Showing papers on "Totipotent published in 2006"

Germ cell lineage differentiation in non-seminomatous germ cell tumours.

Abstract: Human germ cell tumours (GCTs) have long fascinated investigators for a number of reasons. Being pluripotential tumours, they can differentiate into both extra-embryonic and embryonic (somatic) tissues. However, it has never been shown convincingly that, in humans, these tumours are truly totipotent and can also give rise to the germ lineage, the third major differentiation lineage occurring early during embryonic life. Using a number of newly available, distinct, immunohistochemical markers, such as OCT3/4, VASA and TSPY, the occurrence of germ cells was investigated in a number of germ cell tumours. Development of germ cells was identified in three independent non-seminomas, including two pure yolk sac tumours and one mixed tumour composed of yolk sac tumour and immature teratoma. Our finding indicates a previously unknown totipotent potential of human GCTs and raises the question of whether, under certain culture conditions, primordial germ cells could be derived from human GCT cell lines.

Re)defining stem cells.

Abstract: Summary Stem-cell nomenclature is in a muddle! So-called stem cells may be self-renewing or emergent, oligopotent (uniand multipotent) or pluri- and totipotent, cells with perpetual embryonic features or cells that have changed irreversibly. Ambiguity probably seeped into stem cells from common usage, flukes in biology’s history beginning with Weismann’s divide between germ and soma and Haeckel’s biogenic law and ending with contemporary issues over the therapeutic efficacy of adult versus embryonic cells. Confusion centers on tissue dynamics, whether stem cells are properly members of emerging or steady-state populations. Clarity might yet be achieved by codifying differences between cells in emergent populations, including embryonic stem and embryonic germ (ES and EG) cells in tissue culture as opposed to self-renewing (SR) cells in steady-state populations. BioEssays 28:301–308, 2006. 2006 Wiley Periodicals, Inc.

Reprogramming somatic gene activity by fusion with pluripotent cells.

Abstract: Fertilized eggs and early blastomeres, that have the potential to develop to fetuses when placed into a uterus, are totipotent. Those cells in the embryo, that can give rise to all cell types of an organism, but not to an organism itself, are pluripotent. Embryonic stem (ES), embryonic carcinoma (EC), and embryonic germ (EG) cells are powerful in vitro artifacts derived from different embryonic stages and are pluripotent. Totipotent and pluripotent cells have the potential to greatly benefit biological research and medicine. One powerful feature is that the genetic program of somatic cells can be converted into that of totipotent or pluripotent cells, as shown by nuclear transfer or cell fusion experiments. During reprogramming by cell fusion various features of pluripotent cells are acquired. These include the typical morphology of the respective pluripotent fusion partner, a specific epigenetic state, a specific gene profile, inactivation of tissue-specific genes expressed in the somatic fusion partner, and the developmental as well as differentiation potential of pluripotent cells. In this review, we will discuss what is known about the reprogramming process mediated by cell fusion and the potential use of fusion-induced reprogramming for therapeutic applications.

Conflict over the timing of breeder replacement in vertebrate and invertebrate societies

Abstract: Conflicts over reproduction are common in social groups, where they often result in more or less pronounced reproductive skew. Conflicts are greatest in groups of reproductively totipotent individuals where a single breeder of each sex monopolizes reproduction. Skew models investigate how reproduction is divided among group members, i.e. how the conflict is settled. Here, we investigate the conflict over the timing of breeder replacement.Using a genetic model we show that some non-breeding individuals should challenge the breeder under a wide set of conditions, rather than queue for a breeding vacancy. Consequently, societies of totipotent individuals may be the stage of an almost perpetual conflict between the breeder and helpful reproductives. However, the outcome of this conflict may be determined by non-breeding individuals that are not helpful reproductives (policing behaviours), or constrained by ecological conditions such as high costs of independent breeding or incest avoidance. We discuss our model in the light of skew models and model of matricide, and review the literature of highly skewed vertebrate and invertebrate societies of totipotent individuals (naked and Damaraland mole-rats, African wild dogs, dwarf mongooses, queenless ants, Polistine wasps). This cross-taxonomic review reveals that some non-breeders attempt to replace the breeder or position themselves so as to be able to do so when the opportunity arises, which supports the predictions of the model.

MOVE processors that self-replicate and differentiate

Abstract: This article describes an implementation of a basic multi-processor system that exhibits replication and differentiation abilities on the POEtic tissue, a programmable hardware designed for bio-inspired applications [1,2]. As for a living organism, whose existence starts with only one cell that first divides, our system begins with only one totipotent processor, able to implement any of the cells required by the final organism, which can also fully replicate itself, using the functionalities of the POEtic substrate. Then, analogously to the cells in a developing organism, our just replicated totipotent processors differentiate in order to execute their specific part of the complete organism functionality. In particular, we will present a working realization using MOVE processors whose instructions define the flow of data rather than the operations to be executed [3]. It starts with one basic MOVE processor that first replicates itself three times; the four resulting processors then differentiate and connect together to implement a multi-processor modulus-60 counter.

Germline Recruitment in Mice: A Genetic Program for Epigenetic Reprogramming

Abstract: Germ cells provide an enduring link between generations and therefore must possess the fundamental ability of reprogramming their genome to generate a totipotent state. We wish to understand the molecular basis of the unique properties of the mammalian germ line. Recently we identified Blimp1, a potent transcriptional repressor of a histone methyltransferase subfamily, as a critical determinant of the germ cell lineage in mice. Surprisingly, Blimp1 expression marks the origin of the germ line in proximal epiblast cells in pregastrulation embryos, substantially earlier than previously thought. Furthermore, we showed that established primordial germ cells undergo extensive erasure of genome-wide histone H3 lysine 9 dimethylation (H3K9me2) and DNA methylation, two major repressive epigenetic modifications, and instead acquire high levels of H3-K27 trimethylation (H3K27me3) in their migration period. We suggest that germline specification is a genetic system for the orderly reprogramming of the cells’ epigenome toward a totipotent state, with reacquisition of totipotency-associated transcription factors and continued Blimp1 expression preventing their reversion to an explicit pluripotent state or somatic differentiation.

[Teratoma of umbilical cord: a case report and literature review]

Abstract: Teratomas are tumors that arise from totipotent embryonic germ cells. The umbilical cord is an extremely rare site for this tumor, only 12 cases have been reported in the medical literature. Herein we describe an umbilical cord mass presenting necrosis with clinical and histopathological features that can be considered as another case of umbilical cord teratoma. We discuss the differential diagnosis and review the complete literature on this subject.

Totipotent, nearly totipotent or pluripotent mammalian cells homozygous or hemizygous for one or more histocompatibility antigen genes

Abstract: The present invention relates to totipotent, nearly totipotent and pluripotent stem cells that are hemizygous or homozygous for MHC antigens and methods of making and using them. These cells are useful for reduced immunogenicity during transplantation and cell therapy. The cells of the present invention may be assembled into a bank with reduced complexity in the MHC genes.

Bio-Inspired Computing Machines with Artificial Division and Differentiation

Abstract: In order to design computing machines able to self-repair and self-replicate, we have borrowed from nature two major mechanisms which are embedded in silicon: cell division and cell differentiation. Based on the so-called Tom Thumb algorithm, cellular division leads to a novel self-replicating loop endowed with universal construction. The self-replication of the totipotent cell of the “LSL” acronym serves as an artificial cell division example of the loop and results in the growth and differentiation of a multicellular organism.

Isolation and analysis of SSEA-4 positive cells derived from fetal marrow mesenchymal stem cells

Abstract: A big issue in stem cell research is to derive prospective totipotential stem cells. In this study, fMSC-SSEA-4 cells expressing SSEA-4 antigen were isolated from fetal marrow masenchymal stem cells (fMSCs) using immunomagnetic bead sorting technique. The totipotent cells were identified and their biological characteristics were further studied. The expression of Oct-4 and SSEA-4, carcinogenicity, and the ability to differentiation of fMSC-SSEA-4 cells were evaluated to verify the totipotent potential. fMSC-SSEA-4 cells were isolated successfully from fMSCs (2.5% among fMSCs), while no obvious differences were seen in morphology, growth curve, cell cycle and immunophenotype, Oct-4 and SSEA-4 expression between fMSC-SSEA-4 cells and fMSCs. fMSC-SSEA-4 cells showed normal diploid chromosome karyotype and no carcinoma was induced after inoculation into nude mice. fMSC-SSEA-4 cells could be induced to fat cells, osteogenic cells and neuron-like cells in vitro with different induced factors. The results indicated that there may be a few totipotent cells among the fMSCs and it may offer the experimental basis for the further study and application of fMSCs.

Internal standards in differentiating embryonic stem cells in vitro.

Abstract: Embryonic stem (ES) cell lines are important for use in developmental biology studies, and because these cells are totipotent, they may provide a much-needed source of differentiated cells for certain therapeutic applications. The phenotype of the ES cell in culture is often assessed by (semi)quantitative RNA analyses. In such cases, it is critical to use appropriate internal standards to correct for experimentally induced sources of error. This is particularly true for ES cell differentiation because it is heterogeneous in nature. We describe protocols for determining the suitability of housekeeping genes to act as internal controls in differentiating ES cell cultures. Such assessment is needed for every experimental condition under investigation. The protocol focuses on polymerase chain reaction; however, the principle and experimental design are applicable to any (semi)quantitative RNA assay.

Cloning of transgenic ungulate animals comprising artificial chromosomes

Abstract: The invention is directed in part to totipotent cells that have one or more artificial chromosomes; processes for producing such cells; processes for using such cells (e.g., nuclear transfer); transgenic embryos and transgenic animals cloned from such cells; and processes for producing such embryos and animals.