Developing an integrating biological dosimeter for spaceflight

A major safety concern of human activities in outer-space is the exposure to harmful radiation in the environment. It is well known that radiation can induce mutational damage which can result in diseases such as cancer, and death due to radiation poisoning. Much of our understanding of the effect of radiation on living animals comes from genetic analysis of model organisms. As a well-established model organism, C. elegans is an excellent system for the studies of mutational effects of radiation since it has a DNA damage response similar to humans (Reviewed by O’Neil and Rose [1]). C. elegans has been used extensively to study the phenotypic consequences of exposure to radiation. Rosenbluth and colleagues originally established the eT1 balancer system and used it to genetically analyze the mutational effects in C. elegans by X-irradiation and γ-irradiation [2,3]. Using this system, along with other detection methods such as chromosome non-disjunction and unc-22 mutagenesis, Nelson and colleagues carried out further investigations on the mutational effects of C. elegans under different types of radiation such as high and low linear energy transfer (LET) ionizing radiation [4,5]. Features of C. elegans, such as small size, simplicity of maintenance, and variety of research resources, have made it a model system for space biology studies (reviewed by Johnson and Nelson [6]; Zhao et al. [7]). C. elegans has been previously sent into space and it has been shown that it can reproduce and develop normally during the spaceflight [8]. Analysis on dormant worms exposed to natural space radiation during the same flight revealed an elevated mutation rate compared to ground controls [9]. More recent studies by Hartman and colleagues compared mutations in a single C. elegans gene induced by accelerated iron particles and low earth orbit space radiation, indicating that high LET charged particles are an important mutagenic component of space radiation [10]. While previous studies have focused on the immediate effects of natural space radiation (single generation), we were more interested in understanding the long term effects (multiple gen-