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New Insight Into Birth Defect Characterized By Digit Duplication And Fusion

Date:
December 27, 2008
Source:
Journal of Clinical Investigation
Summary:
Birth defects characterized by malformation of the limbs are relatively common. New insight into one form of the birth defect synpolydactyly, where individuals have 1 or more digit (finger or toe) duplicated and 2 or more digits fused together, has now been provided researchers in Germany who studied a mouse model of the condition.
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Birth defects characterized by malformation of the limbs are relatively common. New insight into one form of the birth defect synpolydactyly, where individuals have 1 or more digit (finger or toe) duplicated and 2 or more digits fused together, has now been provided by Stefan Mundlos and colleagues, at Universitätsmedizin Berlin, Germany, who studied a mouse model of the condition.

The results of their research are published online Dec. 15 in the Journal of Clinical Investigation.

One form of synpolydactyly is caused by mutations in the HOXD13 gene. To understand how these mutations cause disease the authors analyzed mice carrying one of these mutations, Spdh/Spdh mice.

Surprisingly, the protein generated by the mutated gene was found to have lost a function of the normal Hoxd13 protein and to have gained a new function. Specifically, the mutant protein was unable to facilitate normal levels of production of the soluble factor RA, and intrauterine treatment with RA restored normal digit formation in Spdh/Spdh mice. As RA was shown to normally suppress the generation of cells that produce and maintain cartilage, the loss-of-function mutated Hoxd13 therefore indirectly promotes the formation of cartilage.

Importantly, further analysis indicated the mutated protein also directly induced the generation of cells that produce and maintain cartilage, whereas normal Hoxd13 did not. Thus, mutated Hoxd13 causes syndpolydactyly by inducing the generation of cells that produce and maintain cartilage, both directly and indirectly.


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The above post is reprinted from materials provided by Journal of Clinical Investigation. Note: Materials may be edited for content and length.


Journal Reference:

  1. Kuss et al. Mutant Hoxd13 induces extra digits in a mouse model of synpolydactyly directly and by decreasing retinoic acid synthesis. Journal of Clinical Investigation, 2008; DOI: 10.1172/JCI36851

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Journal of Clinical Investigation. "New Insight Into Birth Defect Characterized By Digit Duplication And Fusion." ScienceDaily. ScienceDaily, 27 December 2008. <www.sciencedaily.com/releases/2008/12/081215183953.htm>.
Journal of Clinical Investigation. (2008, December 27). New Insight Into Birth Defect Characterized By Digit Duplication And Fusion. ScienceDaily. Retrieved August 29, 2015 from www.sciencedaily.com/releases/2008/12/081215183953.htm
Journal of Clinical Investigation. "New Insight Into Birth Defect Characterized By Digit Duplication And Fusion." ScienceDaily. www.sciencedaily.com/releases/2008/12/081215183953.htm (accessed August 29, 2015).

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