Abstracts - Society for Developmental Biology

92
Program/Abstract # 281
Identification and functional characterization of Nrdp1 as a potential new regulator of planar cell polarity
signaling
Hutchinson, Sarah; Trinh, Jason; Naito, Mizue; Ciruna, Brian, The Hospital for Sick Children, Toronto, Canada
Planar cellpolarity (PCP) signaling coordinates the polarized structure, orientation and movement of cells within a tissue.
Activation of PCP begins with asymmetricWnt/Fz signaling at the cell membrane, which is regulated by the
transmembrane protein Van Gogh-like (Vangl). Vangl is a core PCP signaling protein and, in contrast to Wnt/Fz, is
specific to PCP. While the role for Vangl in PCP signaling is well established, the molecular mechanisms underlying
Vanglactivity remain unclear. To address this question, we performed a membrane yeast two-hybrid (MYTH) screen to
identify novel Vangl-interacting proteins.Among our hits, we identified the E3 ubiquitin ligase Neuregulin receptor
degredation protein (Nrdp1). Zebrafish Nrdp1is maternally and ubiquitously expressed early in development, but by 28
hours post fertilization (hpf) it becomes highly expressed in the central nervous system. Remarkably, Nrdp1 protein
localizes to neuronal membranes, axons andcilia. To assay the function of Nrdp1 we used targeted zinc finger nucleases to
generate zebrafish mutants with a two base pair deletion in nrdp1. This mutation, within the highly conserved RING
domain of Nrdp1, results in a premature stop codon. Homozygous mutants are morphologically normal and viable until at
least 7 days postfertilization. However, strong maternal nrdp1expression may rescue early embryonic development. We are
currently generating maternal-zygotic mutant embryos that have a complete loss of nrdp1. Future experiments will
elucidate the function of Nrdp1 in PCP signaling ciliogenesis and neuronal development.
Program/Abstract # 282
The adhesion GPCR Gpr125 modulates Dishevelled distribution and planar cell polarity signaling
Li, Xin, Vanderbilt University, Nashville, United States; Sepich, Diane (WUSTL, St. Louis, United States); Ni, Mingwei
(Flushing, United States); Hamm, Heidi (Nashville, United States); Marlow, Florence L. (Bronx, New York, United
States); Solnica-Krezel, Lilianna (St. Louis, United States)
During embryogenesis, gastrulation establishes the three germ layers and the animal body plan. Vertebrate gastrulation
relies on polarized cell behaviors to drive convergence and extension (C&E) movements that narrow embryonic tissues
mediolaterally and elongate them anteroposteriorly 1. Although planar cell polarity (PCP) signaling is a key regulator of
C&E movements, how it polarizes cells during gastrulation is not well understood 2, 3. Here, we identified the adhesion G
protein-coupled receptor Gpr125 asa novel modulator of PCP signaling. Excess Gpr125 impaired C&E movements and the
underlying cell polarity of wild-type gastrulae. Reduced Gpr125 function exacerbated the C&E and facial branchiomotor
neuron migration defects of PCP mutants. Intriguingly, Gpr125 recruited Dishevelled (Dvl), the signal transducer of PCP
signaling 2, 3, to the cell membrane and promoted Dvl clustering into discrete membrane subdomains and reciprocally,
Dvl promoted the clustering of Gpr125into such membrane subdomains. Pull-down assays suggested Gpr125 and Dvl
influence their mutual subcellular distribution via direct interaction. We hypothesize that Gpr125 modulates PCP signaling
and polarized cell behaviors in part by promoting formation of PCP protein supramolecular membrane complexes.
Program/Abstract # 283
Drosophila Maf1 controls body size and developmental timing by modulating tRNAiMet synthesis and systemic
insulin signaling
Rideout, Elizabeth; Marshall, Lynne; Grewal, Savraj, University of Calgary, Canada
How growth and size are controlled during animal development is an important question in biology. Several families of
conserved cell-cell signaling pathways regulate organ size by controlling cell growth, proliferation and survival. In
addition, environmental factors such as nutrients, oxygen and temperature influence tissue and organismal growth during
development. The conserved Target-of-Rapamycin (TOR) kinase is perhaps the best-understood nutrient-dependent
regulator of cell metabolism and growth in animals. The key effectors underlying this growth are, however, unclear. Here
we show that Maf1,a repressor of RNA Polymerase III-dependent tRNA transcription, is an important mediator of nutrientdependent
growth in Drosophila. We find nutrients promote tRNA synthesis during larval development by inhibiting
Maf1. Genetic inhibition of Maf1 accelerates development and increases body size. These phenotypes are due to a non
cell-autonomous effect of Maf1 inhibition in the larval fat body, the main larval endocrine organ. Inhibiting Maf1 in the fat
body increases growth by promoting the expression of brain-derived insulin-like peptides and consequently enhanced
systemic insulin signaling. Remarkably, the effects of Maf1 inhibition were reproduced in fliescarrying one extra copy of
the initiator methionine tRNA, tRNAiMet. These findings suggest the stimulation of tRNAiMet synthesis via inhibition of
dMaf1 is limiting for nutrition-dependent growth during development.