Dynamic expression of manganese superoxide dismutase during mouse embryonic organogenesis JUNG-MIN YON 1 , IN-JEOUNG BAEK 2 , BEOM JUN LEE 1 , YOUNG WON YUN 1 and SANG-YOON NAM* ,1 1 College of Veterinary Medicine and Research Institute of Veterinary Medicine (RIVM), Chungbuk National University, Cheongju, South Korea and 2 Laboratory of Mammalian Molecular Genetics, Department of Biochemistry, College of Science, Yonsei University, Seoul, South Korea ABSTRACT The balance between reactive oxygen species production and antioxidant defense enzymes in embryos is necessary for normal embryogenesis.To determine the dynamic expression profile of manganese superoxide dismutase (MnSOD) in embryos, which is an essential antioxidant enzyme in embryonic organogenesis, the expression level and distribution of MnSOD mRNA and protein were investigated in mouse embryos, as well as extraembryonic tissues on embryonic days (EDs) 7.5-18.5. MnSOD mRNA levels were remarkably high in extraembryonic tissues rather than in embryos during these periods. MnSOD protein levels were also higher in extraembryonic tissues than in embryos until ED 16.5, but the opposite trend was found after ED 17.5. MnSOD mRNA was observed in the chorion, allantois, amnion, ectoderm, ectoplacental cone and neural fold at ED 7.5 and in the neural fold, gut, ectoplacental cone, outer extraembryonic membranes and primitive heart at ED 8.5. After removing the extraembryonic tissues, the prominent expression of MnSOD mRNA in embryos was seen in the sensory organs, central nervous system and limbs on EDs 9.5- 12.5 and in the ganglia, spinal cord, sensory organ epithelia, lung, blood cells and vessels, intestinal and skin epithelia, hepatocytes and thymus on EDs 13.5-18.5. Strong MnSOD immunoreactivity was observed in the choroid plexus, ganglia, myocardium, blood vessels, heapatocytes, pancreatic acinus, osteogenic tissues, brown adipose tissue, thymus and skin. These findings suggest that MnSOD is mainly produced from extraembryonic tissues and then may be utilized to protect the embryos against endogenous or exogenous oxidative stress during embryogenesis. KEY WORDS: 5V;7, W`QLI\Q^M [\ZM[[ WZOIVWOMVM[Q[ UW][M MUJZaW M`XZM[[QWV XZWﾅTM Normally, metabolism of mammalian cell continuously generates UHDFWLYH R[\JHQ VSHFLHV 526 ZKLFK LQﾁXHQFH FHOO VLJQDOLQJ pathways including those involved in proliferation, differentiation, and apoptosis during embryo development. Balance between ROS production and antioxidant enzymes prevents lipid peroxidation, DNA and RNA breakages, protein degradation, and inactivation of many enzymes (Valko et al., 2007). In the defense system against R[LGDWLYH VWUHVV VXSHUR[LGH GLVPXWDVH 62' LV WKH ﾀUVW HQ]\PDWLF step that converts superoxide ions (O 2 ï ) to hydrogen peroxide (H 2 O 2 ). O 2 ï is generated under physiological conditions as a by-product of mitochondrial respiration. At present, three distinct isoforms of SOD KDYH EHHQ LGHQWLﾀHG LQ PDPPDOV 7KHUH DUH WZR LPSRUWDQW W\SHV of intracellular SODs: the cytoplasmic copper/zinc SOD (SOD1) and mitochondrial manganese SOD (MnSOD: SOD2). MnSOD is located in the mitochondrial matrix and protects mitochondria from the O 2 ï WKDW LV GHWULPHQWDO WR WKHVH RUJDQHOOHV 7KHUHIRUH 0Q62' Int. J. Dev. Biol. 55: 327-334 (2011) doi: 10.1387/ijdb.103270jy www.intjdevbiol.com *Address correspondence to: Sang-Yoon Nam. Laboratory of Veterinary Anatomy, College of Veterinary Medicine, Chungbuk National University, Cheongju 361- 763, South Korea. Tel: +82-43-261-2596 - Fax: +82-43-271-3246 - e-mail: synam@cbu.ac.kr Accepted: 4 May 2011. Final, author-corrected PDF published online: 31 May 2011. Edited by: Makoto Asashima. ISSN: Online 1696-3547, Print 0214-6282 © 2011 UBC Press Printed in Spain Abbreviations used in this paper: ED, embryonic day; MnSOD, manganese superoxide dismutase. is highly expressed in organs whose tissues contain a large number of mitochondria such as the heart, liver, and kidney (Beyer et al.,  )ULGRYLFK  /DQGLV DQG 7RZHU  MnSOD knockout mice died of severe dilated cardiomyopathy, neurodegeneration, and severe metabolic acidosis during develo- pment within a few days after birth (Lebovitz et al., 1996; Huang et al., 2001). Knockout mice with targeted disruption of MnSOD are more susceptible to damage than their wild-type counterparts (Grzeschik et al., 2003; Ong et al., 2006). For example, animals lacking MnSOD develop a variety of abnormalities such as sidero- blastic anemia, increased incidence of cancer, genomic instability, spongiform encephalopathy, optic neuropathy, movement disor-