Expression of putative upstream Hippo pathway regulators during pituitary development. RNAscope mRNA in situ hybridization using probes against Dchs1, Fat3 and Fat4 on sections of wild type CD1 embryos between 10.5dpc and 17.5dpc. (A–E)
Dchs1 is expressed in mesenchyme surrounding Rathke's pouch and in neural tissue but absent from Rathke's pouch epithelium (A). Expression in mesenchyme and neural tissue persists at 12.5dpc (B) and 13.5dpc (C) where transcripts are also detectable in RP (arrowhead in B). Expression in all pituitary lobes, the hypothalamus and surrounding mesenchyme is detectable at 15.5dpc (D) and 17.5dpc (E). Note the reduced expression of Dchs1 in the epithelium surrounding the third ventricle in (D,E). (F–J)
Fat3 is strongly expressed in Rathke's pouch (arrowheads), surrounding mesenchyme, and neural tissue at 10.5dpc (F). Reduced levels are detected in all tissues between 12.5dpc and 17.5dpc. At 12.5dpc there is a dorsal bias in expression in RP (G), more clearly visible at 13.5dpc (arrowheads in H). Strong expression is detected in the epithelium surrounding the third ventricle at 15.5dpc and 17.5dpc (arrowheads in I,J) and in the posterior pituitary (arrow in J). (K–O)
Fat4 transcripts are detected in RP at 10.5dpc (arrowheads in K), in surrounding mesenchyme and neural tissue but excluded from the pharyngeal endoderm (arrow in K). Note the very strong expression in the rostral tip of the anterior pituitary (arrowheads in L,M) at 12.5pc and 13.5dpc and in the ventral diencephalon and infundibulum (arrows in L,M), persisting in the posterior lobe (arrows in N,O). Expression is high in surrounding mesenchyme (arrowheads in N). The box in (N) shows the epithelium around the third ventricle displaying low-level expression. The outlines in (D,E,I,J,N,O) surround anterior pituitary tissue derived from Rathke's pouch. Abbreviations: rp, Rathke's pouch; vd, ventral diencephalon; m, mesenchyme; oe, oral ectoderm; pe, pharyngeal endoderm; inf, infundibulum; sph, sphenoid; rt, rostral tip; pl, posterior lobe; al, anterior lobe; il, intermediate lobe; hy, hypothalamus; 3v, third ventricle. Sagittal sections between 10.5dpc and 13.5dpc and frontal between 15.5dpc and 17.5dpc. Axes in (A) applicable to (A–C,F–H,K–M: d, dorsal; v, ventral; r, rostral; c, caudal). Axes in (D) applicable to (D–E,I–J,N–O: d, dorsal; v, ventral; ri, right; le, left). Scale bars 200 μm.