PTPN12 and colorectal carcinoma: In this study we have performed whole-exome sequencing on germline DNA from 55 mismatch repair-proficient early-onset CRC cases and identified multiple potentially damaging variants in two colon-expressed genes: PTPN12 and LRP6. The germline variants identified in these genes appeared to affect highly conserved amino acids and were absent, or present at extremely low frequencies, in control populations.