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Importance: Sexual reproduction allows eukaryotic organisms to produce genetically diverse progeny. This process relies on meiosis, a reductional division that enables ploidy maintenance and genetic recombination. Meiotic differentiation also involves the renewal of cell functioning to promote offspring rejuvenation. Research in the model fungus Podospora anserina has shown that this process involves a complex regulation of the function and dynamics of different organelles, including peroxisomes. These organelles are critical for meiosis induction and play further significant roles in meiotic development. Here we show that PEX13-a key constituent of the protein conduit through which the proteins defining peroxisome function reach into the organelle-is subject to a developmental regulation that almost certainly involves its selective ubiquitination-dependent removal and that modulates its abundance throughout meiotic development and at different sexual differentiation processes. Our results show that meiotic development involves a complex developmental regulation of the peroxisome protein translocation system., Competing Interests: The authors declare no conflict of interest.

The endoplasmic reticulum (ER) is an elaborate organelle composed of distinct structural and functional domains. ER structure and dynamics involve membrane-shaping proteins of the reticulon and Yop1/DP1 families, which promote membrane curvature and regulate ER shaping and remodeling. Here, we analyzed the function of the reticulon (RTN1) and Yop1 proteins (YOP1 and YOP2) of the model fungus Podospora anserina and their contribution to sexual development. We found that RTN1 and YOP2 localize to the peripheral ER and are enriched in the dynamic apical ER domains of the polarized growing hyphal region. We discovered that the formation of these domains is diminished in the absence of RTN1 or YOP2 and abolished in the absence of YOP1 and that hyphal growth is moderately reduced when YOP1 is deleted in combination with RTN1 and/or YOP2 . In addition, we found that RTN1 associates with the Spitzenkörper. Moreover, RTN1 localization is regulated during meiotic development, where it accumulates at the apex of growing asci (meiocytes) during their differentiation and at their middle region during the subsequent meiotic progression. Furthermore, we discovered that loss of RTN1 affects ascospore (meiotic spore) formation, in a process that does not involve YOP1 or YOP2. Finally, we show that the defects in ascospore formation of rtn1 mutants are associated with defective nuclear segregation and spindle dynamics throughout meiotic development. Our results show that sexual development in P. anserina involves a developmental remodeling of the ER that implicates the reticulon RTN1, which is required for meiotic nucleus segregation. IMPORTANCE Meiosis consists of a reductional cell division, which allows ploidy maintenance during sexual reproduction and which provides the potential for genetic recombination, producing genetic variation. Meiosis constitutes a process of foremost importance for eukaryotic evolution. Proper partitioning of nuclei during this process relies on accurate functioning and positioning of the spindle, the microtubule cytoskeletal apparatus that conducts chromosome segregation. In this research, we show that in the model fungus Podospora anserina this process requires a protein involved in structuring the endoplasmic reticulum (ER)-the reticulon RTN1. The ER is a complex organelle composed of distinct structural domains, including different peripheral domains and the nuclear envelope. Our findings suggest that spindle dynamics during meiosis relies on remodeling of the ER membrane, which involves the activity of RTN1. Our research discloses that the proteins implicated in shaping the ER are main contributors to the regulation of nuclear dynamics during the sexual cycle.

Introduction: Periodontal disease (PD) is a chronic inflammation of the soft tissues that support the structure of the tooth, and miRNAs are highly dynamic molecules that participate in the regulation of gene expression interfering with multiple genetic targets. The dysregulation of the expression of miRNAs has been associated with different types of pathologies; therefore, they are excellent molecules to be studied as biomarkers. Material and Methods . A search was made in the electronic databases of PubMed, Scopus, and Science Direct. The following key words were used: "microRNAs," "miRNAs," "periodontal disease," "periodontitis," and "biomarker"; employee independent search strategies with the Boolean operators "OR" and "AND"; a further search of the references of the selected studies was performed to detect potential studies that met the selection criteria. The data recollected from each article were author, country, year of publication, sample size, type of sample used to identify miRNAs, methodology used to identify miRNAs, type of periodontal disease, and miRNAs identified., Results: Of the 13 selected studies, 6 used gingival tissue as a sample for the identification of miRNAs, 3 used gingival fluid, 2 used saliva, 1 used serum, and another used periodontal tissue. Chronic periodontitis was the most studied periodontal disease in 9 of the 13 selected articles; 7 used microarrays as the main technique for the identification of miRNAs. qRT-PCR was the assay choice to validate the identified miRNAs., Conclusion: The main type of periodontal disease on which most studies are focused is chronic periodontitis, with the main miRNAs being hsa-miR-146a, hsa-miR-146b, hsa-miR-155, and hsa-miR-200. This systematic review is one of the first to carry out an analysis of the current role of miRNAs in PD as biomarkers., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2021 María Verónica Cuevas-González et al.)

Peroxisomes and mitochondria are organelles that perform major functions in the cell and whose activity is very closely associated. In fungi, the function of these organelles is critical for many developmental processes. Recent studies have disclosed that, additionally, fungal development comprises a dynamic regulation of the activity of these organelles, which involves a developmental regulation of organelle assembly, as well as a dynamic modulation of the abundance, distribution, and morphology of these organelles. Furthermore, for many of these processes, the dynamics of peroxisomes and mitochondria are governed by common factors. Notably, intense research has revealed that the process that drives the division of mitochondria and peroxisomes contributes to several developmental processes-including the formation of asexual spores, the differentiation of infective structures by pathogenic fungi, and sexual development-and that these processes rely on selective removal of these organelles via autophagy. Furthermore, evidence has been obtained suggesting a coordinated regulation of organelle assembly and dynamics during development and supporting the existence of regulatory systems controlling fungal development in response to mitochondrial activity. Gathered information underscores an important role for mitochondrial and peroxisome dynamics in fungal development and suggests that this process involves the concerted activity of these organelles.

Alu elements are primate-specific repeats and represent the most abundant type of transposable elements (TE) in the human genome. Genome-wide analysis of the enrichment of histone post-translational modifications suggests that human Alu sequences could function as transcriptional enhancers; however, no functional experiments have evaluated the role of Alu sequences in the control of transcription in situ . The present study analyses the regulatory activity of a human Alu sequence from the AluSx family located in the second intron of the long intergenic non-coding RNA Linc00441 , found in divergent orientation to the RB1 gene. We observed that the Alu sequence acts as an enhancer element based on reporter gene assays while CRISPR-Cas9 deletions of the Alu sequence in K562 cells resulted in a marked transcriptional upregulation of Linc00441 and a decrease in proliferation. Our results suggest that an intragenic Alu sequence with enhancer activity can act as a transcriptional attenuator of its host lincRNA., (Copyright © 2020 Pérez-Molina, Arzate-Mejía, Ayala-Ortega, Guerrero, Meier, Suaste-Olmos and Recillas-Targa.)

In the last two decades, alginate scaffolds have been variously studied as extracellular matrix analogs for tissue engineering. However, relevant evidence is still lacking concerning their ability to mimic the microenvironment of hierarchical tissues such as bone. Hence, an increasing amount of attention has recently been devoted to the fabrication of macro/microporous sponges with pore anisotropy able to more accurately replicate the cell niche structure as a trigger for bioactive functionalities. This paper presents an in vivo study of alginate sponges with anisotropic microporous domains (MAS) formed by ionic crosslinking in the presence of different fractions (30 or 50% v) of hydroxyapatite (HA). In comparison with unloaded sponges (MAS0), we demonstrated that HA confers peculiar physical and biological properties to the sponge, depending upon the inorganic fraction used, enabling the sponge to bio-mimetically support the regeneration of newly formed bone. Scanning electron microscopy analysis showed a preferential orientation of pores, ascribable to the physical constraints exerted by HA particles during the pore network formation. Energy dispersive spectroscopy (EDS) and X-Ray diffraction (XRD) confirmed a chemical affinity of HA with the native mineral phase of the bone. In vitro studies via WST-1 assay showed good adhesion and proliferation of human Dental Pulp-Mesenchymal Stem Cells (hDP-MSC) that increased in the presence of the bioactive HA signals. Moreover, in vivo studies via micro-CT and histological analyses of a bone model (e.g., a rat calvaria defect) confirmed that the maximum osteogenic response after 90 days was achieved with MAS30, which supported good regeneration of the calvaria defect without any evidence of inflammatory reaction. Hence, all of the results suggested that MAS is a promising scaffold for supporting the regeneration of hard tissues in different body compartments., (Copyright © 2020 Serrano-Bello, Cruz-Maya, Suaste-Olmos, González-Alva, Altobelli, Ambrosio, Medina, Guarino and Alvarez-Perez.)

Mitochondria and peroxisomes are organelles whose activity is intimately associated and that play fundamental roles in development. In the model fungus Podospora anserina , peroxisomes and mitochondria are required for different stages of sexual development, and evidence indicates that their activity in this process is interrelated. Additionally, sexual development involves precise regulation of peroxisome assembly and dynamics. Peroxisomes and mitochondria share the proteins mediating their division. The dynamin-related protein Dnm1 (Drp1) along with its membrane receptors, like Fis1, drives this process. Here we demonstrate that peroxisome and mitochondrial fission in P. anserina depends on FIS1 and DNM1. We show that FIS1 and DNM1 elimination affects the dynamics of both organelles throughout sexual development in a developmental stage-dependent manner. Moreover, we discovered that the segregation of peroxisomes, but not mitochondria, is affected upon elimination of FIS1 or DNM1 during the division of somatic hyphae and at two central stages of sexual development-the differentiation of meiocytes (asci) and of meiotic-derived spores (ascospores). Furthermore, we found that FIS1 and DNM1 elimination results in delayed karyogamy and defective ascospore differentiation. Our findings reveal that sexual development relies on complex remodeling of peroxisomes and mitochondria, which is driven by their common fission machinery., (Copyright © 2020 Navarro-Espíndola, Takano-Rojas, Suaste-Olmos and Peraza-Reyes.)

Chromatin regulation and organization are essential processes that regulate gene activity. The CCCTC-binding factor (CTCF) is a protein with different and important molecular functions related with chromatin dynamics. It is conserved since invertebrates to vertebrates, posing it as a factor with an important role in the physiology. In this work, we aimed to understand the distribution and functional relevance of CTCF during the embryonic development of the zebrafish (Danio rerio). We generated a zebrafish specific anti-Ctcf antibody, and found this protein to be ubiquitous, through different stages and tissues. We used the CRISPR-Cas9 system to induce molecular alterations in the locus. This resulted in early lethality. We delayed the lethality performing knockdown morpholino experiments, and found an aberrant embryo morphology involving malformations in structures through all the length of the embryo. These phenotypes were rescued with human CTCF mRNA injections, showing the specificity of the morpholinos and a partial functional conservation between the fish and the human proteins. Lastly, we found that the pro-apoptotic genes p53 and bbc3/PUMA are deregulated in the ctcf morpholino-injected embryos. In conclusion, CTCF is a ubiquitous factor during the zebrafish development, which regulates the correct formation of different structures of the embryo, and its deregulation impacts on essential cell survival genes. Overall, this work provides a basis to look for the particular functions of CTCF in the different developing tissues and organs of the zebrafish., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Peroxisomes are versatile organelles essential for diverse developmental processes. One such process is the meiotic development of Podospora anserina. In this fungus, absence of the docking peroxin PEX13, the RING-finger complex peroxins, or the PTS2 co-receptor PEX20 blocks sexual development before meiocyte formation. However, this defect is not seen in the absence of the receptors PEX5 and PEX7, or of the docking peroxins PEX14 and PEX14/17. Here we describe the function of the remaining uncharacterized P. anserina peroxins predictably involved in peroxisome matrix protein import. We show that PEX8, as well as the peroxins potentially mediating receptor monoubiquitination (PEX4 and PEX22) and membrane dislocation (PEX1, PEX6 and PEX26) are indeed implicated in peroxisome matrix protein import in this fungus. However, we observed that elimination of PEX4 and PEX22 affects to different extent the import of distinct PEX5 cargoes, suggesting differential ubiquitination-complex requirements for the import of distinct proteins. In addition, we found that elimination of PEX1, PEX6 or PEX26 results in loss of peroxisomes, suggesting that these peroxins restrain peroxisome removal in specific physiological conditions. Finally, we demonstrate that all analyzed peroxins are required for meiocyte formation, and that PEX20 function in this process depends on its potential monoubiquitination target cysteine. Our results suggest that meiotic induction relies on a peroxisome import pathway, which is not dependent on PEX5 or PEX7 but that is driven by an additional cycling receptor. These findings uncover a collection of peroxins implicated in modulating peroxisome activity to facilitate a critical developmental cell fate decision., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The three-dimensional architecture of genomes provides new insights about genome organization and function, but many aspects remain unsolved at the local genomic scale. Here we investigate the regulation of two erythroid-specific loci, a folate receptor gene (FOLR1) and the β-globin gene cluster, which are separated by 16kb of constitutive heterochromatin. We found that in early erythroid differentiation the FOLR1 gene presents a permissive chromatin configuration that allows its expression. Once the transition to the next differentiation state occurs, the heterochromatin spreads into the FOLR1 domain, concomitant with the dissociation of CTCF from a novel binding site, thereby resulting in irreversible silencing of the FOLR1 gene. We demonstrate that the sequences surrounding the CTCF-binding site possess classical insulator properties in vitro and in vivo. In contrast, the chicken cHS4 β-globin insulator present on the other side of the heterochromatic segment is in a constitutive open chromatin configuration, with CTCF constantly bound from the early stages of erythroid differentiation. Therefore, this study demonstrates that the 16kb of constitutive heterochromatin contributes to silencing of the FOLR1 gene during erythroid differentiation., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In this work we characterize the function of the flagellar protein FliL in Rhodobacter sphaeroides. Our results show that FliL is essential for motility in this bacterium and that in its absence flagellar rotation is highly impaired. A green fluorescent protein (GFP)-FliL fusion forms polar and lateral fluorescent foci that show different spatial dynamics. The presence of these foci is dependent on the expression of the flagellar genes controlled by the master regulator FleQ, suggesting that additional components of the flagellar regulon are required for the proper localization of GFP-FliL. Eight independent pseudorevertants were isolated from the fliL mutant strain. In each of these strains a single nucleotide change in motB was identified. The eight mutations affected only three residues located on the periplasmic side of MotB. Swimming of the suppressor mutants was not affected by the presence of the wild-type fliL allele. Pulldown and yeast two-hybrid assays showed that that the periplasmic domain of FliL is able to interact with itself but not with the periplasmic domain of MotB. From these results we propose that FliL could participate in the coupling of MotB with the flagellar rotor in an indirect fashion.