Showing papers on "Totipotent published in 2015"

Early embryonic-like cells are induced by downregulating replication-dependent chromatin assembly

Abstract: Cellular plasticity is essential for early embryonic cells. Unlike pluripotent cells, which form embryonic tissues, totipotent cells can generate a complete organism including embryonic and extraembryonic tissues. Cells resembling 2-cell-stage embryos (2C-like cells) arise at very low frequency in embryonic stem (ES) cell cultures. Although induced reprogramming to pluripotency is well established, totipotent cells remain poorly characterized, and whether reprogramming to totipotency is possible is unknown. We show that mouse 2C-like cells can be induced in vitro through downregulation of the chromatin-assembly activity of CAF-1. Endogenous retroviruses and genes specific to 2-cell embryos are the highest-upregulated genes upon CAF-1 knockdown. Emerging 2C-like cells exhibit molecular characteristics of 2-cell embryos and higher reprogrammability than ES cells upon nuclear transfer. Our results suggest that early embryonic-like cells can be induced by modulating chromatin assembly and that atypical histone deposition may trigger the emergence of totipotent cells.

Methods and compositions for targeted genetic modifications and methods of use

Abstract: Methods and compositions are provided for generating targeted genetic modifications on the Y chromosome or a challenging target locus. Compositions include an in vitro culture comprising an XY pluripotent and/or totipotent animal cell (i.e., XY ES cells or XY iPS cells) having a modification that decreases the level and/or activity of an Sry protein; and, culturing these cells in a medium that promotes development of XY F0 fertile females. Such compositions find use in various methods for making a fertile female XY non-human mammal in an F0 generation.

Direct somatic lineage conversion.

Abstract: The predominant view of embryonic development and cell differentiation has been that rigid and even irreversible epigenetic marks are laid down along the path of cell specialization ensuring the proper silencing of unrelated lineage programmes. This model made the prediction that specialized cell types are stable and cannot be redirected into other lineages. Accordingly, early attempts to change the identity of somatic cells had little success and was limited to conversions between closely related cell types. Nuclear transplantation experiments demonstrated, however, that specialized cells even from adult mammals can be reprogrammed into a totipotent state. The discovery that a small combination of transcription factors can reprogramme cells to pluripotency without the need of oocytes further supported the view that these epigenetic barriers can be overcome much easier than assumed, but the extent of this flexibility was still unclear. When we showed that a differentiated mesodermal cell can be directly converted to a differentiated ectodermal cell without a pluripotent intermediate, it was suggested that in principle any cell type could be converted into any other cell type. Indeed, the work of several groups in recent years has provided many more examples of direct somatic lineage conversions. Today, the question is not anymore whether a specific cell type can be generated by direct reprogramming but how it can be induced.

Adult stem cells in neural repair： Current options,limitations and perspectives

Abstract: Stem cells represent a promising step for the future ofregenerative medicine. As they are able to differentiateinto any cell type, tissue or organ, these cells are greatcandidates for treatments against the worst diseasesthat defy doctors and researchers around the world.Stem cells can be divided into three main groups （1）embryonic stem cells; （2） fetal stem cells; and （3） adultstem cells. In terms of their capacity for proliferation,stem cells are also classified as totipotent, pluripotentor multipotent. Adult stem cells, also known as somaticcells, are found in various regions of the adult organism,such as bone marrow, skin, eyes, viscera and brain.They can differentiate into unipotent cells of theresiding tissue, generally for the purpose of repair.These cells represent an excellent choice in regenerativemedicine, every patient can be a donor of adult stemcells to provide a more customized and efficient therapyagainst various diseases, in other words, they allow theopportunity of autologous transplantation. But in orderto start clinical trials and achieve great results, we needto understand how these cells interact with the hosttissue, how they can manipulate or be manipulated bythe microenvironment where they will be transplantedand for how long they can maintain their multipotentstate to provide a full regeneration.

Totipotency in the absence of CAF-I: unhindered choices when the chaperone is out

Abstract: Embryonal totipotent cells can produce both embryonic and extraembryonic tissues and can generate whole organisms. In mice this level of genome plasticity is preserved in the 2-cell embryos, but is absent in embryonic cells from later stages of development. Recently it has been demonstrated that totipotent-like cells spontaneously appear in embryonic stem cell cultures and that the depletion of the histone chaperone Chromatin Assembly Factor I (CAF-I) increases the abundance of 2cell-like cells. On the other hand, earlier studies have demonstrated that CAF-I is necessary for epigenetic conversions at the telomeres of S. cerevisiae. This commentary proposes that the absence of CAF-I confers totipotency of embryonic cells and that its activation triggers chromatin changes that reset the epigenome toward cell differentiation.

Want reprogramming? Cut back on the chromatin assembly!

Abstract: Totipotency, the ability of early embryonic cells to generate a complete adult organism as well as extraembryonic tissue, is a fleeting property found only in very early embryonic cells. A breakthrough study now shows that inhibition of DNA replication–linked nucleosome assembly causes embryonic stem cells to resemble totipotent cells. Notably, inhibition of chromatin assembly stimulates reprogramming during somatic-cell nuclear transfer experiments.

The generation of sex cells

Abstract: Primordial germ cells (PGCs) are the earliest population of germ cells established during embryonic development and constitute the beginning of the totipotent state. A recent study provides a new protocol for the efficient generation of PGC-like cells from human embryonic stem cells, providing an in vitro platform to study human PGC differentiation and specification.

Stimulus-triggered Fate Conversion of Somatic Cells into Pluripotency in Chronic Wounds in Human Beings?

Abstract: Bone-marrow derived stem cells are multi potential or totipotent and are able to differentiate into numerous cell types. Their application is indicated in various reconstructive and restorative surgeries for rapid healing. A technique for creating cells that have the embryonic ability to turn into almost any cell type in the mammalian body has been reported. Recently, an u n e x p e c t e d p h e n o m e n o n o f s o m a t i c c e l l reprogramming into pluripotent cells by exposing to sublethal stimuli such as citrate based acidic medium has been reported. With the concept of creating acidic environment in chronic infected wounds to make a condition unsuitable for growth and multiplication of bacteria using 3% citric acid has been reported. It would be interesting to study whether the phenomenon of pluripotency takes place in chronic infected wounds in human beings following the application of 3% citric acid and plays an important role in formation of healthy granulation tissue.

Cloning and its Applications

Abstract: In mammalian fertilization process, female pronucleus share male pronucleus to form the zygote which undergoes mitotic division yielding totipotent cells. After morula compaction, the embryonic cells differentiate into two types of cells; the inner cell mass cells which have the pluripotent stemness criteria to form the embryo proper, and the trophectoderm which would share the placenta formation.

Cellular Reprogramming in Basic and Applied Biomedicine: The Dawn of Regenerative Medicine.

Abstract: Fertilization triggers a cascade of cellular and molecular events restoring the totipotent state and the potential for all cell types. However, the program quickly directs differentiation and cellular commitment. Under the genetic and epigenetic control of this process, Waddington likened this to a three-dimensional landscape where cells could not ascend the slope or traverse once canalized thus leading to cell fate decisions and the progressive restriction of cellular potency. But this is not the only possible outcome at least experimentally. Somatic cell nuclear transfer and overexpression of key transcription factors to generate induced pluripotent cells have challenged this notion. The return to pluripotency and the reinstatement of plasticity and heterogeneity once thought to be the exclusive remit of the developing embryo can now be replicated in vitro. The following chapter introduces some of these ideas and suggests that the fundamental principles learned may constitute the first step toward the opportunity for specific tissue renewal and replacement in healthy aging and the treatment of chronic diseases-the age of regenerative medicine.

Methods for producing a mouse XY embryonic (ES) cell line capable of producing a fertile XY female mouse in an F0 generation

Abstract: Methods and compositions are provided for generating targeted genetic modifications on the Y chromosome or a challenging target locus. Compositions include an in vitro culture comprising an XY pluripotent and/or totipotent animal cell (i.e., XY ES cells or XY iPS cells) having a modification that decreases the level and/or activity of an Sry protein; and, culturing these cells in a medium that promotes development of XY F0 fertile females. Such compositions find use in various methods for making a fertile female XY non-human mammal in an F0 generation.