MSX1 and tooth agenesis: In our study, a novel frameshift insertion of 5 bp (TGTCC) in the homeodomain of the MSX1 gene (NM_002448) was also identified in a Chinese family with autosomal dominant non-syndromic tooth agenesis, affecting the amino acid sequence of the homeodomain at p. 197Leu, changing the amino acid sequence from position 199.