DLX5, FGF8 and the Pin1 isomerase control ΔNp63α protein stability during limb development: a regulatory loop at the basis of the SHFM and EEC congenital malformations

Abstract

Ectrodactyly, or Split-Hand/Foot Malformation (SHFM), is a congenital condition characterized by the loss of central rays of hands and feet. The p63 and the DLX5;DLX6 transcription factors, expressed in the embryonic limb buds and ectoderm, are disease genes for these conditions. Mutations of p63 also cause the ectodermal dysplasia–ectrodactyly–cleft lip/palate (EEC) syndrome, comprising SHFM. Ectrodactyly is linked to defects of the apical ectodermal ridge (AER) of the developing limb buds. FGF8 is the key signaling molecule in this process, able to direct proximo-distal growth and patterning of the skeletal primordial of the limbs. In the limb buds of both p63 and Dlx5;Dlx6 murine models of SHFM, the AER is poorly stratified and FGF8 expression is severely reduced. We show here that the FGF8 locus is a downstream target of DLX5 and that FGF8 counteracts Pin1–ΔNp63α interaction. In vivo, lack of Pin1 leads to accumulation of the p63 protein in the embryonic limbs and ectoderm. We show also that ΔNp63α protein stability is negatively regulated by the interaction with the prolyl-isomerase Pin1, via proteasome-mediated degradation; p63 mutant proteins associated with SHFM or EEC syndromes are resistant to Pin1 action. Thus, DLX5, p63, Pin1 and FGF8 participate to the same time- and location-restricted regulatory loop essential for AER stratification, hence for normal patterning and skeletal morphogenesis of the limb buds. These results shed new light on the molecular mechanisms at the basis of the SHFM and EEC limb malformations.

ΔNp63/DGCR8-Dependent MicroRNAs Mediate Therapeutic Efficacy of HDAC Inhibitors in Cancer

“…Therefore, we focused on E3 ubiquitin ligases reported to target ΔNp63: Fbw7 (Galli et al, 2010; Restelli et al, 2014), Itch (Rossi et al, 2006a; Rossi et al, 2006b), HDM2 (Galli et al, 2010), Pirh2 (Jung et al, 2013; Yan et al, 2013), and WWP1 (Li et al, 2008). Colo16 cells were transfected with siRNAs against each of these factors individually and treated with the HDACi, JNJ-26481585, or the vehicle alone, DMSO.…”

The p53 family orchestrates the regulation of metabolism: physiological regulation and implications for cancer therapy

“…Intriguingly, their tumour suppressive activities are associated with the ability of these proteins to control lipid and glucose metabolism and mitochondrial function, respectively (Rufini et al , 2012; Su et al , 2012). On the other hand, Δ Np63 and Δ Np73 knockout mice have developmental defects in the epidermis and limbs, and in the nervous system, respectively (Wilhelm et al , 2010; Chakravarti et al , 2014; Restelli et al , 2014). Both proteins act as dominant negative by binding to the other members of the family and inhibiting their functions.…”

Genetic regulatory pathways of split‐hand/foot malformation

“…This is supported by the SHFM observed in Dlx2/5 −/− mice (Figure ) . The split hindlimbs in Dlx5/6 −/− mice are the result of a cell‐autonomous failure of the central AER to regulate p63 and to maintain and express morphogenetic signals (Figure ) . The degeneration of the AER in Dlx5/6 −/− mice led to SHFM phenotype which is similar to the phenotype of Dactylaplasia mice .…”