Nude mouse embryo: ectodermal nature of the primordial thymic defect.

Sterile female homozygous nude mice were rendered fertile through a graft of thymic epithelium from heterozygous littermates 3 days after birth. Homozygous nude embryos were compared with embryos age (8-18 days). In nude mice, the embryological anomaly is noticeable from the 11th day of gestation and essentially consists of a failure of the ectoderm from the 3rd branchial cleft to proliferate and differentiate into a cervical vesicle. As a result, the endoderm from the 3rd pouch degenerates into cystic formations instead of differentiating.