Early and dynamic expression of cSfrp1 during chick embryo development.

Secreted frizzled related proteins (SFRPs) are a new class of signalling molecules that appear to antagonise the activity of the Wnt proteins. Here we report the dynamic expression pattern of cSfrp1, a new member of this family, at early stages of chick embryo development. cSfrp1 transcripts are first detected at pre-streak stages throughout the chick blastula but, during early primitive streak formation, expression is restricted to the anterior primitive streak and later to the blastoderm anterior to the Hensen' s node. This pattern of expression overlaps with that of Otx2 and is complementary to that of cWnt8c. During neural plate formation cSfrp1 mRNAs are abundantly localized only to the anterior domain of the embryo but, as neural tube closes, the expression extends caudally. Later, the main sites of expression in the neural tissue are the telencephalic vesicles, the epiphysis, the developing eyes and the ventral hindbrain and neural tube. Additionally, cSfrp1 transcripts were found in the axial and lateral mesoderm, the otic placode, the trigeminal ganglia, the mesoderm of the branchial arches, the developing limb buds, as well as in the mesodermal component of the developing kidney.