoptosis when compared with HEK293 cells expressing another truncated mutant of LMNA (R321X) which similarly accumulates within the ER. Of note, HEK293-LMNA D243Gfs*4 cells showed a significant reduction of connexin 43 (CX43) expression level, which was completely rescued by activation of the WNT/β-catenin signaling pathway. When expressed in HL-1 cardiomyocytes, D243Gfs*4 significantly impaired the spontaneous Ca2+ oscillations recorded in these cells as result of propagation of the depolarizing waves through the gap junctions between non-transfected cells surrounding a cell harboring the mutation. Furthermore, mCh-D243Gfs*4 HL-1 cardiomyocytes showed reduced CX43-dependent Lucifer Yellow (LY) loading and propagation. Of note, activation of β-catenin rescued both LY loading and LMNA D243Gfs*4 -HL-1 cells spontaneous activity propagation. Conclusion: Overall, the present results clearly indicate the involvement of the aberrant CX43 expression/activity as a pathogenic mechanism for the conduction defects associated to this LMNA truncating alteration.

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Multiple mechanisms are responsible for altered expression of gap junction genes during oncogenesis in rat liver

Journal of Cell Science ◽

10.1242/jcs.107.1.83 ◽

1994 ◽

Vol 107 (1) ◽

pp. 83-95

Author(s):

M.J. Neveu ◽

J.R. Hully ◽

K.L. Babcock ◽

E.L. Hertzberg ◽

B.J. Nicholson ◽

...

Keyword(s):

Gap Junction ◽

Cellular Localization ◽

Molecular Mechanisms ◽

Northern Blotting ◽

Mrna Abundance ◽

Common Mechanism ◽

Cx43 Expression ◽

Bile Duct Proliferation ◽

Altered Expression ◽

Connexin Expression

Although several abnormalities in gap junction (GJ) structure and/or function have been described in neoplasms, the molecular mechanisms responsible for many of the alterations remain unknown. The identification of a family of GJ proteins, termed connexins, prompted this study of connexin32 (Cx32), connexin26 (Cx26) and connexin43 (Cx43) expression during rat hepatocarcinogenesis. Using antibody, cDNA and cRNA probes, we investigated connexin mRNA and protein expression in preneoplastic and neoplastic rat livers. In normal liver, Cx32 is expressed in hepatocytes throughout the hepatic acinus, Cx26 is restricted to periportal hepatocytes, and Cx43 is expressed by mesothelial cells forming Glisson's capsule. Most preneoplastic altered hepatic foci generated by diethylnitrosamine (DEN) initiation and either phenobarbital (PB) or 2,3,7,8-dichlorodibenzo-p-dioxin (TCDD) promotion exhibited decreased Cx32 or increased Cx26 staining. Foci from either protocol failed to display Cx43 immunoreactivity. In the majority of PB-promoted foci, Cx32 immunoreactivity decreased independently of changes in mRNA abundance. Continuous thymidine labeling, following cessation of PB promotion, showed that downregulation of Cx32 staining is reversible in foci that are promoter-dependent for growth, but irreversible in lesions that are promoter-independent for growth. Hepatic neoplasms from rats initiated with DEN and promoted with PB or TCDD also displayed modified connexin expression. While all 24 neoplasms studied were deficient in normal punctate Cx32 and Cx26 staining, altered cellular localization of these proteins was apparent in some tumors. Immunoblotting of crude tissue extracts revealed that neoplasms with disordered Cx32 staining showed immunoreactive bands with altered electrophoretic mobility. These observations show that hepatomas may downregulate Cx32 expression through changes in the primary structure of Cx32 or by post-translational modifications. Northern blotting of total tumor mRNAs failed to demonstrate consistent changes in the abundance of Cx32, Cx26 or Cx43 transcripts. Some tumors expressed steady-state transcripts without observable immunoreactivity, indicating that some hepatomas downregulate connexin immunoreactivity independently of mRNA abundance. Increased levels of Cx43 mRNA and protein were found in several neoplasms, but immunostaining was always localized to nonparenchymal cells. Areas of bile duct proliferation and cholangiomas displayed Cx43 staining, whereas, cholangiocarcinomas were deficient in immunoreactivity. These findings show that alterations in the expression of connexins, by either downregulation or differential induction, represent common modifications during hepatocarcinogenesis. Although our results imply that connexins represent useful markers for the boundary between tumor promotion and progression, preneoplastic and neoplastic rat hepatocytes fail to use a common mechanism to modify connexin expression.

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Systematic functional characterization of antisense eRNA of protocadherin α composite enhancer

Genes & Development ◽

10.1101/gad.348621.121 ◽

2021 ◽

Vol 35 (19-20) ◽

pp. 1383-1394

Author(s):

Yuxiao Zhou ◽

Siyuan Xu ◽

Mo Zhang ◽

Qiang Wu

Keyword(s):

Gene Expression ◽

Molecular Mechanisms ◽

Single Cells ◽

Functional Characterization ◽

Three Dimensional ◽

Elongation Factor ◽

Locked Nucleic Acid ◽

Loop Formation ◽

Long Distance ◽

Enhancer Region

Enhancers generate bidirectional noncoding enhancer RNAs (eRNAs) that may regulate gene expression. At present, the eRNA function remains enigmatic. Here, we report a 5′ capped antisense eRNA PEARL (Pcdh eRNA associated with R-loop formation) that is transcribed from the protocadherin (Pcdh) α HS5-1 enhancer region. Through loss- and gain-of-function experiments with CRISPR/Cas9 DNA fragment editing, CRISPRi, and CRISPRa, as well as locked nucleic acid strategies, in conjunction with ChIRP, MeDIP, DRIP, QHR-4C, and HiChIP experiments, we found that PEARL regulates Pcdhα gene expression by forming local RNA–DNA duplexes (R-loops) in situ within the HS5-1 enhancer region to promote long-distance chromatin interactions between distal enhancers and target promoters. In particular, increased levels of eRNA PEARL via perturbing transcription elongation factor SPT6 lead to strengthened local three-dimensional chromatin organization within the Pcdh superTAD. These findings have important implications regarding molecular mechanisms by which the HS5-1 enhancer regulates stochastic Pcdhα promoter choice in single cells in the brain.

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Transcriptome profiling of laser-captured germ cells and functional characterization of zbtb40 during MT-induced spermatogenesis in orange-spotted grouper (Epinephelus coioides)

10.21203/rs.2.11289/v2 ◽

2019 ◽

Author(s):

Xiaochun Liu ◽

Xi Wu ◽

Yang Yang ◽

Chaoyue Zhong ◽

Yin Guo ◽

...

Keyword(s):

Germ Cells ◽

Cellular Localization ◽

Molecular Mechanisms ◽

Expression Patterns ◽

Functional Characterization ◽

Transcriptome Profiling ◽

Sex Reversal ◽

Epinephelus Coioides ◽

Isolated Cells ◽

Male Germ Cells

Abstract Background: Spermatogenesis is an intricate process regulated by a finely organized network. The orange-spotted grouper (Epinephelus coioides) is a protogynous hermaphroditic fish, but the process of its spermatogenesis is not well-understood. In the present study, transcriptome sequencing of the male germ cells from orange-spotted grouper was performed to explore the molecular mechanisms underlying spermatogenesis. Results: In this study, the orange-spotted grouper was induced to change sex from female to male by 17alpha-methyltestosterone implantation. During the artificial spermatogenesis, different cell types from cysts containing spermatogonia, spermatocytes, spermatids, and spermatozoa were isolated by laser capture microdissection. Subsequently, transcriptomic analysis for the isolated cells were performed. A series of genes was used to verify and investigate the expression patterns in spermatogenesis. Furthermore, we also analyzed the expression of the same set of genes involved with steroid metabolism and sex throughout spermatogenesis (early-mid, late, and maturing stages) in the orange-spotted grouper. Several generally female-related genes took significantly changes in sex reversal hinted that the female-related genes in previously recognized may also play vital roles in spermatogenesis and sex reversal. In the transcriptomic data, we focused on zbtb family genes, which may be related to the process of spermatogenesis. Their expression patterns and cellular localization were examined, and the location of Eczbtb40 in different gonadal stages was investigated. We found that Eczbtb40 was expressed throughout spermatogenesis. These preliminary findings suggest that Eczbtb40 is highly conserved during vertebrate evolution and plays roles in spermatogenesis. Besides, the expression of Eczbtb40 and Eccyp17a1a overlapped in male germ cells, especially spermatogonium and spermatocyte, which suggested that Eczbtb40 might interact with Eccyp17a1a participant in spermatogenesis and sex reversal. Conclusions: The present study first depicted RNA sequencing of the male germ cells from orange-spotted grouper, and identified many important functional genes and pathways involved in spermatogenesis. The Eczbtb40 gene was subjected to molecular characterization and expression pattern analysis. These results will contribute to future studies of the molecular mechanism of spermatogenesis and sex reversal.

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Functional characterization of a novel truncating mutation in Lamin A/C gene in a family with a severe cardiomyopathy with conduction defects

Vascular Pharmacology ◽

10.1016/j.vph.2017.12.028 ◽

2018 ◽

Vol 103-105 ◽

pp. 57

Author(s):

A. Gerbino ◽

I. Bottillo ◽

S. Milano ◽

R. De Zio ◽

G. Procino ◽

...

Keyword(s):

Functional Characterization ◽

Lamin A ◽

Truncating Mutation

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AMPKα1 deletion in myofibroblasts exacerbates post-myocardial infarction fibrosis by a connexin 43 mechanism

Basic Research in Cardiology ◽

10.1007/s00395-021-00846-y ◽

2021 ◽

Vol 116 (1) ◽

Author(s):

Cécile Dufeys ◽

Evangelos-Panagiotis Daskalopoulos ◽

Diego Castanares-Zapatero ◽

Simon J. Conway ◽

Audrey Ginion ◽

...

Keyword(s):

Myocardial Infarction ◽

Connexin 43 ◽

Molecular Mechanisms ◽

Cardiac Fibrosis ◽

Left Ventricular ◽

Conditional Knockout ◽

Fibroblast Proliferation ◽

Cx43 Expression ◽

Amp Activated Protein Kinase ◽

Specific Deletion

AbstractWe have previously demonstrated that systemic AMP-activated protein kinase α1 (AMPKα1) invalidation enhanced adverse LV remodelling by increasing fibroblast proliferation, while myodifferentiation and scar maturation were impaired. We thus hypothesised that fibroblastic AMPKα1 was a key signalling element in regulating fibrosis in the infarcted myocardium and an attractive target for therapeutic intervention. The present study investigates the effects of myofibroblast (MF)-specific deletion of AMPKα1 on left ventricular (LV) adaptation following myocardial infarction (MI), and the underlying molecular mechanisms. MF-restricted AMPKα1 conditional knockout (cKO) mice were subjected to permanent ligation of the left anterior descending coronary artery. cKO hearts exhibit exacerbated post-MI adverse LV remodelling and are characterised by exaggerated fibrotic response, compared to wild-type (WT) hearts. Cardiac fibroblast proliferation and MF content significantly increase in cKO infarcted hearts, coincident with a significant reduction of connexin 43 (Cx43) expression in MFs. Mechanistically, AMPKα1 influences Cx43 expression by both a transcriptional and a post-transcriptional mechanism involving miR-125b-5p. Collectively, our data demonstrate that MF-AMPKα1 functions as a master regulator of cardiac fibrosis and remodelling and might constitute a novel potential target for pharmacological anti-fibrotic applications.

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Transcriptome profiling of laser-captured germ cells and functional characterization of zbtb40 during MT-induced spermatogenesis in orange-spotted grouper (Epinephelus coioides)

10.21203/rs.2.11289/v1 ◽

2019 ◽

Author(s):

Xiaochun Liu ◽

Xi Wu ◽

Yang Yang ◽

Chaoyue Zhong ◽

Yin Guo ◽

...

Keyword(s):

Germ Cells ◽

Cellular Localization ◽

Molecular Mechanisms ◽

Expression Patterns ◽

Functional Characterization ◽

Transcriptome Profiling ◽

Sex Reversal ◽

Epinephelus Coioides ◽

Isolated Cells ◽

Male Germ Cells

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P11.29 Development of ex vivo models for deeper insights into the biology and therapeutic targeting of tumor microtube networks in gliomas

Neuro-Oncology ◽

10.1093/neuonc/noz126.175 ◽

2019 ◽

Vol 21 (Supplement_3) ◽

pp. iii49-iii49

Author(s):

E Jung ◽

D Domínguez Azorín ◽

D Hausmann ◽

M Mall ◽

P Koch ◽

...

Keyword(s):

Tumor Cell ◽

Connexin 43 ◽

Laser Scanning ◽

Molecular Mechanisms ◽

Ex Vivo ◽

Therapy Resistance ◽

Laser Scanning Microscopy ◽

Live Cells ◽

Fluorescent Reporter ◽

Cell Networks

Abstract BACKGROUND The formation of multicellular networks via thin cellular protrusions named tumor microtubes (TMs) emerged as a novel mechanism of therapy resistance in malignant glioma. TMs are also involved in tumor cell invasion and growth. Within these tumor cell networks, connected tumor cells communicate via intercellular calcium waves (ICWs). Only few molecular drivers of TMs (Gap43, Ttyh1, Connexin 43) have been identified until now. Furthermore, the molecular mechanisms underlying ICWs as well as their specific biological role in glioma remains to be elucidated. A better understanding of the biology and the identification of molecular key drivers is essential for the development of drugs targeting TM formation and function. MATERIAL AND METHODS For this purpose, we have developed novel ex vivo models that not only provide insights into TM biology but further allow medium throughput drug screening. As classical response parameters such as the inhibition of cell growth or cytotoxicity do not necessarily correlate with effects on TM formation or function, a morphometrical approach employing laser scanning microscopy and machine-learning based image analysis tools is used. The application of fluorescent probes and genetic fluorescent reporter systems provides novel longitudinal insights into cytoskeletal dynamics, the role and exchange of organelles such as mitochondria, mechanisms of homeostasis within tumor cell networks (e.g. redox homeostasis) and ICWs in live cells. In addition to 2D glioma cell and co-culture models we have developed a fully human and mature brain organoid model. Here, complex 3D tumor cell networks corresponding to the morphology and exhibiting calcium communication patterns observed in our mouse model can be established and studied ex vivo. Furthermore, with these models not only the role of the brain microenvironment on TM formation but also direct interactions of glioma cells with neurons and glial cells as well as drug effects such as cytotoxicity on these brain cells can be investigated ex vivo. CONCLUSION In summary, novel tumor models enable further insights into TM biology and hence provide the basis for development of TM- and network disrupting drugs. First results of this screening opportunity will be presented.

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Phosphoregulation of Nap1 Plays a Role in Septin Ring Dynamics and Morphogenesis in Candida albicans

mBio ◽

10.1128/mbio.00915-13 ◽

2014 ◽

Vol 5 (1) ◽

Cited By ~ 13

Author(s):

Zhen-Xing Huang ◽

Pan Zhao ◽

Gui-Sheng Zeng ◽

Yan-Ming Wang ◽

Ian Sudbery ◽

...

Keyword(s):

Candida Albicans ◽

Mouse Model ◽

Cellular Localization ◽

Molecular Mechanisms ◽

Functional Characterization ◽

Content Type ◽

Septin Ring ◽

Wide Range ◽

Ring Dynamics ◽

And Function

ABSTRACT Nap1 has long been identified as a potential septin regulator in yeasts. However, its function and regulation remain poorly defined. Here, we report functional characterization of Nap1 in the human-pathogenic fungus Candida albicans. We find that deletion of NAP1 causes constitutive filamentous growth and changes of septin dynamics. We present evidence that Nap1’s cellular localization and function are regulated by phosphorylation. Phos-tag gel electrophoresis revealed that Nap1 phosphorylation is cell cycle dependent, exhibiting the lowest level around the time of bud emergence. Mass spectrometry identified 10 phosphoserine and phosphothreonine residues in a cluster near the N terminus, and mutation of these residues affected Nap1’s localization to the septin ring and cellular function. Nap1 phosphorylation involves two septin ring-associated kinases, Cla4 and Gin4, and its dephosphorylation occurs at the septin ring in a manner dependent on the phosphatases PP2A and Cdc14. Furthermore, the nap1Δ/Δ mutant and alleles carrying mutations of the phosphorylation sites exhibited greatly reduced virulence in a mouse model of systemic candidiasis. Together, our findings not only provide new mechanistic insights into Nap1’s function and regulation but also suggest the potential to target Nap1 in future therapeutic design. IMPORTANCE Septins are conserved filament-forming GTPases involved in a wide range of cellular events, such as cytokinesis, exocytosis, and morphogenesis. In Candida albicans, the most prevalent human fungal pathogen, septin functions are indispensable for its virulence. However, the molecular mechanisms by which septin structures are regulated are poorly understood. In this study, we deleted NAP1, a gene encoding a putative septin regulator, in C. albicans and found that cells lacking NAP1 showed abnormalities in morphology, invasive growth, and septin ring dynamics. We identified a conserved N-terminal phosphorylation cluster on Nap1 and demonstrated that phosphorylation at these sites regulates Nap1 localization and function. Importantly, deletion of NAP1 or mutation in the N-terminal phosphorylation cluster strongly reduced the virulence of C. albicans in a mouse model of systemic infection. Thus, this study not only provides mechanistic insights into septin regulation but also suggests Nap1 as a potential antifungal target.

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Molecular Mechanisms of ZC3H12C/Reg-3 Biological Activity and Its Involvement in Psoriasis Pathology

International Journal of Molecular Sciences ◽

10.3390/ijms22147311 ◽

2021 ◽

Vol 22 (14) ◽

pp. 7311

Author(s):

Mateusz Wawro ◽

Jakub Kochan ◽

Weronika Sowinska ◽

Aleksandra Solecka ◽

Karolina Wawro ◽

...

Keyword(s):

Family Member ◽

Cellular Localization ◽

Molecular Mechanisms ◽

Inflammatory Diseases ◽

Association Studies ◽

Psoriasis Patient ◽

Genome Wide Association Studies ◽

Mrna Levels ◽

Transcript Levels

The members of the ZC3H12/MCPIP/Regnase family of RNases have emerged as important regulators of inflammation. In contrast to Regnase-1, -2 and -4, a thorough characterization of Regnase-3 (Reg-3) has not yet been explored. Here we demonstrate that Reg-3 differs from other family members in terms of NYN/PIN domain features, cellular localization pattern and substrate specificity. Together with Reg-1, the most comprehensively characterized family member, Reg-3 shared IL-6, IER-3 and Reg-1 mRNAs, but not IL-1β mRNA, as substrates. In addition, Reg-3 was found to be the only family member which regulates transcript levels of TNF, a cytokine implicated in chronic inflammatory diseases including psoriasis. Previous meta-analysis of genome-wide association studies revealed Reg-3 to be among new psoriasis susceptibility loci. Here we demonstrate that Reg-3 transcript levels are increased in psoriasis patient skin tissue and in an experimental model of psoriasis, supporting the immunomodulatory role of Reg-3 in psoriasis, possibly through degradation of mRNA for TNF and other factors such as Reg-1. On the other hand, Reg-1 was found to destabilize Reg-3 transcripts, suggesting reciprocal regulation between Reg-3 and Reg-1 in the skin. We found that either Reg-1 or Reg-3 were expressed in human keratinocytes in vitro. However, in contrast to robustly upregulated Reg-1 mRNA levels, Reg-3 expression was not affected in the epidermis of psoriasis patients. Taken together, these data suggest that epidermal levels of Reg-3 are negatively regulated by Reg-1 in psoriasis, and that Reg-1 and Reg-3 are both involved in psoriasis pathophysiology through controlling, at least in part different transcripts.

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A Concerted Action of UBA5 C-Terminal Unstructured Regions Is Important for Transfer of Activated UFM1 to UFC1

International Journal of Molecular Sciences ◽

10.3390/ijms22147390 ◽

2021 ◽

Vol 22 (14) ◽

pp. 7390

Author(s):

Nicole Wesch ◽

Frank Löhr ◽

Natalia Rogova ◽

Volker Dötsch ◽

Vladimir V. Rogov

Keyword(s):

Cellular Localization ◽

Molecular Mechanisms ◽

Biochemical Characterization ◽

Effective Interaction ◽

Regulatory Region ◽

Titration Calorimetry ◽

Enzymatic Reactions ◽

Cellular Processes ◽

Mechanism Of Interaction

Ubiquitin fold modifier 1 (UFM1) is a member of the ubiquitin-like protein family. UFM1 undergoes a cascade of enzymatic reactions including activation by UBA5 (E1), transfer to UFC1 (E2) and selective conjugation to a number of target proteins via UFL1 (E3) enzymes. Despite the importance of ufmylation in a variety of cellular processes and its role in the pathogenicity of many human diseases, the molecular mechanisms of the ufmylation cascade remains unclear. In this study we focused on the biophysical and biochemical characterization of the interaction between UBA5 and UFC1. We explored the hypothesis that the unstructured C-terminal region of UBA5 serves as a regulatory region, controlling cellular localization of the elements of the ufmylation cascade and effective interaction between them. We found that the last 20 residues in UBA5 are pivotal for binding to UFC1 and can accelerate the transfer of UFM1 to UFC1. We solved the structure of a complex of UFC1 and a peptide spanning the last 20 residues of UBA5 by NMR spectroscopy. This structure in combination with additional NMR titration and isothermal titration calorimetry experiments revealed the mechanism of interaction and confirmed the importance of the C-terminal unstructured region in UBA5 for the ufmylation cascade.

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