The 42nd Annual Meeting for the Japanese Society of Developmental Biologists (日本発生生物学会第42回大会)
Toki Messe, Niigata, Japan
May 30, 2009
WS1-12 (Workshop 1: Evolution & development)
Oral presentation

Evolution and developmental expression of chordate microRNAs
Rie Kusakabe1, Saori Tani1, Shigehiro Kuraku2, Yuki Miyamoto3, Kohji Okamura4, Kenta Nakai4, Takehiro G. Kusakabe3, and Kunio Inoue1
1Dept. Biol., Grad. Sch. Sci., Kobe Univ., 2Dept. Biol., Univ. Konstanz, Germany, 3Dept. Biol., Fac. Sci. Eng., Konan Univ., 4Inst. Med. Sci., Univ. Tokyo
Gene regulation by microRNAs, which consist a large group of non-coding RNAs of 21-25 nt having silencing activity on specific target mRNAs, is one of the emerging research fields in developmental biology. Many of the microRNAs are shared across different animal taxa, and are expressed in conserved tissue-specific manners. We launched a comparative analysis of microRNAs in urochordate ascidians, cyclostome lampreys, and several teleost species. Expression patterns of identified microRNAs have been analyzed by Northern blotting and whole mount in situ hybridization using locked-nucleic-acid-modified (LNA) probes.
Our results have suggested that ascidians possess fewer copy number of each microRNA family compared to vertebrate counterparts. For example, the miR-1(206)/miR-133 cluster exists as a single copy in both C. intestinalis and C. savigni, whereas probably two copies in the lamprey L. japonicum and more than three copies in teleosts and mammals. In all species examined, these microRNAs are specifically expressed in muscle cells, although prominent expression was detected in different muscle tissues at different developmental stages.
It has been suggested that miRNA-mRNA interaction 'fine-tunes' the differential levels of protein expression in neighboring cells or tissues. Changes in regulation by microRNAs might have potentially enabled phenotypic modification without drastic alteration of the core developmental mechanisms.