Syndactyly and preaxial synpolydactyly in the single Sfrp 2 deleted mutant mice

Secreted Frizzled‐related protein 2 (Sfrp2) or Stromal Cell Derived Factor‐5 (SDF‐5) is highly expressed in the developing limbs. Here we showed the single Sfrp2 inactivation in mice resulted in syndactyly and preaxial synpolydactyly, predominantly in the hindlimbs. Tails were often kinked. A penetrance of the syndactyly was highest in 129/SvJ or CBA/N × 129/SvJ background and the phenotype was haploinsufficient. Preaxial synpolydactyly was seen in homozygous mutants in C57BL/6 × 129/SvJ. Of note, syndactyly showed retarded apoptosis of the second and the third interdigital spaces; concomitantly, mesodermal Msx2 expression was down‐regulated. Impaired digital anlagen maturation was also noticeable in the same position. Preaxial synpolydactyly of the Sfrp2 mutants was a non‐mirror image type and Shh independent. Although joint formation was not disrupted, chondrocyte maturation was preaxially disturbed. Our results suggest that the Sfrp2 deleted mice can be a useful animal model to study human syndactyly/preaxial synpolydactyly defects. Developmental Dynamics 237:2506–2517, 2008. © 2008 Wiley‐Liss, Inc.