CLSTN2 and Astigmatism: Furthermore, the association described above for markers in the vicinity of the SDCBP gene, encoding syntenin, lends support to the putative involvement of CLSTN2. One of the two regions on chromosome 4p15 (lead SNP rs2871434; Fig. 2e) contains the PCDH7 (protocadherin-7) gene, which given its role in cell adhesion is a plausible candidate gene for astigmatism.