Int J Dev Biol
September 1, 2003;
Sox9, a novel pancreatic marker in Xenopus.
is a mixed exocrine and endocrine gland involved in the control of many homeostatic functions. During embryogenesis, the pancreas
arises from dorsal and ventral
evaginations of the foregut
that will subsequently fuse
into a single organ. The characterization of early genes expressed in the developing pancreas
is critical to understand its specification and differentiation. Here we report the expression pattern of Sox9
, a member of the Sox family of transcription factors, during development of the Xenopus pancreas
and compare its expression to that of a well characterized pancreatic marker, Pdx1
. By whole-mount in situ hybridization, Sox9
was first detected at stage 25 in the pancreatic anlagen--dorsally in the prospective foregut
and ventrally on each side of the liver
diverticulum. As development proceeds, Sox9
expression can be used to trace the development of the dorsal and ventral
pancreatic buds and their repositioning associated with the dynamic movements of the gastrointestinal tract. Sox9
expression in the pancreatic rudiment was identical to that of Pdx1
. However, while Pdx1
is expressed in both the pancreatic buds and the duodenum
was restricted to ventral
and dorsal pancreatic buds. Sox9
are thus two of the earliest genes expressed in the presumptive pancreatic tissue
Int J Dev Biol
[+] show captions
Fig. 1. Pancreatic expression of Sox9 at stages 25-40 in whole guts and tissue sections. (A) Whole-mount in situ hybridization of Sox9 on embryonic guts at different stages. Dissected whole embryonic guts are viewed from the lateral, dorsal or ventral sides. Sox9 is detected in the dorsal (white arrows) and ventral (black arrows) pancreatic rudiments/buds from stage 25 through stage 40. Sox9 is also expressed in the lung buds (blue arrows) at stage 40. (B) Transverse sections of a stage 35/36 embryo. Sox9 is expressed in the dorsal (white arrow, upper panel) and ventral (black arrow, lower panel) pancreatic rudiments. At this stage Sox9 is also expressed in the notochord and the neural tube. ld, liver diverticulum; nt, neural tube; n, notochord; s, somite.
Fig. 2. Whole-mount in situ hybridization of Sox9 on dissected and uncoiled embryonic guts at stages 42 and 45. Sox9 expression persists in the pancreas at stage 42 as the dorsal and ventral rudiments fuses into a single organ located ventrally (black arrow). At stage 45, Sox9 is detected in the pancreas (black arrow) and the main pancreatic duct (white arrow). Right panels are higher magnification views of the panels on the left.
Fig. 3 (Above). Comparison of Sox9 and Pdx1 expression at stage 31 and stage 40. Dissected whole embryonic guts are viewed from the lateral, dorsal or ventral sides. The position of the dorsal pancreatic bud (white arrows), ventral pancreatic bud (black arrows) and duodenum (red arrows) is indicated. Pdx1 is expressed in the pancreatic buds and the duodenum. Sox9 is restricted to ventral and dorsal pancreatic rudiments. In all panels, anterior is to the left.