PAX9 and tooth agenesis: Consistently, the dental mesenchyme-specific transcription factors (Msx1, Pax9, and Lhx6) were decreased in cultured mDMCs, and the mutation of these transcription factors was shown to cause tooth agenesis disorders (Peters et al., 1998; Satokata & Maas, 1994; Zhao et al., 2013).