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Fig. 2. Conduction system maturation failure in Tbx5del/+ mice.
The atrioventricular canal conduction system in minKlacZ/+
(A,B) and Tbx5del/+/minKlacZ/+ (C,D)
hearts was studied in newborn (A,C) and adult (B,D) mice. The atria were
removed and the atrioventricular canal was viewed from the superior/posterior,
with the tricuspid annulus on the right and the mitral annulus on the left.
Rings of specialized conduction cells observed in the atrioventricular canal
of newborn minKlacZ/+ mouse hearts (A) matured into a
well-defined atrioventricular node (arrow) and atrioventricular bundle in
adult minKlacZ/+ mouse hearts (B). (A) Scale bar: 200
µm. (B) Scale bar: 800 µm. Rings of specialized conduction cells in the
atrioventricular canal of newborn
Tbx5del/+/minKlacZ/+ mouse hearts (C)
failed to mature into a discrete atrioventricular node or atrioventricular
bundle in adult Tbx5del/+/minKlacZ/+
mouse hearts (D). Instead the neonatal pattern (rings of specialized
conduction tissue) was maintained. Arrow denotes expected location of the
atrioventricular node.