Other authors include PhD graduate student Rachana Chandran, visiting researcher Yonghua Yang from Fudan University, and former undergraduate biology majors Mina Essak and Nicholas Blackstone.
The introduction of this article begins
“Branched tubular organs such as the lung, vascular system, and kidney are essential for transporting oxygen, nutrients, and cells in all multicellular organisms. The optimal flow of transported fluids depends on the uniform length and diameter of the tubes. Aberrant tube sizes that arise during development lead to devastating human illnesses, such as polycystic kidney disease and blood vessel stenosis. While the early patterning and branching of tubular networks have been studied extensively in several systems, the cellular and molecular mechanisms of tube-size regulation remain poorly understood….
In this paper, we describe the role of Drosophila Expansion (Exp, CG13188), a novel Smad-like protein in tube-size regulation. exp mutants develop bubble-like cysts in unicellular and intracellular, but not multicellular tubes, suggesting that exp is required for branch specific tube-size regulation….
To test the idea that Exp regulates tube size using a similar mechanism as RPTPs [receptor tyrosine phosphatases], we examined genetic interactions between Exp and components of the RTK [receptor tyrosine kinase] signaling pathways... Activating RTK signaling enhanced the cyst phenotype in exp mutants whereas inhibiting RTK signaling reduced the cyst phenotype. Our results strongly suggest that Exp functions as a negative regulator of RTK signaling to control tube size in unicellular and intracellular branches. The functional analysis of this novel Smad protein reveals a previously unidentified role for Smad family proteins in regulating RTK signaling to control epithelial tube formation.”