  We show that, in the low-scale type-I seesaw model, renormalization group
running of neutrino parameters may lead to significant modifications of the
leptonic mixing angles in view of so-called seesaw threshold effects.
Especially, we derive analytical formulas for radiative corrections to neutrino
parameters in crossing the different seesaw thresholds, and show that there may
exist enhancement factors efficiently boosting the renormalization group
running of the leptonic mixing angles. We find that, as a result of the seesaw
threshold corrections to the leptonic mixing angles, various flavor symmetric
mixing patterns (e.g., bi-maximal and tri-bimaximal mixing patterns) can be
easily accommodated at relatively low energy scales, which is well within the
reach of running and forthcoming experiments (e.g., the LHC).
