title: Wnt signaling inhibits adrenal steroidogenesis by cell-autonomous and non-cell-autonomous mechanisms.
abstract: Wnt/β-catenin (βcat) signaling is critical for adrenal homeostasis. To elucidate how Wnt/βcat signaling elicits homeostatic maintenance of the adrenal cortex, we characterized the identity of the adrenocortical Wnt-responsive population. We find that Wnt-responsive cells consist of sonic hedgehog (Shh)-producing adrenocortical progenitors and differentiated, steroidogenic cells of the zona glomerulosa, but not the zona fasciculata and rarely cells that are actively proliferating. To determine potential direct inhibitory effects of βcat signaling on zona fasciculata-associated steroidogenesis, we used the mouse ATCL7 adrenocortical cell line that serves as a model system of glucocorticoid-producing fasciculata cells. Stimulation of βcat signaling caused decreased corticosterone release consistent with the observed reduced transcription of steroidogenic genes Cyp11a1, Cyp11b1, Star, and Mc2r. Decreased steroidogenic gene expression was correlated with diminished steroidogenic factor 1 (Sf1; Nr5a1) expression and occupancy on steroidogenic promoters. Additionally, βcat signaling suppressed the ability of Sf1 to transactivate steroidogenic promoters independent of changes in Sf1 expression level. To investigate Sf1-independent effects of βcat on steroidogenesis, we used Affymetrix gene expression profiling of Wnt-responsive cells in vivo and in vitro. One candidate gene identified, Ccdc80, encodes a secreted protein with unknown signaling mechanisms. We report that Ccdc80 is a novel βcat-regulated gene in adrenocortical cells. Treatment of adrenocortical cells with media containing secreted Ccdc80 partially phenocopies βcat-induced suppression of steroidogenesis, albeit through an Sf1-independent mechanism. This study reveals multiple mechanisms of βcat-mediated suppression of steroidogenesis and suggests that Wnt/βcat signaling may regulate adrenal homeostasis by inhibiting fasciculata differentiation and promoting the undifferentiated state of progenitor cells.
authors.affiliation: Cellular and Molecular Biology Graduate Program (E.M.W., G.D.H.) and Program in Biomedical Sciences (N.B.), University of Michigan Medical School; Center for Cancer Biostatistics (R.K.), Department of Biostatistics, University of Michigan School of Public Health; Department of Internal Medicine (I.F., G.D.H.), Division of Metabolism, Endocrinology and Diabetes; Department of Internal Medicine (S.M.H., D.M.W.), Division of Molecular Medicine and Genetics; and Endocrine Oncology Program (G.D.H.), Comprehensive Cancer Center, University of Michigan, Ann Arbor, Michigan 48109.
authors.forename: Elisabeth M
authors.initials: EM
authors.lastname: Walczak
authors.forename: Rork
authors.initials: R
authors.lastname: Kuick
authors.forename: Isabella
authors.initials: I
authors.lastname: Finco
authors.forename: Natacha
authors.initials: N
authors.lastname: Bohin
authors.forename: Steven M
authors.initials: SM
authors.lastname: Hrycaj
authors.forename: Deneen M
authors.initials: DM
authors.lastname: Wellik
authors.forename: Gary D
authors.initials: GD
authors.lastname: Hammer
mesh_terms: D000302:Adrenal Cortex / Q000378:metabolism*; D000305:Adrenal Cortex Hormones / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000378:metabolism; D016326:Extracellular Matrix Proteins; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005938:Glucocorticoids / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D057809:HEK293 Cells; D053823:Hedgehog Proteins / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D016296:Mutagenesis; D020411:Oligonucleotide Array Sequence Analysis; D000072260:RNA Splicing Factors; D013256:Steroids / Q000378:metabolism*; D013347:Subcellular Fractions; D014157:Transcription Factors / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D000305:Adrenal Cortex Hormones; C448780:Ccdc80 protein, mouse; D004268:DNA-Binding Proteins; D016326:Extracellular Matrix Proteins; D005938:Glucocorticoids; D006023:Glycoproteins; D053823:Hedgehog Proteins; D036341:Intercellular Signaling Peptides and Proteins; D000072260:RNA Splicing Factors; C107467:SF1 protein, human; C491514:Sf1 protein, mouse; C465570:Shh protein, mouse; D013256:Steroids; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin