  Supersymmetric $SO(10)$ grand unified models with renormalizable Yukawa
couplings involving only ${\bf 10}$ and $\overline{\bf 126}$ Higgs fields have
been shown to realize the fermion masses and mixings economically. In previous
works, the sum rule of the fermion mass matrices are given by inputting the
quark matrices, and the neutrino mixings are predicted in this framework. Now
the three neutrino mixings have been measured, and in this paper, we give the
sum rule by inputting the lepton mass matrices, which makes clear certain
features of the solution, especially if the vacuum expectation values of ${\bf
126}+ \overline{\bf126}$ ($v_R$) are large and the right-handed neutrinos are
heavy. We perform the $\chi^2$ analyses to fit the fermion masses and mixings
using the sum rule. In previous works, the best fit appears at $v_R \sim
10^{13}$ GeV, and the fit at the large $v_R$ scale ($\sim 10^{16}$ GeV) has
been less investigated. Our expression of the sum rule has a benefit to
understand the flavor structure in the large $v_R$ solution. Using the fit
results, we perform the calculation of the $\mu \to e\gamma$ process and the
electric dipole moment of electron, and the importance of $v_R$ dependence
emerges in low energy phenomena. We also show the prediction of the CP phase in
the neutrino oscillations, which can be tested in the near future.
