Ana Ledesma / Biology / Faculty Mentor: Esther Betran
In Drosophila, many of the recent gene duplications are expressed only in the testes, and their proteins are rapidly evolving or changing between species under positive selection. To provide light on the function and evolutionary pressures that lead to their retention and expression in the testis, we are studying two recently duplicated nuclear transport genes: Ran-like and Ntf-2r. Fusions of Ran-like and Ntf-2r gene duplicates with fluorescent proteins have been developed and loss of function mutants generated using CRISPR-Cas9 technology. Based on the distribution of Ran-like and Ntf-2r proteins we propose that they might have roles in meiosis and sperm formation. However, previous short-term investigations demonstrated that these retro copies are not necessary for male fertility, contrary to the hypothesis that eliminating the function of either Ntf-2r or Ran-like would have an impact on fertility. To determine whether there is a long-term effect, a cage experiment was conducted. In this experiment we set up bottles where the wildtype is put in competition with the loss of function mutants (Ran-like knockout and Ntf-2r knockout, separately). Since the null mutants were produced replacing the duplicated gene by a Ds-Red protein driven in the eye (red fluorescence), we can monitor the change in frequency of the mutant allele every five generations. We observe an increase in the average frequency of the wildtype allele out of five replicates, supporting that these genes have a significant role in spermatogenesis, but their effects are only significant enough to be seen long-term. The functional investigations conducted on testis-biased duplicated genes in Drosophila have broadened our comprehension of the mechanisms they impact, the potential selection benefits they offer to the organism, and the reasons behind their persistence in the male germline.
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