TrkA is necessary for the normal development of the murine thymus

Nerve growth factor (NGF) and its signal-transducing receptor TrkA are expr essed in the thymus. However, their possible role during thymic organogenes is is unknown. Here we analyze the thymus of trkA-kinase deficient 2-week-o ld mice. trkA-kinase +/+ and +/- mice had a normal thymus, whereas the thym us of trkA-kinase -/- mice showed lack of delimitation between the cortex a nd medulla, lower thymocyte density, and the presence of epithelial cell is lands and numerous cysts lined with endodermal epithelium. The present resu lts indicate that TrkA is necessary for the normal development of the thymu s, and that its absence causes an arrest in the differentiation of endoderm al epithelial cells. Whether this lack of differentiation has functional im plication has yet to be determined. (C) 2000 Elsevier Science B.V. All righ ts reserved.