Molecular analysis of mutations in T-lymphocytes from experienced Soviet cosmonauts.

Somatic mutation in five cosmonauts who have completed spaceflights of 7 to 365 days was analyzed using the clonal HPRT assay. The doses received in space by the cosmonauts ranged from 4 to 127 mGy. hprt mutant frequencies were 2.4-5.0-fold higher than age-corrected values established for healthy, unexposed subjects in western countries [Tates et al. (1991): Mutat Res 253: 199-213; Branda et al. (1993): Mutat Res 285: 267-279] and 2- to 3-fold higher than those determined for unexposed individuals residing in Russia [Jones et al. (1995): Mutat Res 338: 129-139]. A total of 107 collected mutant clones were analyzed by multiplex PCR. No excess of deletions was detected and their frequency did not correlate with either accumulated dose or the age of the cosmonauts. In 62 mutants cDNA was isolated by RT-PCR and sequenced. Those with splicing errors, as well as the mutants that did not produce cDNA, were further analyzed by the sequencing of exon(s)-containing fragments amplified from genomic DNA. The mutational spectrum recovered from the cosmonauts differed substantially from that of unexposed healthy subjects (P = 0.042), and exhibited an increased incidence of splicing errors, frameshifts, and complex mutations. Higher frequencies of contribution of AT-->GC transitions and GC-->TA transversions were also observed. The increased mutant frequencies and observed shifts in mutational spectra likely indicate a combination of potential influences, including environment, lifestyle, and occupational exposures. Further elucidation of these potential influences will require a more extensive study involving the general population sharing similar environment, cosmonauts in training and cosmonauts participating in space flights.