FRP/FrzB genes and interactions with Wnts (updated January 2008)

These molecules are secreted forms of frizzleds, containing the cysteine rich domain (CRD) of frizzled, but no transmembrane segments. They may bind to Wnt proteins in solution and thereby change the activity of Wnts.

gene linked to Genecards	interacts with	Expression Pattern See Leimeister, 1998	mutant phenotype
SFRP1		heart, kidney, lung, brain, aorta, otic vesicle, neural crest	increased trabecular bone mineral density, volume and mineral apposition rate Bodine et al, 2004 growth of retinal ganglion cell axons (Rodriguez, 2005) anteroposterior axis elongation defects (with SFRP2 mutation) Satoh, 2006
SFRP2	wingless (Rattner, 1997)	gut, eye retina, lung, brain	anteroposterior axis elongation defects (with SFRP1 mutation) Satoh, 2006 Regulating Nkx2.2 Expression Lei, 2006
FrzB	wingless (Rattner, 1997); XWnt-8 (Wang 1997; Leyns 1997); Wnt-1 (Leyns 1997)	cartilage, anterior and posterior mesoderm, limb bud, kidney, testis
SFRP4		ovary, brain, kidney,lung, endometrium
SFRP5		pancreas
Sizzled		ventrolateral mesoderm	ogon locus in Zebrafish, ventralized phenotypes similar to the chordino (dino) mutant Yabe et al, 2003 Inhibits tolloid proteases Muraoka 2006, Lee, 2006,

Alignment of Five human or mouse SFRPs

Several other proteins contain a CRD motif similar to the frizzleds:

• the alpha 1 chain of mouse type XVIII collagen (Rehn M, 1995 )
• human carboxypeptidase Z (Song L, 1997).
• several receptor tyrosine kinases (Xu and Nusse, 1998, Masiakowski 1998
• Corin, a mosaic transmembrane serine protease (Yan 1999)