The Splotch mutant mouse shows defects in neural crest-derived cell populations. The septation of the truneus arteriosus and the development of the aortic arch-derived blood vessels was studied in homozygotes of the Splotch mutant allele Sp1H. It is shown that in homozygous mutant embryos, the septation of the truncus arteriosus does not proceed normally, resulting in persistent truncus arteriosus. The ostium of the persistent truncus arteriosus opens to the right ventricle. Frequently, variations of the aortic arch-derived blood vessels are observed. The development of the thymus, the parathyroid and the ultimobranchial bodies are also variably affected in mutants.
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