Knockdown of slit signaling during limb development leads to a reduction in humerus length.

Abstract

Slits (1-3) and their Robo (1-3) receptors play multiple non-neuronal roles in development, including in development of muscle, heart and mammary gland. Previous work has demonstrated expression of Slit and Robo family members during limb development, where their functions are unclear. In situ hybridisation confirmed strong expression of Slit2, Slit3, Robo1, and Robo2 throughout mouse limb and joint development. No expression of Slit1 or Robo3 was detected. Analysis of Slit1/2 or Slit3 knockout mice revealed normal limb development. In contrast, locally blocking Slit signaling though grafting of cells expressing a dominant-negative Robo2 construct in the proximo-central region of developing chicken limb buds caused significant shortening of the humerus. These findings demonstrate an essential role for Slit/Robo signaling in regulating bone length during chicken limb development.