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Fig. 2. Defects in enteric nervous system development in
RetDN/+mice. (A) The intestines from a P21
RetDN/+ mouse with a contracted distal colon (double
arrow) and a dilated distal small bowel (triple arrowheads). The intestines of
wild-type (wt), Ret9/+ and RetTGM/+
mice are normal (arrow, ileocecal junction; Es, esophagus; Re, rectum). (B)
Intestinal aganglionosis and hypoganglionosis in P21
RetDN/+ mice. Hematoxylin and Eosin (HE) staining revealed
the presence of neurons (arrowheads) in the muscularis externa of the colon in
wild-type (wt) but not RetDN/+ mice. Acetylcholinesterase
(AChE) staining demonstrated neuronal (black arrows) and nerve fiber (black
arrowheads) loss in RetDN/+ colon (the brown fibers in the
RetDN/+ colon are extrinsic innervations characteristic of
HSCR). Both AChE- and nicotinamide adenine dinucleotide phosphate
(NADPH)-stained RetDN/+ proximal small intestines display
a reduced number of neurons (arrows) and nerve fibers (arrowheads), when
compared with an identical region from wild-type mice. Scale bars: 100 µm
(HE); 400 µm (AChE); 200 µm (NADPH). (C) The aganglionosis is fully
penetrant but variable in RetDN/+ mice. The schematic
shows the extent of aganglionosis determined by AChE staining in various
RetDN/+ mice (each red mark represents one
RetDN/+ mouse, n=16). The numbers correspond to
the percentage of the respective intestinal segment (small or large intestine)
successfully colonized by neurons. Ret9/+ (n=7),
RetDNneo/+ (n=3) and RetTGM/+
(n=3) intestines were normal, and RetTGM/TGM (Ret
null) had total intestinal aganglionosis. (D) Quantitative analysis of
neuronal number and fiber density in the ENS of P21 wild-type and
RetDN/+ mice demonstrated a dramatic reduction in the
number of neurons and neuronal fiber density in the proximal small bowel
(n=3, *=P<0.01, mean±s.e.m.).
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