Meiotic cohesin REC8 marks the axial elements of rat synaptonemal complexes before cohesins SMC1β and SMC3

In meiotic prophase, the sister chromatids of each chromosome develop a common axial element (AE) that is integrated into the synaptonemal complex (SC). We analyzed the incorporation of sister chromatid cohesion proteins (cohesins) and other AE components into AEs. Meiotic cohesin REC8 appeared shortly before premeiotic S phase in the nucleus and formed AE-like structures (REC8-AEs) from premeiotic S phase on. Subsequently, meiotic cohesin SMC1β, cohesin SMC3, and AE proteins SCP2 and SCP3 formed dots along REC8-AEs, which extended and fused until they lined REC8-AEs along their length. In metaphase I, SMC1β, SMC3, SCP2, and SCP3 disappeared from the chromosome arms and accumulated around the centromeres, where they stayed until anaphase II. In striking contrast, REC8 persisted along the chromosome arms until anaphase I and near the centromeres until anaphase II. We propose that REC8 provides a basis for AE formation and that the first steps in AE assembly do not require SMC1β, SMC3, SCP2, and SCP3. Furthermore, SMC1β, SMC3, SCP2, and SCP3 cannot provide arm cohesion during metaphase I. We propose that REC8 then provides cohesion. RAD51 and/or DMC1 coimmunoprecipitates with REC8, suggesting that REC8 may also provide a basis for assembly of recombination complexes

Silencing markers are retained on pericentric heterochromatin during murine primordial germ cell development

Background: In the nuclei of most mammalian cells, pericentric heterochromatin is characterized by DNA methylation, histone modifications such as H3K9me3 and H4K20me3, and specific binding proteins l

An ES-Like Pluripotent State in FGF-Dependent Murine iPS cells

Recent data demonstrates that stem cells can exist in two morphologically, molecularly and functionally distinct pluripotent states; a naïve LIF-dependent pluripotent state which is represented by murine embryonic stem cells (mESCs) and an FGF-dependent primed pluripotent state represented by murine and rat epiblast stem cells (EpiSCs). We find that derivation of induced pluripotent stem cells (iPSCs) under EpiSC culture conditions yields FGF-dependent iPSCs from hereon called FGF-iPSCs) which, unexpectedly, display naïve ES-like/ICM properties. FGF-iPSCs display X-chromosome activation, multi-lineage differentiation, teratoma competence and chimera contribution in vivo. Our findings suggest that in 129 and Bl6 mouse strains, iPSCs can dominantly adopt a naive pluripotent state regardless of culture growth factor conditions

MOESM4 of Silencing markers are retained on pericentric heterochromatin during murine primordial germ cell development

Additional file 4. Summary of the immunosignals at pericentric heterochromatin of PGCs. The table displays whether a certain histone modification or chromatin-binding protein at the pericentric heterochromatin is detected (+), not detected (−) or detected in some but not all (*) nuclei of PGCs at the embryonic stages indicated. Differences in the degree of enrichment between the pericentric heterochromatin of PGCs and somatic cells are only taken into account in the last column, whereby less enrichment or more enrichment at pericentromeric heterochromatin in PGCs compared to the soma is indicated as , respectively. n.d.: not determined

MOESM2 of Silencing markers are retained on pericentric heterochromatin during murine primordial germ cell development

Additional file 2. Immunofluorescent analysis of HP1β in paraffin sections using regular and extended fixation protocols. A Using the regular fixation protocol, HP1β signal is enriched at DAPI (blue)-dense regions of E10.5 and E11.5 PGCs and somatic cells. HP1β is then substantially reduced in E13.5 female and male germ cells. B With the extended fixation protocol, HP1β signal is retained in pericentric heterochromatin of PGCs throughout development. For each stage, two embryos were analysed per fixation protocol and at least 20 nuclei were recorded. E10.5 and E11.5 PGCs were marked with OCT4 (red). E13.5 male and female germ cells were identified by the presence of TRA98 (red). Representative images are shown with germ cells highlighted by dashed yellow circles, and scale bars represent 5 μm

The Growth Factor Environment Defines Distinct Pluripotent Ground States in Novel Blastocyst-Derived Stem Cells

Pluripotent stem cell lines can be derived from blastocyst embryos, which yield embryonic stem cell lines (ES cells), as well as the postimplantation epiblast, which gives rise to epiblast stem cell lines (EpiSCs). Remarkably, ES cells and EpiSCs display profound differences in the combination of growth factors that maintain their pluripotent state. Molecular and functional differences between these two stem cell types demonstrate that the tissue of origin and/or the growth factor milieu may be important determinants of the stem cell identity. We explored how developmental stage of the tissue of origin and culture growth factor conditions affect the stem cell pluripotent state. Our findings indicate that novel stem cell lines, with unique functional and molecular properties, can be generated from murine blastocyst embryos. We demonstrate that the culture growth factor environment and cell-cell interaction play a critical role in defining several unique and stable stem cell ground states