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60 that developmental patterning downstream of Wnt16/Ror1, required for HSC specification, is aberrantly reawakened in leukemic transformation. Program/Abstract # 182 Interactions between transplanted mouse embryonic stem cell-derived neural progenitors and endogenous brain vasculature Becker, Sandy; Lassiter, Chelsea; McGill, Sean; Grabel, Laura, Wesleyan University, Middletown, United States Embryonic Stem Cell-derived Neural Progenitors (ESNPs) have potential clinical uses as replacement therapies for a variety of brain disorders. However, how transplanted cells recruit a blood supply, or how they migrate in the host brain, remains unclear. Angiogenesis can occur in the adult mouse brain in response to several insults, for example a tumor, ischemia, or an epileptic seizure. Conversely, the adult brain vasculature has been shown to act as a scaffold and signal source for migrating neural progenitors in the SVZ and SGZ. We have used an ESNP transplant paradigm to investigate both the ability of transplanted cells to recruit endogenous blood vessels and their migration in the host brain. We observe that ESNPs transplanted into the hippocampi of adult mice initially display a relatively avascular core, which after 4 weeks becomes abundantly vascularized. We also observe proliferating (Ki67+) endothelial (CD31+) cells in the transplant and surrounding hippocampus, but not on the contralateral side that did not receive a transplant. We find putative fractones (slender laminin-positive stems attached to blood vessels) in and near the transplant, but never on the contralateral side. These data suggest that the transplanted ESNPs stimulate an angiogenic response in the host brain. We also observe transplanted cells migrating on endogenous blood vessels. In addition, ESNPs cultured with hippocampal slices associate with the blood vessels in the slices. These data suggest that transplanted ESNPs use endogenous blood vessels as a scaffold for migration. Program/Abstract # 183 Presynaptic input from corticotropin-releasing hormone-expressing neurons promotes adult-born neuron circuit integration Garcia, Isabella; Huang, Longwen; Arenkiel, Benjamin, Baylor College of Medicine, Houston, United States The brain undergoes neurogenesis throughout life, but the programs guiding newborn neuron circuit integration are unknown. Thousands of neurons are born daily in the olfactory system, yet only half form long-lasting circuits. Many activities, including learning, stress, and neuropathology affect this process.To reveal how activity influences neurogenesis, we aimed to identify the cell types providing inputs onto newborn neurons in the mouse olfactory bulb (OB). By targeting newborn neurons for transsynaptic tracing with Rabies Virus, we mapped local Corticotropin-Releasing Hormone (CRH)- expressing neurons with extensive inputs onto newborn neurons. CRH is implicated in diverse medical and psychological conditions, many of which influence neurogenesis. To elucidate the role for CRH input onto newborn neurons, we tested the following hypothesis: Presynaptic input from CRH-expressing neurons promotes newborn neuron circuit integration and synapse formation. Using novel viral tracing, mouse genetics, electrophysiological recordings, and optical imaging, we have found that 1) local CRH-expressing neurons are presynaptic to newborn neurons, 2) newborn neurons dynamically express the CRH receptor during periods of circuit integration, and 3) newborn neuron integration and survival is negatively impacted in mouse models lacking CRH or its receptor. We are currently investigating the programs that underlie CRH signaling to promote newborn neuron synapse formation, survival, and circuit integration in the OB. Our discovery that CRH-expressing neuron sprovide presynaptic inputs onto newborn neurons represents a novel and important mechanism to promote synapse formation and circuit integration in the adult mammalian brain. Program/Abstract # 184 Genome-wide analysis of the basic Helix-Loop-Helix gene family in planarians identifies factors involved in neurogenesis Cowles, Martis W., San Diego State University, San Diego, United States; Brown, David R. (Toronto, Canada); Stanley, Brianna; Nisperos, Sean V. (San Diego, United States); Pearson, Bret J. (Toronto, Canada); Zayas, Ricardo M. (San Diego, United States) Nervous system development requires the spatial and temporal specification of diverse neuronal populations, a process that is partly regulated by transcription factors from the basic Helix-Loop-Helix (bHLH) proneural gene family. Due to the limited regenerative capacity of most well-studied model organisms, little is known about the potential role these factors might play during replacement of damaged or missing neural tissues. We are characterizing the bHLH gene family in the freshwater planarian Schmidtea mediterranea. Following amputation, these animals can completely regenerate their central nervous system (CNS) from a population of pluripotent adult stem cells they maintain throughout their lives. Furthermore, planarians possess an easily-accessible nervous system with diverse neural subtypes, making them excellent models to
61 examine stem cell-based CNS regeneration invivo. To investigate the role of planarian bHLH genes, we identified 44 genes encoding bHLH domains in the S.mediterranea genome. Expression analysis using whole mount in situ hybridization revealed that a majority of these genes are enriched in the stem cells and/or CNS. We are currently using RNA interference to test the roles of these genes during CNS regeneration. Thus far, we have identified candidate bHLH genes that regulate neurogenesis such as achaete-scute and atonal homologs, which are known to play major roles in neural specification in other organisms. Understanding the factors that control neurogenesis in planarians will help us elucidate potential molecular mechanisms that direct stem cells in vivo to regenerate new neurons in adult animals. [Supported by NSERC grant to B.J.P., and CIRM Grant RN2-00940-1 to R.M.Z.] Program/Abstract # 185 Epigenetic regulation of planarian stem cells by the SET1/MLL family of histone methyltransferases Hubert, Amy M.; Henderson, Jordana M.; Torres, Jessica; Ross, Kelly G.; Zayas, Ricardo M., San Diego State University Biology, San Diego, United States Chromatin regulation is a fundamental mechanism underlying stem cell pluripotency and differentiation and the establishment of the gene expression profiles of different cell types. A complete understanding of chromatin state changes during stem cell regulation will enhance our ability to identify pathways leading to developmental disorders and disease. To examine chromatin regulation in stem cells in vivo, we study regeneration in the freshwater planarian Schmidtea mediterranea. These animals possess a high concentration of pluripotent stem cells known as neoblasts, which are capable of restoring any damaged or lost tissues after injury or amputation. The SET1/MLL family regulates gene expression by methylating lysine4 of histone H3. This mark leads to an active chromatin state and recruitment of RNA polymerase II, thus promoting transcription. In order to identify set1/mll genes involved in neoblast regulation, we searched the S.mediterranea genome and found six homologues (set1, mll1/4, mll2/3, trr, mll5.1 and mll5.2). Using whole-mount in situ hybridization, we determined that four of these genes (set1, mll2/3, trr, and mll5.1) are expressed in the neoblasts. RNA interference (RNAi) knockdown of set1, mll1/4, trr, and mll5.2 results in animals that fail to regenerate properly after amputation. Most notably, set1 RNAi leads to a partial loss of the stem cell population. Future experiments will focus on identifying genes targeted by the SET1/MLL family in planarians and expanding the work to include other histone methyl transferases to help uncover epigenetic mechanisms that underlie stem cell regulation. [Supportedby CIRM Grant RN2- 00940-1 to R.M.Z. and by NIH-IRACDAPostdoctoral Fellowship GM68524-08 to A.H.] Program/Abstract # 186 Follistatin is required for head regeneration in the planarian, Schmidtea mediterranea Roberts-Galbraith, Rachel H.; Newmark, Phillip, Howard Hughes Medical Institute and University of Illinois in Urbana- Champaign, Urbana, United States Planarians possess an extraordinary capacity for regeneration. Upon amputation, these freshwater flatworms replace missing tissues and organ systems, partly through the function of pluripotent stem cells called neoblasts. Importantly, axial polarity respecification during regeneration enables the proper repatterning of new tissues and the formation of organs in the correct place. Anterior/posterior polarity in planarians requires Wnt signals from the tail and Wnt inhibition by Notum and secreted Frizzled-related proteins (sFRPs) in the head. However, the mechanisms underlying reestablishment of these signaling centers after amputation remain unknown. Here, we show that the Schmidtea mediterranea homolog of follistatin plays an essential role during head regeneration. follistatin expression is limited to a small number of notum+ cells in the anterior of the animal and to non-neural cells distributed near the planarian nervous system. After amputation, Smedfollistatin (RNAi) animals fail to regenerate cephalic ganglia and fail to reinitiate sFRP1 and notum expression in new anterior tissue. Concomitant RNAi of Smed-activin or Smed-ActRI rescues these phenotypes, suggesting that Follistatin antagonizes Activin signaling during regeneration. We propose a model in which a Follistatin/Activin axis controls respecification of axial patterning during planarian regeneration. We also hypothesize that Follistatin and Activin signaling might influence specification of cell fates during the regenerative process. Program/Abstract # 187 Novel antibodies to track cell differentiation in planarians Ross, Kelly; Taylor, Matthew; Munday, Roma; Hubert, Amy; Zayas, Ricardo, San Diego State University, San Diego, United States Planarians are well known for their ability to replace any of their tissues from a population of adult pluripotent stem cells (neoblasts). However, our knowledge of the spatial distribution and temporal sequence of neoblast differentiation during normal tissue homeostasis or regeneration is limited. To gain insights into the cellular events underlying regeneration, we have developed new monoclonal antibodies (mAbs) for the planarian Schmidtea mediterranea. Thus far, we have
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1 Program/Abstract # 1 Role of the
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3 Program/Abstract # 7 Forward gene
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5 Program/Abstract # 13 Evolution a
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7 Program/Abstract # 19 Lethal gian
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Page 31 and 32: 31 and migration (ADAM13). They act
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Page 35 and 36: 35 Program/Abstract # 107 Shroom3-d
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Page 39 and 40: 39 (Queens College, Flushing, Unite
Page 41 and 42: 41 these data imply that Dynamin is
Page 43 and 44: 43 Congenital renal malformations a
Page 45 and 46: 45 Elevated nuclear translocation o
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Page 51 and 52: 51 malformations in murine limb bud
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Page 57 and 58: 57 Program/Abstract # 173 The role
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Page 91 and 92: 91 Program/Abstract # 278 Heterogen
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111 that maternally-supplied Lkb1 i
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113 Program/Abstract # 341 Coordina
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115 partners. Our transgenic gain o
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117 delayed and stunted as monitore
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119 Program/Abstract # 359 The meth
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121 Misregulation of molecular path
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123 back to the midbody in cbp-1 RN
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125 versus asymmetric cell division
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127 spinal cord. Iulianella, Angelo
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129 determine cell cycle activity i
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131 in expanded Lmx1a/b+ progenitor
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133 ROS levels. Collectively, our r
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135 limbs. Apoptosis was also pertu
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137 Henkels, Julia; Zamir, Evan, Ge
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139 however, and its role in CSF ma
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141 embryonic precursors to form an
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143 with fork retarding Replication
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145 homeodomain (HD) transcription
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147 fate, potentially acting downst
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149 involved in Drosophila ventral
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151 Program/Abstract # 456 Thoracic
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153 ureteric insertion into the bla
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155 of p16, a known cyclin kinase i
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157 rax mutant was recently found i
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Abstracts - Society for Developmental Biology

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