Different regulation of limb development by p63 transcript variants.
The apical ectodermal ridge (AER), located at the distal end of each limb bud, is a key signaling center which controls outgrowth and patterning of the proximal-distal axis of the limb through secretion of various molecules. Fibroblast growth factors (FGFs), particularly Fgf8 and Fgf4, are representative molecules produced by AER cells, and essential to maintain the AER and cell proliferation in the underlying mesenchyme, meanwhile Jag2-Notch pathway negatively regulates the AER and limb development. p63, a transcription factor of the p53 family, is expressed in the AER and indispensable for limb formation. However, the underlying mechanisms and specific roles of p63 variants are unknown. Here, we quantified the expression of p63 variants in mouse limbs from embryonic day (E) 10.5 to E12.5, and found that ΔNp63γ was strongly expressed in limbs at all stages, while TAp63γ expression was rapidly increased in the later stages. Fluorescence-activated cell sorting analysis of limb bud cells from reporter mouse embryos at E11.5 revealed that all variants were abundantly expressed in AER cells, and their expression was very low in mesenchymal cells. We then generated AER-specific p63 knockout mice by mating mice with a null and a flox allele of p63, and Msx2-Cre mice (Msx2-Cre;p63Δ/fl). Msx2-Cre;p63Δ/fl neonates showed limb malformation that was more obvious in distal elements. Expression of various AER-related genes was decreased in Msx2-Cre;p63Δ/fl limb buds and embryoid bodies formed by p63-knockdown induced pluripotent stem cells. Promoter analyses and chromatin immunoprecipitation assays demonstrated Fgf8 and Fgf4 as transcriptional targets of ΔNp63γ, and Jag2 as that of TAp63γ. Furthermore, TAp63γ overexpression exacerbated the phenotype of Msx2-Cre;p63Δ/fl mice. These data indicate that ΔNp63 and TAp63 control limb development through transcriptional regulation of different target molecules with different roles in the AER. Our findings contribute to further understanding of the molecular network of limb development.
Sensory & Motor System Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
Manabu
M
Kawata
Sensory & Motor System Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
Yuki
Y
Taniguchi
Sensory & Motor System Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.|Bone and Cartilage Regenerative Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
Daisuke
D
Mori
Bone and Cartilage Regenerative Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.|Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
Fumiko
F
Yano
Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
Shinsuke
S
Ohba
Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
Ung-Il
UI
Chung
Shimogori Research Unit, RIKEN Brain Science Institute. 2-1 Hirosawa, Wako, Saitama, Japan.
Tomomi
T
Shimogori
Cold Spring Harbor Laboratory. Cold Spring Harbor, New York, United States of America.
Alea A
AA
Mills
Sensory & Motor System Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
Sakae
S
Tanaka
Sensory & Motor System Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.|Bone and Cartilage Regenerative Medicine, Faculty of Medicine, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
Taku
http://orcid.org/0000-0003-4911-3930
T
Saito
D000818:Animals; D000831:Animals, Newborn; D051519:Fibroblast Growth Factor 4 / Q000502:physiology; D051524:Fibroblast Growth Factor 8 / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D018878:Limb Buds / Q000254:growth & development* / Q000502:physiology; D051379:Mice / Q000196:embryology; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*
C496446:Fgf4 protein, mouse; C496457:Fgf8 protein, mouse; D051519:Fibroblast Growth Factor 4; D010750:Phosphoproteins; D015534:Trans-Activators; C486419:Trp63 protein, mouse; D051524:Fibroblast Growth Factor 8