An evolutionary perspective on the sequence, mechanism, and regulatory function of animal microRNAs

(cont.) The vertebrate-specific miR-196 family is encoded at three paralogous loci in the mammalian Hox clusters, and has complementarity to messages of several Hox genes, including Hox8 paralogues. RNA fragments diagnostic of miR-196-directed cleavage of Hoxb8 were detected in mouse embryos. Cell culture experiments demonstrated down-regulation of Hoxb8, Hoxc8, Hoxd8, and Hoxa7 and supported a cleavage mechanism for miR-196-directed repression of Hoxb8. These results point to a miRNA-mediated mechanism for the posttranscriptional restriction of Hox gene expression during vertebrate development and demonstrate that metazoan miRNAs can repress expression of their natural targets through mRNA cleavage in addition to inhibiting a translational step. Inhibition of the two Hox miRNAs in chick embryos, resulted in axial skeletal patterning defects in domains that overlap considerably with Hox target and miRNA expression, supporting a specialization of miRNAs in Hox gene regulation, and consistent with action by miR-196 and miR-10 to refine posterior boundaries at relative levels of expression for multiple Hox genes. The genomic distribution of target sites and Hox patterns of expression suggest that the miRNAs further act in concert with more posteriorly expressed Hox genes to impose a functional hierarchy over more anterior ones, a molecular mechanism consistent with 'posterior prevalence'. The posttranscriptional downregulation of more 3' and anteriorly expressed Hox genes by miR-196 constitutes an evolutionarily recent regulatory layer of the highly constrained Hox network, one which recapitulates modes of interactions existing at multiple levels of gene expression.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Biology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Yekta, Soraya

Advisor dc:contributor.advisor

• David P. Bartel.

• Biology.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/43791

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/43791