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Date and Time 2013-02-01 11:00 - 12:00
Venue Auditorium C1F
Speaker Mamiko Yajima
BioMed MCB Department, Brown University
Title Engineering Developmental Plasticity: Mechanisms of Germ Cell and Multipotent Cell Development.
Poster click here to download (PDF)
Host Shibata Tatsuo
Summary Developmental plasticity is an essential and fundamental ability for a living individual to develop, regenerate and survive successfully in response to a various environment, and the cellular multipotency plays a key role in this survival process. The cellular multipotency is controlled by a fine combination of both genetic and epigenetic mechanisms, and thus an integrative approach is important to understand its complex mechanism especially in germ cell and stem cell development. Echinoderms, a sister group to chordates, are known for having remarkable developmental plasticity. Adults can regenerate entire segments including even gonads, and embryonic cells maintain multipotency until late in their development: Cells from other lineages can transfate and compensate for a missing part of the embryo. Echinoderms yet have a fundamental similarity to Vertebrates in their developmental style such as having three tissue layers (ectoderm, endoderm and mesoderm) to regulate. The amazing plasticity of echinoderm cells serves as a good experimental tool to study the basic mechanisms of cellular multipotency conserved among deuterostomes. In this seminar, by using echinoderms’ multipotent cells, I would like to share our recent findings that include, 1) the mechanisms of Primordial Germ Cell (PGC) specification, 2) the molecular mechanism and function of Vasa in a cell cycle progression, and 3) the mechanisms of chromatin activity that epigenetically regulate multipotent cell and germ cell development.

1) We have recently identified that small micromeres formed at the 5th division in the sea urchin contribute to the germ line and share many more typical characters of PGCs than previously thought, implying a more widely conserved system of germ line specification among metazoans. From other evidence we hypothesize that sea urchins have recently acquired changes to adopt a more autonomous manner of PGC specification. This evolutionarily distinct feature of sea urchin embryos among echinoderms will be a useful tool to reveal mechanisms of germ line evolution and the multipotent cell specification program that might be widely conserved throughout the animal kingdom (Yajima and Wessel, Development 2011a & 2012; Yajima et al., Dev. Dyn. 2012).
2) Vasa is a conserved germ line marker among metazoans. We found that Vasa localized to the mitotic apparatus during M-phase and inhibition of Vasa synthesis prevents cells from exiting mitosis. Furthermore, we found that Vasa interacts with mRNAs important for embryogenesis and is required for its efficient translation. This novel function of Vasa in rapid cell cycle progression appears to be conserved among organisms and thus may explain its ancestral function as a multipotent cell regulator (Yajima and Wessel, Development 2011b & Mol. Repro. Dev. 2011).
3) Insulators are genomic elements that regulate transcriptional activity by forming chromatin boundaries. The Arylsulfatase insulator (ArsI) found originally in the sea urchin is known to function as an insulator in diverse organisms among metazoans. We identified a small set of proteins specifically bound to the minimal ArsI region, including ISWI, a known chromatin-remodeling protein. During embryogenesis, ISWI was found to interact with select ArsI sites throughout the genome, and when inactivated led to misregulation of select gene expression, loss of insulator activity and aberrant morphogenesis. These studies revealed a mechanistic basis and importance of ArsI function in the gene regulatory network of early development (Yajima et al., Development 2012).
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