XB-IMG-158696
Xenbase Image ID: 158696
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Fig. 4. Summary of gene expression patterns within the pronephros.
Circles represent the pronephric anlage at various stages of
development. Dorsal is up, ventral is down, lateral is left and medial is
right. Black represents high levels of gene expression, gray represents
lower levels, and white represents no expression. The circle is divided
into the three components of the pronephros, the tubules coming from
the upper left quarter, the duct from the lower left quarter, and the
glomus from the right half. The small black triangles within the stage
38 anlage represent the distal tubules. Xlim is activated throughout
the entire anlage at stage 14. Its expression leads to the expression of
xWnt-4 within the entire pronephric anlage and xWT-1 in the medial
half ( the cells in the embryo that are adjacent to the endoderm) at
stage 18. Expression of xWT-1 represses Xlim1 and xWnt-4 and
prevents XPax-2 from ever being expressed in the medial portion of
the anlage. A late signal from the somites maintains high levels of
Wnt-4, Xlim, and XPax-2 in the distal tips of the tubules. Absence of this
signal in the more ventral part of the anlage results in a decrease in Wnt-4
expression and thus indirectly (or directly) leads to the duct fate. Image published in: Carroll TJ et al. (1999) Copyright © 1999. Image reproduced with permission of the Publisher, John Wiley & Sons. Larger Image Printer Friendly View |