Physiology Quantifying the genetic influence on mammalian vascular tree structure

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Quantifying the genetic influence on mammalian vascular tree structure

Robb Glenny *, Susan Bernard *, Blazej Neradilek , and Nayak Polissar

*Division of Pulmonary and Critical Care Medicine, School of Medicine, Box 356522, and Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195; and Mountain-Whisper-Light Statistical Consulting, 1827 23rd Avenue East, Seattle, WA 98112

Edited by James H. Brown, University of New Mexico, Albuquerque, NM, and approved March 1, 2007 (received for review December 11, 2006)

The ubiquity of fractal vascular trees throughout the plant and animal kingdoms is postulated to be due to evolutionary advantages conferred through efficient distribution of nutrients to multicellular organisms. The implicit, and untested, assertion in this theory is that the geometry of vascular trees is heritable. Because vascular trees are constructed through the iterative use of signaling pathways modified by local factors at each step of the branching process, we sought to investigate how genetic and nongenetic influences are balanced to create vascular trees and the regional distribution of nutrients through them.

We studied the spatial distribution of organ blood flow in armadillos because they have genetically identical littermates, allowing us to quantify the genetic influence. We determined that the regional distribution of blood flow is strongly correlated between littermates (r2 = 0.56) and less correlated between unrelated animals (r2 = 0.36). Using an ANOVA model, we estimate that 67% of the regional variability in organ blood flow is genetically controlled.

We also used fractal analysis to characterize the distribution of organ blood flow and found shared patterns within the lungs and hearts of related animals, suggesting common control over the vascular development of these two organs.

We conclude that the geometries of fractal vascular trees are heritable and could be selected through evolutionary pressures. Furthermore, considerable postgenetic modifications may allow vascular trees to adapt to local factors and provide a flexibility that would not be possible in a rigid system.


Author contributions: R.G. designed research; R.G., S.B., B.N., and N.P. performed research; R.G., B.N., and N.P. analyzed data; and R.G. wrote the paper.

The authors declare no conflict of interest.

To whom correspondence should be addressed.

Robb Glenny, E-mail:


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