In this research topic we aim at exploring the recent advancements in stem cell biology. We have a particular focus on molecular mechanisms driving cellular differentiation in various organs, and how these are dysregulated in a disease context. We further aim at reporting on optimization and use of novel model systems and techniques. Keywords : Stem cells, Cellular differentiation, Organoids, Organ development and homeostasis, Disease modeling. Important Note : All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements.
Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review. With their unique mixes of varied contributions from Original Research to Review Articles, Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author. Submission closed. In this process, called gastrulation , three germ layers arise: the endoderm , mesoderm , and ectoderm.
Cells in these three layers will give rise to different parts of the organism. The endoderm eventually becomes the gut. The mesoderm develops into muscle, the skeletal system, some organs, and connective tissue. The ectoderm differentiates into the nervous system and skin. As the embryo continues to develop, individual cells continue to differentiate.
These differentiated cell types are made from what were initially the same types of pluripotent embryonic stem cells. An assortment of physiological mechanisms guides certain cells towards particular developmental pathways, creating varying cell types.
Every cell contains DNA within the nucleus , containing the blueprint to build many different proteins in the cell. Different signals can cause embryonic cells to select specific parts of the DNA which can then be used to synthesize proteins, eventually building different cell types.
Differentiation of cells in the embryo is brought about by both internal cellular factors as well as extracellular factors that act on the cell from the outside. This page has been archived and is no longer updated. Within multicellular organisms, tissues are organized communities of cells that work together to carry out a specific function.
The exact role of a tissue in an organism depends on what types of cells it contains. For example, the endothelial tissue that lines the human gastrointestinal tract consists of several cell types.
Some of these cells absorb nutrients from the digestive contents, whereas others called goblet cells secrete a lubricating mucus that helps the contents travel smoothly.
However, the multiple cell types within a tissue don't just have different functions. They also have different transcriptional programs and may well divide at different rates.
Proper regulation of these rates is essential to tissue maintenance and repair. The spatial organization of the cells that form a tissue is also central to the tissue's function and survival. This organization depends in part on polarity , or the orientation of particular cells in their place. Of course, external signals from neighboring cells or from the extracellular matrix are also important influences on the arrangement of cells in a tissue. Without cell division, long-term tissue survival would be impossible.
Inside every tissue, cells are constantly replenishing themselves through the process of division, although the rate of turnover may vary widely between different cell types in the same tissue. For example, in adult mammal brains, neurons rarely divide. However, glial cells in the brain continue to divide throughout a mammal's adult life. Mammalian epithelial cells also turn over regularly, typically every few days.
Neurons are not the only cells that lose their ability to divide as they mature. In fact, many differentiated cells lose this ability. To help counteract this loss, tissues maintain stem cells to serve as a reservoir of undifferentiated cells. Stem cells typically have the capacity to mature into many different cell types. Transcription factors — proteins that regulate which genes are transcribed in a cell — appear to be essential to determining the pathway particular stem cells take as they differentiate.
For example, both intestinal absorptive cells and goblet cells arise from the same stem cell population, but divergent transcriptional programs cause them to mature into dramatically different cells Figure 1. Whenever stem cells are called upon to generate a particular type of cell, they undergo an asymmetric cell division. With asymmetric division, each of the two resulting daughter cells has its own unique life course.
In this case, one of the daughter cells has a finite capacity for cell division and begins to differentiate, whereas the other daughter cell remains a stem cell with unlimited proliferative ability. Figure 1: Transcriptional regulators can act at different stages, and in different combinations, through the path of cell development and differentiation.
Transcription factors can turn on at different times during cell differentiation. As cells mature and go through different stages arrows , transcription factors colored balls can act on gene expression and change the cell in different ways. This change affects the next generation of cells derived from that cell. In subsequent generations, it is the combination of different transcription factors that can ultimately determine cell type.
Although most of the tissues in adult organisms maintain a constant size, the cells that make up these tissues are constantly turning over. Therefore, in order for a particular tissue to stay the same size, its rates of cell death and cell division must remain in balance.
A variety of factors can trigger cell death in a tissue. For example, the process of apoptosis, or programmed cell death, selectively removes damaged cells — including those with DNA damage or defective mitochondria. During apoptosis, cellular proteases and nucleases are activated, and cells self-destruct.
Cells also monitor the survival factors and negative signals they receive from other cells before initiating programmed cell death.
0コメント