On the burrows of Echiuram worms (Echiura): a survey

Estudou-se o biótopo e a arquitetura das galerias dos equiúros Lissomyema exilii e Ochetostoma erythrogrammons comparando-se os resultados com os existentes na literatura para outros equiuros. Lissomyema exilii constrói, com areia fina e lôdo, uma galeria em forma de U, dentro de conchas de moluscos e de carapaças de equinóides irregulares. As conchas estão enterradas entre 100 e 220 mm de profundidade na areia lodosa; o verme comunica-se com a superfície através de um par de canais estreitos, situados entre a galeria e o sedimento da superfície da praia. Os canais e a galeria são revestidos, internamente, com muco endurecido. No sedimento superficial as galerias de equiúros são identificadas, principalmente, por pequenos montes de pelotas fecais. Lissomyema exilii povoa uma pequena área de fundo de mar da região entre-marés no litoral norte de São Paulo, Brasil; a densida de populacional é de 11 animais/m2. A macrofauna da área em estudo é composta principalmente de poliquetos, moluscos e crustáceos, a maioria dos quais vive em galerias ou apresenta tendências cavadoras. As galerias de Lissomyjema exilii acomodam vários comensais entre eles, cinco espécies de poliquetos, duas de nematodes, duas de entoproctos, uma de nudibrânquio e um crustáceo. Ochetostoma erythrogvammon constrói tubos em forma de L, em praias de areia clara e grossa. Até o momento não foram encontrados comensais nestas galerias

On a new species of Alomasoma (Eichiura: Bonelliidae) from Antarctica

Alomasoma lanai é uma nova espécie de Bonelliidae (Echiura) coletada na Antartica. A nova espécie é de tamanho médio e abriga muitos machos anões presos a pele do tronco. A espécie mostra uma característica única na forma de umsulco transversal que contem a cova genital

Sipunculus marcusi spec. nov. (Sipuncula) from southern Brazil

Descreve-se Sipunculus marcusi spec. nov. da costa do Estado de São Paulo. A espécie em questão difere das outras do gênero Sipunculus principalmente pelas imensas bases dos músculos retrato res da probóscide; estas bases estão unidas umas às outras abrangendo cerca de 18 faixas musculares longitudinais em cada lado do cordão nervoso ventral

T Lymphocyte Potential Marks the Emergence of Definitive Hematopoietic Progenitors in Human Pluripotent Stem Cell Differentiation Cultures

SummaryThe efficient generation of hematopoietic stem cells from human pluripotent stem cells is dependent on the appropriate specification of the definitive hematopoietic program during differentiation. In this study, we used T lymphocyte potential to track the onset of definitive hematopoiesis from human embryonic and induced pluripotent stem cells differentiated with specific morphogens in serum- and stromal-free cultures. We show that this program develops from a progenitor population with characteristics of hemogenic endothelium, including the expression of CD34, VE-cadherin, GATA2, LMO2, and RUNX1. Along with T cells, these progenitors display the capacity to generate myeloid and erythroid cells. Manipulation of Activin/Nodal signaling during early stages of differentiation revealed that development of the definitive hematopoietic progenitor population is not dependent on this pathway, distinguishing it from primitive hematopoiesis. Collectively, these findings demonstrate that it is possible to generate T lymphoid progenitors from pluripotent stem cells and that this lineage develops from a population whose emergence marks the onset of human definitive hematopoiesis

Primitive Erythropoiesis Is Regulated by miR-126 via Nonhematopoietic Vcam-1+ Cells

SummaryPrimitive erythropoiesis defines the onset of hematopoiesis in the yolk sac of the early embryo and is initiated by the emergence of progenitors assayed as colony-forming cells (EryP-CFCs). EryP-CFCs are detected for only a narrow window during embryonic development, suggesting that both their initiation and termination are tightly controlled. Using the embryonic stem differentiation system to model primitive erythropoiesis, we found that miR-126 regulates the termination of EryP-CFC development. Analyses of miR-126 null embryos revealed that this miR also regulates EryP-CFCs in vivo. We identified vascular cell adhesion molecule-1 (Vcam-1) expressed by a mesenchymal cell population as a relevant target of miR-126. Interaction of EryP-CFCs with Vcam-1 accelerated their maturation to ßh1-globin+ and Ter119+ cells through a Src family kinase. These findings uncover a cell nonautonomous regulatory pathway for primitive erythropoiesis that may provide insight into the mechanism(s) controlling the developmental switch from primitive to definitive hematopoiesis

Extracellular laminin regulates hematopoietic potential of pluripotent stem cells through integrin β1-ILK-β-catenin-JUN axis

血液細胞へ効率よく変化させる弱い接着を明らかに --血液細胞の産生効率を向上--. 京都大学プレスリリース. 2021-03-31.Stuck stem cells are no good at making blood. 京都大学プレスリリース. 2021-03-31.Recombinant matrices have enabled feeder cell-free maintenance cultures of human pluripotent stem cells (hPSCs), with laminin 511-E8 fragment (LM511-E8) being widely used. However, we herein report that hPSCs maintained on LM511-E8 resist differentiating to multipotent hematopoietic progenitor cells (HPCs), unlike hPSCs maintained on LM421-E8 or LM121-E8. The latter two LM-E8s bound weakly to hPSCs compared with LM511-E8 and activated the canonical Wnt/β-catenin signaling pathway. Moreover, the extracellular LM-E8-dependent preferential hematopoiesis was associated with a higher expression of integrin β1 (ITGB1) and downstream integrin-linked protein kinase (ILK), β-catenin and phosphorylated JUN. Accordingly, the lower coating concentration of LM511-E8 or addition of a Wnt/β-catenin signaling activator, CHIR99021, facilitated higher HPC yield. In contrast, the inhibition of ILK, Wnt or JNK by inhibitors or mRNA knockdown suppressed the HPC yield. These findings suggest that extracellular laminin scaffolds modulate the hematopoietic differentiation potential of hPSCs by activating the ITGB1-ILK-β-catenin-JUN axis at the undifferentiated stage. Finally, the combination of low-concentrated LM511-E8 and a revised hPSC-sac method, which adds bFGF, SB431542 and heparin to the conventional method, enabled a higher yield of HPCs and higher rate for definitive hematopoiesis, suggesting a useful protocol for obtaining differentiated hematopoietic cells from hPSCs in general

The LARGE Principle of Cellular Reprogramming: Lost, Acquired and Retained Gene Expression in Foreskin and Amniotic Fluid-Derived Human iPS Cells

Human amniotic fluid cells (AFCs) are routinely obtained for prenatal diagnostics procedures. Recently, it has been illustrated that these cells may also serve as a valuable model system to study developmental processes and for application in regenerative therapies. Cellular reprogramming is a means of assigning greater value to primary AFCs by inducing self-renewal and pluripotency and, thus, bypassing senescence. Here, we report the generation and characterization of human amniotic fluid-derived induced pluripotent stem cells (AFiPSCs) and demonstrate their ability to differentiate into the trophoblast lineage after stimulation with BMP2/BMP4. We further carried out comparative transcriptome analyses of primary human AFCs, AFiPSCs, fibroblast-derived iPSCs (FiPSCs) and embryonic stem cells (ESCs). This revealed that the expression of key senescence-associated genes are down-regulated upon the induction of pluripotency in primary AFCs (AFiPSCs). By defining distinct and overlapping gene expression patterns and deriving the LARGE (Lost, Acquired and Retained Gene Expression) Principle of Cellular Reprogramming, we could further highlight that AFiPSCs, FiPSCs and ESCs share a core self-renewal gene regulatory network driven by OCT4, SOX2 and NANOG. Nevertheless, these cell types are marked by distinct gene expression signatures. For example, expression of the transcription factors, SIX6, EGR2, PKNOX2, HOXD4, HOXD10, DLX5 and RAXL1, known to regulate developmental processes, are retained in AFiPSCs and FiPSCs. Surprisingly, expression of the self-renewal-associated gene PRDM14 or the developmental processes-regulating genes WNT3A and GSC are restricted to ESCs. Implications of this, with respect to the stability of the undifferentiated state and long-term differentiation potential of iPSCs, warrant further studies

Clonal Characterization of Rat Muscle Satellite Cells: Proliferation, Metabolism and Differentiation Define an Intrinsic Heterogeneity

Satellite cells (SCs) represent a distinct lineage of myogenic progenitors responsible for the postnatal growth, repair and maintenance of skeletal muscle. Distinguished on the basis of their unique position in mature skeletal muscle, SCs were considered unipotent stem cells with the ability of generating a unique specialized phenotype. Subsequently, it was demonstrated in mice that opposite differentiation towards osteogenic and adipogenic pathways was also possible. Even though the pool of SCs is accepted as the major, and possibly the only, source of myonuclei in postnatal muscle, it is likely that SCs are not all multipotent stem cells and evidences for diversities within the myogenic compartment have been described both in vitro and in vivo. Here, by isolating single fibers from rat flexor digitorum brevis (FDB) muscle we were able to identify and clonally characterize two main subpopulations of SCs: the low proliferative clones (LPC) present in major proportion (∼75%) and the high proliferative clones (HPC), present instead in minor amount (∼25%). LPC spontaneously generate myotubes whilst HPC differentiate into adipocytes even though they may skip the adipogenic program if co-cultured with LPC. LPC and HPC differ also for mitochondrial membrane potential (ΔΨm), ATP balance and Reactive Oxygen Species (ROS) generation underlying diversities in metabolism that precede differentiation. Notably, SCs heterogeneity is retained in vivo. SCs may therefore be comprised of two distinct, though not irreversibly committed, populations of cells distinguishable for prominent differences in basal biological features such as proliferation, metabolism and differentiation. By these means, novel insights on SCs heterogeneity are provided and evidences for biological readouts potentially relevant for diagnostic purposes described