Ribosomal Dysfunction Is a Common Pathomechanism in Different Forms of Trichothiodystrophy.

Mutations in a broad variety of genes can provoke the severe childhood disorder trichothiodystrophy (TTD) that is classified as a DNA repair disease or a transcription syndrome of RNA polymerase II. In an attempt to identify the common underlying pathomechanism of TTD we performed a knockout/knockdown of the two unrelated TTD factors TTDN1 and RNF113A and investigated the consequences on ribosomal biogenesis and performance. Interestingly, interference with these TTD factors created a nearly uniform impact on RNA polymerase I transcription with downregulation of UBF, disturbed rRNA processing and reduction of the backbone of the small ribosomal subunit rRNA 18S.

TFIIH mutations can impact on translational fidelity of the ribosome.

TFIIH is a complex essential for transcription of protein-coding genes by RNA polymerase II, DNA repair of UV-lesions and transcription of rRNA by RNA polymerase I. Mutations in TFIIH cause the cancer prone DNA-repair disorder xeroderma pigmentosum (XP) and the developmental and premature aging disorders trichothiodystrophy (TTD) and Cockayne syndrome. A total of 50% of the TTD cases are caused by TFIIH mutations.

TFIIH stabilization recovers the DNA repair and transcription dysfunctions in thermo-sensitive trichothiodystrophy.

Trichothiodystrophy (TTD) is a rare hereditary disease whose prominent feature is brittle hair. Additional clinical signs are physical and neurodevelopmental abnormalities and in about half of the cases hypersensitivity to UV radiation. The photosensitive form of TTD (PS-TTD) is most commonly caused by mutations in the ERCC2/XPD gene encoding a subunit of the transcription/DNA repair complex TFIIH.

Cockayne syndrome group A and ferrochelatase finely tune ribosomal gene transcription and its response to UV irradiation.

CSA and CSB proteins are key players in transcription-coupled nucleotide excision repair (TC-NER) pathway that removes UV-induced DNA lesions from the transcribed strands of expressed genes. Additionally, CS proteins play relevant but still elusive roles in other cellular pathways whose alteration may explain neurodegeneration and progeroid features in Cockayne syndrome (CS). Here we identify a CS-containing chromatin-associated protein complex that modulates rRNA transcription.

Reduced levels of prostaglandin I synthase: a distinctive feature of the cancer-free trichothiodystrophy.

The cancer-free photosensitive trichothiodystrophy (PS-TTD) and the cancer-prone xeroderma pigmentosum (XP) are rare monogenic disorders that can arise from mutations in the same genes, namely or Both XPD and XPB proteins belong to the 10-subunit complex transcription factor IIH (TFIIH) that plays a key role in transcription and nucleotide excision repair, the DNA repair pathway devoted to the removal of ultraviolet-induced DNA lesions. Compelling evidence suggests that mutations affecting the DNA repair activity of TFIIH are responsible for the pathological features of XP, whereas those also impairing transcription give rise to TTD. By adopting a relatives-based whole transcriptome sequencing approach followed by specific gene expression profiling in primary fibroblasts from a large cohort of TTD or XP cases with mutations in gene, we identify the expression alterations specific for TTD primary dermal fibroblasts.

Protein instability associated with AARS1 and MARS1 mutations causes trichothiodystrophy.

Trichothiodystrophy (TTD) is a rare hereditary neurodevelopmental disorder defined by sulfur-deficient brittle hair and nails and scaly skin, but with otherwise remarkably variable clinical features. The photosensitive TTD (PS-TTD) forms exhibits in addition to progressive neuropathy and other features of segmental accelerated aging and is associated with impaired genome maintenance and transcription. New factors involved in various steps of gene expression have been identified for the different non-photosensitive forms of TTD (NPS-TTD), which do not appear to show features of premature aging.

Expansion of the clinical and molecular spectrum of an XPD-related disorder linked to biallelic mutations in ERCC2 gene.

Bi-allelic inactivation of XPD protein, a nucleotide excision repair (NER) signaling pathway component encoded by ERCC2 gene, has been associated with several defective DNA repair phenotypes, including xeroderma pigmentosum, photosensitive trichothiodystrophy, and cerebro-oculo-facio-skeletal syndrome. We report a pediatric patient harboring two compound heterozygous variants in ERCC2 gene, c.361-1G>A and c.

Bi-allelic TARS Mutations Are Associated with Brittle Hair Phenotype.

Brittle and "tiger-tail" hair is the diagnostic hallmark of trichothiodystrophy (TTD), a rare recessive disease associated with a wide spectrum of clinical features including ichthyosis, intellectual disability, decreased fertility, and short stature. As a result of premature abrogation of terminal differentiation, the hair is brittle and fragile and contains reduced cysteine content. Hypersensitivity to UV light is found in about half of individuals with TTD; all of these individuals harbor bi-allelic mutations in components of the basal transcription factor TFIIH, and these mutations lead to impaired nucleotide excision repair and basal transcription.

Heterogeneity and overlaps in nucleotide excision repair disorders.

Nucleotide excision repair (NER) is an essential DNA repair pathway devoted to the removal of bulky lesions such as photoproducts induced by the ultraviolet (UV) component of solar radiation. Deficiencies in NER typically result in a group of heterogeneous distinct disorders ranging from the mild UV sensitive syndrome to the cancer-prone xeroderma pigmentosum and the neurodevelopmental/progeroid conditions trichothiodystrophy, Cockayne syndrome and cerebro-oculo-facio-skeletal-syndrome. A complicated genetic scenario underlines these disorders with the same gene linked to different clinical entities as well as different genes associated with the same disease.

Epigenetic Regulation of Skin Cells in Natural Aging and Premature Aging Diseases.

Skin undergoes continuous renewal throughout an individual's lifetime relying on stem cell functionality. However, a decline of the skin regenerative potential occurs with age. The accumulation of senescent cells over time probably reduces tissue regeneration and contributes to skin aging.

Cockayne Syndrome Type A Protein Protects Primary Human Keratinocytes from Senescence.

Defects in Cockayne syndrome type A (CSA), a gene involved in nucleotide excision repair, cause an autosomal recessive syndrome characterized by growth failure, progressive neurological dysfunction, premature aging, and skin photosensitivity and atrophy. Beyond its role in DNA repair, the CSA protein has additional functions in transcription and oxidative stress response, which are not yet fully elucidated. Here, we investigated the role of CSA protein in primary human keratinocyte senescence.

From Structure to Phenotype: Impact of Collagen Alterations on Human Health.

The extracellular matrix (ECM) is a highly dynamic and heterogeneous structure that plays multiple roles in living organisms. Its integrity and homeostasis are crucial for normal tissue development and organ physiology. Loss or alteration of ECM components turns towards a disease outcome.

Functional and clinical relevance of novel mutations in a large cohort of patients with Cockayne syndrome.

Background: Cockayne syndrome (CS) is a rare, autosomal recessive multisystem disorder characterised by prenatal or postnatal growth failure, progressive neurological dysfunction, ocular and skeletal abnormalities and premature ageing. About half of the patients with symptoms diagnostic for CS show cutaneous photosensitivity and an abnormal cellular response to UV light due to mutations in either the / or / gene. Studies performed thus far have failed to delineate clear genotype-phenotype relationships.

Digital PCR identifies changes in CDH1 (E-cadherin) transcription pattern in intestinal-type gastric cancer.

E-cadherin is a cell-cell adhesion protein encoded by CDH1 tumor-suppressor gene. CDH1 inactivating mutations, leading to loss of protein expression, are common in gastric cancer of the diffuse histotype, while alternative mechanisms modulating E-cadherin expression characterize the more common intestinal histotype. These mechanisms are still poorly understood.

Overexpression of parkin rescues the defective mitochondrial phenotype and the increased apoptosis of Cockayne Syndrome A cells.

The ERCC8/CSA gene encodes a WD-40 repeat protein (CSA) that is part of a E3-ubiquitin ligase/COP9 signalosome complex. When mutated, CSA causes the Cockayne Syndrome group A (CS-A), a rare recessive progeroid disorder characterized by sun sensitivity and neurodevelopmental abnormalities. CS-A cells features include ROS hyperproduction, accumulation of oxidative genome damage, mitochondrial dysfunction and increased apoptosis that may contribute to the neurodegenerative process.

GTF2E2 Mutations Destabilize the General Transcription Factor Complex TFIIE in Individuals with DNA Repair-Proficient Trichothiodystrophy.

The general transcription factor IIE (TFIIE) is essential for transcription initiation by RNA polymerase II (RNA pol II) via direct interaction with the basal transcription/DNA repair factor IIH (TFIIH). TFIIH harbors mutations in two rare genetic disorders, the cancer-prone xeroderma pigmentosum (XP) and the cancer-free, multisystem developmental disorder trichothiodystrophy (TTD). The phenotypic complexity resulting from mutations affecting TFIIH has been attributed to the nucleotide excision repair (NER) defect as well as to impaired transcription.

Studies on the ATP Binding Site of Fyn Kinase for the Identification of New Inhibitors and Their Evaluation as Potential Agents against Tauopathies and Tumors.

Fyn is a member of the Src-family of nonreceptor protein-tyrosine kinases. Its abnormal activity has been shown to be related to various human cancers as well as to severe pathologies, such as Alzheimer's and Parkinson's diseases. Herein, a structure-based drug design protocol was employed aimed at identifying novel Fyn inhibitors.

Reference genes for gene expression analysis in proliferating and differentiating human keratinocytes.

Abnormalities in keratinocyte growth and differentiation have a pathogenic significance in many skin disorders and result in gene expression alterations detectable by quantitative real-time RT-PCR (qRT-PCR). Relative quantification based on endogenous control (EC) genes is the commonly adopted approach, and the use of multiple reference genes from independent pathways is considered a best practice guideline, unless fully validated EC genes are available. The literature on optimal reference genes during in vitro calcium-induced differentiation of normal human epidermal keratinocytes (NHEK) is inconsistent.

TFIIH-dependent MMP-1 overexpression in trichothiodystrophy leads to extracellular matrix alterations in patient skin.

Mutations in the XPD subunit of the DNA repair/transcription factor TFIIH result in distinct clinical entities, including the cancer-prone xeroderma pigmentosum (XP) and the multisystem disorder trichothiodystrophy (TTD), which share only cutaneous photosensitivity. Gene-expression profiles of primary dermal fibroblasts revealed overexpression of matrix metalloproteinase 1 (MMP-1), the gene encoding the metalloproteinase that degrades the interstitial collagens of the extracellular matrix (ECM), in TTD patients mutated in XPD compared with their healthy parents. The defect is observed in TTD and not in XP and is specific for fibroblasts, which are the main producers of dermal ECM.

From laboratory tests to functional characterisation of Cockayne syndrome.

The significant progress made over the last few years on the pathogenesis of Cockayne syndrome (CS) greatly improved our knowledge on several aspects crucial for development and ageing, demonstrating that this disorder, even if rare, represents a valuable tool to clarify key aspects of human health. Primary cells from patients have been instrumental to elucidate the multiple roles of CS proteins and to approach the dissection of the complex interplay between repair and transcription that is central to the CS clinical phenotype. Here we discuss the results of the cellular assays applied for confirmation of the clinical diagnosis as well as the results of genetic and molecular studies in DNA repair defective patients.

XPD mutations in trichothiodystrophy hamper collagen VI expression and reveal a role of TFIIH in transcription derepression.

Mutations in the XPD subunit of the transcription/DNA repair factor (TFIIH) give rise to trichothiodystrophy (TTD), a rare hereditary multisystem disorder with skin abnormalities. Here, we show that TTD primary dermal fibroblasts contain low amounts of collagen type VI alpha1 subunit (COL6A1), a fundamental component of soft connective tissues. We demonstrate that COL6A1 expression is downregulated by the sterol regulatory element-binding protein-1 (SREBP-1) whose removal from the promoter is a key step in COL6A1 transcription upregulation in response to cell confluence.

A UV-sensitive syndrome patient with a specific CSA mutation reveals separable roles for CSA in response to UV and oxidative DNA damage.

UV-sensitive syndrome (UV(S)S) is a recently-identified autosomal recessive disorder characterized by mild cutaneous symptoms and defective transcription-coupled repair (TC-NER), the subpathway of nucleotide excision repair (NER) that rapidly removes damage that can block progression of the transcription machinery in actively-transcribed regions of DNA. Cockayne syndrome (CS) is another genetic disorder with sun sensitivity and defective TC-NER, caused by mutations in the CSA or CSB genes. The clinical hallmarks of CS include neurological/developmental abnormalities and premature aging.

Genotype-phenotype relationships in trichothiodystrophy patients with novel splicing mutations in the XPD gene.

Trichothiodystrophy (TTD) is a rare, autosomal recessive neurodevelopmental disorder most commonly caused by mutations in ERCC2 (XPD), a gene that encodes a subunit of the transcription/repair factor IIH (TFIIH). Here, we describe two TTD cases in which detailed biochemical and molecular investigations offered a clue to explain their moderately affected phenotype. Patient TTD22PV showed new mutated XPD alleles: one contains a nonsense mutation (c.

In vivo destabilization and functional defects of the xeroderma pigmentosum C protein caused by a pathogenic missense mutation.

Xeroderma pigmentosum group C (XPC) protein plays an essential role in DNA damage recognition in mammalian global genome nucleotide excision repair (NER). Here, we analyze the functional basis of NER inactivation caused by a single amino acid substitution (Trp to Ser at position 690) in XPC, previously identified in the XPC patient XP13PV. The Trp690Ser change dramatically affects the in vivo stability of the XPC protein, thereby causing a significant reduction of its steady-state level in XP13PV fibroblasts.

Transfer of a human chromosomal vector from a hamster cell line to a mouse embryonic stem cell line.

Two transchromosomic mouse embryonic stem (ES) sublines (ESMClox1.5 and ESMClox2.1) containing a human minichromosome (MC) were established from a sample of hybrid colonies isolated in fusion experiments between a normal diploid mouse ES line and a Chinese hamster ovary line carrying the MC.