Ectodysplasin has a dual role in ectodermal organogenesis: inhibition of Bmp activity and induction of Shh expression.
Ectodermal organogenesis is regulated by inductive and reciprocal signalling cascades that involve multiple signal molecules in several conserved families. Ectodysplasin-A (Eda), a tumour necrosis factor-like signalling molecule, and its receptor Edar are required for the development of a number of ectodermal organs in vertebrates. In mice, lack of Eda leads to failure in primary hair placode formation and missing or abnormally shaped teeth, whereas mice overexpressing Eda are characterized by enlarged hair placodes and supernumerary teeth and mammary glands. Here, we report two signalling outcomes of the Eda pathway: suppression of bone morphogenetic protein (Bmp) activity and upregulation of sonic hedgehog (Shh) signalling. Recombinant Eda counteracted Bmp4 activity in developing teeth and, importantly, inhibition of BMP activity by exogenous noggin partially restored primary hair placode formation in Eda-deficient skin in vitro, indicating that suppression of Bmp activity was compromised in the absence of Eda. The downstream effects of the Eda pathway are likely to be mediated by transcription factor nuclear factor-kappaB (NF-kappaB), but the transcriptional targets of Edar have remained unknown. Using a quantitative approach, we show in cultured embryonic skin that Eda induced the expression of two Bmp inhibitors, Ccn2/Ctgf (CCN family protein 2/connective tissue growth factor) and follistatin. Moreover, our data indicate that Shh is a likely transcriptional target of Edar, but, unlike noggin, recombinant Shh was unable to rescue primary hair placode formation in Eda-deficient skin explants.
Pummila
Marja
M
Institute of Biotechnology, Developmental Biology Program, University of Helsinki, 00014 Helsinki, Finland.
Fliniaux
Ingrid
I
Jaatinen
Risto
R
James
Martyn J
MJ
Laurikkala
Johanna
J
Schneider
Pascal
P
Thesleff
Irma
I
Mikkola
Marja L
ML
D000818:Animals; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors*; D055513:Connective Tissue Growth Factor; D003433:Crosses, Genetic; D004475:Ectoderm / Q000378:metabolism*; D053331:Ectodysplasins / Q000235:genetics / Q000378:metabolism*; D053339:Edar Receptor / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D005260:Female; D038681:Follistatin / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D017874:Immediate-Early Proteins / Q000378:metabolism; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D009924:Organ Culture Techniques; D038081:Organogenesis; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; C526318:CCN2 protein, mouse; D053331:Ectodysplasins; D053339:Edar Receptor; D038681:Follistatin; D053823:Hedgehog Proteins; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D011994:Recombinant Proteins; D055513:Connective Tissue Growth Factor