Department of Development and Differentiation,
Institute for Frontier Medical Sciences, Kyoto University
53 Kawahara-cho Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
NOTE: Japanese page is here
In the cytoplasm of germ-line cells, characteristic electron-dense, amorphous granules, called nuages, are present in many animals. In mice, nuages are most prominent in postnatal meiotic spermatocytes and postmeiotic round spermatids, and are often called chromatoid bodies. The functions of the mammalian chromatoid bodies/nuages are not known, and only a few components of the structures have been identified so far, which include the mouse vasa homologue protein. We have isolated Mouse tudor repeat-1 (Mtr-1) that encodes a MYND domain and four copies of the tudor domain. Multiple tudor domains are a characteristic of the TUDOR protein, a component of Drosophila nuages. Mtr-1 is expressed in male germ cells, and MTR-1 constitutes a novel component of chromatoid bodies/nuages. We have also shown that MTR-1 forms a complex with snRNP, a spliceosomal complex, which also accumulates in chromatoid bodies/nuages. We have also isolated Mtr-2, which encodes seven repeats of the tudor domain. Mtr-2 is predominantly expressed in the adult testis, and the major transcript is about 7.5 kb in size, while 5Õ RACE of Mtr-2 showed that the gene has multiple transcription initiation sites. MTR-2 is present in the cytoplasm of postnatal spermatocytes and round spermatids, but is not detectable in oocytes, fetal germ cells or in embryos at early stages of development. A truncated form of MTR-2 protein is also present in the colon, where MTR-1 is not detectable. In spermatocytes and round spermatids, MTR-2 shows characteristic granular distribution in the cytoplasm, and the granules show precise co-localization with those of MTR-1, demonstrating that MTR-2 constitutes a novel component of chromatoid bodies/nuages. Localization of MTR-2 to chromatoid bodies/nuages, however, occurs later than that of MTR-1, and MTR-2 remains in the structures after the disappearance of MTR-1. This result demonstrates that mammalian chromatoid bodies/nuages are not static organelles, but their constituents change along with their differentiation process.
We have established many ES cell lines from various mouse strains. Using such cell lines, we are studying regulation of cell differentiation in culture. we have also established several primate ES cell lines from monkey blastocysts, as the first step of the application study for regenerative medicine.
Institute for Frontier Medical Sciences, Japan
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