Fig 2: Myosin II is required for proper incisor invagination.(a) Timeline depicting the onset of CreER induction by tamoxifen (Tam) through oral gavage at E10.5 (red arrowhead) and sample collections at E13.5-E15.5 (yellow arrowheads). (b-g) Sagittal sections through control (CreER-negative) and mutant (Myh9/10epi-cko) incisors at E13.5, E14.5, and E15.5 show reduced invagination and a wider dental cord in the mutant incisor epithelium. Pink arrowheads denote the dental cord region. Open yellow arrowheads in (e and g) mark the cysts that are formed in mutant incisors. mGFP is a Cre-reporter. (h-k) Whole mount 2-photon images of control and Myh9/10epi-cko incisor epithelia at E13.5 and E14.5. Inset in (k) is a single z-section and the open yellow arrowhead marks the cyst. (l and m) Quantifications of the epithelial depth and the neck width in control and Myh9/10epi-cko incisors at E13.5 (n = 8 controls and 13 mutants) and E14.5 (n = 3 controls and 3 mutants). (n) Quantification of the incisor epithelial volume at E13.5 (n = 4 per genotype) and E14.5 (n = 3 per genotype). Dashed lines outline the incisor epithelium. Asterisks (*) mark the tip of the vestibular lamina. Representative images are shown. All quantitative data are presented as mean ± SD. The p values were determined using an unpaired Student’s t-test (* p < 0.05 and ** p < 0.01). Scale bar in (g) represents 50 μm in (b and c), 90 μm in (d and e) and 125 μm in (f and g), scale bar in (k) represents 50 μm in (h-k).

Fig 3: Myosin II is essential for cell adhesion in the incisor epithelium.(a) Timeline depicting the onset of CreER induction by tamoxifen (Tam) through oral gavage at E10.5 (red arrowhead) and sample collections at E13.0 (yellow arrowhead). (b-g) Immunostaining of total E-cadherin (E-cad) (b and c), homophilically bound E-cad (ECCD2 in d and e), and β-catenin (β-cat) (f and g) in control and Myh9/10epi-cko samples. (d’-g’) The corresponding signal intensity heatmap for ECCD2 (d’ and e’) and β-catenin (f’ and g’). (h and i) Quantifications of the average signal intensity per pixel for ECCD2 (h) (n = 5 per genotype) and β-cat (i) (n = 4 controls and 9 mutants) immunostaining in different sub-regions of the incisor epithelium. The basal (b), lower suprabasal (sb) and upper suprabasal sub-regions are determined as shown in (b). Dashed lines outline the incisor epithelium. Representative images are shown. All quantitative data are presented as mean ± SD. The p values were determined using an unpaired Student’s t-test (* p < 0.05 and ** p < 0.01). Scale bar in (g’) represents 50 μm in (b-g’).