Abstracts - Society for Developmental Biology

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partners. Our transgenic gain of function and interference approaches with Bucky ball and its interacting proteins provide
insight into Buc regulation and have identified potential roles for RNA binding proteins in oocyte polarity and follicle cell
fates.
Program/Abstract # 348
A novel, maternally expressed gene, SMCR7L1, is important for Xenopus early development
Grant, Paaqua A.; Johnson, Diana; Moody, Sally, The George Washington School of Medicine and Health Sciences,
Washington, DC, United States
Maternal factors, such as mRNAs, that are localized asymmetrically in the cytoplasm of eggs, are important for proper
development in many organisms. In Xenopus, these factors specify the body axes and delimit the germ layers. We
identified nearly 100 transcripts that are highly enriched in animal blastomeres of fertilized Xenopus embryos. One of
these, SMCR7L1, is a novel, vertebrate specific gene whose function is poorly understood. At blastula stages it is
expressed in animal cap ectoderm, at gastrulation/neural plate stages it is dorsally enriched in the ectoderm and by tail bud
stages it is highly enriched in the neural tube. Knockdown of SMCR7L1 with high doses of MOs results in developmental
arrest at gastrulation, whereas low doses result in down-regulation of neural genes. In contrast, injection of SMCR7L1
mRNA into a single blastomere of 8-cell embryos expands the domains of early neural and neural crest genes, and
ectopically induces geminin in ventral ectoderm. These data indicate an early role in neural fate specification.
Program/Abstract # 349
DV and AP axial patterning are coordinated by an identical patterning clock
Hashiguchi, Megumi; Mullins, Mary, University of Pennsylvania, Philadelphia, United States
The coordinated timing of embryonic patterning along the body axes is a crucial step in establishing the body plan in
vertebrates. Our laboratory has shown that BMP signaling patterns dorsoventral (DV) tissues progressively temporally
along the anteroposterior (AP) axis. To examine if DV patterning by BMP signaling along the AP axis is coordinated with
AP patterning by the same patterning clock or independently of AP patterning, we altered AP patterning by inhibition or
activation of FGF, Wnt, and RA signaling in combination with temporal inhibition of BMP signaling. We found that the
anteriorized or posteriorized tissues were patterned at the same temporal interval by BMP signaling as the normally
positioned tissues, indicating that DV patterning and AP patterning are temporally coordinated along the AP axis. We then
examined the molecular mechanism coordinating DV and AP patterning. Phosphorylation of Smad1 by MAPK and GSK3
inhibits the activity of the BM Preceptor phosphorylated form of Smad1, P-Smad1Cter, in Xenopus embryos (Fuentealba
et al., 2007). This regulation is postulated to coordinate DV and AP patterning of the ectoderm by BMP, FGF/MAPK and
Wnt/GSK3 signaling. To investigate if a similar mechanism regulates P-Smad1/5Cter function in zebrafish, we examined
the localization pattern of P-Smad1/5MAPKand P-Smad1/5GSK3. The localization of P-Smad1/5MAPK was maintained
in the ventral marginal zone, where FGF/MAPK and BMP/Smad1/5 signaling coexist during gastrulation, whereas P-
Smad1/5GSK3 was not.We also found that FGF/MAPK could affect the timing of patterning of DV tissues along the AP
axis during gastrulation. These data provide novel insight into the spatiotemporal coordination of DV and AP patterning.
Program/Abstract # 350
Characterization of the presomitic mesoderm progenitor cell and its niche
Jakuba, Caroline M.; Kudra, Randy; El-Sessi, Sahar; Mandoiu, Ion; Nelson, Craig, University of Connecticut Molecular
and Cell Biology, Storrs, United States
Diseases of the mesodermal tissues of the body including wound healing, arthritis, osteoporosis and muscular wasting
diseases, affect millions of people across the globe. If existing barriers to the efficient derivation of mesodermal tissues
from readily available, patient-matched stem cells could be overcome, these diseases could be treated with stem cell-based
regenerative medicine. Unfortunately, reproducible protocols for the differentiation of muscle, cartilage, and connective
tissues, or more specifically, those mesodermal derivatives produced solely from pre-somitic mesoderm (PSM), have yet to
emerge. While it is possible to obtain some cell types of the PSM from human ESC, these efficiencies (commonly