BMP4-directed trophoblast differentiation of human embryonic stem cells is mediated through a ΔNp63+ cytotrophoblast stem cell state

The placenta is a transient organ that is necessary for proper fetal development. Its main functional component is the trophoblast, which is derived from extra-embryonic ectoderm. Little is known about early trophoblast differentiation in the human embryo, owing to lack of a proper in vitro model system. Human embryonic stem cells (hESCs) differentiate into functional trophoblast following BMP4 treatment in the presence of feeder-conditioned media; however, this model has not been widely accepted, in part owing to a lack of proof for a trophoblast progenitor population. We have previously shown that p63, a member of the p53 family of nuclear proteins, is expressed in proliferative cytotrophoblast (CTB), precursors to terminally differentiated syncytiotrophoblast (STB) in chorionic villi and extravillous trophoblast (EVT) at the implantation site. Here, we show that BMP4-treated hESCs differentiate into bona fide CTB by direct comparison with primary human placental tissues and isolated CTB through gene expression profiling. We show that, in primary CTB, p63 levels are reduced as cells differentiate into STB, and that forced expression of p63 maintains cyclin B1 and inhibits STB differentiation. We also establish that, similar to in vivo events, hESC differentiation into trophoblast is characterized by a p63(+)/KRT7(+) CTB stem cell state, followed by formation of functional KLF4(+) STB and HLA-G(+) EVT. Finally, we illustrate that downregulation of p63 by shRNA inhibits differentiation of hESCs into functional trophoblast. Taken together, our results establish that BMP4-treated hESCs are an excellent model of human trophoblast differentiation, closely mimicking the in vivo progression from p63(+) CTB stem cells to terminally differentiated trophoblast subtypes.

Bone morphogenetic protein 4 promotes mammalian oogonial stem cell differentiation via Smad1/5/8 signaling

OBJECTIVE

To test whether bone morphogenetic protein 4 (BMP4) directly regulates differentiation of adult mouse ovary-derived oogonial stem cells (OSCs) in vitro.

DESIGN

Animal study.

SETTING

Research laboratory.

ANIMAL(S)

Adult C57BL/6 female mice.

INTERVENTION(S)

After purification from adult ovaries by fluorescence-activated cell sorting, OSCs were cultured without or with BMP4 in the absence or presence of the BMP4 antagonist, Noggin.

MAIN OUTCOME MEASURE(S)

Rates of in vitro-derived (IVD) oocyte formation and changes in gene expression were assessed.

RESULT(S)

Cultured OSCs expressed BMP receptor (BMPR) 1A (BMPR1A), BMPR1B, and BMPR2, suggesting that BMP signaling can directly affect OSC function. In agreement with this, BMP4 significantly increased the number of IVD oocytes formed by cultured OSCs in a dose-dependent manner, and this response was inhibited in a dose-dependent fashion by cotreatment with Noggin. Exposure of OSCs to BMP4 was associated with rapid phosphorylation of BMPR-regulated Smad1/5/8 proteins, and this response was followed by increased expression of the meiosis initiation factors, stimulated by retinoic acid gene 8 (Stra8), muscle-segment homeobox 1 (Msx1), and Msx2. In keeping with the IVD oocyte formation data, the ability of BMP4 to activate Smad1/5/8 signaling and meiotic gene expression in OSCs was abolished by cotreatment with Noggin.

CONCLUSION(S)

Engagement of BMP4-mediated signaling in adult mouse ovary-derived OSCs cultured in vitro drives differentiation of these cells into IVD oocytes through Smad1/5/8 activation and transcriptional up-regulation of key meiosis-initiating genes.

AMOTL2 interaction with TAZ causes the inhibition of surfactant proteins expression in lung cells

BACKGROUND

TAZ (Transcriptional co-Activator with PDZ-binding motif), is a biologically potent transcriptional coactivator and functions by binding to the PPXY motif present in several transcription factors. Notably, TAZ behaves as a transducer linking cytoplasmic signaling events to transcriptional regulation in the nucleus. Several different factors regulate TAZ expression and/or function. In particular, a major regulation of TAZ activity occurs through the Hippo pathway by a phosphorylation-mediated mechanism that causes its cytoplasmic sequestration or degradation.

RESULTS

Here we demonstrate that AMOTL2 robustly co-immunoprecipitates with TAZ, and their interaction is dependent on the WW domain of TAZ and the PPXY motif in the N-terminus of AMOTL2. Furthermore, we show that AMOTL2 colocalizes with TAZ in the cytoplasm of H441 human lung cells and regulates TAZ cytoplasm-to-nucleus translocation through direct protein-protein interaction. Interestingly, the overexpression of AMOTL2 inhibits the functional cooperation between the transcription factor TTF-1 and TAZ on the Surfactant C gene promoter, as well as the expression of other known target genes of these regulatory factors.

CONCLUSIONS

Taken together, our results suggest an inhibitory role of AMOTL2 on TAZ ability to co-activate transcription and describe a different mechanism, Hippo pathway-independent, that modulates the activity of TAZ in lung cells through the interaction with Angiomotin-like 2 (AMOTL2).

Non-invasive neural stem cells become invasive in vitro by combined FGF2 and BMP4 signaling

Neural stem cells (NSCs) typically show efficient self-renewal and selective differentiation. Their invasion potential, however, is not well studied. In this study, Sox2-positive NSCs from the E14.5 rat cortex were found to be non-invasive and showed only limited migration in vitro. By contrast, FGF2-expanded NSCs showed a strong migratory and invasive phenotype in response to the combination of FGF2 and BMP4. Invasive NSCs expressed Podoplanin (PDPN) and p75NGFR (Ngfr) at the plasma membrane after exposure to FGF2 and BMP4. FGF2 and BMP4 together upregulated the expression of Msx1, Snail1, Snail2, Ngfr, which are all found in neural crest (NC) cells during or after epithelial-mesenchymal transition (EMT), but not in forebrain stem cells. Invasive cells downregulated the expression of Olig2, Sox10, Egfr, Pdgfra, Gsh1/Gsx1 and Gsh2/Gsx2. Migrating and invasive NSCs had elevated expression of mRNA encoding Pax6, Tenascin C (TNC), PDPN, Hey1, SPARC, p75NGFR and Gli3. On the basis of the strongest upregulation in invasion-induced NSCs, we defined a group of five key invasion-related genes: Ngfr, Sparc, Snail1, Pdpn and Tnc. These genes were co-expressed and upregulated in seven samples of glioblastoma multiforme (GBM) compared with normal human brain controls. Induction of invasion and migration led to low expression of differentiation markers and repressed proliferation in NSCs. Our results indicate that normal forebrain stem cells have the inherent ability to adopt a glioma-like invasiveness. The results provide a novel in vitro system to study stem cell invasion and a novel glioma invasion model: tumoral abuse of the developmental dorsoventral identity regulation.

Tendon-bone attachment unit is formed modularly by a distinct pool of Scx- and Sox9-positive progenitors

The assembly of the musculoskeletal system requires the formation of an attachment unit between a bone and a tendon. Tendons are often inserted into bone eminences, superstructures that improve the mechanical resilience of the attachment of muscles to the skeleton and facilitate movement. Despite their functional importance, little is known about the development of bone eminences and attachment units. Here, we show that bone eminence cells are descendants of a unique set of progenitors and that superstructures are added onto the developing long bone in a modular fashion. First, we show that bone eminences emerge only after the primary cartilage rudiments have formed. Cell lineage analyses revealed that eminence cells are not descendants of chondrocytes. Moreover, eminence progenitors were specified separately and after chondroprogenitors of the primary cartilage. Fields of Sox9-positive, Scx-positive, Col2a1-negative cells identified at presumable eminence sites confirm the identity and specificity of these progenitors. The loss of eminences in limbs in which Sox9 expression was blocked in Scx-positive cells supports the hypothesis that a distinct pool of Sox9- and Scx-positive progenitors forms these superstructures. We demonstrate that TGFβ signaling is necessary for the specification of bone eminence progenitors, whereas the SCX/BMP4 pathway is required for the differentiation of these progenitors to eminence-forming cells. Our findings suggest a modular model for bone development, involving a distinct pool of Sox9- and Scx-positive progenitor cells that form bone eminences under regulation of TGFβ and BMP4 signaling. This model offers a new perspective on bone morphogenesis and on attachment unit development during musculoskeletal assembly.

Enhanced in vivo osteogenesis by nanocarrier-fused bone morphogenetic protein-4

Purpose

Bone defects and nonunions are major clinical skeletal problems. Growth factors are commonly used to promote bone regeneration; however, the clinical impact is limited because the factors do not last long at a given site. The introduction of tissue engineering aimed to deter the diffusion of these factors is a promising therapeutic strategy. The purpose of the present study was to evaluate the in vivo osteogenic capability of an engineered bone morphogenetic protein-4 (BMP4) fusion protein.

Methods

BMP4 was fused with a nanosized carrier, collagen-binding domain (CBD), derived from fibronectin. The stability of the CBD-BMP4 fusion protein was examined in vitro and in vivo. Osteogenic effects of CBD-BMP4 were evaluated by computer tomography after intramedullary injection without a collagen–sponge scaffold. Recombinant BMP-4, CBD, or vehicle were used as controls. Expressions of bone-related genes and growth factors were compared among the groups. Osteogenesis induced by CBD-BMP4, BMP4, and CBD was also assessed in a bone-defect model.

Results

In vitro, CBD-BMP4 was retained in a collagen gel for at least 7 days while BMP4 alone was released within 3 hours. In vivo, CBD-BMP4 remained at the given site for at least 2 weeks, both with or without a collagen–sponge scaffold, while BMP4 disappeared from the site within 3 days after injection. CBD-BMP4 induced better bone formation than BMP4 did alone, CBD alone, and vehicle after the intramedullary injection into the mouse femur. Bone-related genes and growth factors were expressed at higher levels in CBD-BMP4-treated mice than in all other groups, including BMP4-treated mice. Finally, CBD-BMP4 potentiated more bone formation than did controls, including BMP4 alone, when applied to cranial bone defects without a collagen scaffold.

Conclusion

Altogether, nanocarrier-CBD enhanced the retention of BMP4 in the bone, thereby promoting augmented osteogenic responses in the absence of a scaffold. These results suggest that CBD-BMP4 may be clinically useful in facilitating bone formation.

Clinical and mutation analysis of 51 probands with anophthalmia and/or severe microphthalmia from a single center

Clinical evaluation and mutation analysis was performed in 51 consecutive probands with severe eye malformations - anophthalmia and/or severe microphthalmia - seen in a single specialist ophthalmology center. The mutation analysis consisted of bidirectional sequencing of the coding regions of SOX2, OTX2, PAX6 (paired domain), STRA6, BMP4, SMOC1, FOXE3, and RAX, and genome-wide array-based copy number assessment. Fifteen (29.4%) of the 51 probands had likely causative mutations affecting SOX2 (9/51), OTX2 (5/51), and STRA6 (1/51). Of the cases with bilateral anophthalmia, 9/12 (75%) were found to be mutation positive. Three of these mutations were large genomic deletions encompassing SOX2 (one case) or OTX2 (two cases). Familial inheritance of three intragenic, plausibly pathogenic, and heterozygous mutations was observed. An unaffected carrier parent of an affected child with an identified OTX2 mutation confirmed the previously reported nonpenetrance for this disorder. Two families with SOX2 mutations demonstrated a parent and child both with significant but highly variable eye malformations. Heterozygous loss-of-function mutations in SOX2 and OTX2 are the most common genetic pathology associated with severe eye malformations and bi-allelic loss-of-function in STRA6 is confirmed as an emerging cause of nonsyndromal eye malformations.

Functional Concentrations of BMP4 on Differentiation of Mouse Embryonic Stem Cells to Primordial Germ Cells

BACKGROUND

Bone morphogenetic protein 4 (BMP4) has a significant role in primordial germ cells (PGCs) differentiation from mouse embryonic stem cell (mESC). The aim of this study is to determine the best concentration of BMP4 at a time of two days on differentiation PGCs from mESC.

MATERIALS AND METHODS

To differentiate PGCs, embryoid bodies (EBs) from mESCs were cultured in concentrations of 0, 5 and 10 ng/ml BMP4 for two days. Germ cell markers Oct4 (Pou5f1), Stella (Dppa3) and Mvh (Ddx4) were analyzed by flow cytometry, immunocytochemistry and reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Flow cytometry data demonstrated most Mvh-positive cells were observed only in the treated groups. Immunocytochemistry of EBs in the treated groups identified cells positive for Mvh. PCR results showed expression of Oct4 in the control group and treated groups. Stella and Mvh were expressed only in the treated groups.

CONCLUSION

Low concentrations of BMP4 during two days had an optimal effect on differentiation of PGCs from mESC.

What determines the switch between atrophic and neovascular forms of age related macular degeneration? - the role of BMP4 induced senescence

Age-related macular degeneration (AMD), the leading cause of blindness in the elderly, targets the retinal pigment epithelium (RPE), a monolayer of cells at the back of the eye. As AMD progresses, it can develop into two distinct forms of late AMD: "dry," atrophic AMD, characterized by RPE senescence and geographic RPE loss, and "wet," neovascular AMD, characterized by RPE activation with abnormal growth of choroidal vessels. The genetic and molecular pathways that lead to these diverse phenotypes are currently under investigation. We have found that bone morphogenetic protein-4 (BMP4) is differentially expressed in atrophic and neovascular AMD. In atrophic AMD, BMP4 is highly expressed in RPE, and mediates oxidative stress induced RPE senescencein vitro via Smad and p38 pathways. In contrast, in neovascular AMD lesions, BMP4 expression in RPE is low, possibly a result of local expression of pro-inflammatory mediators. Thus, BMP4 may be involved in the molecular switch determining which phenotypic pathway is taken in the progression of AMD.