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Presenting Author(s) Brian Harfe
Abstract Title Role of Dicer and microRNAs in vertebrate limb development.
Full author List Mike McManus (1) and Brian D. Harfe (2)
Text of abstract Recently, the protein Dicer and the novel family of RNA molecules it processes, the microRNAs, have been shown to be involved in regulating gene expression in lower organisms. Dicer and microRNAs are present in vertebrates, but the functions of these genes during vertebrate development have not been analyzed. In my laboratory we are investigating how microRNAs and Dicer regulate gene expression during the development of the mouse limb. As a first step, we have shown that at least one family of microRNA molecules, the let-7 family, is expressed in the developing vertebrate limb. As an alternative to knocking out individual let-7 microRNAs, we have created a conditional null allele of the microRNA-processing enzyme Dicer. To demonstrate that our allele is null, we have analyzed fibroblast cells that are homozygous deleted for our conditional allele. In these cells, microRNAs, including let-7, are not processed correctly. To remove Dicer specifically in the limbs, the Dicer floxed allele was crossed to two different limb-expressing Cre lines: prxcre, and shhgfpcre. Removal of Dicer from the limb mesoderm using the prxcre allele resulted in an abnormal limb but, surprisingly, the limb still contained a number of well differentiated tissue types, including bone and muscle. Using the shhgfpcre allele, we removed Dicer from a specific subdomain of the distal limb mesoderm that normally gives rise to the two most posterior digits and part of digit three. Removal of Dicer from this region of the limb caused defects in the patterning of the posterior digits. These results suggest that Dicer and microRNAs play an important role in the development of the vertebrate limb. We are presently analyzing molecular markers in Dicer-minus limbs and we are crossing the conditional allele to additional cre lines to better characterize the roles of Dicer and microRNAs in limb development.
Which session is your work most relevant to: Limb patterning