FIG. 2.

Expression of MDC9 mRNA in mouse embryos. All sections were hybridized with an antisense MDC9 mRNA probe. Digital images were acquired using bright-field (A, C, F, and J) or dark-field (B, D, E, G, H, I, K, and L) microscopy. (A and B) A section of E7.5 at magnifications of 10× (A) and 20× (B). MCD9 mRNA is expressed in all cell layers. Within the embryonic portion, a stronger signal was detected in the heart mesoderm (blue arrow in panel B) than in other regions of the embryo, including the head fold region (HF in panel A), which has a weaker signal despite having a higher cell density. (C to E) A section of E9.5. (C) Image at magnification of 5×, showing the mesencephalon (MC) and the heart (HT). (D and E) Images of the MC and HT regions in panel C at magnifications of 10×. Blue arrows in panel D point to autoradiographic grains in the head mesenchyme. Strong expression signals in panel E outline the heart atrium (AT) and ventricle (VT). (F to I) A sagittal section of E11.5. (F) Image at magnification of 2.5×. TC, telencephalon; HT, heart. (G, H, and J) images of regions in panel F at a magnification of 10×. The blue arrow in panel G points to a strong signal in the facial mesenchyme, anterior to the TC. Panel H represents part of the dorsal region of the embryo, where the loose mesenchyme surrounding the somites (indicated by blue arrows) shows strong gene expression. The white autoradiographic grains of the image in panel I show strong signal in the atrium (AT), ventricle (VT), and bulbus arteriosus (BA) of the heart. (J to L) Images of E15.5. (J) Image of a lateral section at a magnification of 1.25×. DC, diencephalon; VT, heart ventricle. (K and L) portions of the image in panel J, at a magnification of 10×. The blue arrow in panel K shows an area of strong expression in the head mesenchyme close to DC, and the blue arrow in panel L shows strong expression in VT.