High impact information on Dbf

• To determine whether Dbf maps to the Ihh locus, which is also on chromosome 1, we performed an interspecific backcross [1].
• We show here that Shh is expressed normally in Dbf mutants [1].
• Dbf is a dominant mutation which maps to chromosome 1 [1].
• We propose that misexpression of Ihh, and not a novel Smoothened ligand as recently suggested (Hayes et al., 1998), is responsible for the Dbf phenotype [1].
• However, mesenchyme from the anterior aspects of Dbf/+ mutant limb buds, when transplanted to the anterior side of chick wing buds, induces duplication of the distal skeletal elements [2].

Biological context of Dbf

• These observations dissociate polarising activity from Shh gene expression in the Dbf/+ limb bud [2].
• Prenatally, Dbf/+ heterozygotes can first be recognized at 11 1/2 days gestation by abnormally broad fore limb buds [3].
• Putative Dbf/Dbf homozygotes at 12 1/2 days have similar limbs defects and also split face, due to failure of the maxillae to fuse in the midline [3].
• In this study of the embryonic and fetal development of Dbf animals, we focus on the morphogenesis of the limbs and head, and discuss the possible molecular developmental mechanisms [4].
• Here we review current understanding of this mutant, and briefly report new results indicating (1) that limb bud expansion is concomitant with ectopic lhh expression and with extension of the posterior high cell proliferation rate into the anterior region, and (2) that the Dbf mutation is epistatic to Shh in the limb [5].

Anatomical context of Dbf

• In contrast, a second Hh family member, Indian hedgehog (Ihh) which maps close to Dbf, is ectopically expressed in the distal limb bud [1].
• At 14 1/2 days Dbf/Dbf fetuses may have oedema and some are dead [3].

Other interactions of Dbf

• The mouse mutant Doublefoot (Dbf) shows preaxial polydactyly of all four limbs [2].

References