The heart is the first functional organ to form during the development of an embryo, which, in humans, occurs during the third week post-fertilization. It primarily involves the following sequence of events: the specification of cardiac precursor cells from pluripotent embryonic stem cells and their differentiation into cardiac progenitor cells or cardiomyocytes, the organization of cardiomyocytes into a cardiac tube, followed by septation of the cardiac tube into four chambers as well as the paired arterial trunks. In the past two decades, a plethora of studies using advanced technologies and suitable animal models have provided a detailed account of the various cellular and molecular changes that take place during cardiomyocyte differentiation, the formation of the heart tube, and the development of the four cardiac chambers.
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Cells must replicate their DNA before they can divide. This ensures that each daughter cell gets a copy of the genome, and therefore, successful inheritance of genetic traits. DNA replication is an essential process and the basic mechanism is conserved in all organisms. Read more..
The basic steps during tube formation, including cell polarization, the formation of small multiple lumens and the coalescence of multiple lumens into a single lumen, and subsequent tube elongation, are directly regulated by mechanical signals arising from neighbouring cells as well as the extracellular matrix. Read more..
The various events during cardiac development are driven by mechanical signals sensed through cellular communication with its immediate environment, which include both the extracellular matrix as well as intercellular cell-cell contacts. Read more..
Cardiomyocytes are the chief cell type in the heart and their coordinated contraction as a mass is responsible for the pumping of blood around the developing embryo. Cardiac specification occurs very early on during embryonic development. Read more..
The heart is derived from the splanchnic lateral mesoderm and initially forms as two crescent-shaped endocardial plates inside the evolving pericardial cavity. As the embryo undergoes lateral and cranial folding, the two plates come closer to each other and eventually fuse at the midline, forming a primordial cardiac tube. Read more..
The heart is the first functional organ to form during the development of an embryo, which, in humans, occurs during the third week post-fertilization. Read more..
The transitioning of cells from a mesenchymal to an epithelial lineage is marked by changes in cell polarity, cell motility, cell-cell contact formation, cytoskeletal organization, and extracellular matrix composition. Read more..
During development, the transitioning of epithelial cells to a mesenchymal lineage is not an irreversible process. Instead, a number of developmental programs are accompanied by a reversal of EMT, during which the mesenchyme gets dedifferentiated into the epithelial lineage through a series of molecular events, known as mesenchymal to epithelial transition (MET). Read more..
Mechanical signals, such as the rigidity of the cell’s microenvironment, play a role in the regulation of epithelial to mesenchymal transitions (EMT). Lee et al. observed that mammary epithelial cells underwent EMT when placed on hard substrates and treated with matrix metalloproteinase-3 (MMP3). This was not observed in cells grown on soft substrates. Read more..
Epithelial to mesenchymal transition (EMT) is the process whereby epithelial cells are transformed into mesenchymal cells. Epithelial cells form the epithelium tissue which covers the internal and external body surface of an organism. These cells are polarized and form extensive cell-cell adhesions, including adherens junctions and tight junctions, with each other. Read more..
Based on findings from a large number of anatomical, biochemical, and genetic studies carried out over the years, three major theories have been put forth to describe the cellular origin of hematopoietic stem cells: the hemangioblast theory, the hemogenic endothelium theory,and the mesodermal prehematopoietic precursor theory. Read more..
Once blood circulation is established during the earliest stages of hematopoiesis, the pulsatile nature of blood flow within the aorta generates a range of biomechanical forces, such as fluid shear stress, hydrodynamic pressure, and circumferential stress. A number of studies have shown that the hemodynamic environment within the blood vessels has a direct influence on the structural and functional characteristics of the endothelial cells lining the inner walls of the vascular tissue. Read more..
The hematopoietic system, which comprises all the cellular components of the blood, is one of the earliest organ systems to evolve during embryo development. Hematopoietic stem cells (HSCs), which are rare blood cells residing in the bone marrow of the adult organism, are the founder cells that give rise to the entire hematopoietic system. Read more..
A number of studies, which describe the cellular mechanisms and signaling pathways underlying dorsal closure, have pointed towards a mechanical basis for the morphogenetic changes associated with this process. It is now evident that a coordinated interplay of forces generated within the two major cell types involved, the lateral epithelial cells and the amnioserosal cells, is essential for driving the various stages in dorsal closure. Read more..
Dorsal closure is a well-defined moprhogenetic event that occurs during the early stages of Drosophila embryogenesis. It involves the closing of an elliptical gap at the dorsal midline of the embryo by the convergence and fusion of epithelial cell sheets on either side of the embryo. Read more..
As well as the asymmetric organization of cellular components, polarity can also be defined through the structural orientation of the cytoskeleton, in particular filaments and microtubules. This is important in cell migration and motility, which requires a front-rear polarity in order to determine the direction of movement. Read more..
In polarized epithelial cells, the apical membrane is rich in PIP2 and houses the PAR and Crumbs polarity complexes while the basal membrane contains PIP3 and the Scribble polarity complex. Read more..
Cell polarity refers to the intrinsic asymmetry observed in cells, either in their shape, structure, or organization of cellular components. Most epithelial cells, migrating cells and developing cells require some form of cell polarity for their function. Read more..
Depending on whether the tubular organs are formed from already polarized cells or they require de novo polarization of cells, cellular organization during tubulogenesis can be categorized into one of these five general mechanisms: wrapping, budding, cavitation, cord hollowing, and cell hollowing. Read more..
Tubulogenesis, or the formation of tubes, is one of the fundamental morphogenetic events taking place during development. Several major organs, such as the respiratory, circulatory, and secretory systems, are constituted by an interconnected network of tubes. Read more..
Development in higher order organisms commences at conception and continues into old age. With every stage of development, changes in the physical properties of cells and tissues. In some cases these changes result from fluctuations in the biochemical or metabolic activity of cells, however in other cases, changes in the physical microenvironment drive the biochemical and genomic changes within cells. Read more..
The Hippo signaling pathway is a complex network of proteins that controls organ size via regulation of cellular proliferation, survival and differentiation. Initially discovered by genetic mosaic screens in Drosophila, the core of the Hippo pathway is comprised of two highly conserved kinases centering on the mammalian effector proteins Yes-associated protein (YAP) and its paralogue Transcriptional co-activator with PDZ-binding motif (TAZ, also known as WWTR1). Read more..
The dense network of tight junction strands along the apical region acts a fence to prevent the mixing up of components between the apical and basolateral surfaces. This is essential for the structural and functional differentiation of the two domains and ultimately leads to cell polarity. Read more..
As well as the asymmetric organization of cellular components, polarity can also be defined through the structural orientation of the cytoskeleton, in particular, actin filaments and microtubules. This is important in cell migration and motility, which requires a front-rear polarity in order to determine the direction of movement… Read more…
In polarized epithelial cells, the apical membrane is rich in PIP2 and houses the PAR and Crumbs polarity complexes while the basal membrane contains PIP3 and the Scribble polarity complex. The phosphatase PTEN, which is recruited by tight junction proteins such as Magi 1-3, stabilizes PIP2 distribution at the apical membrane by reversing PI3K-mediated phosphorylation of PIP2 to PIP3… Read more…
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