Rat hypodactyly (hd) is an autosomal recessive mutation manifesting in homozygotes as reduction or loss of digits II and III. We mapped the hd allele to a short segment of chromosome 10, containing 16 genes. None of these genes has been shown to influence limb development yet. In situ hybridization showed no changes in several important patterning genes (Shh, Fgf8, Bmp2, 4, 7). However, we found that expression of cartilage condensation marker Sox9, and Bmp receptor Bmpr1b (acting as an upstream activator of Sox9 expression) is absent from the subepithelial mesenchyme of the digit condensations II and III. The failure of the chondrogenic condensations to extend towards the subepithelial mesenchyme may reduce the size of digit primordia and underlie the subsequent loss of phalanges and reduction of metacarpals/metatarsals in hd rats.

• MeSH
• Embryo, Mammalian anatomy & histology   metabolism   MeSH
• Phenotype MeSH
• Financing, Organized MeSH
• Homeodomain Proteins genetics   metabolism   MeSH
• Limb Buds abnormalities   metabolism   MeSH
• Extremities MeSH
• Rats MeSH
• Mutation MeSH
• Rats, Wistar MeSH
• Bone Morphogenetic Protein Receptors, Type I genetics   metabolism   MeSH
• Body Patterning genetics   MeSH
• SOX9 Transcription Factor genetics   metabolism   MeSH
• Gene Expression Regulation, Developmental MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Female MeSH
• Animals MeSH

Lx mutation in SHR.Lx rat manifests in homozygotes as hindlimb preaxial polydactyly. It was previously mapped to a chromosome 8 segment containing the Plzf gene. Plzf (promyelocytic leukemia zinc finger protein) influences limb development as a direct repressor of posterior HoxD genes. However, the Plzf coding sequence is intact in the Lx mutants. Using linkage mapping in F2 hybrids, we downsized the segment containing Lx to 155 kb and sequenced conserved noncoding elements (CNEs) inside. A 2,964-bp deletion in Plzf intron 2, never detected in control animals, is the only candidate for Lx. The deletion removes the most deeply conserved CNE in the 155-kb segment, suggesting a regulatory influence on Plzf expression. Correspondingly, using in situ hybridization and quantitative real-time polymerase chain reaction, we found a decrease of Plzf expression in Lx/Lx limb buds with concomitant anterior expansion of expression domains of its targets, Hoxd10-13 genes, in the absence of ectopic Sonic hedgehog expression. Upstream regulation of Plzf in limb buds is currently unknown. We present here the first candidate Plzf cis-regulatory sequence. (c) 2009 Wiley-Liss, Inc.

• MeSH
• Gene Deletion MeSH
• DNA-Binding Proteins genetics   metabolism   MeSH
• Down-Regulation genetics   MeSH
• Embryo, Mammalian embryology   metabolism   MeSH
• Financing, Organized MeSH
• Introns genetics   MeSH
• Limb Buds abnormalities   metabolism   MeSH
• Conserved Sequence MeSH
• Rats MeSH
• RNA, Messenger genetics   MeSH
• RNA, Untranslated genetics   MeSH
• Polydactyly genetics   metabolism   MeSH
• Body Patterning MeSH
• Base Sequence MeSH
• Gene Expression Regulation, Developmental MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH