Trichothiodystrophy, a transcription syndrome

摘要: Trichothiodystrophy (TTD) is a rare genetic disorder characterized by hair dysplasia and associated with numerous symptoms affecting mainly organs derived from the neuroectoderm. About half of TTD patients exhibit photosensitivity because their nucleotide-excision repair pathway (NER) does not remove UV-induced DNA lesions efficiently. However, they do present skin cancer susceptibility expected such an NER disorder. Their deficiencies result phenotype-specific mutations in either XPB or XPD. These genes encode helicase subunits TFIIH, factor that also required for transcription class II genes. Thus, time- tissue-specific impairments might explain developmental neurological TTD. In third group photosensitive patients, TTD-A, no mutation has been identified, although TFIIH amount reduced.