Inheritance of DNA transferred from American trypanosomes to human hosts.

Etienne Joly

Etienne Joly

Etienne Joly

+ -1 Evaluators

I found this article very interesting because it reports the disturbing observation that DNA from trypanosome parasites very frequently integrate with the germline of the humans they infect, and could thus lead to significant modifications of the genome of their offspring (in addition to causing Chagas disease in one third of cases). Until last year, retroviruses were the only microbes known to be capable of horizontal gene transfer into mammalian genomes, albeit rather efficiently since sequences of retroviral origin may represent as much as 8% of our genomic DNA. As part of its life cycle, Trypanosoma cruzi multiplies inside various cell types, including those of the male and female germ lines. In infected patients, Hecht and colleagues not only document numerous instances of kinetoplast DNA of T. cruzi having integrated the genome of their hosts' cells, but also the transmission of that DNA to their uninfected offspring. The sites of integration are preferentially found in LINE-1 retrotransposable elements, but also in many other places in the genome, including in coding regions in 10% of cases. On a more negative note, although I found the results reported convincing, I also found the overall presentation of this paper rather difficult to follow. This may contribute to explaining why this very important finding was reported in a less prestigious journal than the almost simultaneous report of the identification, in various mammalian genomes, of a handful of sequences that were most probably derived from Borna viruses over the past few dozens of million years {1}. In comparison, trypanosomes seem to be much more proficient vector of horizontal gene transfer into the germ line of their hosts than Borna viruses.