  Under the assumption of symmetric four zero texture for fermion mass matrices
in SO(10) model, the neutrino Dirc mass matrix is derived from the up-quark
mass matrix. By adjusting two scales of the Majorana mass sector, we can derive
observed neutrino two large mixing angles very naturally. It is indeed
remarkable that all the masses and mixings of neutrinos are expressed in terms
of only three known parameters, $m_t,m_c,m_u$. A typical example of our model
is \tan^2 2\theta_{\tau \mu}=\frac{4}{(1-2\frac{m_c}{\sqrt{m_u m_t}})^2}.
