A zebrafish orthologue (whnb) of the mouse nude gene is expressed in the epithelial compartment of the embryonic thymic rudiment

Abstract

The cloning and characterization of the zebrafish orthologue of the mouse nude (Whn/Foxn1) gene, whnb are reported. A previously described Whn-like gene from zebrafish, now designated as whna, is shown to be the orthologue of the mouse Foxn4 gene. The whnb gene is specifically expressed in the thymic rudiment of zebrafish embryos at day 3 after fertilization, whereas the whna gene is expressed in eye and brain structures. Whnb expression is maintained in cloche mutants, where endothelial and haematopoietic cell differentiation is defective, but absent in casanova mutants where endoderm formation is impaired. In adult thymi, whnb is expressed throughout cortical and medullary areas, whereas whna expression is observed in rare cell clusters only. Our results provide the first specific marker for the epithelial compartment of the zebrafish thymus.

Genetic Evidence for an Evolutionarily Conserved Role of IL-7 Signaling in T Cell Development of Zebrafish

“…3B), properly assembled tcrb genes are expressed and detectable by RT-PCR. The expression of foxn1, a characteristic marker for thymic epithelial cells (29,35), is unaffected, although foxn1-positive cells are less dispersed in the thymic rudiment as a result of the reduced number of hematopietic cells (Fig. 3C).…”

Ddx46 Is Required for Multi-Lineage Differentiation of Hematopoietic Stem Cells in Zebrafish

“…7C-F). However, the expression of forkhead box N1 (foxn1) [36], a thymus epithelial marker, was indistinguishable between Ddx46 hi2137/ + and Ddx46 hi2137/hi2137 larvae (Fig. 7G, H), indicating that thymus formation is normal in these mutants.…”

Maintenance of Thymic Epithelial Phenotype Requires Extrinsic Signals in Mouse and Zebrafish

“…Although functional evidence is still lacking, it has been suggested that Foxn1 homologues in other vertebrates possess the same function. Indeed, a Foxn1 homologue, initially termed whnb and now called foxn1, was identified and shown to be expressed in the larval thymic anlage of zebrafish (3). It is currently unknown how Foxn1 expression is initiated in the prospective thymic anlage and which signal(s) maintain its expression.…”