Recent studies have aimed to convert cultured human pluripotent cells to a naive state, but it remains unclear to what extent the resulting cells recapitulate in vivo naive pluripotency. Here we ...propose a set of molecular criteria for evaluating the naive human pluripotent state by comparing it to the human embryo. We show that transcription of transposable elements provides a sensitive measure of the concordance between pluripotent stem cells and early human development. We also show that induction of the naive state is accompanied by genome-wide DNA hypomethylation, which is reversible except at imprinted genes, and that the X chromosome status resembles that of the human preimplantation embryo. However, we did not see efficient incorporation of naive human cells into mouse embryos. Overall, the different naive conditions we tested showed varied relationships to human embryonic states based on molecular criteria, providing a backdrop for future analysis of naive human pluripotency.
Display omitted
•Naive human ESCs share a unique transposon signature with cleavage-stage embryos•Global DNA demethylation in naive human ESCs is reversible except at imprinted loci•The X chromosome status of naive human ESCs resembles the preimplantation embryo•Naive human ESCs incorporate into the mouse morula or blastocyst very inefficiently
Theunissen et al. use molecular criteria based on transposon expression, DNA methylation, and X chromosome status to compare naive human pluripotent cells to human preimplantation embryos. Current approaches yield cells that most closely resemble the morula/early blastocyst stage.
Human pluripotent stem cells hold potential for regenerative medicine, but available cell types have significant limitations. Although embryonic stem cells (ES cells) from in vitro fertilized embryos ...(IVF ES cells) represent the 'gold standard', they are allogeneic to patients. Autologous induced pluripotent stem cells (iPS cells) are prone to epigenetic and transcriptional aberrations. To determine whether such abnormalities are intrinsic to somatic cell reprogramming or secondary to the reprogramming method, genetically matched sets of human IVF ES cells, iPS cells and nuclear transfer ES cells (NT ES cells) derived by somatic cell nuclear transfer (SCNT) were subjected to genome-wide analyses. Both NT ES cells and iPS cells derived from the same somatic cells contained comparable numbers of de novo copy number variations. In contrast, DNA methylation and transcriptome profiles of NT ES cells corresponded closely to those of IVF ES cells, whereas iPS cells differed and retained residual DNA methylation patterns typical of parental somatic cells. Thus, human somatic cells can be faithfully reprogrammed to pluripotency by SCNT and are therefore ideal for cell replacement therapies.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Oocyte defects lie at the heart of some forms of infertility and could potentially be addressed therapeutically by alternative routes for oocyte formation. Here, we describe the generation of ...functional human oocytes following nuclear transfer of first polar body (PB1) genomes from metaphase II (MII) oocytes into enucleated donor MII cytoplasm (PBNT). The reconstructed oocytes supported the formation of de novo meiotic spindles and, after fertilization with sperm, meiosis completion and formation of normal diploid zygotes. While PBNT zygotes developed to blastocysts less frequently (42%) than controls (75%), genome-wide genetic, epigenetic, and transcriptional analyses of PBNT and control ESCs indicated comparable numbers of structural variations and markedly similar DNA methylation and transcriptome profiles. We conclude that rescue of PB1 genetic material via introduction into donor cytoplasm may offer a source of oocytes for infertility treatment or mitochondrial replacement therapy for mtDNA disease.
Display omitted
•Metaphase II oocytes can be reconstructed by polar body nuclear transfer (PBNT)•Reconstructed PBNT oocytes complete meiosis after fertilization with sperm•PBNT-derived blastocysts can give rise to phenotypically normal hESC lines
Ma et al. show regeneration of functional human oocytes through polar body transfer into enucleated oocyte cytoplasts. In addition to providing proof of principle for this process, the approach could be helpful clinically for some forms of infertility and genetic disease.
Cytokinin fulfills its diverse roles in planta through a series of transcriptional responses. We identify the in vivo DNA binding site profiles for three genetically redundant type-B ARABIDOPSIS ...RESPONSE REGULATORS (B-ARRs): ARR1, ARR10, and ARR12. The expression and genome-wide DNA binding locations of the three B-ARRs extensively overlap. Constructing a primary cytokinin response transcriptional network reveals a recurring theme of widespread cross-regulation between the components of the cytokinin pathway and other plant hormone pathways. The B-ARRs are found to have similar DNA binding motifs, though sequences flanking the core motif were degenerate. Cytokinin treatments amalgamate the three different B-ARRs motifs to identical DNA binding signatures (AGATHY, H(a/t/c), Y(t/c)) which suggests cytokinin may regulate binding activity of B-ARR family members. Furthermore, we find that WUSCHEL, a key gene required for apical meristem maintenance, is a cytokinin-dependent B-ARR target gene, demonstrating the importance of the cytokinin transcription factor network in shoot development.
The original version of this Article contained an error in Fig. 3. Panel b was inadvertently duplicated and the correct panel c was originally omitted. This error has been corrected in both the PDF ...and HTML versions of the Article.
Systematic review.
To identify whether there is an advantage to instrumented or noninstrumented spinal fusion over decompression alone for patients with degenerative lumbar spondylolisthesis.
The ...operative management of degenerative spondylolisthesis includes spinal decompression with or without instrumented or noninstrumented spinal fusion. Evidence on the operative management of degenerative spondylolisthesis is still divisive.
Relevant RCT and comparative observational studies between 1966 and June 2005 were identified. Abstracted outcomes included clinical outcome, reoperation rate, and solid fusion status. Analyses were separated into: 1) fusion versus decompression alone and 2) instrumented fusion versus noninstrumented fusion.
Thirteen studies were included. The studies were generally of low methodologic quality. A satisfactory clinical outcome was significantly more likely with fusion than with decompression alone (relative risk, 1.40; 95% confidence interval, 1.04-1.89; P < 0.05). The use of adjunctive instrumentation significantly increased the probability of attaining solid fusion (relative risk, 1.37; 95% confidence interval, 1.07-1.75; P < 0.05), but no significant improvement in clinical outcome was recorded (relative risk, 1.19; 95% confidence interval, 0.92-1.54). There was a nonsignificant trend toward lower repeat operations with fusion compared with both decompression alone and instrumented fusion.
Spinal fusion may lead to a better clinical outcome than decompression alone. No conclusion about the clinical benefit of instrumenting a spinal fusion could be made. However, there is moderate evidence that the use of instrumentation improves the chance of achieving solid fusion.
The monolithic gallium arsenide demodulator described herein demodulates the in-phase (I) and quadrature (Q) components of two signal channels on carriers identical in frequency but in quadrature ...phase relationships. The present demodulator is shown to be closely matched because of close matching of component parameters achieved by fabricating the entire demodulator on a single gallium arsenide chip. The demodulator can be developed to, replace diode ring demodulators to obtain the following advantages.
PDF
