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Abnormal microenvironmental signals underlie intestinal aganglionosis in Dominant megacolon mutant mice
R P Kapur1, R Livingston, B Doggett
1Department of Laboratories, Children's Hospital and Medical Center, Seattle, Washington 98105, USA. rkapur@chmc.org
Abstract:
Dominant megacolon (Dom) is a mutation in an uncharacterized murine gene which is associated with intestinal aganglionosis and the focal absence of melanocytes in heterozygous animals. The phenotype of Dom/+ heterozygotes is similar to the lethal spotted and piebald lethal mutations, which are due to defects in endothelin-mediated intercellular signals. In this study, the DbetaH-nlacZ transgenic marker for enteric neural crest cells is used to study the distribution of enteric neurons and their precursors in Dom/+ mice and embryos. Vagal neural crest-derived cells in wild-type embryos colonize the gut in a cranial-to-caudal progression. In Dom/+ embryos, colonization was retarded from the earliest stages examined (embryonic Day 11.0), including progression through the small intestine. The early onset of this defect contrasts with impaired neural crest colonization associated with the lethal spotted and piebald lethal mutations which manifest only in the large intestine. Analysis of Dom/+ - +/+ aggregation chimeras indicated that defective colonization is not an autonomous (intrinsic) property of Dom/+ neuroblasts, but like lethal spotted and piebald lethal, the Dominant megacolon mutation directly or indirectly affects microenvironmental signals which influence the migration, proliferation, and/or survival of enteric neural crest cells.
Insights
The Dominant megacolon mutation in mice disrupts enteric neural crest cell colonization of the gut early in development. This defect affects migration, proliferation, or survival, unlike similar mutations affecting later stages.
Area of Science:
- Developmental biology
- Genetics
- Neuroscience
Background:
- Dominant megacolon (Dom) is a murine mutation causing intestinal aganglionosis and melanocyte absence.
- Dom/+ heterozygotes share phenotypes with lethal spotted and piebald lethal mutations, linked to endothelin signaling defects.
Purpose of the Study:
- To investigate the distribution of enteric neurons and their precursors in Dom/+ mice and embryos using a transgenic marker.
- To determine the stage at which neural crest colonization is affected in Dominant megacolon mutants.
Main Methods:
- Utilized the DbetaH-nlacZ transgenic marker to trace enteric neural crest cells in wild-type and Dom/+ embryos.
- Analyzed gut colonization patterns from embryonic Day 11.0 onwards.
- Conducted aggregation chimeras using Dom/+ and wild-type cells to assess cell-autonomous defects.
Main Results:
- Vagal neural crest-derived cells showed retarded gut colonization in Dom/+ embryos from embryonic Day 11.0.
- The colonization defect in Dom/+ embryos occurred earlier and affected the small intestine, unlike lethal spotted and piebald lethal mutations.
- Aggregation chimeras revealed that the defective colonization is not an intrinsic property of Dom/+ neuroblasts.
Conclusions:
- The Dominant megacolon mutation impacts microenvironmental signals affecting enteric neural crest cell migration, proliferation, and/or survival.
- This contrasts with mutations like lethal spotted and piebald lethal, suggesting distinct mechanisms in neural crest development.
- The study elucidates an early developmental defect associated with the Dominant megacolon mutation, impacting gut innervation.