Figure 1.
Expression of Cripto and Cryptic in mouse embryos at 3.5 to 6.75 days post coitum (dpc). (A–D) Cripto expression in wild-type (A, B) and Cryptic null mutant (C, D) embryos. (A) Expression of Cripto in the wild-type blastocyst at 3.5 dpc is restricted to the inner cell mass, and is not found in the trophectoderm. (B) Cripto expression is restricted to the epiblast at 4.5 dpc, and is not found in the primitive endoderm. (C, D) Expression of Cripto in the proximal epiblast of a Cryptic null mutant at 6.0 dpc (C) and in the posterior epiblast at 6.5 dpc (D) is indistinguishable from the wild-type pattern (Ding et al., 1998). In panel D, proximal (P) and distal (D) are indicated. (E–O) Expression of Cryptic in wild-type (E–K, M, N) and Cripto null mutant (L, O) embryos. (E) Cryptic expression in cells of the nascent primitive endoderm (arrow) at 4.0 dpc. (F, G) Expression of Cryptic in the primitive endoderm and newly formed parietal endoderm at 4.5 dpc (F) and 4.75 dpc (G). (H) Longitudinal section of the embryo in (G), showing absence of expression in the epiblast; nuclei are counterstained with methyl green. (I) Cryptic expression at 5.5 dpc in the proximal visceral endoderm at the level of the boundary between extraembryonic ectoderm and epiblast (arrowheads). (J) Expression of Cryptic at 6.0 dpc in the proximal visceral endoderm, including the anterior visceral endoderm; the junction between extraembryonic ectoderm and epiblast is indicated (arrowheads); proximal (P) and distal (D) are indicated. (K) Cryptic expression in the embryonic and extraembryonic visceral endoderm at 6.75 dpc, including the anterior visceral endoderm. (L) Expression of Cryptic in the visceral endoderm is unaltered in a Cripto−/− embryo at 6.5 dpc. (M, N) Cross-sections of the embryo at the indicated levels in (K), showing Cryptic expression in the anterior visceral endoderm, and low-level expression in the visceral endoderm and nascent mesoderm. (O) Cross-section of the embryo in (L). Scale bars correspond to 100 microns. Abbreviations: ave, anterior visceral endoderm; epi, epiblast; exe, extraembryonic ectoderm; icm, inner cell mass; mes, mesoderm; par, parietal endoderm; pe, primitive endoderm; ps, primitive streak; tro, trophectoderm; ve, visceral endoderm.