Jordan Huber and Dr. Jeffery Barrow, Physiology and Developmental Biology
Introduction
The Wnt family of secreted proteins consists of 19 family members (in the mouse) and is known to signal through multiple pathways that regulate crucial processes in the development of almost all tissues. Dissecting the roles of individual Wnts has been hampered due to functional redundancy that exists between family members. By making a conditional allele of the O-acyltransferase, Porcupine (Porcn), that is required for the secretion of all Wnt ligands, and a tissue specific enhancer to drive Cre expression, we are able to eliminate the secretion of all Wnt ligands in tissues of interest. We eliminated the secretion of ventral limb ectodermal Wnts with the use of the conditional allele of Porcn and the Msx2Cre deleter, and observed a loss and reduction of underlying musculature as shown in Figure 2 below.
This shows a role for ectodermal Wnts in the patterning of underlying musculature. Hypothesizing that the elimination of mesenchymal Wnts would result in inner musculature defects, we utilized the conditional allele of Porcn and the Prx1Cre deleter to eliminate the secretion of mesenchymal Wnts.
Materials/Methods
At E14.5 Porcnlox/Y; Prx1Cre mutant and control limbs were collected from mice. Limbs were embedded and then sectioned. The limb sections were then stained using immunohistochemistry by taking advantage of a myosin heavy chain antibody that highlights all musculature present in the sections. The stained sections were then imaged by using the confocal located in Dr. Stark’s lab. The images were then assembled and the musculature is compared in the Porcnlox/Y; Prx1Cre mutant and controls.
Results
When we compared musculature present in the limbs of Porcnlox/Y; Prx1Cre mutant and controls we discovered that the inner musculature of Porcnlox/Y; Prx1Cre mutant limbs to be greatly absent or greatly reduced. Thus, our hypothesis that mesenchymal Wnts are required for the normal development of inner musculature is supported by our data as shown in Figure 3 below.
Discussion
Our research demonstrates the necessity of Wnts in the development of limb musculature in both ectodermal and mesenchymal tissues. Through future studies and experiments we hope to further uncover the process and mechanism by which limb musculature develops. We hope that a further understanding of limb developmental processes will help lead to fewer developmental defects in the future.