First mutations in isolated tooth agenesis were detected in MSX1 (ENSG00000163132, OMIM 106600) and PAX9 (ENSG00000198807, OMIM 604625) and subsequently numerous heterozygous loss of function mutations have been reported in these genes coding for transcription factors active in the dental mesenchyme [10–12]. This evidence concerns the gene PAX9 and tooth agenesis.