International Mammalian Genome Society

The 16th International Mouse Genome Conference (2002)


POSTER 51 - POSITIONAL CLONING OF A PREAXIAL POLYDACTYLY MUTATION, HX, CLOSELY LINKED TO SONIC HEDGEHOG GENE (SHH)

T Sagai
National Institute of Genetics

1) Masuya H, 2) Shimizu K, 3) Yada Y, 4) Tamura M, 5) Shiroishi T
1) RIKEN GSC, 2) Nihon University, 3) Ochanomizu University, National Institute of Genetics, 4) National Institute of Genetics, 5) National Institute of Genetics, RIKEN GSC

Preaxial polydactyly is the most common limb abnormality in human and mouse. A locus for the major form of the human preaxial polydactyly has been mapped to7q36. In the mouse syntenic region, which is closely linked to shh on chromosome 5, several preaxial polydactyly mutations have been mapped. Their phenotypes are characterized by mirror image digit duplication and ectopic expression of shh in the anterior limb margin. The human LMBR1 and the mouse homologue Lmbr1 genes that reside at 1Mb apart from shh is one of the most possible candidates for these mutations. In a human mutation, Acheiropodia, which exhibits limb truncation, the LMBR1gene has a large deletion including exon4. By contrast, in the mouse mutations no alteration was observed in the Lmbr1 gene. Very recently, it was reported that the alteration of a cis-element of shh, which resides in intron 5 of Lmbr1, may result in a preaxtial polydactyly mutation, Ssq (Lettice et al, 2002). We have carried out positional cloning for another preaxial polydactyly mutation, Hx, and narrowed down the critical region to about 100kb. In addition, we found that the preaxial polydactyly of Hx is abrogated when the mutation is located in cis-position to the shh knockout allele. The result indicated that the Hx mutation is also attributed to the alteration of the cis-acting regulator of shh. We show the results of the mutation analysis in the Hx critical region.


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