  We propose an A_4 flavor-symmetric SU(3)xSU(2)xU(1) seesaw model where lepton
number is broken spontaneously. A consistent two-zero texture pattern of
neutrino masses and mixing emerges from the interplay of type-I and type-II
seesaw contributions, with important phenomenological predictions. We show
that, if the Majoron becomes massive, such seesaw scenario provides a viable
candidate for decaying dark matter, consistent with cosmic microwave background
lifetime constraints that follow from current WMAP observations. We also
calculate the sub-leading one-loop-induced decay into photons which leads to a
mono-energetic emission line that may be observed in future X-ray missions such
as Xenia.
