Each PCR product of probands and controls was screened by heteroduplex analysis with the use of denaturing high-performance liquid chromatography (DHPLC WAVE, Transgenomic)26,27 or directly sequenced with the use of ABI 3700 capillary automated-sequencing system (Applied Biosystems, Foster City, CA).Suspected variants were subjected to PCR at least twice and confirmed by digestionor sequences of parents.