Doctor of Philosophy, Shanghai Institute Of Cell Biology (2011)
Bachelor of Science, Tsinghua University (2005)
Seung Kim, Postdoctoral Faculty Sponsor
The ectoderm has the capability to generate epidermis and neuroectoderm and plays imperative roles during the early embryonic development. Our recent study uncovered a region with ectodermal progenitor potential in mouse embryo at embryonic day 7.0 and revealed that Nodal inhibition is essential for its formation. Here, we demonstrate that through brief inhibition of Nodal signaling in vitro, mouse embryonic stem cell (ESC)-derived epiblast stem cells (ESD-EpiSCs) could be committed to transient ectodermal progenitor populations, which possess the ability to give rise to neural or epidermal ectoderm in the absence or presence of BMP4, respectively. Mechanistic studies reveal that BMP4 recruits distinct transcriptional targets in ESD-EpiSCs and ectoderm-like cells. Furthermore, FGF-Erk signaling may also be alleviated during the generation of ectoderm-like cells. Thus, our data suggest that instructive interactions among several extracellular signals participate in the commitment of ectoderm from ESD-EpiSCs, which shed new light on the understanding of the formation of ectoderm during the gastrulation in early mouse embryo development.
View details for DOI 10.1093/jmcb/mjv030
View details for Web of Science ID 000363201800007
View details for PubMedID 25990320
Ectoderm is one of the three classic germ layers in the early mouse embryo, with the capacity to develop into both the central nervous system and epidermis. Because it is a transient phase of development with few molecular markers, the early ectoderm is the least understood germ layer in mouse embryonic development. In this work, we studied the differentiation potential of isolated ectoderm tissue in response to BMP signaling at various developmental stages (E6.5, E7.0 and E7.5), and identified a transient region in the anterior-proximal side of the embryo at E7.0 that possesses the ability to become neural or epidermal ectoderm in response to the absence or presence of BMP4, respectively. Furthermore, we demonstrated that inhibition of Nodal signaling could direct the pluripotent E6.5 epiblast cells towards ectoderm lineages during differentiation in explants in vitro. Our work not only improves our understanding of ectodermal layer development in early embryos, but also provides a framework for regenerative differentiation towards ectodermal tissues.
View details for DOI 10.1242/dev.092866
View details for Web of Science ID 000326681900009
View details for PubMedID 24131634
During early embryonic development, bone morphogenetic protein (BMP) signaling is essential for neural/non-neural cell fate decisions. BMP signaling inhibits precocious neural differentiation and allows for proper differentiation of mesoderm, endoderm, and epidermis. However, the mechanisms underlying the BMP pathway-mediated cell fate decision remain largely unknown. Here, we show that the expression of Ovol2, which encodes an evolutionarily conserved zinc finger transcription factor, is down-regulated during neural differentiation of mouse embryonic stem cells. Knockdown of Ovol2 in embryonic stem cells facilitates neural conversion and inhibits mesendodermal differentiation, whereas Ovol2 overexpression gives rise to the opposite phenotype. Moreover, Ovol2 knockdown partially rescues the neural inhibition and mesendodermal induction by BMP4. Mechanistic studies further show that BMP4 directly regulates Ovol2 expression through the binding of Smad1/5/8 to the second intron of the Ovol2 gene. In the chick embryo, cOvol2 expression is specifically excluded from neural territory and is up-regulated by BMP4. In addition, ectopic expression of cOvol2 in the prospective neural plate represses the expression of the definitive neural plate marker cSox2. Taken together, these results indicate that Ovol2 acts downstream of the BMP pathway in the cell fate decision between neuroectoderm and mesendoderm to ensure proper germ layer development.
View details for DOI 10.1074/jbc.M112.418376
View details for Web of Science ID 000315820700013
View details for PubMedID 23319585
Bone morphogenetic protein (BMP) signaling plays a crucial role in maintaining the pluripotency of mouse embryonic stem cells (ESCs) and has negative effects on ESC neural differentiation. However, it remains unclear when and how BMP signaling executes those different functions during neural commitment. Here, we show that a BMP4-sensitive window exists during ESC neural differentiation. Cells at this specific period correspond to the egg cylinder stage epiblast and can be maintained as ESC-derived epiblast stem cells (ESD-EpiSCs), which have the same characteristics as EpiSCs derived from mouse embryos. We propose that ESC neural differentiation occurs in two stages: first from ESCs to ESD-EpiSCs and then from ESD-EpiSCs to neural precursor cells (NPCs). We further show that BMP4 inhibits the conversion of ESCs into ESD-EpiSCs during the first stage, and suppresses ESD-EpiSC neural commitment and promotes non-neural lineage differentiation during the second stage. Mechanistic studies show that BMP4 inhibits FGF/ERK activity at the first stage but not at the second stage; and IDs, as important downstream genes of BMP signaling, partially substitute for BMP4 functions at both stages. We conclude that BMP signaling has distinct functions during different stages of ESC neural commitment.
View details for DOI 10.1242/dev.049494
View details for Web of Science ID 000278559900003
View details for PubMedID 20504958
The present study describes the details about the acid phosphatase forms in the pearl oyster, Pinctada fucata. Two isoenzymes (AcPase I and II) of acid phosphatase were separated and purified from viscera of pearl oyster, P. fucata to homogeneity by chromatography on DEAE-Sepharose Fast Flow, Sephadex G-200 superfine and ConA Sepharose 4B, and partial biochemical properties of AcPase I and II were studied. AcPase I and AcPase II had molecular weights of 208.8 and 64.3 kDa, respectively. AcPase I was a single polypeptide chain, while AcPase II was a dimeric enzyme composed of two equivalent subunits. AcPase I and II showed optimal pHs at 4.6 and 3.2 with p-nitrophenylphosphate as substrate. The optimal catalytic reaction temperature was 47 degrees C for AcPase I and 57 degrees C for AcPase II. Both enzyme forms were stable when incubated at 50 degrees C for 40 min. Tartrate and fluoride were the most effective inhibitors of the enzymes. Fe(3+), Zn(2+), Cu(2+) and Pb(2+) inhibited the activity of AcPase I and II to differing extents. AcPase I and II were apparently nonspecific and hydrolyzed various phosphoric esters. The different properties of AcPase I and II suggested that the two enzymes may play different roles in the pearl oyster.
View details for DOI 10.1016/j.cbpb.2005.11.008
View details for Web of Science ID 000235705700013
View details for PubMedID 16380281