• Thp;
  • twLub2;
  • overgrowth;
  • enlarged heart;
  • cystic hygroma;
  • animal model;
  • genomic imprinting;
  • Wiedemann-Beckwith syndrome

ABSTRACT Thp/+ mouse is known to have differing phenotypes depending on gender of the ThP parent. In the present study, fetuses with maternally [Group A (until day 18 of pregnancy) and Group C (day 19)] and paternally [Group B] inherited ThP were examined with particular reference to the developmental abnormalities of hearts. In addition, a small number of fetuses with maternally inherited twLub2 on day 19 were compared with Thp. Group A ThP fetuses had greater body weight, possibly larger body size, generalized edema (100%), marked enlargement of the hearts (100%) and hypoplastic pulmonary trunk (73.7%). There were no such malformations in Group B ThP fetuses or in the controls (+/+) for both groups. The bilaterally thickened ventricular wall of fetal hearts in Group A and C ThP fetuses bulged into ventricular cavity. The pulmonary valve was also thickened. The labeling indices of the ventricular myocardial cells by BrdU were inclined to be higher in Group A ThP than in the control (+/+) fetuses. Fetuses of twLub2 had abnormalities of the cardiovascular system similar to Group C Thp. The results suggest that cardiac lesions in fetuses with maternally inherited ThP and twLub2 correspond to cardiomyopathy. Overgrowth and enlarged heart indicate the possibility of ThP as an animal model for Wiedemann-Beckwith syndrome.