Yukawaon model and unified description of quark and lepton mass matrices

In the so-called yukawaon model, where effective Yukawa coupling constants Y_f^{eff} (f=e,\nu,u,d) are given by vacuum expectation values of gauge singlet scalars (yukawaons) Y_f with 3\times 3 flavor components, it is tried to give a unified description of quark and lepton mass matrices. Especially, without assuming any discrete symmetry in the lepton sector, nearly tribimaximal mixing is derived by assumed a simple up-quark mass matrix form.