Fig. 5. The svs mutation is allelic with Fgfr2. A genetic complementation test to determine if svs is an allele of Fgfr2. (A) P5 seminal vesicles from Fgfr2^flox/svs mice initiated normal branching morphogenesis indicating that a functional Fgfr2 gene complements the svs mutation. Arrows indicate branched tips of the seminal vesicle. (B) Conversely, p5 seminal vesicles from Fgfr2/svs mice failed to initiate branching morphogenesis, indicating that a null allele of Fgfr2 fails to complement the svs mutation. (C) A p5 svs homozygous mutant seminal vesicle is shown for comparison. (D,E) Frozen sections of seminal vesicles from fully developed Fgfr2^flox/svs and Fgfr2/svs adult mice were stained with Hematoxylin and Eosin. (D) Upper image depicts a cross-section of seminal vesicles from Fgfr2^flox/svs mice with a complex branched structure. The bottom image shows the same seminal vesicle at increased magnification showing the presence of macroscopic clefts (arrowhead) that result from developmental branching morphogenesis. (E) Upper image depicts seminal vesicles from Fgfr2/svs mice that lack all branching. The bottom image shows the same seminal vesicle at increased magnification showing the lack of macroscopic clefts.