Ortholgue of mammalian Pax-2. Cloned by Tom Carroll in Peter Vize's laboratory, figures supplied by P.Vize. Expressed in the mid-hindbrain junction, presumptive pronephros, rectal diverticulum, pharyngeal aches, otic vesicle and spinal chord. Although sequence homology indicates that this gene is a Pax-2 orthologue, it is expressed in the thyroid gland, normally a site of Pax-8 expressionin mammals. In mice the thyroid is not effected by Pax-2 disruption, but it is by Pax-8 disruption. Conversely, the Xenopus gene most closely related to mammalian Pax-8, XPax-8, is not expressed in the thyroid gland. The in press paper by Carroll and Vize shows that XPax-8 and XPax-2 are functionally redundant, and it appears that these orthologues have retained different promoter elements in different taxa.
Anterior is to the left in all panels. Dorsal is up in panels C,D,E,G and H. A and B are dorsal views, and F is a ventral view.
A and B are dorsal views, C, D, E and H are lateral views and F is a ventral view
A: Stage 12.5 embryo. White arrow indicates one of two neural patches of XPax-2 expression. Staining corresponds to the future mid-hindbrain junction.
B: Stage 17. Black arrow indicates eye field expression. Black double arrow indicates blastopore expression.
C: Stage 20. Yellow arrow indicates future otic vesicle expression. Red double arrow indicates pronephric anlage expression.
D: Stage 29. Red arrow indicates pharyngeal arch staining. White arrowhead indicates pronephric duct expression. Yellow arrow indicates spinal cord staining. Note periodic pattern. E: Stage 35/36. Red arrowhead indicates thyroid gland expression. White arrow indicates increased expression in the nephrostomes of the nephric tubules.
F: Stage 33/34. Ventral view of thyroid gland.
G: Stage 33/34. Close-up of posterior end of tadpole. Black arrow indicates lack of expression between non-fused posteriorly migrating nephric duct and anteriorly migrating rectal diverticula.
H: Stage 35/36. Black arrow indicates region of increased XPax-2 expression where duct and rectal diverticula are fusing.
References: Carroll, T.J. and Vize, P.D. (1999) Synergism between Pax-8 and lim-1 in embryonic kidney development. in press.
Heller, N. and Brandli, A.W. (1997) Xenopus Pax-2 displays multiple splice forms during embryogenesis and pronephric kidney development. Mechanisms of Development 69,83-104.
