Compared to the previously described TTD compound heterozygotes for the Arg722Trp change, Patient TTD24PV's cells show similar level of TFIIH but increased repair activity, suggesting that even low amounts of normal XPD subunits are able to partially rescue the functionality of TFIIH complexes.
Our results suggested a link between TTD- but not XP-associated XPD mutations, placental maldevelopment and risk of pregnancy complications, possibly due to impairment of TFIIH-mediated functions in placenta.
Overexpression of the XPB-A355C (TTD) gene in an XP/CS cell gives rise to a cellular phenotype of increased repair similar to that of TTD6VI cells, while equal expression of the two mutated genes leads to an intermediate cellular phenotype between XP/CS and TTD.
XPB and XPD genetic defects can also cause premature aging with profound neurological defects without increased cancers: Cockayne syndrome (CS) and trichothiodystrophy (TTD).
To understand the relationship between deficient NER and tumor susceptibility, we used a mouse model for TTD that mimics an XPD point mutation of a TTD patient in the mouse germline.
Thus, mutations in TFIIH components may, on top of a repair defect, also cause transcriptional insufficiency, which may explain part of the non-XP clinical features of TTD.
Persistence of repair proteins at unrepaired DNA damage distinguishes diseases with ERCC2 (XPD) mutations: cancer-prone xeroderma pigmentosum vs. non-cancer-prone trichothiodystrophy.
Our cases confirm the severe phenotype associated with the p.Arg722Trp mutation and expand the known genetic mutations associated with trichothiodystrophy by demonstrating a novel pathogenic mutation in ERCC2.
Most trichothiodystrophy (TTD) patients present mutations in the xeroderma pigmentosum D (XPD) gene, coding for a subunit of the transcription/repair factor IIH (TFIIH) complex involved in nucleotide excision repair (NER) and transcription.
Patients with the rare neurodevelopmental repair syndrome known as group A trichothiodystrophy (TTD-A) carry mutations in the gene encoding the p8 subunit of the transcription and DNA repair factor TFIIH.
The genetic disorder trichothiodystrophy (which is not cancer-prone) can also result from mutations in the ERCC2 gene, some of which are the same as those found in XP-D.
Trichothiodystrophy group A (TTD-A) is one of the three types of photosensitive TTD and is a very rare genodermatosis with deficient post-ultraviolet (UV) DNA repair.
No major modifications of the ERCC-2 gene were detected with two cDNA probes in either XP-D or TTD patients indicating that the association between TTD and XP-D is not likely to result from a large deletion or rearrangement involving this gene.
We report a case of a combined immunodeficiency (CID) in a child affected by trichothiodystrophy (TTD) characterized by an altered response to ultraviolet (UV) light due to a defect in the XPD gene.
Trichothiodystrophy is a rare condition associated with autosomal recessive or X-linked dominant variants in the ERCC2, ERCC3, GTF2H5, MPLKIP, RNF113A or GTF2E2 genes.
Two individuals with features of both xeroderma pigmentosum and trichothiodystrophy highlight the complexity of the clinical outcomes of mutations in the XPD gene.
In conclusion, the expression of the XPD/ERCC2 repair gene completely corrected UV hypersensitivity and almost all types of mutations of TTD group D cells, whereas hypermutagenesis was partially corrected.