The Netrin-related domain of Sfrp1 interacts with Wnt ligands and antagonizes their activity in the anterior neural plate

Table 1 Anteriorised phenotypes induced by over-expression of different Sfrp variants

Injected mRNA	Percentage of embryos showing an enlarged forebrain
Sfrp1 (200 ng/μl; n = 70)	91
Sfrp1_CRD(100 ng/μl; n = 162)	0 (55)*
Sfrp1_CRD-2(100 ng/μl; n = 86)	0 (48)*
Sfrp1_NTR(120 ng/μl; n = 158)	65
Sfrp1_{NTR-C 177S;C 180S}(120 ng/μl; n = 48)	13
Sfrp2 (200 ng/μl; n = 62)	93
Sfrp2_NTR(120 ng/μl; n = 47)	47
Sfrp3 (200 ng/μl; n = 51)	4 (42; n = 40)^†
Sfrp3_NTR(120 ng/μl; n = 38)	3 (27; n = 56)^†
Sfrp3_CRD(100 ng/μl; n = 36)	0 (0; n = 75)^†
Netrin-1_NTR(120 ng/μl; n = 61)	56
Netrin-1_{NTR-C 471S;C 475S}(120 ng/μl; n = 40)	42

Percentage of embryos showing an anteriorised phenotype upon injection of equimolecular amounts of mRNAs encoding different variants of Sfrp or Netrin-1 proteins, as shown in Figures 1 and 3 and Additional file 2. The anteriorised phenotype was scored by an evident morphological expansion of the prosencephalic tissue at late neurula stages. The percentage in brackets marked with asterisks represent the frequency of embryos showing a reduction in the size of the forebrain (instead of an increase; see text for details). The percentages in brackets marked with a dagger represent the frequency of appearance of the phenotype at higher concentration: 500 ng/μl for Sfrp3 and 300 ng/μl for Sfrp3_NTRand Sfrp3_CRD.