A homolog of the hydrolase Notum is expressed during segmentation and appendage formation in the Central American hunting spider Cupiennius salei.

The hydrolase Notum (also known as Wingful) has been implicated in shaping the distribution gradient of the morphogen Wingless in Drosophila by modifying the Wingless-binding heparan sulfate proteoglycan (HSPG) core glypicans Dally and Dally-like. Here we report on the expression of a Notum homolog during the embryonic development of the spider Cupiennius salei. Notum is expressed in two to three stripes in the posterior region of the germband where new segments are formed. At this location no Wingless expression is present, suggesting that Notum may be involved in the regulation of another HSPG-binding morphogen, possibly Hedgehog. In older segments, however, expression of Notum and Wingless roughly coincides. In the appendages, Notum is expressed in ventral mesodermal cells, directly adjacent to the Wingless expressing ectodermal cells. This could indicate a role for the mesoderm in regulating morphogen gradient formation in the ectoderm.