Fig. 1.

Comparative expression analysis with NE, SE, and stem cell markers during primary neurulation. (A) Schematic expression patterns in E8.0 (somite stages 1–3) and E8.25 (somite stages 3–5) embryos. (B–M, P–R) Images of section (B–E, P, Q) and whole-mount (F–M, R) immunohistochemistry stained at E8.0 (B, C), E8.25 (D, E) and E8.5 (somite stages 5–8) (F–I, J–M, R) with Sox2/TROMAI (B, C, E), N-cadherin/TROMAI (D, F–H), N-cadherin/E-cadherin (I), OCT4 (J, K), OCT4/TROMAI/N-cadherin (L, M) KLF5 (P, Q) and SSEA4 (R). (N, O) Whole mount in situ hybridization using Klf5 probe at E8.5 (dorsolateral view, N; dorsal view, O). Each panel shows a region where neither SE nor NE markers are expressed as dotted lines (C–E) and arrowheads (F–I). The expression of OCT4, a stem marker, specifically labels the boundary between NE and SE at E8.5, although the expression level is lower than that of primordial germ cells (J–M). Klf5, which is a Krüppel-like transcription factor that plays crucial roles in maintaining embryonic stem (ES) cell pluripotency, is expressed in the neural plate border (arrowheads, N–Q). SSEA4 is a cell surface marker of human ES, embryonic germ (EG), and induced pluripotent stem (iPS) cells and is expressed in the proximity of the neural plate border (arrowheads, R). NPB, neural plate border; PGCs, primordial germ cells. Scale bar represents 300 μm in N; 200 μm in F–J, L, M; 100 μm in B, O, P, R; 50 μm in K, Q; and 20 μm in C–E.