Congress Abstracts - Society for Developmental Biology

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differentiation potential acting as a molecular switch between osteoblast and chondrocyte cell fates according the culture or environmental conditions. This study paves the way for developing specific therapeutic approaches for cartilage and bone repair. Program/Abstract # 527 Evaluating of hematopoietic and mesenchymal stem cell markers during limb bud development Camargo Sosa, Karen; Marin Llera, Jessica Cristina; Soldevila Melgarejo, Gloria; Chimal Monroy, Jesús (UNAM-Mexico City, Mexico) As it is proposed, “undifferentiated zone” of developing limb is the source of skeletal structures, tendons and dermis. Also, interdigital mesenchymal cells are competent to cartilage differentiation, proven by exogenous implantation of TGF-β soaked beads. Therefore, these undifferentiated cells have potential to generate several cell types. Another undifferentiated and multipotent population has been described in adult bone marrow, these are MSC (Mesenchymal Stem Cells) and HSC (Hematopoietic Stem Cells). How and when do these cells population appear within limbs during embryo development remain unknown. Mouse HSC has been described as Sca-1 and c-Kit positives, and considered negatives for lineage specific markers (Lin-). By contrast, mouse MSC have not been that well characterized, but the most accepted immunophenotype in humans, is CD73 + , CD90 + and CD105 + , as well as Lin - . In this work, we evaluate if described adult HSC and MSC markers are expressed and can be detected by flow cytometry during early limb bud development. Results showed MSC markers CD73 and CD105 are present in a low percentage of limb bud cells but not CD90 in the evaluated stage, it will be interesting to determinate if the same cells are expressing both markers at the time they are negative for hematopoietic lineage specific markers like CD45 also expressed in a low percentage of limb bud cells. In the evaluated stages, CD117 was not detected but Sca-1 did. Since both markers expressions are necessary for HSC identification, next, we will be looking for their expressions at later stages. This study was partially supported by CONACyT grants 53484 and 168642, DGAPA-UNAM grants IN214511 and IN220808. Program/Abstract # 528 Defining the origins of the hemogenic endothelium, the source of hematopoietic stem cells Naiche, L.A. (National Cancer Institute, USA); Klarmann, Kimberly; Keller, Jonathan (SAIC-Frederick National Lab,USA); Lewandoski, Mark (National Cancer Institute, USA) Differentiation generally proceeds linearly from less to more differentiated cell fates, and exceptions are usually pathological (i.e. cancer) or artificial (i.e. iPS cells). However, during normal development, hematopoietic stem cells (HSCs) arise from apparently differentiated, functional endothelial cells in the endothelial walls of specific embryonic vessels, called the hemogenic endothelium. An unanswered question is the difference between hemogenic and non-hemogenic endothelium, which both express markers of differentiated endothelium. The vasculature of the placenta and umbilical cord, which are hemogenic tissues, originates in an embryonic organ called the allantois. We have observed that the bulk of the allantois is formed from cells that express Tbx4 or their descendants (the Tbx4 lineage), but the allantois-derived endothelium arises from two different lineages. The endothelium of the umbilical cord and proximal placenta are derived from a distinct population of cells that are not part of the Tbx4 lineage, while the endothelium of the distal placenta is derived from the Tbx4 lineage. This spatial distribution correlates with observed hemogenic fate and non-hemogenic fate, respectively. Despite abundant Tbx4 lineage endothelium in the placenta, the Tbx4 lineage does not populate circulating blood or HSC niches. These results indicate that endothelium can be sorted into two populations: a hemogenic lineage that has never expressed Tbx4, and the non-hemogenic Tbx4 lineage. Because the Tbx4 lineage is defined several days prior to hematopoietic activity, isolation of these lineages allows us to investigate the underlying factors that determine the potential of endothelium for future stem cell differentiation. Program/Abstract # 529 SOX2 is Required for Correct Pituitary Morphogenesis Goldsmith, Sam; Rizzoti, Karine; Lovell-Badge, Robin (MRC NIMR, UK) Pituitary hormonal deficiencies, or hypopituitarism, can be caused in humans and mice by haploinsufficiency of the HMG box transcription factor SOX2 (Kelberman et al, 2006). During embryogenesis, Sox2 is expressed ubiquitously in the pituitary anlagen or Rathke’s Pouch, (RP) and is then down-regulated, as endocrine cells differentiate. In the adult gland, a small population of SOX2 +ve progenitors remains (Fauquier et al, 2008). We, and others, have shown that SOX2 is required for proper pituitary morphogenesis. Conditional deletion of Sox2 in RP leads to a hypoplastic pituitary, likely caused by a reduction in progenitor proliferation (Jayakody et al 2012, S. G. unpublished). Using different Cre strains, we show that Sox2 deletion efficiency correlates with further reduction in pituitary size. The Sine Oculis homeodomain protein SIX6, required for progenitor proliferation in particular in the eye and the pituitary (Li et al 2002, Tetreault et al 2009), is downregulated upon Sox2 deletion while expression of LHX3, a LIM homeodomain transcription factor also required for RP progenitor proliferation is maintained. This suggests that SOX2 may directly up-regulate Six6 expression, as shown in other tissues, promoting RP progenitor proliferation. Later on, as endocrine cells differentiate, lineage tracing experiments show that the endocrine differentiation potential of Sox2 deleted progenitors is impaired. These data suggest that during normal development SOX2 drives early progenitor proliferation through the upregulation of Six6. Later on, Sox2 deleted progenitors are largely unable to give rise to endocrine cells. Ongoing experiments address a direct role of SOX2 for Six6 transcriptional regulation in RP. 152
Program/Abstract # 530 The MADS protein XAANTAL2 (XAL2/AGL14) is required to control auxin transport via direct PIN regulation during Arabidopsis root development Garay, Adriana; Ortiz-Moreno, Enrique; Sánchez, María de la Paz (UNAM, Mexico); Murphy, Angus S. (Purdue, USA); Marsch- Martínez, Nayelli; de Folter, Stefan (CINVESTAV-Langebio, Mexico); García-Ponce, Berenice; Corvera-Poiré, Adriana; Jaimes- Miranda, Fabiola; Pacheco-Escobedo, Mario A. (UNAM, Mexico); Dubrovsky, Joseph G. (UNAM-Cuernavaca, Mexico); Pelaz, Soraya (Barcelona, Spain); Álvarez-Buylla, Elena R. (UNAM, Mexico) Molecular links between cell-fate regulatory networks and dynamic patterning modules are key for understanding development. Auxin is important for plant patterning and particulary for root development, where it provides important positional information for cell-fate decisions. PIN genes codify for plasma membrane proteins that are important auxin efflux transporters and their mutants have altered root meristems and stem-cell patterning. However, PIN direct regulators have remained elusive. Here, we show that a MADS-box gene (XAANTAL2, XAL2/AGL14) whose mutants also have altered stem-cell patterning, root meristems and growth, control auxin transport via PIN transcriptional regulation during Arabidopsis root development. Concordantly, XAL2 is necessary for normal shootward and rootward auxin transport, as well as for maintaining normal auxin distribution along the root. Furthermore, this MADSdomain transcription factor up-regulates PIN1 and PIN4 by direct binding to their regulatory regions and it is required for PIN4 dependent auxin response. Interestingly, XAL2 responds to auxin levels thus establishing a positive feedback loop between auxin levels and PIN regulation that is likely important for robustness of root patterning. This work is supported by CONACyT (180098; 180380; 167705; 152649; 105678) and DGAPA, UNAM (IN204011-3; IN203113-3; IN226510-3; IB201212-2) grants. Program/Abstract # 531 A protein network controls protective quiescence in the Arabidopsis root stem cell organizer Cruz Ramírez, Luis Alfredo (Univ de La salle Bajío, Mexico); Diaz Trivino, Sara; Wachsman, Guy; Du, YuJuan (Wageningen Univ, Netherlands); Arteaga-Vazquez, Mario (Universidad Veracruzana, Mexico); Zhang, Hongtao; Blilou, Ikram (Wageningen Univ, Netherlands); Chandler, Vicky (U AZ, USA); Scheres, Ben (Wageningen Univ, Netherlands) Quiescent long-term somatic stem cells reside in plant and animal stem cell niches. Within the Arabidopsis root stem cell population, the Quiescent Centre (QC), which contains slowly dividing cells, maintains surrounding short-term stem cells and may act as a longterm reservoir for stem cells. The RETINOBLASTOMA-RELATED (RBR) protein cell-autonomously reinforces mitotic quiescence in the QC. RBR interacts with the stem cell transcription factor SCR through an LxCxE motif. Disruption of this interaction by point mutation in SCR or RBR promotes asymmetric divisions in the QC that renew short-term stem cells. Analysis of the in vivo role of quiescence in the root stem cell niche reveals that slow cycling within the QC is not needed for structural integrity of the niche but allows the growing root to cope with DNA damage. Program/Abstract # 532 Intestinal stem cell dynamics in induced human intestinal organoids Finkbeiner, Stacy; Rockich, Briana (U Michigan-Ann Arbor, USA); Vallance, Jeff; Shroyer, Noah (Cincinnati Children's Hospital, USA); Spence, Jason (U Michigan-Ann Arbor, USA) Our understanding of human intestine development and regulation has largely been inferred from animal models and limited cell culture systems due to a lack of suitable, realistic 3-dimensional models for studying human intestine. However, we have recently reported the use of a directed differentiation scheme, which mimics stages of intestinal organogenesis, to generate 3-dimensional intestinal tissue from pluripotent stem cells, called “induced human intestinal organoids” (iHIOs). iHIOs contain a pseudo-lumen and an epithelial layer containing differentiated cell types surrounded by a layer of mesenchymal cells. They also contain LGR5+/ASCL2+ cells suggesting the presence of intestinal stem cells (ISCs). However, it is still unclear if the LGR5+/ASCL2+ cells are bona fide ISCs. In our current studies we have begun to analyze the presence and function of putative ISCs in iHIOs. We demonstrate expression of ISC markers at the RNA and protein levels and show responsiveness of the ISC populations to Wnt and Notch signaling. This work is an important step in further understanding the promising iHIO model so that it can be used to study mechanisms of stem cell maintenance, intestinal development, tissue regeneration, intestinal physiology, and enteric microbiology among many other avenues of research. Program/Abstract # 533 Totipotent embryonic stem cells arise in ground state culture conditions Morgani, Sophie (Danstem Ctr, Denmark); Canham, Maurice (MRC Ctr Regen Med, UK); Nichols, Jennifer (Wellcome Trust Ctr for Stem Cell Res, UK); Sharov, Alexei (NIA/NIH, USA); Migueles, Rosa (MRC Ctr Regen Med, UK); Ko, Minoru (Keio U, Japan); Brickman, Joshua (Danstem Ctr, Denmark) Embryonic stem cells (ESCs) are derived from mammalian embryos during the transition from totipotency, when individual blastomeres can make all lineages, to pluripotency, when they are competent only to make embryonic lineages. ESCs maintained with signalling inhibitors (2i), are thought to represent a homogeneous pluripotent, embryonic ground state. Using a mouse line containing a sensitive reporter for the endoderm marker Hex we observed that embryos cultured in 2i exhibited endoderm precursor specification, but no lineage segregation. Similarly 2i ESC cultures contained a Hex positive fraction primed to differentiate into trophoblast and extraembryonic endoderm. Single Hex positive ESCs coexpressed epiblast and extraembryonic genes and contributed to all lineages in 153
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International Society of Developmen
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neural crest cells (hNCC)) human em
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activity may determine the orientat
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Developmental cell signaling pathwa
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opposed roles during early gastrula
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functions by the recruitment of add
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function validated with explant stu
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Program/Abstract # 48 Modeling regu
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surface of the embryo. In zebrafish
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morphologies. Our analyses not only
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junctional proteins (RPE patterning
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Program/Abstract # 78 In vivo recep
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Program/Abstract # 85 Guts and gast
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Program/Abstract # 92 The C. elegan
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Program/Abstract # 98 A gradient of
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Program/Abstract # 106 Developing a
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NSCs, but not in neurons, bind not
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abnormalities in the development of
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Tbx4 and contributes to Tbx4 repres
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downregulated by polycomb-group pro
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Zac1 expression in the developing c
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understanding the mechanisms that u
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Program/Abstract # 156 Systematic I
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Program/Abstract # 163 Size regulat
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TACC3 was localized around the DNA
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Penaeid shrimp represent an importa
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tubule. Using live imaging of cultu
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show that cell polarity is disrupte
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process. However, a clear mechanist
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Zhang, Haoran; Wong, Elaine Yee-man
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condition. Kanyon embryos have a mi
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Program/Abstract # 218 Lfng regulat
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works in concert with basal cues fr
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medaka genome. These miRs are encod
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facilitan cambio en patrón morfoge
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coordinately regulate the expressio
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downstream asymmetric signals. The
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viability and morphology of over 20
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owser. The genomic differences obse
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evolutionary analysis to study the
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teleostei. Our data evidenced that
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ontogeny. The typical condition for
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examples whose Shh expression requi
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insights into the ancestral role of
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Program/Abstract # 308 Mechanistic
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Patients with Joubert Syndrome and
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Program/Abstract # 323 Drosophila g
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signalling during gut and enteric n
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normally form, hence producing prox
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survival in Shh mutant embryos foll
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Page 133 and 134: Program/Abstract # 462 Retinaldehyd
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Congress Abstracts - Society for Developmental Biology

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