Mutations in the interferon regulatory factor 6 gene (IRF6) cause either popliteal pterygium syndrome (PPS) or Van der Woude syndrome (VWS), allelic autosomal dominant orofacial clefting conditions. To further investigate the IRF6 mutation profile in PPS, we performed mutation analysis of patients from two unrelated Japanese families with PPS and identified mutations in IRF6: c.251G>T (R84L) and c.1271C>T (S424L). We also found R84L, which together with previous reports on R84 mutations, provided another line of evidence that both syndromes could result from the same mutation probably under an influence of a modifier gene(s). This supports the idea that the R84 residue in the DNA binding domain of IRF6 is a mutational hot spot for PPS. A luciferase assay of the S424L protein in the other family demonstrated that the mutation decreased the IRF6 transcriptional activity significantly to 6% of that of the wild-type. This finding suggests that the C-terminus region of IRF6 could have an important function in phosphorylation or protein interaction. To our knowledge, this is the first report of mutations observed in Japanese PPS patients.
A high dose of ionizing external radiation damage to the skin and soft tissue results in changes in function as well as in the general body condition. Once radiation surpasses the tissue safety or survival level, progressive alteration in the damaged tissue results in tissue loss and then flap loss. Local expression and action of stem cells or local growth factors in the irradiated tissue is mitigated, and external administration is sought to investigate the possibility of skin and soft tissue survival after an elevating flap. Basic fibroblast growth factor (bFGF) is primarily considered as a potent angiogenic growth factor. In burns, resurfacing with a dermal component is required, and bFGF stimulates wound healing and enhances human skin-derived mesenchymal stem cells under serum-free conditions in a dose-dependent manner. Thirty-five male, 4- to 8-week-old CLAWN miniature pigs received radiation exposure to assess the effectiveness of bFGF in terms of the progressive clinical course relevant to human skin and soft tissue. At 2 weeks following 10-Gy irradiation, tissue was preserved in the group receiving subcutaneous placement of a round-type tissue expander and bFGF. The expander plus bFGF group demonstrated significantly greater dermo-epidermal proliferation than the radiation alone, radiation plus bFGF, or expander plus radiation plus vehicle-solution groups, and new blood vessel formation was significantly increased in the expander tissue with bFGF after irradiation (p < 0.01). Electron microscopy revealed that tissue with expander and bFGF maintained more stable skin adnexae with preserved intact epidermis and dermis. Thus, bFGF improved and maintained the tissue viability after immediate irradiation in the skin and soft tissue.
Our results suggest that the 8q24.21 locus is not associated with susceptibility to NSCL±P in Japanese patients and provide further evidence that ethnicity is a strong factor in determining susceptibility loci, albeit using a limited number of samples. Further studies are needed to identify regions involved in the development of NSCL±P in the Japanese population.
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