RESUMEN
The homeodomain transcription factors play crucial roles in many developmental processes ranging from organization of the body plan to differentiation of individual tissues. The homeodomain protein Distal-less-3 (DLX3) has an essential role in epidermal stratification and development of ectodermal appendages, placenta and bones. A four-nucleotide deletion in the human DLX3 gene is etiologic for the human hereditary tricho-dento-osseous (TDO) ectodermal dysplasia, a dominant syndrome characterized by abnormalities in hair, nails, teeth, and bones. We have previously demonstrated that DLX3 gene expression induces degradation of ΔNp63α, a specific product of the TP63 gene, a master regulator of multi-layered epithelia. Here we show that the DLX3(TDO) mutant protein is unable to promote ΔNp63α protein degradation and impairs the expression of cell cycle regulatory proteins and skin differentiation markers. However, we found that in cell expressing equal amounts of mutant and wild-type DLX3, ΔNp63α protein level is efficiently regulated implying that genetic heterozygosity at the DLX3 locus protects TDO patients from developing severe p63-associated skin defects.
Asunto(s)
Genes Dominantes , Proteínas de Homeodominio/metabolismo , Factores de Transcripción/metabolismo , Proteínas Supresoras de Tumor/metabolismo , Anomalías Múltiples/genética , Biomarcadores/análisis , Proteínas de Ciclo Celular/genética , Diferenciación Celular/genética , Línea Celular , Células Cultivadas , Anomalías Craneofaciales , Hipoplasia del Esmalte Dental/genética , Hipoplasia del Esmalte Dental/metabolismo , Regulación hacia Abajo , Displasia Ectodérmica/genética , Femenino , Enfermedades del Cabello/genética , Enfermedades del Cabello/metabolismo , Proteínas de Homeodominio/genética , Humanos , Eliminación de Secuencia/genética , Piel/metabolismo , Factores de Transcripción/genéticaRESUMEN
p63 mutations have been associated with several human hereditary disorders characterized by ectodermal dysplasia such as EEC (ectrodactyly, ectodermal dysplasia, clefting) syndrome, ADULT (acro, dermato, ungual, lacrimal, tooth) syndrome and AEC (ankyloblepharon, ectodermal dysplasia, clefting) syndrome (also called Hay-Wells syndrome). The location and functional effects of the mutations that underlie these syndromes reveal a striking genotype-phenotype correlation. Unlike EEC and ADULT that result from missense mutations in the DNA-binding domain of p63, AEC is solely caused by missense mutations in the SAM domain of p63. In this paper we report a study on the TAp63alpha isoform, the first to be expressed during development of the embryonic epithelia, and on its naturally occurring Q540L mutant derived from an AEC patient. To assess the effects of the Q540L mutation, we generated stable cell lines expressing TAp63alpha wt, DeltaNp63alpha or the TAp63alpha-Q540L mutant protein and used them to systematically compare the cell growth regulatory activity of the mutant and wt p63 proteins and to generate, by microarray analysis, a comprehensive profile of differential gene expression. We found that the Q540L substitution impairs the transcriptional activity of TAp63alpha and causes misregulation of genes involved in the control of cell growth and epidermal differentiation.