FGF signalling through Fgfr2 isoform IIIb regulates adrenal cortex development

Abstract

Developmental signalling pathways are implicated in the formation and maintenance of the adrenal gland, but their roles are currently not well defined. In recent years it has emerged that Sonic hedgehog (Shh) and Wnt/β catenin signalling are crucial for the growth and development of the adrenal cortex. Here we demonstrate that Fibroblast growth factor receptor (Fgfr) 2 isoforms IIIb and IIIc are expressed mainly in the adrenal subcapsule during embryogenesis and that specific deletion of the Fgfr2 IIIb isoform impairs adrenal development, causing reduced adrenal growth and impaired expression of SF1 and steroidogenic enzymes. The hypoplastic adrenals also have thicker, disorganised capsules which retain Gli1 expression but no longer express Dlk1. Fgfr2 ligands were detected in both the capsule and the cortex, suggesting the importance of signalling between the capsule and the cortex in adrenal development.

Fig. 1

(A–F) NR-ISH analysis of e15.5 mouse adrenal glands using Fgfr2 IIIb (B and C) and IIIc (E and F) specific probes combined with Cyp11b1 immunolocalization. Fgfr2 positive cells are labelled red, Cyp11b1 cells are labelled green and cell nuclei are labelled blue (Cap. = capsule, Med. = medulla). (G-L) Hematoxylin and eosin staining of wild-type (^+/+, G–I) and fgfr2 IIIb knock out (^-/-, J–L) adrenals. (M, N) Immunohistochemical analysis of PCNA expression in wild-type (^+/+, M) and fgfr2 IIIb knock-out (^-/-, N) adrenals. Arrows in N point to PCNA-positive cells in the adrenal capsule. Scale bars = F, 50 μm (applies to A–F); J, 150 μm (applies to G and J); L, 50 μm (applies to H, I, K, and L); M and N = 100 μm. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Expression of Scc (A–D), Cyp11b1 (E–H) and Sf1 in e15.5 WT (A, B, E, F, and I) and Fgfr2 IIIb KO (C, D, G, H, and J) adrenals. Scale bar = 200 μm (A, C, E, and G); 50 μm (B, D, F, H, I, and J). Med. = medulla, Cx. = cortex.

Fig. 3

NR-ISH of WT (^+/+) and Fgfr2 IIIb KO (^-/-) e15.5 mouse adrenals using Gli1 (A and B) and Dlk1 (C–F) riboprobes. Arrows in A and B indicate clusters of Gli1 positive cells in the capsule. Capsule cells in A, B, E and F are between the brackets. Scale bars = 100 μm. Med. = medulla.

Fig. 4

RT-PCR analysis of Fgfs and Fgfrs expression in laser capture microdissected e15.5 adrenal capsule and cortex. Control cDNA was made from pooled tissues including lung, heart, liver, bone and gut.