Int. J. Dev. Biol. 53: 1483 - 1494 (2009)

https://doi.org/10.1387/ijdb.072430nm

Vol 53, Issue 8-9-10

Special Issue: Developmental Biology in Hispania (Spain & Portugal)

Ectopic Meis1 expression in the mouse limb bud alters P-D patterning in a Pbx1-independent manner

Published: 1 November 2009

Nadia Mercader¹, Licia Selleri², Luis Miguel Criado¹, Pilar Pallares¹, Carlos Parras³, Michael L. Cleary⁴ and Miguel Torres*¹

¹Centro Nacional de Investigaciones Cardiovasculares (CNIC), Instituto de Salud Carlos III, Madrid, Spain, ²Department of Cell and Developmental Biology, Cornell University Weill Medical School, New York, USA, ³INSERM U711, Université Pierre et Marie Curie, IFR de Neuroscience, Hôpital de la Salpêtrière, Paris, France and ⁴Department of Pathology, Stanford University School of Medicine, Stanford, USA

Abstract

During limb development, expression of the TALE homeobox transcription factor Meis1 is activated by retinoic acid in the proximal-most limb bud regions, which give rise to the upper forelimb and hindlimb. Early subdivision of the limb bud into proximal Meis-positive and distal Meis-negative domains is necessary for correct proximo-distal (P-D) limb development in the chick, since ectopic Meis1 overexpression abolishes distal limb structures, produces a proximal shift of limb identities along the P-D axis, and proximalizes distal limb cell affinity properties. To determine whether Meis activity is also required for P-D limb specification in mammals, we generated transgenic mice ectopically expressing Meis1 in the distal limb mesenchyme under the control of the Msx2 promoter. Msx2:Meis1 transgenic mice display altered P-D patterning and shifted P-D Hox gene expression domains, similar to those previously described for the chicken. Meis proteins function in cooperation with PBX factors, another TALE homeodomain subfamily. Meis-Pbx interaction is required for nuclear localization of both proteins in cell culture, and is important for their DNA-binding and transactivation efficiency. During limb development, Pbx1 nuclear expression correlates with the Meis expression domain, and Pbx1 has been proposed as the main Meis partner in this context; however, we found that Pbx1 deficiency did not modify the limb phenotype of Msx2:Meis1 mice. Our results indicate a conserved role of Meis activity in P-D specification of the tetrapod limb and suggest that Pbx function in this context is either not required or is provided by partners other than Pbx1.

Keywords

mouse limb development, proximo-distal axis, Meis1, Pbx