Expression of the hormonal FGF Co-receptor Klotho beta in the Xenopus laevis Model.

Klotho beta (Klb), a single-pass transmembrane protein, has been described as a co-receptor for endocrine FGFs, such as FGF15/19 and FGF21, to regulate critical metabolic processes in multiple organs and tissues in adult mice. However, its function during early embryonic development remains largely unknown. In this paper, we evaluated for the first time the expression of klb mRNA during early development of Xenopus laevis by RT-PCR and whole mount in situ hybridization. RT-PCR experiments showed that the expression of klb was initially detected at late gastrula stage followed by a quick increasing and continued expression throughout embryonic development. Whole mount in situ hybridization detected specific expression of klb in many primordial organs at tailbud stage such as liver primordium and pancreatic buds, implying that the hormonal FGF signaling may play a role in the foregut development. The dynamic and specific expression patterns of klb also suggest that Xenopus laevis can serve a convenient model for the function of the hormonal FGF signaling in organogenesis and metabolism regulation during embryonic development.