Abstract
Secreted Frizzled‐Related Proteins (SFRPs) are extracellular modulators of Wnt and Bmp signaling. Previous studies in birds and fishes have shown that Sfrp1, a member of this family, is strongly expressed throughout the development of the eye contributing to the specification of the eye field, retina neurogenesis and providing guidance information to retina ganglion cell axons. Here, we report that in medaka fish (Oryzias latipes) the expression of ol__Sfrp5__, which is closely related to ol__Sfrp1__, largely overlaps with that of ol__Sfrp1__ in the eye, but is additionally expressed in the developing midbrain and gut primordium. Morpholino‐based interference with ol__Sfrp5__ expression causes microphthalmia and reduction of the tectum size associated with an increase in apoptotic cell death in these structures. Furthermore, interference with the levels of ol__Sfrp5__ expression impairs the patterning of the ventral portion of the optic cup, leading in some cases to a fissure coloboma. These early defects are followed by an abnormal retinal and tectal neurogenesis. In particular, only reduced numbers of photoreceptor and RGC were generated in ol__Sfrp5__ morphants retinas. The results point to an important role of ol__Sfrp5__ in visual system formation and indicate that ol__Sfrp1__ and ol__Sfrp5__, despite their overlapping expression, have only partially redundant function during eye development. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2009