 Mutation analysis: About 2 ml of venous blood sampled from each subject and collected in Vacutainer tubes Sanjiu Medical Technology Co., Ltd., Liuyang, China containing EDTA. Genomic DNA was extracted from each blood using a genomic DNA mini kit for blood Life Technologies, All coding exons, with flanking intronic regions, of FOXC1 and PITX2 were amplified using PCR with primers. The amplifed DNA was purifed by agarose gel electrophoresis and sequenced on a 37303700xl automated DNA sequencer Applied Biosystems. 