Fig. 3.

NNE width expansion in NT folding. (A) Measured NP width ($w_{\text{NP}}$) during NT folding progression along the rostrocaudal axis in developing mouse embryos. $N=1\text{–}3$ (SI Appendix, Table S1). (B) Measured NP width ($w_{\text{NP}}$) along the rostrocaudal axis in human embryos (SS4, SS6, SS7, and SS13). (C) Measured NNE width ($w_{\text{NNE}}$) during NT folding progression along the rostrocaudal axis in developing mouse embryos. $N=1\text{–}3$ (SI Appendix, Table S1). (D) Measured NNE width ($w_{\text{NNE}}$) along the rostrocaudal axis in human embryos (SS4, SS6, SS7, and SS13). (E) Measured NNE height ($h_{\text{NNE}}$) along the rostrocaudal axis in human embryos (SS4, SS6, SS7, and SS13). Lines in A–E represent linear least-squares fits, C1 in A–E indicates closure 1 rostrocaudal position, and error bars in A and C indicate SEM. In B, D, and E, open circles indicate that NP is in the process of folding; closed circles indicate that NP is closed. (F) Model I simulations rendered between t = 0 and t = 1. First row, midline thinning + midline intrinsic curvature; second row, previous simulation + NNE thickness profile; third row, previous simulation + differential width expansion; fourth row, previous simulation + NP border intrinsic curvature. Red, inward (midline) intrinsic curvature; blue, outward (NP border) intrinsic curvature.