OPN3 and tooth agenesis: To date, a number of genes have been found to be associated with non-syndromic tooth agenesis, including axin inhibition protein 2 (AXIN2), muscle segment homeobox 1 (MSX1), paired box 9 (PAX9), ectodysplasin A (EDA), wingless-type mouse mammary tumor virus integration site family member 10A (WNT10A), wingless-type mouse mammary tumor virus integration site family member 10B, low-density lipoprotein receptor-related protein 6 (LRP6), and opsin 3 (OPN3) [2,7,8,9,10,11,12,13,14,15,16].