Congress Abstracts - Society for Developmental Biology

accumulation is decreased. This work was supported in part by grants 104350 from Consejo Nacional de Ciencia y Tecnología and
PICDS08-8 from ICyTDF (Mexico). CJLV is a graduate student supported by the PICDS08-8 scholarship from ICyTDF.
Program/Abstract # 449
Importance of Intersectin1 isoforms during proper embryonic development of Xenopus laevis
Cheng, Cheng; Jimenez, Oscar; Thorn, Judith (Knox College, USA)
Intersectin 1 (ITSN1), located on the human chromosome 21, is associated with neurodegenerative diseases such as Down Syndrome,
Alzheimer disease and Hungtington disease. Itsn1 interacts with many proteins, forming complexes implicated in endocytic and
mitogenic pathways important in neurogenesis and maintenance. In this study, we reported the abnormality caused by itsn1 depletion
and overexpression during the early Xenopus development. We microinjected the embryos at 1 cell stage with translation blocking
itsn1 morpholino, in which no abnormal phenotype was observed; however, the itsn1 morpholino injection in the oocytes followed by
host transfer results in the slow of blastopore closure, abnormal pigmentatation and a general shortening of the embryo axis. Similar
phenotype is also observed in embryos microinjected with Intersectin1-short (itsn1-S) mRNA at the 2-cell stage. Our analysis of the
relative expression of itsn1 during embryonic development along with our microinjection results indicates that sufficient itsn1 protein
is necessary pre-zygotically for early embryonic development, and regulating cell movement. Further research is going to be focusing
on the overexpression of itsn1 long isoform (itsn1-L) and the causality of the axis defects due to protein overexpression and depletion.
Program/Abstract # 450
Chromatin state transitions and epigenetic constraints during early Xenopus embryogenesis
Veenstra, Gert Jan (Radboud Univ, Netherlands)
Chromatin state is essential for pluripotency, competence and cell lineage commitment. It specifies how genes are marked for
activation or repression by epigenetic mechanisms. Little is known however, about the developmental origins of chromatin state and
its regulation. We have generated chromatin state maps of Xenopus tropicalis embryos by ChIP-sequencing to explore the
developmental origins of chromatin state with respect to inheritance, sequence features and molecular mechanisms. To assess
chromatin state dynamics we profiled promoter histone modifications, enhancer histone modifications, facultative and constitutive
heterochromatin modifications and DNA methylation at multiple stages of development. We find blastula stage marking of promoters
and enhancers by histone H3 lysine 4 tri- and mono methylation (H3K4me3, H3K4me1) respectively, followed by dynamic
commisioning of enhancers by the enhancer-bound p300 co-activator during gastrulation and subsequent development. The Polycomb
Repressor Complex 2 (PRC2) binds widely to enhancers, but the Polycomb mark H3K27me3 is only deposited at a small subset of
these sites. This mark is newly deposited from blastula stages onward within constrained domains lacking prior DNA methylation.
Unmethylated regions represent two epigenetically different loci: Polycomb-regulated genes and constitutive house-keeping
unmethylated promoters which gain H3K4me3 but not H3K27me3. These loci can be differentiated on the basis of specific DNA
sequence signatures which are conserved between humans, frogs and fish. The results imply a genetic-default model in which genomic
sequence is the major determinant of unmethylated regions. Unmethylated DNA triggers H3K27me3 deposition by an allosteric loop
when not opposed by transcriptional activation. The sequence signature involved provides an epigenetically marked but genetically
inheritable constraint on Polycomb regulation and serves as a scaffold to guide deposition of H3K27me3 during exit of pluripotency.
Program/Abstract # 451
The lysine acetyltransferase HBO1 is essential for maintaining the poised chromatin state of neural stem cells
Tim Thomas, Andrew Kueh, Anne Voss (Inst. of Medical Research, Australia)
The five MYST proteins (KAT5-8) constitute one third of the mammalian genome's capacity to regulate transcription and chromatin
conformation at the level of histone acetylation. We have reported the biological and molecular roles of the MYST histone
acetyltransferases in vivo in mice. 1-7 MOZ (MYST3) and QKF (MYST4) are essential for the development and self-renewal of
haematopoietic stem cells and neural stem cells, respectively. 2,3 MOF (MYST1) is required genome-wide histone 4 lysine 16
acetylation (H4K16ac). 4 However, MOZ is unexpectedly specific and regulates H3K9ac at Hox and Tbx loci, correspondingly, Moz
mutation leads to homeotic transformation of the axial skeleton 5 and DiGeorge-like defects in heart development. 6 Unpublished data
will be presented showing that neural stem cells lacking HBO1 (MYST2) are devoid of H3K14ac, yet undergo self-renewing
proliferation for months in culture. Wild type neural stem cells are multipotent. In contrast, Hbo1 null neural stem cells are unable
differentiate into neurons, forming only astrocytes. In vivo, Hbo1 null cortical neurons fail to express key regulators of cortex
development. Re-expression of HBO1 in neural stem cells restores H3K14ac and multipotency when conducted 3 days, but not 5
weeks after decline in HBO1 protein, suggesting irreversible changes to the chromatin after prolonged absence of HBO1. Our data
suggest that HBO1 and H3K14ac are essential for the maintenance of multipotency and the poised chromatin state. 1. Thomas et al
(2000) Development 127:2537 2. Thomas et al (2006) Genes Dev 20:1175 3. Merson et al (2006) J Neurosci 26:11359 4. Thomas et al
(2008) Mol Cell Biol 28:5093 5. Voss et al (2009) Dev Cell 17:674 6. Voss et al (2012) Dev Cell 23:652
Program/Abstract # 452
AMPK (AMP-activated kinase) buffers adverse transgenerational consequences on growth and reproduction following a
single exposure to nutrient stress in C. elegans
Richard Roy, Emilie Demoinet (McGill U, Canada)
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