[Prevalence of congenital malformations in newborns in the Araucanía region]. / Prevalencia de malformaciones congénitas en recién nacidos de la región de la Araucanía.

INTRODUCTION: Annually, 7.9 million neonates in the world have developmental anomalies. Together with prema turity, they constitute the main causes of mortality during the first year of life in developed and de veloping countries. In Chile, the estimated prevalence is 3.9% of all live births. There are no reports on the prevalence of malformations in the Araucanía Region. OBJECTIVE: to estimate the prevalence of congenital malformations at birth in neonates hospitalized in a Neonatology Service. PATIENTS AND METHOD: cross-sectional study. Reference population: 54,241 live births at the Regional Hospi tal of Temuco over a 10-year period. Cases came from the neonatology hospital discharge database according to the ICD 10 classification, from January 1, 2009, to December 31, 2018. Descriptive and analytical statistics were performed with the STATA 15 software. RESULTS: 949 neonates with one or more congenital malformations were identified. The overall prevalence of neonates with malforma tions was 1.7%, the most prevalent being ventricular septal defect 40.9 x 10,000 live newborns (LNB), atrial septal defect 21.5 x 10,000 LNB, cleft lip and palate 14.0 x 10,000 LNB, congenital hypertrophic cardiomyopathies 8.1 x 10,000 LNB, and congenital rectal atresia and stenosis or absence of the anus 7.9 x 10,000 LNB. CONCLUSIONS: the overall prevalence of malformations is similar to that reported for the country. When analyzing by type, we found significantly higher incidences than those repor ted in previous studies.

The Importance of Therapeutically Targeting the Binary Toxin from Clostridioides difficile.

Novel therapeutics are needed to treat pathologies associated with the Clostridioides difficile binary toxin (CDT), particularly when C. difficile infection (CDI) occurs in the elderly or in hospitalized patients having illnesses, in addition to CDI, such as cancer. While therapies are available to block toxicities associated with the large clostridial toxins (TcdA and TcdB) in this nosocomial disease, nothing is available yet to treat toxicities arising from strains of CDI having the binary toxin. Like other binary toxins, the active CDTa catalytic subunit of CDT is delivered into host cells together with an oligomeric assembly of CDTb subunits via host cell receptor-mediated endocytosis. Once CDT arrives in the host cell's cytoplasm, CDTa catalyzes the ADP-ribosylation of G-actin leading to degradation of the cytoskeleton and rapid cell death. Although a detailed molecular mechanism for CDT entry and host cell toxicity is not yet fully established, structural and functional resemblances to other binary toxins are described. Additionally, unique conformational assemblies of individual CDT components are highlighted herein to refine our mechanistic understanding of this deadly toxin as is needed to develop effective new therapeutic strategies for treating some of the most hypervirulent and lethal strains of CDT-containing strains of CDI.

Smooth Muscle α-Actin Deficiency Leads to Decreased Liver Fibrosis via Impaired Cytoskeletal Signaling in Hepatic Stellate Cells.

In the liver, smooth muscle α-actin (SM α-actin) is up-regulated in hepatic stellate cells (HSCs) as they transition to myofibroblasts during liver injury and the wound healing response. Whether SM α-actin has specific functional effects on cellular effectors of fibrosis such as HSC is controversial. Here, the relationship between SM α-actin and type 1 collagen expression (COL1A1), a major extracellular matrix protein important in liver fibrosis, is investigated with the results demonstrating that knockout of SM α-actin leads to reduced liver fibrosis and COL1 expression. The mechanism for the reduction in fibrogenesis in vivo is multifactorial, including not only a reduction in the number of HSCs, but also an HSC-specific reduction in COL1 expression in Acta2-deficient HSCs. Despite a compensatory increase in expression of cytoplasmic ß-actin and γ-actin isoforms in Acta2-/- HSCs, defects were identified in each transforming growth factor beta/Smad2/3 and ET-1/Erk1/2 signaling in Acta2-/- HSCs. These data not only suggest a molecular link between the SM α-actin cytoskeleton and classic fibrogenic signaling cascades, but also emphasize the relationship between SM α-actin and fibrogenesis in hepatic myofibroblasts in vivo.

RNA interference of muscle actin and ATP synthase beta increases mortality of the phytoplasma vector Euscelidius variegatus.

BACKGROUND: RNA interference (RNAi) techniques have emerged as powerful tools to develop novel management strategies for the control of insect pests. The leafhopper Euscelidius variegatus is a natural vector of chrysanthemum yellows phytoplasma and a laboratory vector of Flavescence dorée phytoplasma. Phytoplasmas are insect-borne bacterial plant pathogens that cause economically relevant crop losses worldwide. RESULTS: In this study, we demonstrated that microinjection of muscle actin and ATP synthase ß double-stranded (ds)RNAs into adult insects caused an exponential reduction in the expression of both genes, which began within 72 h of dsRNA administration and lasted for 14 days, leading to almost complete silencing of the target genes. Such silencing effects on muscle actin expression appeared to be both time- and dose-dependent. Our results also showed that the knockdown of both genes caused a significant decrease in survival rates in comparison with green fluorescent protein (GFP) dsRNA-injected control insects. CONCLUSION: The effectiveness of RNAi-based gene silencing in E. variegatus guarantees the availability of a powerful reverse genetic tool for the functional annotation of its genes and the identification of those potentially involved in the interaction with phytoplasmas. In addition, this study demonstrated that muscle actin and ATP synthase ß may represent candidate genes for RNAi-based control of E. variegatus. © 2018 Society of Chemical Industry.

ß-actin regulates a heterochromatin landscape essential for optimal induction of neuronal programs during direct reprograming.

During neuronal development, ß-actin serves an important role in growth cone mediated axon guidance. Consistent with this notion, in vivo ablation of the ß-actin gene leads to abnormalities in the nervous system. However, whether ß-actin is involved in the regulation of neuronal gene programs is not known. In this study, we directly reprogramed ß-actin+/+ WT, ß-actin+/- HET and ß-actin-/- KO mouse embryonic fibroblast (MEFs) into chemically induced neurons (CiNeurons). Using RNA-seq analysis, we profiled the transcriptome changes among the CiNeurons. We discovered that induction of neuronal gene programs was impaired in KO CiNeurons in comparison to WT ones, whereas HET CiNeurons showed an intermediate levels of induction. ChIP-seq analysis of heterochromatin markers demonstrated that the impaired expression of neuronal gene programs correlated with the elevated H3K9 and H3K27 methylation levels at gene loci in ß-actin deficient MEFs, which is linked to the loss of chromatin association of the BAF complex ATPase subunit Brg1. Together, our study shows that heterochromatin alteration in ß-actin null MEFs impedes the induction of neuronal gene programs during direct reprograming. These findings are in line with the notion that H3K9Me3-based heterochromatin forms a major epigenetic barrier during cell fate change.

Myotonic dystrophy type 1 and pseudo-obstruction in a child with smooth muscle α-actin deficiency and eosinophilic myenteric plexitis.

Myotonic dystrophy (MD) frequently involves the gastrointestinal tract, where it can manifest as chronic intestinal pseudo-obstruction (CIPO), particularly in adults. This manifestation is quite uncommon in children. We report the case of a 12-year-old boy with MD type 1 and CIPO, in which a pathologic assessment revealed an association with smooth muscle α-actin deficiency in the external muscular layer of the ileum, and with features of eosinophilic plexitis and eosinophilic muscle infiltration in the colon. In this peculiar case, the clinical aspects of CIPO might have been due to the involvement of several neuromuscular mechanisms.

Absence of the Drosophila jump muscle actin Act79B is compensated by up-regulation of Act88F.

BACKGROUND: Actins are structural components of the cytoskeleton and muscle, and numerous actin isoforms are found in most organisms. However, many actin isoforms are expressed in distinct patterns allowing each actin to have a specialized function. Numerous studies have demonstrated that actin isoforms both can and cannot compensate for each other under specific circumstances. This allows for an ambiguity of whether isoforms are functionally distinct. RESULTS: In this study, we analyzed mutants of Drosophila Act79B, the predominant actin expressed in the adult jump muscle. Functional and structural analysis of the Act79B mutants found the flies to have normal jumping ability and sarcomere structure. Analysis of actin gene expression determined that expression of Act88F, an actin gene normally expressed in the flight muscles, was significantly up-regulated in the jump muscles of mutants. This indicated that loss of Act79B caused expansion of Act88F expression. When we created double mutants of Act79B and Act88F, this abolished the jump ability of the flies and resulted in severe defects in myofibril formation. CONCLUSIONS: These results indicate that Act88F can functionally substitute for Act79B in the jump muscle, and that the functional compensation in actin expression in the jump muscles only occurs through Act88F. Developmental Dynamics 247:642-649, 2018. © 2018 Wiley Periodicals, Inc.

Loss of Smooth Muscle α-Actin Leads to NF-κB-Dependent Increased Sensitivity to Angiotensin II in Smooth Muscle Cells and Aortic Enlargement.

RATIONALE: Mutations in ACTA2, encoding the smooth muscle isoform of α-actin, cause thoracic aortic aneurysms, acute aortic dissections, and occlusive vascular diseases. OBJECTIVE: We sought to identify the mechanism by which loss of smooth muscle α-actin causes aortic disease. METHODS AND RESULTS: Acta2-/- mice have an increased number of elastic lamellae in the ascending aorta and progressive aortic root dilation as assessed by echocardiography that can be attenuated by treatment with losartan, an angiotensin II (AngII) type 1 receptor blocker. AngII levels are not increased in Acta2-/- aortas or kidneys. Aortic tissue and explanted smooth muscle cells from Acta2-/- aortas show increased production of reactive oxygen species and increased basal nuclear factor κB signaling, leading to an increase in the expression of the AngII receptor type I a and activation of signaling at 100-fold lower levels of AngII in the mutant compared with wild-type cells. Furthermore, disruption of smooth muscle α-actin filaments in wild-type smooth muscle cells by various mechanisms activates nuclear factor κB signaling and increases expression of AngII receptor type I a. CONCLUSIONS: These findings reveal that disruption of smooth muscle α-actin filaments in smooth muscle cells increases reactive oxygen species levels, activates nuclear factor κB signaling, and increases AngII receptor type I a expression, thus potentiating AngII signaling in vascular smooth muscle cells without an increase in the exogenous levels of AngII.

Global expression profiling reveals shared and distinct transcript signatures in arrested act2(-) and CDPK4(-) Plasmodium berghei gametocytes.

Gametocytogenesis and gametogenesis in malaria parasites are complex processes of cell differentiation and development likely involving many gene products. Gametocytes develop in the blood of the vertebrate host but mature gametocytes are not activated until taken up by the mosquito vector. Several distinct mutants have been described that block gametogenesis but the detailed molecular causes for the mutant phenotypes are not understood. To investigate whether a block in gametogenesis also results in a changed transcriptional profile we studied two gene deletions mutants; act2(-) lacking stage-specific actin II and CDPK4(-) lacking calcium-dependent protein kinase 4. Whole genome microarray analysis was performed from RNA of mature gametocytes to compare the transcriptomes of the mutants with wild-type Plasmodium berghei. The microarray analysis identified ∼12% of all genes being differentially expressed in either or both mutants compared to normal gametocytes, as defined by at least two-fold change in transcript abundance. A large proportion of the differentially expressed genes overlapped in the two mutants, consistent with a related outcome of gametocyte arrest. Distinct profiles in each mutant were also observed. Among the down-regulated genes were thioredoxin 2 and members of the merozoite surface protein 7 family. Generation and characterization of a msp7(-)/mspr1(-)/mspr2(-) triple mutant and re-analysis of trx2(-) parasites revealed no impairment of life cycle progression. Together, our analysis provides a resource for molecular signatures of Plasmodium berghei gametogenesis and exemplifies the potential of expression profiling of distinct genetically arrested parasites.

Beta-actin deficiency with oxidative posttranslational modifications in Rett syndrome erythrocytes: insights into an altered cytoskeletal organization.

Beta-actin, a critical player in cellular functions ranging from cell motility and the maintenance of cell shape to transcription regulation, was evaluated in the erythrocyte membranes from patients with typical Rett syndrome (RTT) and methyl CpG binding protein 2 (MECP2) gene mutations. RTT, affecting almost exclusively females with an average frequency of 1∶10,000 female live births, is considered the second commonest cause of severe cognitive impairment in the female gender. Evaluation of beta-actin was carried out in a comparative cohort study on red blood cells (RBCs), drawn from healthy control subjects and RTT patients using mass spectrometry-based quantitative analysis. We observed a decreased expression of the beta-actin isoforms (relative fold changes for spots 1, 2 and 3: -1.82±0.15, -2.15±0.06, and -2.59±0.48, respectively) in pathological RBCs. The results were validated by western blotting and immunofluorescence microscopy. In addition, beta-actin from RTT patients also showed a dramatic increase in oxidative posttranslational modifications (PTMs) as the result of its binding with the lipid peroxidation product 4-hydroxy-2-nonenal (4-HNE). Our findings demonstrate, for the first time, a beta-actin down-regulation and oxidative PTMs for RBCs of RTT patients, thus indicating an altered cytoskeletal organization.

Visceral smooth muscle α-actin deficiency associated with chronic intestinal pseudo-obstruction in a Bengal cat (Felis catus x Prionailurus bengalensis).

An adult Bengal cat (Felis catus × Prionailurus bengalensis) with a prolonged history of partial anorexia, regurgitation, and weight loss and a clinical, radiographic, and ultrasonographic diagnosis of persistent megaesophagus and gastrointestinal ileus was submitted for necropsy. The intestinal tract was diffusely distended by gas and fluid with appreciable loss of muscle tone and an absence of luminal obstruction, consistent with the clinical history of chronic intestinal pseudo-obstruction. Histologically, the autonomic nervous system was intact, but the smooth muscle within the gastrointestinal wall exhibited a marked basophilia that was most pronounced in the jejunum. Immunohistochemistry for neurofilament, synaptophysin, CD117, and desmin demonstrated that the number of myenteric ganglia, number of interstitial cells, and leiomyocyte desmin content were similar when compared with the unaffected age- and species-matched control. Immunohistochemistry for smooth muscle α-actin demonstrated a striking loss of immunoreactivity, predominantly in the circular layer of the jejunum, that corresponded with the tinctorial change in leiomyocytes. Transmission electron microscopy revealed loss of myofibrils, loss of organelle polarity, and significantly larger central mitochondria (megamitochondria) in affected leiomyocytes, as well as nonspecific degenerative changes. Although the presence of a primary leiomyopathy and a causal relationship could not be confirmed in this case, leiomyopathies are considered a cause of chronic intestinal pseudo-obstruction in human medicine, and loss of smooth muscle α-actin immunoreactivity is one recognized marker for intestinal dysmotility.

ß-Actin knock-out mouse embryonic fibroblasts show increased expression of LIM-, CH-, EFh-domain containing proteins with predicted common upstream regulators.

ß-actin depletion from mouse embryonic fibroblasts results in an altered transcriptional response rendering these cells a myofibroblast like phenotype. The proteins and upstream regulatory factors responsible for this acquired phenotype, with prominent focal adhesions and stress fibres, are unknown. Data-mining of the changed proteome revealed that actin binding proteins associated with stress fiber or focal adhesion formation are overexpressed in the ß-actin knock-out cells and that many of these contain CH-, LIM- or EFh- domains. Furthermore in silico analysis predicts potential common upstream regulators that may, at least partly, coordinate the altered transcriptional response.

Aortopathies: etiologies, genetics, differential diagnosis, prognosis and management.

Aortic root and ascending aortic dilatation are indicators associated with risk of aortic dissection, which varies according to underlying etiologic associations, indexed aortic root size, and rate of progression. Typical aortic involvement is most commonly seen in syndromic cases for which there is increasing evidence that aortic aneurysm represents a spectrum of familial inheritance associated with variable genetic penetrance and phenotypic expression. Aortic root and ascending aortic dimensions should be measured routinely with echocardiography. Pharmacologic therapy may reduce the rate of progression. Timing of surgical intervention is guided by indexed aortic size and rate of change of aortic root and ascending aorta dimensions. Lifelong surveillance is recommended.

ß-Actin and fascin-2 cooperate to maintain stereocilia length.

Stereocilia are actin-based protrusions on auditory sensory hair cells that are deflected by sound waves to initiate the conversion of mechanical energy to neuronal signals. Stereocilia maintenance is essential because auditory hair cells are not renewed in mammals. This process requires both ß-actin and γ-actin as knock-out mice lacking either isoform develop distinct stereocilia pathology during aging. In addition, stereocilia integrity may hinge on immobilizing actin, which outside of a small region at stereocilia tips turns over with a very slow, months-long half-life. Here, we establish that ß-actin and the actin crosslinking protein fascin-2 cooperate to maintain stereocilia length and auditory function. We observed that mice expressing mutant fascin-2 (p.R109H) or mice lacking ß-actin share a common phenotype including progressive, high-frequency hearing loss together with shortening of a defined subset of stereocilia in the hair cell bundle. Fascin-2 binds ß-actin and γ-actin filaments with similar affinity in vitro and fascin-2 does not depend on ß-actin for localization in vivo. Nevertheless, double-mutant mice lacking ß-actin and expressing fascin-2 p.R109H have a more severe phenotype suggesting that each protein has a different function in a common stereocilia maintenance pathway. Because the fascin-2 p.R109H mutant binds but fails to efficiently crosslink actin filaments, we propose that fascin-2 crosslinks function to slow actin depolymerization at stereocilia tips to maintain stereocilia length.

Cytokine secretion by CD4+ T cells at the immunological synapse requires Cdc42-dependent local actin remodeling but not microtubule organizing center polarity.

Cytokine secretion by T lymphocytes plays a central role in mounting adaptive immune responses. However, little is known about how newly synthesized cytokines, once produced, are routed within T cells and about the mechanisms involved in regulating their secretions. In this study, we investigated the role of cytoskeleton remodeling at the immunological synapse (IS) in cytokine secretion. We show that a key regulator of cytoskeleton remodeling, the Rho GTPase Cdc42, controls IFN-γ secretion by primary human CD4+ T lymphocytes. Surprisingly, microtubule organizing center polarity at the IS, which does not depend on Cdc42, is not required for cytokine secretion by T lymphocytes, whereas microtubule polymerization is required. In contrast, actin remodeling at the IS, which depends on Cdc42, controls the formation of the polymerized actin ring at the IS, the dynamic concentration of IFN-γ-containing vesicles inside this ring, and the secretion of these vesicles. These results reveal a previously unidentified role of Cdc42-dependent actin remodeling in cytokine exocytosis at the IS.

The actin family member Arp6 and the histone variant H2A.Z are required for spatial positioning of chromatin in chicken cell nuclei.

The spatial organization of chromatin in the nucleus contributes to genome function and is altered during the differentiation of normal and tumorigenic cells. Although nuclear actin-related proteins (Arps) have roles in the local alteration of chromatin structure, it is unclear whether they are involved in the spatial positioning of chromatin. In the interphase nucleus of vertebrate cells, gene-dense and gene-poor chromosome territories (CTs) are located in the center and periphery, respectively. We analyzed chicken DT40 cells in which Arp6 had been knocked out conditionally, and showed that the radial distribution of CTs was impaired in these knockout cells. Arp6 is an essential component of the SRCAP chromatin remodeling complex, which deposits the histone variant H2A.Z into chromatin. The redistribution of CTs was also observed in H2A.Z-deficient cells for gene-rich microchromosomes, but to lesser extent for gene-poor macrochromosomes. These results indicate that Arp6 and H2A.Z contribute to the radial distribution of CTs through different mechanisms. Microarray analysis suggested that the localization of chromatin to the nuclear periphery per se is insufficient for the repression of most genes.

Heterocomplex formation by Arp4 and ß-actin is involved in the integrity of the Brg1 chromatin remodeling complex.

Although nuclear actin and Arps (actin-related proteins) are often identified as components of multi-protein chromatin-modifying enzyme complexes, such as chromatin remodeling and histone acetyltransferase (HAT) complexes, their molecular functions still remain largely elusive. Here, we investigated the role of human Arp4 (BAF53, also known as actin-like protein 6A) in Brg1-containing chromatin remodeling complexes. Depletion of Arp4 by RNA interference impaired the integrity of these complexes and accelerated the degradation of Brg1, indicating a crucial role in their maintenance, at least in certain human cell lines. We further found that Arp4 can form a heterocomplex with ß-actin. Based on structural similarities between conventional actin and Arp4, and the assumption that actin-Arp4 binding might mimic actin-actin binding, we introduced a series of mutations in Arp4 that might be expected to impair its interaction with ß-actin. Some of them indeed caused reduced binding to ß-actin. Interestingly, such mutant Arp4 proteins also showed reduced incorporation into Brg1 complexes, and their interaction with Myc-associated complexes as well as Tip60 HAT complexes were also impaired. Based on these findings, we propose that ß-actin-Arp4 complex formation might be a crucial feature in some chromatin-modifying enzyme complexes, such as the Brg1 complex.