Fig. 1
From: FAM20B-catalyzed glycosaminoglycans control murine tooth number by restricting FGFR2b signaling
GAGs in the dental epithelium but not in the dental mesenchyme determine the tooth number in mice. Hematoxylin-eosin (H&E) staining on coronal sections of lower incisors from E15.5 to E18.5 mouse embryos. A–D Native enamel organs of incisors in normal control (Fam20Bfl/fl) mice. d↔m indicates the orientation of distal and mesial sides. E An ectopic thickening of dental epithelium (white arrow) was identified at the mesial-lingual side of the native enamel organ at E15.5 in K14Cre/+;Fam20Bfl/fl mice. F, G The ectopic thickening of dental epithelium formed an extended dental lamina (black arrows) at the mesial-lingual side of native enamel organs and developed into a novel enamel organ (white arrows and dashed lines) at the end of the extended lamina. H At E18.5, the extended dental lamina disappeared, and the extra enamel organs developed into supernumerary incisors (white arrow) at the mesial-lingual side of native teeth. I–L In contrast, disrupting GAGs in the dental mesenchyme did not cause any extra teeth in the Wnt1Cre/+;Fam20Bfl/fl mice. Scale bars: 50 μm