International Mammalian Genome Society

H16 Heavy Ion Beams: An Application to Mouse Mutagenesis

Atsushi Yoshiki,¹ Noriko Hiraiwa,¹ Teruyo Tsukada,¹ Yoshika Yoda,¹ Christophe Poirier,¹ Fumio Ike,¹ Nobuhisa Fukunishi,² Masayuki Kase,³ Yasushige Yano,³ and Moriaki Kusakabe. ¹Division of Experimental Animal Research, The Center for Biogenic Resources, The Institute of Physical and Chemical Research (RIKEN), 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074, Japan; ²RI Beam Factory Project; ³Cyclotron Laboratory, RIKEN, Wako, Saitama 351-01, Japan

Mouse mutants are a quite useful animal model to study the gene functions and pathogenesis of human diseases. In order to reveal gene functions we need more effort to create and find new phenotypes in mouse mutagenesis. Here we report an application of heavy ion beams for mouse mutagenesis. Spermatozoa were collected from the cauda epididymidis of C57BL/6J (B6) mice, suspended in M2 medium. The tubes containing sperm suspension were exposed to heavy ion beams (⁴⁰Ar at 95 MeV/u, ⁵⁶Fe at 90 MeV/u, and ²⁰Ne, ¹⁴N and ¹²C at 135 MeV/u) with dose ranges of 10, 20, 30, 50, and 75 Gy at RIKEN Ring Cyclotron Facility. Mice were created artificially in vitro by injecting a single spermatozoon into the egg cytoplasm. Successfully cleaved 2-cell embryos were transferred into oviducts of pseudopregnant recipients to produce G1 mice. We have also tried to induce mutations in male premeiotic germ cells. B6 male mice were deeply anesthetized and their testes were exposed to heavy ion beams with dose ranges of 1, 3, and 5 Gy. Testis tissues were severely damaged after irradiation. Germ cells in seminiferous epithelium decreased significantly with a higher dose of heavy ion beams. Following the sterile periods, some male mice could restart reproduction. We have paired irradiated males with untreated females to produce G1 mice. We examined G1 during embryonic periods for morphological anomalies to assess which male mice have high potential to produce mutants more effectively. In G1 embryos morphological anomalies were found in different organs and systems, such as microphthalmia, anophthalmia, exencephaly, and pale anemic embryos. We will report the results of morphological screening for external anomalies in G1, G2, and G3 after heavy ion beam treatment, and discuss the feasibility of creating new mutant mice by heavy ion beam.