Dependence of Thymus Development on Derivatives of the Neural Crest

TLDR

Neural crest migration failures can cause congenital defects such as Di George syndrome. The study investigates whether neural crest‑derived mesenchyme directly interacts with pharyngeal epithelium to drive thymus development. Removing specific cephalic neural crest regions in early chick embryos markedly reduces or eliminates thymus size, delays thymic lobe maturation, and often causes parathyroid, thyroid, and heart defects.

Abstract

Elimination of limited areas of the cephalic neural crest in stage 9 or 10 chick embryos markedly reduced the size of the thymus gland or resulted in its absence. Small thymic lobes contained both thymocytes and epithelial cells but showed delayed development. Parathyroid and thyroid glands sometimes were reduced in size or missing from the normal location on one or both sides. Heart defects were consistently present. Thymus development may depend on direct interaction of mesenchymal derivatives of the neural crest with pharyngeal epithelium. Multiple defects, such as the Di George syndrome, may result from failure of neural crest derivatives to migrate and interact properly.