Fig. 5. Fgf8^H/– mutants display glandular phenotypes and T-cell deficiency attributable to altered pharyngeal pouch development. eighty percent of mutants had thymic (Ty) hypo/aplasia and 50% had parathyroid hypo/aplasia. (A-C) Thoracotomies, (D-F) Hematoxylin and Eosin stained paraffin wax-embedded sections. The trachea (tr), esophagus (e) and thyroids (td) are also indicated. (A) Normal bi-lobed thymus in a control E18.5 embryo. (B) Hypoplastic, mono-lobed thymus in a mutant. (C) Thymic aplasia in a mutant (arrowhead). (D) Normal bilateral parathyroid glands in a control E18.5 embryo (arrowheads). (E) Parathyroid aplasia in a mutant (arrowheads), the entire cervical region of this animal was sectioned and no parathyroids were detected. (F) Ectopic, hypoplastic parathyroid (arrowhead) adjacent to internal carotid vessel (v) in a mutant. (G) Representative FACS plots of control and mutant thymi. (H) Percent (left panel) and total (right panel) CD4^–CD8^–double negative (DN) and CD4⁺CD8⁺double positive (DP) thymocytes in n=9 control embryos or n=2 mutant embryos with thymic hypoplasia. Mutants with thymic hypoplasia have 20% of the normal number of T cells. Note that 50% of mutant embryos have no thymus. Data are shown as mean±s.e.m.

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