1306 NEURAL CREST INVOLVEMENT IN MOUSE TRISOMY 16 EMBRYOPATHY

Abstract

Murine Trisomy 16 (Ts16) has been proposed as an animal model for Down Syndrome. We examined serial histologic reconstructions of Ts16 fetuses from day 14 through 18 gestation. We found that 94% (N=52) of Ts16 mice had cardiovascular malformations. Endocardial cushion defects were most common (62%) and were associated frequently with conotruncal abnormalities (DORV, 36%; overriding aorta, 35%; PTA, 6%; TGA, 2%) We found thymic hypoplasia in > 90% of Ts16 mice. Consistent with previous observations (Oster-Granite et al., Ped. Res. 17: 300A (1983)), we found facial, basiocciput, and audiovestibular (otic) abnormalities. In reconstructions of the temporal bones, no specimen showed more than 1.5 turns of the cochlea by day 13 (N=2.5). Kirby et al (Science 220: 1059-1061 (1983); Science 223: 498-500 (1984) demonstrated in chick-quail chimeras the cephalic neural crest contribution to thymus development and to aorticopulmonary septation. The combination of cardiac defects, thymic hypoplasia, auditory, and craniofacial malformations we have observed in the Ts16 mouse is consistent with a generalized rhombencephalic neural crest deficiency. This deficiency may be due to failure of cell proliferation or migration, to excessive cell death, or to abnormal cell-cell interactions.