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Category CDBセミナー
Date and Time 2015-06-08 16:00 - 17:00
Venue Seminar Room A7F
Speaker Takuya Nakayama
Affiliation Department of Biology (Grainger lab), University of Virginia, USA
Title Reverse genetics in Xenopus tropicalis as a model for understanding human genetic diseases involved in eye and brain formation
Poster click here to download(PDF)
Host Masatoshi Takeichi
Summary rax (retina and anterior neural fold homeobox), six3 (SIX homeobox 3) and pax6 (paired box 6) genes are essential for eye and brain formation in vertebrates. In humans RAX mutations result in anophthalmia in compound heterozygotes, SIX3 mutations cause severe eye and brain defects (holoprosencephaly, HPE), and semi-dominant mutations in PAX6 cause aniridia (hypoplasia or absence of the iris). While studies of mutants of these genes in other organisms such as rodents and fish demonstrate that their functions are important during early neurula stages, the molecular mechanisms by which they influence eye and brain development are still largely unclear. Xenopus tropicalis has several advantages as a model organism, i.e. it is a true diploid (unlike fish), embryos are plentiful, easy to obtain and readily accessible for culture or experimental manipulation from the earliest stages of development (unlike mouse). We have obtained frog mutants of these genes using a Targeting Induced Local Lesions IN Genomes (TILLING) screen (rax), or CRISPR- and TALEN-mediated targeted mutagenesis (six3 and pax6, respectively). Briefly, the rax mutant revealed that several genes thought to be genetically downstream of Rax in mouse are actually not immediate early downstream genes, and losing Rax activity resulted in transformation of presumptive retinal tissue into non-retinal forebrain identities in the rax mutant. six3 mutants showed a HPE-like phenotype, and we could also mimic the human aniridia phenotype in pax6 mutant frogs. More detailed data and plans for future studies will be presented.
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