Ortholgue of mammalian Pax-8. Cloned by Tom Carroll in Peter Vize's laboratory. Expressed in the presumptive pronephros and presumptive otic vesicle from late gastrula stages onwards. Although sequence homology indicates that this gene is a Pax-8 orthologue, it is not expressed in the thyroid gland, a site of mammalian Pax-8 expression that is severely effected by targeted disruption of this gene. Conversely, the Xenopus gene most closely related to mammalian Pax-2, XPax-2, is expressed in the same sites as its mammalian relative, plus in the thyroid gland. The in press paper by Carroll and Vize shows that XPax-2 and XPax-8 are functionally redundant, and it appears that these orthologues have retained different promoter elements in different taxa.
Anterior is to the right and dorsal up in all panels. Pronephric expression is indicated with a black arrow, and otic expression with a red arrow. Transient expression in the duct is indicated with a white arrow.
A. Late gastrula, approx. stage 13.5
B. Early neurula, approx. stage 15
C. Stage 19
D. Stage 23
E. Stage 29/30
F. Stage 34
References: Carroll, T.J. and Vize, P.D. (1999) Synergism between Pax-8 and lim-1 in embryonic kidney development. Developmental Biology 214, in press.
