Trichothiodystrophy: update on the sulfur-deficient brittle hair syndromes

Broken strands, broken minds: Exploring the nexus of DNA damage and neurodegeneration

Neurodegenerative disorders are primarily characterized by neuron loss progressively leading to cognitive decline and the manifestation of incurable and debilitating conditions, such as Alzheimer's, Parkinson's, and Huntington's diseases. Loss of genome maintenance causally contributes to age-related neurodegeneration, as exemplified by the premature appearance of neurodegenerative features in a growing family of human syndromes and mice harbouring inborn defects in DNA repair. Here, we discuss the relevance of persistent DNA damage, key DNA repair mechanisms and compromised genome integrity in age-related neurodegeneration highlighting the significance of investigating these connections to pave the way for the development of rationalized intervention strategies aimed at delaying the onset of neurodegenerative disorders and promoting healthy aging.

Effect of RNF113A deficiency on oxidative stress-induced NRF2 pathway

The ring finger protein 113A (RNF113A) serves as an E3 ubiquitin ligase and a subunit of the spliceosome. Mutations in the RNF113A gene are associated with X-linked trichothiodystrophy (TTD). However, the cellular roles of RNF113A remain largely unknown. In this study, we performed transcriptome profiling of RNF113A knockout (KO) HeLa cells using RNA sequencing and revealed the upregulation of NRF2 pathway-associated genes. Further analysis confirmed that the KO of RNF113A promotes nuclear localization of the NRF2 protein and elevates the mRNA levels of NRF2 target genes. RNF113A KO cells showed high levels of intracellular reactive oxygen species (ROS) and decreased resistance to cell death following H2O2 treatment. Additionally, RNF113A KO cells more sensitively formed stress granules (SGs) under arsenite-induced oxidative stress. Moreover, RNF113A KO cells exhibited a decrease in glutathione levels, which could be attributed to a reduction in GLUT1 expression levels, leading to decreased glucose uptake reactions and lower intracellular glucose levels. These alterations potentially caused a reduction in ROS scavenging activity. Taken together, our findings suggest that the loss of RNF113A promotes oxidative stress-mediated activation of the NRF2 pathway, providing novel insights into RNF113A-associated human diseases.

Algorithmic approach toward diagnosis of patients with congenital photosensitivity disorders and review of literature

The congenital photosensitivity disorders present as cutaneous signs and symptoms secondary to photosensitivity, extracutaneous manifestations, and a predisposition to malignancy. Diagnosis of these conditions mainly depend on clinical findings as the molecular analysis is not always feasible. A review of all the related articles collected after a thorough literature search using keywords, "congenital AND photosensitivity NOT acquired" and the individual diseases was done. A total of 264 articles were included in the review. An algorithm for diagnosis of the different congenital photosensitivity disorders based on the various clinical presentations has been proposed. An early suspicion and diagnosis of the different congenital photosensitivity disorders is the cornerstone behind prompt institution of prevention and treatment, and decreasing the associated morbidity.

Trichothiodystrophy

This case report describes an infant with frizzy, coarse, and fragile hair and low-set ears, blepharophimosis, and osteopenia.

Facial clues to the photosensitive trichothiodystrophy phenotype in childhood

Among genodermatoses, trichothiodystrophies (TTDs) are a rare genetically heterogeneous group of syndromic conditions, presenting with skin, hair, and nail abnormalities. An extra-cutaneous involvement (craniofacial district and neurodevelopment) can be also a part of the clinical picture. The presence of photosensitivity describes three forms of TTDs: MIM#601675 (TTD1), MIM#616390 (TTD2) and MIM#616395 (TTD3), that are caused by variants afflicting some components of the DNA Nucleotide Excision Repair (NER) complex and with more marked clinical consequences. In the present research, 24 frontal images of paediatric patients with photosensitive TTDs suitable for facial analysis through the next-generation phenotyping (NGP) technology were obtained from the medical literature. The pictures were compared to age and sex-matched to unaffected controls using 2 distinct deep-learning algorithms: DeepGestalt and GestaltMatcher (Face2Gene, FDNA Inc., USA). To give further support to the observed results, a careful clinical revision was undertaken for each facial feature in paediatric patients with TTD1 or TTD2 or TTD3. Interestingly, a distinctive facial phenotype emerged by the NGP analysis delineating a specific craniofacial dysmorphic spectrum. In addition, we tabulated every single detail within the observed cohort. The novelty of the present research includes the facial characterization in children with the photosensitive types of TTDs through the 2 different algorithms. This result can become additional criteria for early diagnosis, and for subsequent targeted molecular investigations as well as a possible tailored multidisciplinary personalized management.

Peripheral neuropathies associated with DNA repair disorders

Repair of genomic DNA is a fundamental housekeeping process that quietly maintains the health of our genomes. The consequences of a genetic defect affecting a component of this delicate mechanism are quite harmful, characterized by a cascade of premature aging that injures a variety of organs, including the nervous system. One part of the nervous system that is impaired in certain DNA repair disorders is the peripheral nerve. Chronic motor, sensory, and sensorimotor polyneuropathies have all been observed in affected individuals, with specific physiologies associated with different categories of DNA repair disorders. Cockayne syndrome has classically been linked to demyelinating polyneuropathies, whereas xeroderma pigmentosum has long been associated with axonal polyneuropathies. Three additional recessive DNA repair disorders are associated with neuropathies, including trichothiodystrophy, Werner syndrome, and ataxia-telangiectasia. Although plausible biological explanations exist for why the peripheral nerves are specifically vulnerable to impairments of DNA repair, specific mechanisms such as oxidative stress remain largely unexplored in this context, and bear further study. It is also unclear why different DNA repair disorders manifest with different types of neuropathy, and why neuropathy is not universally present in those diseases. Longitudinal physiological monitoring of these neuropathies with serial electrodiagnostic studies may provide valuable noninvasive outcome data in the context of future natural history studies, and thus the responses of these neuropathies may become sentinel outcome measures for future clinical trials of treatments currently in development such as adeno-associated virus gene replacement therapies.

Mechanical anisotropy of hair affected by genetic diseases highlights structural information related to differential crosslinking in keratins

Previous work with Atomic Force Microscope (AFM) nanoindentation, on longitudinal and cross-sections of the human hair fibre, allowed for the derivation of a model for the mechanical behaviour of human hair, called the Anisotropic Index. Expanding that research further, and by applying this model, the nanomechanical behaviour of hairs from patients with the disease Trichothiodystrophy (TTD) has been examined and structural insights, gained from combining the AFM results with Differential Scanning Calorimetry (DSC) experiments and tensile measurements, suggests that TTD-affected hairs have a relatively increased amount of Keratin Intermediate Filaments, contained in compartments of differing crosslinking extent. The associated calculations of axial and transverse Young's Moduli deliver values in good agreement with the measured fibre mechanics. Furthermore, comparing these findings with the results previously obtained from the study of hairs from patients with the disease Monilethrix, it is shown that the Anisotropic Index correlates well with the known deficiencies in both hair types obtained from such patients and allows for discerning between the Control hair and from those affected by the two diseases. AFM nanoindentation along and across the fibre axis and the Anisotropic Index thus appear to reveal structural details of hair not otherwise acquirable, whilst DSC may offer a quick and simple method for distinguishing between different severities of TTD.

Phosphorylation of XPD drives its mitotic role independently of its DNA repair and transcription functions

The helicase XPD is known as a key subunit of the DNA repair/transcription factor TFIIH. However, here, we report that XPD, independently to other TFIIH subunits, can localize with the motor kinesin Eg5 to mitotic spindles and the midbodies of human cells. The XPD/Eg5 partnership is promoted upon phosphorylation of Eg5/T926 by the kinase CDK1, and conversely, it is reduced once Eg5/S1033 is phosphorylated by NEK6, a mitotic kinase that also targets XPD at T425. The phosphorylation of XPD does not affect its DNA repair and transcription functions, but it is required for Eg5 localization, checkpoint activation, and chromosome segregation in mitosis. In XPD-mutated cells derived from a patient with xeroderma pigmentosum, the phosphomimetic form XPD/T425D or even the nonphosphorylatable form Eg5/S1033A specifically restores mitotic chromosome segregation errors. These results thus highlight the phospho-dependent mitotic function of XPD and reveal how mitotic defects might contribute to XPD-related disorders.

Molecular Interactions between Dietary Lipids and Bone Tissue during Aging

Age-related bone disorders such as osteoporosis or osteoarthritis are a major public health problem due to the functional disability for millions of people worldwide. Furthermore, fractures are associated with a higher degree of morbidity and mortality in the long term, which generates greater financial and health costs. As the world population becomes older, the incidence of this type of disease increases and this effect seems notably greater in those countries that present a more westernized lifestyle. Thus, increased efforts are directed toward reducing risks that need to focus not only on the prevention of bone diseases, but also on the treatment of persons already afflicted. Evidence is accumulating that dietary lipids play an important role in bone health which results relevant to develop effective interventions for prevent bone diseases or alterations, especially in the elderly segment of the population. This review focuses on evidence about the effects of dietary lipids on bone health and describes possible mechanisms to explain how lipids act on bone metabolism during aging. Little work, however, has been accomplished in humans, so this is a challenge for future research.

Successful treatment of trichothiodystrophy with dupilumab

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Novel ERCC2 variant in trichothiodystrophy infant: the first case report in China

BACKGROUND

Trichothiodystrophy (TTD) is a rare, autosomal recessive, multisystem disorder most commonly caused by variants in ERCC2.

CASE PRESENTATION

Here, we describe the first Chinese patient with a novel variant in ERCC2. A male infant, who was born to a healthy non-consanguineous couple, exhibited brittle hair, hair loss ichthyosis, eczema, retinal pigmentation and hypospadias. He carried a novel heterozygous ERCC2 variant. The maternal variant (c.2191-18_2213del) is a previous described genomic deletion that affects the splicing of intron 22. The paternal variant (c.1666-1G > A), that occurs in the splice site of intron 17 and likely alters ERCC2 gene function through aberrant splicing, has not been reported previously.

CONCLUSIONS

Our case reported a novel pathogenic variant in ERCC2, which expanded the known genetic variants associated with TTD.

Association of XPD Lys751Gln gene polymorphism with susceptibility and clinical outcome of colorectal cancer in Pakistani population: a case-control pharmacogenetic study

BACKGROUND

XPD Lys751Gln polymorphism may modulate inter-individual variation in repair capacity of DNA, which may enhance a person's susceptibility to develop colorectal cancer (CRC). The analysis of XPD Lys751Gln polymorphism may provide important information for identifying high-risk individuals and for selecting the most appropriate treatment for poor prognostic CRC patients.

OBJECTIVE

The overall objective was to find out the association of XPD Lys751Gln gene polymorphism with the risk of having a colorectal cancer and the ultimate clinical outcomes. In this study a total of 300 subjects (CRC and Controls), were genotyped for XPD Lys751Gln.

METHODS

Using PCR-RFLP methods, the association of XPD Lys751Gln gene polymorphism with the risk of having a colorectal cancer was studied. In addition to overall risk assessment, genotyping results were also investigated with respect to the lifestyle risk factors, patients treated with oxaliplatin-based chemotherapy and clinicopathological characteristics.

RESULTS

The overall correlation between the XPD Lys751Gln genetic variation and the CRC risk was observed to be significant with both the homozygous variant genotype Gln/Gln as well as heterozygous genotype Lys/Gln being associated with the increased risk of CRC. Additional stratified analyses revealed that XPD Lys751Gln variants remarkably increased risk of CRC in males and younger individuals (≤ 50 years), Naswar users (8.09-fold) and high intake of red meat.

CONCLUSIONS

Our findings suggest that the relationship between the XPD Lys751Gln variants and lifestyle factors modulates the risk for CRC in Pakistani population.

XPD/ERCC2 mutations interfere in cellular responses to oxidative stress

Nucleotide excision repair (NER) is a conserved, flexible mechanism responsible for the removal of bulky, helix-distorting DNA lesions, like ultraviolet damage or cisplatin adducts, but its role in the repair of lesions generated by oxidative stress is still not clear. The helicase XPD/ERCC2, one of the two helicases of the transcription complex IIH, together with XPB, participates both in NER and in RNA pol II-driven transcription. In this work, we investigated the responses of distinct XPD-mutated cell lines to the oxidative stress generated by photoactivated methylene blue (MB) and KBrO3 treatments. The studied cells are derived from patients with XPD mutations but expressing different clinical phenotypes, including xeroderma pigmentosum (XP), XP and Cockayne syndrome (XP-D/CS) and trichothiodystrophy (TTD). We show by different approaches that all XPD-mutated cell lines tested were sensitive to oxidative stress, with those from TTD patients being the most sensitive. Host cell reactivation (HCR) assays showed that XP-D/CS and TTD cells have severely impaired repair capacity of oxidised lesions in plasmid DNA, and alkaline comet assays demonstrated the induction of significantly higher amounts of DNA strand breaks after treatment with photoactivated MB in these cells compared to wild-type cells. All XPD-mutated cells presented strong S/G2 arrest and persistent γ-H2AX staining after photoactivated MB treatment. Taken together, these results indicate that XPD participates in the repair of lesions induced by the redox process, and that XPD mutations lead to differences in the response to oxidatively induced damage.

Nucleotide Excision Repair and Transcription-Associated Genome Instability

Transcription is a potential threat to genome integrity, and transcription-associated DNA damage must be repaired for proper messenger RNA (mRNA) synthesis and for cells to transmit their genome intact into progeny. For a wide range of structurally diverse DNA lesions, cells employ the highly conserved nucleotide excision repair (NER) pathway to restore their genome back to its native form. Recent evidence suggests that NER factors function, in addition to the canonical DNA repair mechanism, in processes that facilitate mRNA synthesis or shape the 3D chromatin architecture. Here, these findings are critically discussed and a working model that explains the puzzling clinical heterogeneity of NER syndromes highlighting the relevance of physiological, transcription-associated DNA damage to mammalian development and disease is proposed.

Bald thigh syndrome in sighthounds-Revisiting the cause of a well-known disease

Bald thigh syndrome is a common hair loss disorder in sighthounds. Numerous possible causes, including environmental conditions, trauma, stress, endocrinopathies and genetic components have been proposed, but only endocrinopathies have been ruled out scientifically. The overall goal of our study was to identify the cause of bald thigh syndrome and the pathological changes associated with it. We approached this aim by comparing skin biopsies and hair shafts of affected and control dogs microscopically as well as by applying high-throughput technologies such as genomics, transcriptomics and proteomics. While the histology is rather unspecific in most cases, trichogram analysis and scanning electron microscopy revealed severe structural abnormalities in hair shafts of affected dogs. This finding is supported by the results of the transcriptomic and proteomic profiling where genes and proteins important for differentiation of the inner root sheath and the assembly of a proper hair shaft were downregulated. Transcriptome profiling revealed a downregulation of genes encoding 23 hair shaft keratins and 51 keratin associated proteins, as well as desmosomal cadherins and several actors of the BMP signaling pathway which is important for hair shaft differentiation. The lower expression of keratin 71 and desmocollin 2 on the mRNA level in skin biopsies corresponded with a decreased protein expression in the hair shafts of affected dogs. The genetic analysis revealed a missense variant in the IGFBP5 gene homozygous in all available Greyhounds and other sighthounds. Further research is required to clarify whether the IGFBP5 variant represents a predisposing genetic risk factor. We conclude from our results that structural defects in the hair shafts are the cause for this well-known disease and these defects are associated with a downregulation of genes and proteins essential for hair shaft formation. Our data add important knowledge to further understand the molecular mechanisms of HF morphogenesis and alopecia in dogs.

A case of severe trichothiodystrophy 3 in a neonate due to mutation in the GTF2H5 gene: Clinical report

Trichothiodystrophy (TTD) is a group of predominantly autosomal recessive disorders characterized by sulfur-deficient brittle hair. Clinical features of TTD consist of variable neuroectodermal symptoms including ichthyosis, nail abnormalities, mental retardation, short stature, decreased fertility and proneness to infections. Approximately half of the reported patients with TTD have clinical and cellular photosensitivity associated with mutations in three subunits (ERCC3, ERCC2, GTF2H5) of the basal transcription factor TFHII, which is involved in transcription and nucleotide excision repair. We report on a case of a male neonate with a novel GTF2H5 gene mutation, detected by whole exome sequencing. The GTF2H5 gene's role is to provide stability to the entire TFHII complex. The reported patient was born at 33 weeks' gestation from a pregnancy complicated by intrauterine growth restriction and premature rupture of membranes. His main clinical problems included severe congenital ichthyosis and proneness to infections with episodes of multiorgan failure. The infant's history displays the most severe clinical manifestations among patients with GTF2H5 gene mutations that have so far been reported.

The Spectrum of Fundamental Basic Science Discoveries Contributing to Organismal Aging

Aging research has undergone unprecedented advances at an accelerating rate in recent years, leading to excitement in the field as well as opportunities for imagination and innovation. Novel insights indicate that, rather than resulting from a preprogrammed series of events, the aging process is predominantly driven by fundamental non-adaptive mechanisms that are interconnected, linked, and overlap. To varying degrees, these mechanisms also manifest with aging in bone where they cause skeletal fragility. Because these mechanisms of aging can be manipulated, it might be possible to slow, delay, or alleviate multiple age-related diseases and their complications by targeting conserved genetic signaling pathways, controlled functional networks, and basic biochemical processes. Indeed, findings in various mammalian species suggest that targeting fundamental aging mechanisms (eg, via either loss-of-function or gain-of-function mutations or administration of pharmacological therapies) can extend healthspan; ie, the healthy period of life free of chronic diseases. In this review, we summarize the evidence supporting the role of the spectrum of fundamental basic science discoveries contributing to organismal aging, with emphasis on mammalian studies and in particular aging mechanisms in bone that drive skeletal fragility. These mechanisms or aging hallmarks include: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. Because these mechanisms are linked, interventions that ameliorate one hallmark can in theory ameliorate others. In the field of bone and mineral research, current challenges include defining the relative contributions of each aging hallmark to the natural skeletal aging process, better understanding the complex interconnections among the hallmarks, and identifying the most effective therapeutic strategies to safely target multiple hallmarks. Based on their interconnections, it may be feasible to simultaneously interfere with several fundamental aging mechanisms to alleviate a wide spectrum of age-related chronic diseases, including osteoporosis. © 2018 American Society for Bone and Mineral Research.

Biomarkers of Cellular Senescence and Skin Aging

Cellular senescence is an irreversible growth arrest that occurs as a result of different damaging stimuli, including DNA damage, telomere shortening and dysfunction or oncogenic stress. Senescent cells exert a pleotropic effect on development, tissue aging and regeneration, inflammation, wound healing and tumor suppression. Strategies to remove senescent cells from aging tissues or preneoplastic lesions can delay tissue dysfunction and lead to increased healthspan. However, a significant hurdle in the aging field has been the identification of a universal biomarker that facilitates the unequivocal detection and quantification of senescent cell types in vitro and in vivo. Mammalian skin is the largest organ of the human body and consists of different cell types and compartments. Skin provides a physical barrier against harmful microbes, toxins, and protects us from ultraviolet radiation. Increasing evidence suggests that senescent cells accumulate in chronologically aged and photoaged skin; and may contribute to age-related skin changes and pathologies. Here, we highlight current biomarkers to detect senescent cells and review their utility in the context of skin aging. In particular, we discuss the efficacy of biomarkers to detect senescence within different skin compartments and cell types, and how they may contribute to myriad manifestations of skin aging and age-related skin pathologies.

Relevance of XPD polymorphisms to neuroblastoma risk in Chinese children: a four-center case-control study

Neuroblastoma is a lethal tumor that commonly occurs in children. Polymorphisms in XPD reportedly influence risk for several types of cancer, though their roles in neuroblastoma remain unclear. Here we endeavored to determine the relevance of XPD gene polymorphisms and neuroblastoma susceptibility in Chinese children genotyping three XPD polymorphisms (rs3810366, rs13181 and rs238406) in 505 cases and 1070 controls and assessing their contributions to neuroblastoma risk. Overall, we detected no significant association between any single XPD genotype and neuroblastoma risk. When risk genotypes were combined, however, we found that patients with 2-3 risk genotypes were more likely to develop neuroblastoma (adjusted odds ratio =1.31; 95% confidence interval =1.06-1.62, P=0.013) than those with 0-1 risk genotypes. Stratification analysis of rs3810366 revealed significant relationships between the subgroups age ≤18 months and clinical stage I+II+4s and neuroblastoma risk. Moreover, the presence of 2-3 risk genotypes was significantly associated with increased neuroblastoma risk in the subgroups age ≤18 months, male, tumor originated from others, and clinical stage I+II+4s. Our findings provide novel insight into the genetic underpinnings of neuroblastoma and demonstrate that XPD polymorphisms may have a cumulative effect on neuroblastoma risk.

XPD-The Lynchpin of NER: Molecule, Gene, Polymorphisms, and Role in Colorectal Carcinogenesis

In mammals the bulky DNA adduct lesions known to result in deleterious phenotypes are acted upon and removed from the genomic DNA by nucleotide excision repair (NER) pathway. TFIIH multi-protein complex with its important helicase–Xeroderma Pigmentosum Protein (XPD) serves as the pivotal factor for opening up of the damaged lesion DNA site and carry out the repair process. The initial damage verification step of the TFIIH is in part dependent upon the helicase activity of XPD. Besides, XPD is also actively involved in the initiation steps of transcription and in the regulation of the cell cycle and apoptosis. In this review, we will be exploring the new insights in scientific research on the functioning of the NER pathway, the role of TFIIH as the central complex of NER, the pivotal helicase XPD as the lynchpin of NER and the effects of various single nucleotide polymorphisms (SNPs) of XPD on its functioning and their consequent role in colorectal carcinogenesis.

Nuclear DNA Damage and Ageing

Although the links between defects in DNA repair and cancer are well established, an accumulating body of evidence suggests a series of functional links between genome maintenance pathways, lifespan regulation mechanisms and age-related diseases in mammals. Indeed, the growing number of DNA repair-deficient patients with progeria suggests that persistent DNA damage and genome caretakers are tightly linked to lifespan regulating circuits and age-related diseases. Here, we discuss the impact of irreparable DNA damage events in mammalian physiology highlighting the relevance of DNA repair factors in mammalian development and aging.

Do you know this syndrome? Ichthyosis associated with neurological condition and alteration of hairs

Trichothiodystrophy refers to a heterogeneous group of rare genetic diseases that affects neuroectodermal-derived tissues with multisystem involvement. The hallmark of these syndromes is the deficiency of sulfur in hair matrix proteins, leading to short and brittle hair. Few cases of this rare disorder have been published. The authors report a case of trichothiodystrophy in a male infant with ichthyosis, photosensitivity, spastic paraparesis, short stature, and neurologic and psychomotor retardation. Diagnosis was based on clinical and microscopic features of hair samples.

Trichothiodystrophy without Associated Neuroectodermal Features in Two Siblings

Trichothiodystrophy (TTD) is characterized by the common feature of sulfur-deficient brittle hair associated with a constellation of neuroectodermal symptoms. There is a wide phenotypic variation in the severity; ranging from isolated hair defect to multiple neuroectodermal symptoms such as photosensitivity, ichthyosis, intellectual impairment, decreased fertility, and short stature. This case report describes TTD in two sisters with only hair fragility and no other associated feature. This case highlights the variable clinical presentation of TTD and the need for regular follow-up in such patients for an early detection of any neurological, physical, and sexual impairment.

Hallmarks of progeroid syndromes: lessons from mice and reprogrammed cells

Ageing is a process that inevitably affects most living organisms and involves the accumulation of macromolecular damage, genomic instability and loss of heterochromatin. Together, these alterations lead to a decline in stem cell function and to a reduced capability to regenerate tissue. In recent years, several genetic pathways and biochemical mechanisms that contribute to physiological ageing have been described, but further research is needed to better characterize this complex biological process. Because premature ageing (progeroid) syndromes, including progeria, mimic many of the characteristics of human ageing, research into these conditions has proven to be very useful not only to identify the underlying causal mechanisms and identify treatments for these pathologies, but also for the study of physiological ageing. In this Review, we summarize the main cellular and animal models used in progeria research, with an emphasis on patient-derived induced pluripotent stem cell models, and define a series of molecular and cellular hallmarks that characterize progeroid syndromes and parallel physiological ageing. Finally, we describe the therapeutic strategies being investigated for the treatment of progeroid syndromes, and their main limitations.

Summary: This Review defines the molecular and cellular hallmarks of progeroid syndromes according to the main cellular and animal models, and discusses the therapeutic strategies developed to date.

Updated strategies for the management, pathogenesis and molecular genetics of different forms of ichthyosis syndromes with prominent hair abnormalities

Syndromic ichthyosis is rare inherited disorders of cornification with varied disease complications. This disorder appears in seventeen subtypes associated with severe systematic manifestations along with medical, cosmetic and social problems. Syndromic ichthyosis with prominent hair abnormalities covers five major subtypes: Netherton syndrome, trichothiodystrophy, ichthyosis hypotrichosis syndrome, ichthyosis hypotrichosis sclerosing cholangitis and ichthyosis follicularis atrichia photophobia syndrome. These syndromes mostly prevail in high consanguinity states, with distinctive clinical features. The known pathogenic molecules involved in ichthyosis syndromes with prominent hair abnormalities include SPINK5, ERCC2, ERCC3, GTF2H5, MPLKIP, ST14, CLDN1 and MBTPS2. Despite underlying genetic origin, most of the health professionals solely rely on phenotypic expression of these disorders that leads to improper management of patients, hence making these patients living an orphanage life. After dermal features, association of other systems such as nervous system, skeletal system, hair abnormalities or liver problems may sometimes give clues for diagnosis but still leaving place for molecular screening for efficient diagnosis. In this paper, we have presented a review of ichthyosis syndrome with prominent hair abnormalities, with special emphasis on their updated genetic consequences and disease management. Additionally, we aim to update health professionals about the practice of molecular screening in ichthyosis syndromes for appropriate diagnosis and treatment.

ERCC1-XPF cooperates with CTCF and cohesin to facilitate the developmental silencing of imprinted genes

Inborn defects in DNA repair are associated with complex developmental disorders whose causal mechanisms are poorly understood. Using an in vivo biotinylation tagging approach in mice, we show that the nucleotide excision repair (NER) structure-specific endonuclease ERCC1-XPF complex interacts with the insulator binding protein CTCF, the cohesin subunits SMC1A and SMC3 and with MBD2; the factors co-localize with ATRX at the promoters and control regions (ICRs) of imprinted genes during postnatal hepatic development. Loss of Ercc1 or exposure to MMC triggers the localization of CTCF to heterochromatin, the dissociation of the CTCF-cohesin complex and ATRX from promoters and ICRs, altered histone marks and the aberrant developmental expression of imprinted genes without altering DNA methylation. We propose that ERCC1-XPF cooperates with CTCF and cohesin to facilitate the developmental silencing of imprinted genes and that persistent DNA damage triggers chromatin changes that affect gene expression programs associated with NER disorders.

Potential therapeutic effects of the MTOR inhibitors for preventing ageing and progeria-related disorders

The mammalian target of rapamycin (mTOR) pathway is an highly conserved signal transduction axis involved in many cellular processes, such as cell growth, survival, transcription, translation, apoptosis, metabolism, motility and autophagy. Recently, this signalling pathway has come to the attention of the scientific community owing to the unexpected finding that inhibition of mTOR by rapamycin, an antibiotic with immunosuppressant and chemotherapeutic properties, extends lifespan in diverse animal models. Moreover, rapamycin has been reported to rescue the cellular phenotype in a progeroid syndrome [Hutchinson–Gilford Progeria syndrome (HGPS)] that recapitulates most of the traits of physiological ageing. The promising perspectives raised by these results warrant a better understanding of mTOR signalling and the potential applications of mTOR inhibitors to counteract ageing‐associated diseases and increase longevity. This review is focused on these issues.

DNA Repair Dysfunction and Neurodegeneration: Lessons From Rare Pediatric Disorders

Nucleotide excision repair disorders display a wide range of clinical syndromes and presentations, all associated at the molecular level by dysfunction of genes participating in the nucleotide excision repair pathway. Genotype-phenotype relationships are remarkably complex and not well understood. This article outlines neurodegenerative symptoms seen in nucleotide excision repair disorders and explores the role that nucleotide excision repair dysfunction can play in the pathogenesis of chronic neurodegenerative diseases.

Clinical and anthropological perspectives on chemical relaxing of afro-textured hair

The culturally engrained practice of 'relaxing' afro-textured hair has been linked with hair and scalp disorders. Herein, we discuss the evolution of human hair types, focusing in particular on afro-textured hair. We explore the biological features of this hair type, and discuss the different methods employed to straighten afro-textured hair, focusing in particular on chemical straightening. We also examine clinical, anthropological, and psychological issues associated with this latter practice. Examples of common scalp pathologies associated with chronic hair relaxing, such as alopecia, hair breakage, caustic burns and irritant contact dermatitis, are also highlighted. The data presented herein should enable clinicians to engage in culturally appropriate discussions with their patients about issues of appearance and conformity.

TFIIH subunit alterations causing xeroderma pigmentosum and trichothiodystrophy specifically disturb several steps during transcription

Mutations in genes encoding the ERCC3 (XPB), ERCC2 (XPD), and GTF2H5 (p8 or TTD-A) subunits of the transcription and DNA-repair factor TFIIH lead to three autosomal-recessive disorders: xeroderma pigmentosum (XP), XP associated with Cockayne syndrome (XP/CS), and trichothiodystrophy (TTD). Although these diseases were originally associated with defects in DNA repair, transcription deficiencies might be also implicated. By using retinoic acid receptor beta isoform 2 (RARB2) as a model in several cells bearing mutations in genes encoding TFIIH subunits, we observed that (1) the recruitment of the TFIIH complex was altered at the activated RARB2 promoter, (2) TFIIH participated in the recruitment of nucleotide excision repair (NER) factors during transcription in a manner different from that observed during NER, and (3) the different TFIIH variants disturbed transcription by having distinct consequences on post-translational modifications of histones, DNA-break induction, DNA demethylation, and gene-loop formation. The transition from heterochromatin to euchromatin was disrupted depending on the variant, illustrating the fact that TFIIH, by contributing to NER factor recruitment, orchestrates chromatin remodeling. The subtle transcriptional differences found between various TFIIH variants thus participate in the phenotypic variability observed among XP, XP/CS, and TTD individuals.

Growth and nutrition in children with trichothiodystrophy

OBJECTIVES

Trichothiodystrophy (TTD) is a rare autosomal recessive disorder of DNA repair and transcription. Patients have multisystem abnormalities, including alterations in growth and development. This report characterizes the growth and nutritional status of a cohort of children with TTD.

METHODS

Twenty-five patients with TTD were evaluated through a natural history study of patients with DNA repair diseases at the National Institutes of Health. Mean length of follow-up was 2.7 years. Retrospective and prospective data on nutritional status and height/weight were collected.

RESULTS

In general, patients with TTD had considerable abnormalities in growth, with a mean height-for-age z score of -2.75 and a mean weight-for-age z score of -2.60 at baseline clinical evaluation. The median weight-for-length at baseline was, however, 50th percentile and indicators of adequate nutrition such as serum albumin, hemoglobin, and vitamins D and B12 were largely within normal limits. Changes in growth parameters as children aged were characterized by further separation from standard growth curves (change height-for-age z score/year [-0.18 ± 0.42] and weight-for-age z score/year [-0.36 ± 0.51]). Patients who died during follow-up (n = 5) had significantly lower standardized height (P = 0.03) and weight (P = 0.006), weight-for-length (<0.0001), and higher heart rates (P = 0.02) compared with the remainder of the cohort.

CONCLUSIONS

Children with TTD have markedly diminished weight-for-age and height-for-age relative to reference populations. The cause for this stunted growth remains unclear but does not appear to be related to poor nutrient absorption or malnutrition.

Nucleotide excision repair/transcription gene defects in the fetus and impaired TFIIH-mediated function in transcription in placenta leading to preeclampsia

BACKGROUND

Preeclampsia is a significant cause of maternal and fetal mortality and morbidity worldwide. We previously reported associations between trichothiodystrophy (TTD) nucleotide excision repair (NER) and transcription gene mutations in the fetus and the risk of gestational complications including preeclampsia. TTD NER/transcription genes, XPD, XPB and TTD-A, code for subunits of Transcription Factor (TF)IIH. Interpreting XPD mutations in the context of available biochemical data led us to propose adverse effects on CDK-activating kinase (CAK) subunit of TFIIH and TFIIH-mediated functions as a relevant mechanism in preeclampsia. In order to gain deeper insight into the underlying biologic mechanisms involving TFIIH-mediated functions in placenta, we analyzed NER/transcription and global gene expression profiles of normal and preeclamptic placentas and studied gene regulatory networks.

RESULTS

We found high expression of TTD NER/transcription genes in normal human placenta, above the mean of their expression in all organs. XPD and XPB were consistently expressed from 14 to 40 weeks gestation while expression of TTD-A was strongly negatively correlated (r=-0.7, P<0.0001) with gestational age. Analysis of gene expression patterns of placentas from a case-control study of preeclampsia using Algorithm for Reconstruction of Accurate Cellular Networks (ARACNE) revealed GTF2E1, a component of TFIIE which modulates TFIIH, among major regulators of differentially-expressed genes in preeclampsia. The basal transcription pathway was among the largest dysregulated protein-protein interaction networks in this preeclampsia dataset. Within the basal transcription pathway, significantly down-regulated genes besides GTF2E1 included those coding for the CAK complex of TFIIH, namely CDK7, CCNH, and MNAT1. Analysis of other relevant gene expression and gene regulatory network data also underscored the involvement of transcription pathways and identified JUNB and JUND (components of transcription factor AP-1) as transcription regulators of the network involving the TTD genes, GTF2E1, and selected gene regulators implicated in preeclampsia.

CONCLUSIONS

Our results indicate that TTD NER/transcription genes are expressed in placenta during gestational periods critical to preeclampsia development. Our overall findings suggest that impairment of TFIIH-mediated function in transcription in placenta is a likely mechanism leading to preeclampsia and provide etiologic clues which may be translated into therapeutic and preventive measures.

Integrative transcriptome analysis reveals dysregulation of canonical cancer molecular pathways in placenta leading to preeclampsia

We previously suggested links between specific XPD mutations in the fetal genome and the risk of placental maldevelopment and preeclampsia, possibly due to impairment of Transcription Factor (TF)IIH-mediated functions in placenta. To identify the underlying mechanisms, we conducted the current integrative analysis of several relevant transcriptome data sources. Our meta-analysis revealed downregulation of TFIIH subunits in preeclamptic placentas. Our overall integrative analysis suggested that, in the presence of hypoxia and oxidative stress, EGFR signaling deficiency, which can be caused by TFIIH impairment as well as by other mechanisms, results in ATF3 upregulation, inducing mediators of clinical symptoms of preeclampsia such as FLT1 and ENG. EGFR- and ATF3-dependent pathways play prominent roles in cancer development. We propose that dysregulation of these canonical cancer molecular pathways occurs in preeclampsia and delineate the relevance of TFIIH, providing etiologic clues which could eventually translate into a therapeutic approach.

Further insights in trichothiodistrophy: a clinical, microscopic, and ultrastructural study of 20 cases and literature review

BACKGROUND

Trichothiodistrophy (TTD) is a rare autosomal recessive condition that is characterized by a specific congenital hair shaft dysplasia caused by deficiency of sulfur associated with a wide spectrum of multisystem abnormalities. In this article, we study clinical, microscopic, and ultrastructural findings of 20 patients with TTD with the aim to add further insights regarding to this rare condition. Additionally, analyses of our results are compared with those extracted from the literature in order to enhance its comprehensibility.

MATERIALS AND METHODS

TWENTY CASES OF TTD WERE INCLUDED: 7 from Mexico and 14 from Spain. Clinical, microscopic, scanning electron microscopy (SEM) studies and X-ray microanalysis (XrMa) were carried out in all of them. Genetic studies were performed in all seven Mexican cases. Patients with xeroderma pigmentosum and xeroderma pigmentosum/TTD-complex were excluded.

RESULTS

Cuticular changes and longitudinal crests of the hair shaft were demonstrated. These crests were irregular, disorganized, following the hair longest axis. Hair shaft sulfur deficiency was disposed discontinuously and intermittently rather than uniformly. This severe decrease of sulfur contents was located close to the trichoschisis areas. Only five patients did not show related disturbances. Micro-dolichocephaly was observed in five cases and represented the most frequent facial dysmorphism found. It is also remarkable that all patients with urologic malformations also combined diverse neurologic disorders. Moreover, three Mexican sisters demonstrated the coexistence of scarce pubic vellus hair, developmental delay, onychodystrophy, and maxillar/mandibullar hypoplasia.

CONCLUSIONS

TTD phenotype has greatly varied from very subtle forms to severe alterations such as neurologic abnormalities, blindness, lamellar ichthyosis and gonadal malformations. Herein, a multisystem study should be performed mandatorily in patients diagnosed with TTD.

Xeroderma Pigmentosum-Trichothiodystrophy overlap patient with novel XPD/ERCC2 mutation

Xeroderma Pigmentosum (XP), Trichothiodystrophy (TTD) and Cockayne Syndrome (CS) are rare, recessive disorders caused by mutational defects in the Nucleotide Excision Repair (NER) pathway and/or disruption of basic cellular DNA transcription. To date, a multitude of mutations in the XPD/ERCC2 gene have been described, many of which give rise to NER- and DNA transcription related diseases, which share certain diagnostic features and few overlap patients have been described. Despite increasing understanding of the roles of XPD/ERCC2 in mammalian cells, there is still weak predictability of somatic outcome from many of these mutations. We demonstrate a patient, believed to represent an overlap between XP and TTD/CS. In addition to other organ dysfunctions, the young man presented with Photosensitivity, Ichthyosis, Brittle hair, Impaired physical and mental development, Decreased fertility and Short stature (PIBIDS) suggestive of TTD, but lacking the almost patognomonic “tiger tail” banding of the hair under polarized light. Additionally, he developed basal cell carcinoma aged 28, as well as adult onset kidney failure, features normally not associated with TTD but rather XP/CS. His freckled appearance also suggested XP, but fibroblast cultures only demonstrated x2 UV-sensitivity with expected NER and TFIIH-activity decrease. Genetic sequencing of the XPD/ERCC2 gene established the patient as heterozygote compound with a novel, N-terminal Y18H mutation and a known C-terminal (TTD) mutation, A725P. The possible interplay between gene products and the patient phenotype is discussed.

Inherited ichthyoses/generalized Mendelian disorders of cornification

Inherited ichthyoses, defined as the generalized form of Mendelian disorders of cornification, are characterized by visible scaling and/or hyperkeratosis of most or all of the skin. This etiologically and phenotypically heterogenous group of conditions is caused by mutations in various different genes important for keratinocyte differentiation and epidermal barrier function. Diagnosing a specific entity is a particular challenge for the nonspecialist presented with the common clinical scaling. For the clinician, this review outlines an algorithmic approach for utilizing diagnostic clues to narrow down the differential diagnosis and to guide further testing and treatment options.

Photosensitivity disorders in children: part II

Photosensitivity disorders in children encompass a diverse group of diseases. Some inherited disorders manifest with photosensitivity early in life. Specific extracutaneous association may be the clue to diagnosis in this group of pediatric photodermatoses. Part II of this 2-part review covers hereditary photodermatoses caused by defects in nucleotide excision repair, double strand break repair, or localized or systemic biochemical abnormalities. Diagnosis and management of photoaggravated dermatoses are also discussed. Sun protection strategies are required in all patients with evidence of photosensitivity. Early recognition and prompt diagnosis is essential to minimize the long-term complications associated with inadequate photoprotection.

Effects of compound heterozygosity at the Xpd locus on cancer and ageing in mouse models

XPD is a helicase subunit of transcription factor IIH, an eleven-protein complex involved in a wide range of cellular activities including transcription and nucleotide excision DNA repair (NER). Mutations in NER genes including XPD can lead to a variety of overlapping syndromes with three general categories of symptoms in addition to sun (UV) sensitivity: severe skin cancer predisposition as in xeroderma pigmentosum (XP), segmental progeria as in trichothiodystrophy (TTD) and Cockayne syndrome (CS), and a combination of both as in XP/CS and XP/TTD. Genetic background and compound heterozygosity are two factors potentially complicating straightforward interpretations of genotype-phenotype relationship at the XPD locus. Previously we showed that the presence of two different mutant Xpd alleles in compound heterozygous mice could in principle contribute to disease heterogeneity through biallelic effects, including dominance of one mutant allele over another and interallelic complementation between mutant alleles, in a tissue-specific manner. Here we report on the interaction between different mutant alleles in compound heterozygous mice carrying one XP/CS-associated allele (Xpd(G602D)) and one TTD-associated allele (Xpd(R722W)) relative to homozygous controls in an isogenic background over a range of metabolic and UV-induced DNA damage-related phenotypes. We found complementation of metabolic phenotypes including body weight and insulin sensitivity, but none for any of the measured responses to UV irradiation. Instead, we found dominance of the partially functional TTD allele over the XPCS allele in most aspects of the response to UV irradiation including sunburn and skin cancer in vivo or cellular proliferation and DNA damage foci formation in vitro. These data support to a model of genotype-phenotype relationship at the XPD locus in which interactions between different recessive diseases alleles are a potent source of disease heterogeneity in compound heterozygous patients.