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. Author manuscript; available in PMC: 2010 Jun 28.
Published in final edited form as: Nature. 2008 May 7;453(7196):745–750. doi: 10.1038/nature07005

Figure 6. A formal model of the lung branching program.

Figure 6

(Top) Representation of branching modes as subroutines using different combinations of patterning and morphogenesis operations (boxed; see Fig. 2f). Subroutines are locally modified by input parameters P1–P4 that regulate variables indicated. P-D, proximal-distal. (Bottom) Three subroutine coupling schemes generate the three observed sequences of subroutine use (Fig. 3c). The schemes are related: bypass of step marked by asterisk in Sequence 2 generates Sequence 1, and repeat of domain branching step (dashed line) generates Sequence 3. DB, domain branching; PB, planar bifurcation; OB, orthogonal bifurcation.