Which gene mutations are commonly implicated in tooth agenesis?

• A. MSX1 and PAX9.
• B. SHH and BMP.
• C. WNT10A and FGF8.
• D. DSPP and ENAM.

Answer: (A)

Tooth agenesis results when key genes that guide early tooth development fail to signal properly, disrupting the formation of the tooth germ. The two genes most consistently linked to non-syndromic tooth agenesis are MSX1 and PAX9. They encode transcription factors that regulate the crucial interactions between dental epithelium and mesenchyme as the tooth progresses through the bud, cap, and bell stages. Mutations in these genes interrupt those interactions, leading to missing teeth in specific patterns. PAX9 mutations more often affect molars, while MSX1 mutations can cause multiple missing teeth, including premolars and molars. Although other genes like SHH, BMP, WNT10A, and FGF8 play roles in tooth development, MSX1 and PAX9 are the most consistently implicated for isolated tooth absence. DSPP and ENAM, on the other hand, are associated with dentin and enamel defects, not missing teeth.