Showing papers on "Totipotent published in 2011"

SOX2 Modulates Reprogramming of Gene Expression in Two-Cell Mouse Embryos

Abstract: Sox2 is a key gene that controls transcriptional networks required for pluripotency. The role of Sox2 in the developmental transition of a highly differentiated oocyte to totipotent blastomeres of the early preimplantation embryo, however, is not known. We report that Sox2, which is localized in the nucleus, is first zygotically expressed during the 2-cell stage and that its expression dramatically increases between the morula and blastocyst stages. Injecting a cRNA encoding Sox2 into 1-cell embryos resulted in overexpression of SOX2 by approximately 70% and developmental arrest at the 2-cell stage, whereas injecting cRNAs encoding Pou5f1, Myc (also known as c-Myc), or Klf4 has little effect on the ability of 2-cell embryos to cleave to the 4-cell stage. Global transcription assessed by bromo uridine triphosphate incorporation is reduced by approximately 15%, and transcript profiling revealed that approximately 15% of zygotically expressed genes are dramatically repressed in 2-cell embryos overexpressing SOX2. Furthermore, overexpressing a dominant-negative SOX2 perturbs reprogramming of gene expression in 2-cell embryos, though to a much lesser extent than that observed following overexpression of SOX2, and leads to developmental failure after the 2-cell stage but before the 8-cell stage. Results of these experiments implicate Sox2 as a critical transcriptional regulator in the oocyte-to-embryo transition that entails formation of totipotent blastomeres and indicate that the amount of Sox2 is critical for successful execution of this transition.

Transcriptome Asymmetry Within Mouse Zygotes but Not Between Early Embryonic Sister Blastomeres

Abstract: Transcriptome regionalization is an essential polarity determinant among metazoans, directing embryonic axis formation during normal development. Although conservation of this principle in mammals is assumed, recent evidence is conflicting and it is not known whether transcriptome asymmetries exist within unfertilized mammalian eggs or between the respective cleavage products of early embryonic divisions. We here address this by comparing transcriptome profiles of paired single cells and sub-cellular structures obtained microsurgically from mouse oocytes and totipotent embryos. Paired microsurgical spindle and remnant samples from unfertilized metaphase II oocytes possessed distinguishable profiles. Fertilization produces a totipotent 1-cell embryo (zygote) and associated spindle-enriched second polar body whose paired profiles also differed, reflecting spindle transcript enrichment. However, there was no programmed transcriptome asymmetry between sister cells within 2- or 3-cell embryos. Accordingly, there is transcriptome asymmetry within mouse oocytes, but not between the sister blastomeres of early embryos. This work places constraints on pre-patterning in mammals and provides documentation correlating potency changes and transcriptome partitioning at the single-cell level.

Cell cycle synchronization for the purpose of somatic cell nuclear transfer (SCNT).

Abstract: Somatic cell nuclear transfer (SCNT) is a technically and biologically challenging procedure during which a differentiated committed nucleus undergoes rapid reprogramming into the totipotent state in a few hours SCNT can be utilized to generate patient- and disease-specific embryonic stem cell (ESC) lines, which carry great promise in improving our understanding of major disease conditions and hope for better therapies In this section, we will describe how mouse SCNT is performed and survey the importance of donor cell cycle synchronization and the methods to perform it

Primate totipotent and pluripotent stem cells produced by somatic cell nuclear transfer

Abstract: Purified totipotent stem cells and pluripotent stems cells derived by somatic cell nuclear transfer are disclosed herein, as well as cell lines, multipotent cells and differentiated cells produced from these stem cells. The stem cells are produced from an enucleated host cell from a first donor and nuclear genetic material from a somatic cell of a second donor. Methods for making and using such compositions of such stem cells are also provided.

Screening of genes associated with early stages of adventitious root formation from progenitor adult cells of pine

Abstract: Background In plants, the possibility to regenerate adventitious roots, shoots or embryos directly from adult tissues has been known for more than 60 years and has been exploited in horticulture, agriculture and forestry [1]. However, little is known about the mechanisms that enable a somatic differentiated cell to switch its fate into a multipotent, pluripotent or totipotent cell that can develop a root, shoot or embryo or repair damaged tissues [2]. Although apparent dedifferentiation and respecification of cells seems to occur, whether acquisition of competence to regenerate organs occurs, as in animal cells, through dedifferentiation, or whether it is via transdifferentiation or by the use of pre-existent totipotent, pluripotent or multipotent cells in adult tissues remains unknown. In either case, cell fate switches are characterized by remarkable changes in the pattern of gene expression, as cells switch from an expression pattern typical of a somatic cell to a new one directing a new developmental pathway [3]. Thus, determining the way by which cells reset their gene expression pattern,especially for the timetable and repertoire of gene expression characteristic of the earliest stages of normal development, is crucial to understand cellular plasticity. In forest species, a loss of regeneration capacity is associated with tree age and maturation, which makes forest species representative and reliable systems to study how cell fate becomes fixed during development and how plant cells can manage to retain developmental plasticity [4]. The decline in the capacity to regenerate roots from cuttings is one of the most dramatic effects of tree maturation and has been the subject of investigations on the basic nature of the process [5].

Magnetised stem cells and use thereof

Abstract: The present description relates to magnetized stem cells, pluripotent or totipotent or adult cells reprogrammed to embryonic state, or I PS (induced pluripotent cells); methods for their preparation, their uses and medical and/or pharmaceutical compositions comprising these cells, and their therapeutic methods.

Purging and isolating pluripotent cells, “sweet” dreams become true?

Abstract: The formation of an adult organism could be viewed as a hierarchical process in which the initial totipotent cell, the zygote, progressively loses “potency” by differentiating into pluripotent, multipotent and unipotent states until the final terminally differentiated cells comprising tissues and organs are derived. Such a unidirectional concept trembled when four transcription factors were shown to “revert” the identity of differentiated somatic cells and reprogram them into induced pluripotent stem cells (iPSCs) 1. These findings rapidly fed clinical expectations for regenerative medicine purposes as well as for disease modeling and drug discovery studies 2. Though this discovery represented a promising breakthrough, the technologies applied raised several concerns, as thoroughly discussed in other reports 3. Importantly, and regardless of the methodology used for reprogramming, the lack of efficient differentiation protocols opened the possibility that mixed populations could interfere during in vitro studies. Furthermore, experimental assessment of pluripotency involves the formation of benign tumors, called teratomas. Thus, residual pluripotent stem cells need to be eliminated prior to transplantation in order to reduce the risk of malignant transformations 3. Up to date, efficient selection of residual pluripotent stem cells (PSCs) relied on the use of antibodies recognizing known pluripotency-related surface markers as well as tissue-specific fluorescence reporters combined with sorting procedures 4. Additionally, suicide gene strategies have also been described 5. Yet, such methods can lead to undesired cellular modifications due to antibody binding and/or alteration of the host genome.

Current Approaches in Stem Cell Production

Abstract: Ars.Gor. Irem MATUR, Prof.Dr. Suna SOLMAZ Stem cells are undifferentiated cells that can self-renew themselves and can differentiate to specialized cells. These undifferentiated cells have the ability to convert to many specialized cell types in the body or under appropriate laboratory conditions. Nowadays, stem cells are one of the most exciting fields in biomedical studies and interest about using them in regenerative medicine and studies in this field increases day by day. The distinctive features of stem cells are being capable of self-renewing themselves and differentiating to specialized cells and stemness. These cells are able to divide recurrently and during dividing, they both generate specialized cells and renew themselves. Because these cells have cellular and molecular markers, they are noticeably different from other cells. This feature is called stemness. Stem cells are classified as totipotent, pluripotent and multipotent related to their differentiation capability. The most capable stem cell types are embryonic stem cells. There are also adult stem cells. There are so many data about cancer cells that they derive from stem cells because of the abnormal proliferation and differatiation. Understanding the mechanisms of proliferation and differentiation of stem cells could make therapeutic implications of cancer and the other diseases possible. Key words: