| |
Fig. 1. Embryonic expression characteristics define four distinct groups of liver and intestine marker genes. Embryos were staged according to Nieuwkoop and Faber (1967). Digoxigenin-labeled antisense RNAs of XPTB [ldlrap1] , 3H12 [uncharacterised XB5836725] , 3B6 [fetub.S] , Cyl104 [f13b] , SRBP [rbp4] and Cyl18 [darmin] were used for whole-mount in situ hybridization.
Three embryonic stages were chosen to illustrate the spatial and temporal expression characteristics of liver and intestine marker genes. Genes expressed in the liver diverticulum region are clearly detected at stage 34. Stage 44 is the best developmental stage to simultaneously reveal expression in the gall bladder, liver, pancreas, duodenum and intestine in a ventral view of the embryo. Stage 46 is chosen to show that many genes, which are earlier expressed in both liver and intestine, are now restricted to the embryonic liver. (a) XPTB expression (the LS group): Specific expression in liver diverticulum is observed in stage 34
embryo (a). A very weak expression of XPTB is detected in the liver and gall bladder buds at stage 44 of development (b). During further development, it is
hard to detect the expression of this gene by whole-mount in situ hybridization (c). (d) 3H12 expression (the LIA group): at tailbud stage of development, a
weak expression is observed only in the intestine (d). A strong expression domain appears in the liver and gall bladder at stage 44 of development (e). The
strong expression in liver and gall bladder is maintained, however, the weak expression in the intestine is no longer detectable at stage 46 of development (f).
(g) expression of 3B6, Cyl104 and SRBP (the LIB group): These genes are expressed in both the liver diverticulum and the intestine at tailbud stage of
development (g,j,m). Their expression is restricted to the liver at stage 46 of development (i,l,o). (p) Cyl18 expression (the IS group): At tailbud stages of
development, it is expressed in the whole mid- and hindgut, but not in the foregut (p). At stage 44, strong signals are seen in the whole intestine, but no signals
are detected in the foregut derivatives, such as the oesophagus, stomach, liver, gall bladder, lung, pancreas and duodenum (q). During subsequent development,
expression levels drastically decrease (r). Abbreviations: gb, gall bladder; la, liver anlage; lv, embryonic liver. |
