Wide clinical variability among 13 new Cockayne syndrome cases confirmed by biochemical assays

Senescent cells at the crossroads of aging, disease, and tissue homeostasis

Originally identified as an outcome of continuous culture of primary cells, cellular senescence has moved beyond the culture dish and is now a bona fide driver of aging and disease in animal models, and growing links to human disease. This cellular stress response consists of a stable proliferative arrest coupled to multiple phenotypic changes. Perhaps the most important of these is the senescence-associated secretory phenotype, or senescence-associated secretory phenotype -a complex and variable collection of secreted molecules release by senescent cells with a number of potent biological activities. Senescent cells appear in multiple age-associated conditions in humans and mice, and interventions that eliminate these cells can prevent or even reverse multiple diseases in mouse models. Here, we review salient aspects of senescent cells in the context of human disease and homeostasis. Senescent cells increase in abundance during several diseases that associated with premature aging. Conversely, senescent cells have a key role in beneficial processes such as development and wound healing, and thus can help maintain tissue homeostasis. Finally, we speculate on mechanisms by which deleterious aspects of senescent cells might be targeted while retaining homeostatic aspects in order to improve age-related outcomes.

What Every Internist-Endocrinologist Should Know about Rare Genetic Syndromes in Order to Prevent Needless Diagnostics, Missed Diagnoses and Medical Complications: Five Years of 'Internal Medicine for Rare Genetic Syndromes'

Patients with complex rare genetic syndromes (CRGS) have combined medical problems affecting multiple organ systems. Pediatric multidisciplinary (MD) care has improved life expectancy, however, transfer to internal medicine is hindered by the lack of adequate MD care for adults. We have launched an MD outpatient clinic providing syndrome-specific care for adults with CRGS, which, to our knowledge, is the first one worldwide in the field of internal medicine. Between 2015 and 2020, we have treated 720 adults with over 60 syndromes. Eighty-nine percent of the syndromes were associated with endocrine problems. We describe case series of missed diagnoses and patients who had undergone extensive diagnostic testing for symptoms that could actually be explained by their syndrome. Based on our experiences and review of the literature, we provide an algorithm for the clinical approach of health problems in CRGS adults. We conclude that missed diagnoses and needless invasive tests seem common in CRGS adults. Due to the increased life expectancy, an increasing number of patients with CRGS will transfer to adult endocrinology. Internist-endocrinologists (in training) should be aware of their special needs and medical pitfalls of CRGS will help prevent the burden of unnecessary diagnostics and under- and overtreatment.

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. Besides RNA polymerase I (RNAP1) and specific ribosomal proteins (RPs), the complex includes ferrochelatase (FECH), a well-known mitochondrial enzyme whose deficiency causes erythropoietic protoporphyria (EPP). Impairment of either CSA or FECH functionality leads to reduced RNAP1 occupancy on rDNA promoter that is associated to reduced 47S pre-rRNA transcription. In addition, reduced FECH expression leads to an abnormal accumulation of 18S rRNA that in primary dermal fibroblasts from CS and EPP patients results in opposed rRNA amounts. After cell irradiation with UV light, CSA triggers the dissociation of the CSA–FECH–CSB–RNAP1–RPs complex from the chromatin while it stabilizes its binding to FECH. Besides disclosing a function for FECH within nucleoli, this study sheds light on the still unknown mechanisms through which CSA modulates rRNA transcription.

Atypical features and de novo heterozygous mutations in two siblings with Cockayne syndrome

BACKGROUND

Cockayne syndrome (CS) is a rare autosomal recessive disorder which displays multiorgan dysfunction, especially within the nervous system including psychomotor retardation, cerebral atrophy, microcephaly, cognitive dysfunction, mental retardation, and seizures. Many genetic variations reported were related to this syndrome, but splicing mutations with cardiac anomalies have not been found in previous studies.

METHODS

Herein, we described a pair of brothers and sisters who present essential manifestations of CS including premature feature, developmental delay, growth failure, microcephaly, and characteristic facial features, such as sunken eyes and a beaked nose. Interestingly, the brother also presented with atypical features which included cardiac anomalies such as left atrioventricular enlargement and cardiac dysfunction such as dilated cardiomyopathy. In addition, whole exome sequencing and RNA sequencing were employed to analyze their genetic landscape.

RESULTS

WES analysis showed that these two cases carried double unreported heterozygous spliced mutations in the excision repair cross-complementing group 8 (ERCC8, also known as CSA, NM_000082) gene, which were c.78-2 (IVS1) A>T and c.1042-1 (IVS10) G>A, respectively. Moreover, transcript sequencing analysis validated these mutation sites. In this study, Gene Ontology enrichment and KEGG pathway analyses from RNA sequencing demonstrated similarities but some differences when compared with previous studies.

CONCLUSION

For patients with Cockayne syndrome, cardiac changes need to be monitored carefully, especially for cases with splicing mutations of the ERCC8 gene.

[Anesthesia for a cesarean section on a pregnant patient with Cockayne syndrome: case report]

Cockayne syndrome is an autosomal recessive multi-systemic disorder due to DNA repair failure. It was originally described in 1936 in children of small stature, retinal atrophy and deafness, characterized by dwarfism, cachexia, photosensitivity, premature aging and neurologic deficits. The most typical feature is described as birdlike facies: protruding maxilla, facial lipoatrophy, sunken eyes, large ears and thin nose. Difficult airway management with subglottic stenosis and risk of gastric content aspiration has been described. Although the clinical characteristics of Cockayne syndrome have been well described in pediatric publications, there is only one report in the literature on anesthesia for an obstetric patient. We report the case of a pregnant patient diagnosed with Cockayne syndrome, submitted successfully to spinal anesthesia for a cesarean section due to cephalopelvic disproportion. In view of the difficult decision between inducing general anesthesia in a patient with a likely difficult airway, or neuraxial anesthesia in a patient with cardiovascular, respiratory and neurocognitive limitations, we suggest tailored management to reach the best results for the mother and newborn.

Anesthesia for a cesarean section on a pregnant patient with Cockayne syndrome: case report

Cockayne syndrome is an autosomal recessive multi-systemic disorder due to DNA repair failure. It was originally described in 1936 in children of small stature, retinal atrophy and deafness, characterized by dwarfism, cachexia, photosensitivity, premature aging and neurologic deficits. The most typical feature is described as birdlike facies: protruding maxilla, facial lipoatrophy, sunken eyes, large ears and thin nose. Difficult airway management with subglottic stenosis and risk of gastric content aspiration has been described. Although the clinical characteristics of Cockayne syndrome have been well described in pediatric publications, there is only one report in the literature on anesthesia for an obstetric patient. We report the case of a pregnant patient diagnosed with Cockayne syndrome, submitted successfully to spinal anesthesia for a cesarean section due to cephalopelvic disproportion. In view of the difficult decision between inducing general anesthesia in a patient with a likely difficult airway, or neuraxial anesthesia in a patient with cardiovascular, respiratory and neurocognitive limitations, we suggest tailored management to reach the best results for the mother and newborn.

A complex intragenic rearrangement of ERCC8 in Chinese siblings with Cockayne syndrome

Cockayne syndrome is an autosomal recessive disorder principally characterized by postnatal growth failure and progressive neurological dysfunction, due primarily to mutations in ERCC6 and ERCC8. Here, we report our diagnostic experience for two patients in a Chinese family suspected on clinical grounds to have Cockayne syndrome. Using multiple molecular techniques, including whole exome sequencing, array comparative genomic hybridization and quantitative polymerase chain reaction, we identified compound heterozygosity for a maternal splicing variant (chr5:60195556, NM_000082:c.618-2A > G) and a paternal complex deletion/inversion/deletion rearrangement removing exon 4 of ERCC8, confirming the suspected pathogenesis in these two subjects. Microhomology (TAA and AGCT) at the breakpoints indicated that microhomology-mediated FoSTeS events were involved in this complex ERCC8 rearrangement. This diagnostic experience illustrates the value of high-throughput genomic technologies combined with detailed phenotypic assessment in clinical genetic diagnosis.

[The place of neuropathy in the early diagnosis of Cockayne syndrome: Report on two siblings]

Two siblings affected with Cockayne syndrome (CS) are described: this diagnosis was suggested by the finding of a demyelinating neuropathy on electromyography in both children and consistent clinical features. CS is a rare genetic disorder with severe prognosis and a highly varied phenotype, making early diagnosis difficult. Taking into account these two cases and the literature, the current diagnosis criteria are insufficiently specific and appear late: the diagnosis may be delayed because multi-organ involvement and sensorial impairment suggests more frequent neurometabolic disorders. Neuroradiologic abnormalities are suggestive but may occur later. The finding of a demyelinating peripheral neuropathy seems to be a more useful marker to suspect this disorder in the presence of other clinical features. Further studies are required to better define the chronology of the symptoms, not only for adequate genetic counseling and eventual prenatal diagnosis, but also to assess the efficacy of future therapies.

Cockayne syndrome: Clinical features, model systems and pathways

Cockayne syndrome (CS) is a disorder characterized by a variety of clinical features including cachectic dwarfism, severe neurological manifestations including microcephaly and cognitive deficits, pigmentary retinopathy, cataracts, sensorineural deafness, and ambulatory and feeding difficulties, leading to death by 12 years of age on average. It is an autosomal recessive disorder, with a prevalence of approximately 2.5 per million. There are several phenotypes (1-3) and two complementation groups (CSA and CSB), and CS overlaps with xeroderma pigmentosum (XP). It has been considered a progeria, and many of the clinical features resemble accelerated aging. As such, the study of CS affords an opportunity to better understand the underlying mechanisms of aging. The molecular basis of CS has traditionally been ascribed to defects in transcription and transcription-coupled nucleotide excision repair (TC-NER). However, recent work suggests that defects in base excision DNA repair and mitochondrial functions may also play key roles. This opens up the possibility for molecular interventions in CS, and by extrapolation, possibly in aging.

Why Cockayne syndrome patients do not get cancer despite their DNA repair deficiency

Cockayne syndrome (CS) and xeroderma pigmentosum (XP) are human photosensitive diseases with mutations in the nucleotide excision repair (NER) pathway, which repairs DNA damage from UV exposure. CS is mutated in the transcription-coupled repair (TCR) branch of the NER pathway and exhibits developmental and neurological pathologies. The XP-C group of XP patients have mutations in the global genome repair (GGR) branch of the NER pathway and have a very high incidence of UV-induced skin cancer. Cultured cells from both diseases have similar sensitivity to UV-induced cytotoxicity, but CS patients have never been reported to develop cancer, although they often exhibit photosensitivity. Because cancers are associated with increased mutations, especially when initiated by DNA damage, we examined UV-induced mutagenesis in both XP-C and CS cells, using duplex sequencing for high-sensitivity mutation detection. Duplex sequencing detects rare mutagenic events, independent of selection and in multiple loci, enabling examination of all mutations rather than just those that confer major changes to a specific protein. We found telomerase-positive normal and CS-B cells had increased background mutation frequencies that decreased upon irradiation, purging the population of subclonal variants. Primary XP-C cells had increased UV-induced mutation frequencies compared with normal cells, consistent with their GGR deficiency. CS cells, in contrast, had normal levels of mutagenesis despite their TCR deficiency. The lack of elevated UV-induced mutagenesis in CS cells reveals that their TCR deficiency, although increasing cytotoxicity, is not mutagenic. Therefore the absence of cancer in CS patients results from the absence of UV-induced mutagenesis rather than from enhanced lethality.

The Cockayne Syndrome Natural History (CoSyNH) study: clinical findings in 102 individuals and recommendations for care

Purpose:

Cockayne syndrome (CS) is a rare, autosomal-recessive disorder characterized by microcephaly, impaired postnatal growth, and premature pathological aging. It has historically been considered a DNA repair disorder; fibroblasts from classic patients often exhibit impaired transcription-coupled nucleotide excision repair. Previous studies have largely been restricted to case reports and small series, and no guidelines for care have been established.

Genet Med18 5, 483–493.

Methods:

One hundred two study participants were identified through a network of collaborating clinicians and the Amy and Friends CS support groups. Families with a diagnosis of CS could also self-recruit. Comprehensive clinical information for analysis was obtained directly from families and their clinicians.

Genet Med18 5, 483–493.

Results and Conclusion:

We present the most complete evaluation of Cockayne syndrome to date, including detailed information on the prevalence and onset of clinical features, achievement of neurodevelopmental milestones, and patient management. We confirm that the most valuable prognostic factor in CS is the presence of early cataracts. Using this evidence, we have created simple guidelines for the care of individuals with CS. We aim to assist clinicians in the recognition, diagnosis, and management of this condition and to enable families to understand what problems they may encounter as CS progresses.

Genet Med18 5, 483–493.

Identification of two missense mutations of ERCC6 in three Chinese sisters with Cockayne syndrome by whole exome sequencing

Cockayne syndrome (CS) is a rare autosomal recessive disorder, the primary manifestations of which are poor growth and neurologic abnormality. Mutations of the ERCC6 and ERCC8 genes are the predominant cause of Cockayne syndrome, and the ERCC6 gene mutation is present in approximately 65% of cases. The present report describes a case of Cockayne syndrome in a Chinese family, with the patients carrying two missense mutations (c.1595A>G, p.Asp532Gly and c.1607T>G, p.Leu536Trp) in the ERCC6 gene in an apparently compound heterozygote status, especially, p.Asp532Gly has never been reported. The compound heterozygote mutation was found in three patients in the family using whole exome sequencing. The patients' father and mother carried a heterozygous allele at different locations of the ERCC6 gene, which was confirmed by Sanger DNA sequencing. The two mutations are both located in the highly conserved motif I of ATP-binding helicase and are considered "Damaging," "Probably Damaging," "Disease Causing," and "Conserved", indicating the role of DNA damage in the pathogenetic process of the disease. The results not only enrich the ERCC6 mutations database, but also indicate that whole exome sequencing will be a powerful tool for discovering the disease causing mutations in clinical diagnosis.

Blinded by the UV light: how the focus on transcription-coupled NER has distracted from understanding the mechanisms of Cockayne syndrome neurologic disease

Cockayne syndrome (CS) is a devastating neurodevelopmental disorder, with growth abnormalities, progeriod features, and sun sensitivity. CS is typically considered to be a DNA repair disorder, since cells from CS patients have a defect in transcription-coupled nucleotide excision repair (TC-NER). However, cells from UV-sensitive syndrome patients also lack TC-NER, but these patients do not suffer from the neurologic and other abnormalities that CS patients do. Also, the neurologic abnormalities that affect CS patients (CS neurologic disease) are qualitatively different from those seen in NER-deficient XP patients. Therefore, the TC-NER defect explains the sun sensitive phenotype common to both CS and UVsS, but cannot explain CS neurologic disease. However, as CS neurologic disease is of much greater clinical significance than the sun sensitivity, there is a pressing need to understand its molecular basis. While there is evidence for defective repair of oxidative DNA damage and mitochondrial abnormalities in CS cells, here I propose that the defects in transcription by both RNA polymerases I and II that have been documented in CS cells provide a better explanation for many of the severe growth and neurodevelopmental defects in CS patients than defective DNA repair. The implications of these ideas for interpreting results from mouse models of CS, and for the development of treatments and therapies for CS patients are discussed.

Accumulation of phosphorylated TDP-43 in the CNS of a patient with Cockayne syndrome

Here, we report a case of Cockayne syndrome (CS) in a Japanese man who displayed a unique pathology of phosphorylated trans-activation response (TAR) DNA-binding protein 43 (pTDP-43) with abundant Rosenthal fibers. Many round pTDP-43-positive structures were detected throughout the CNS; however, most of them were located in two regions that also exhibited neuronal depletion: the cerebellar cortex and the inferior olivary nucleus. To a lesser extent, these aggregates were also present in the cerebellar white matter, around the subependymal regions in the brain stem, and in the spinal cord. Intraneuronal pTDP-43 inclusions were only observed in a small number of neurons in the inferior olivary nucleus. Double-label immunofluorescence revealed that many of the aggregates were localized to astrocytes. The observed distribution and the morphology of the pTDP-43-positive structures were unique and have not yet been reported. Therefore, a pTDP-43-related pathology may be implicated in CS as well as in other neurodegenerative diseases such as frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Whether the pathology of these diseases reflects a primary neurodegenerative process or a secondary reaction is not known.

Disorders of nucleotide excision repair

Deficient repair of ubiquitous errors in the genome risks faulty transcription or replication. Its direct and indirect phenotypic consequences are rare, complex, dementing, lethal disorders of children with inadequately understood overlapping genotypes and variable severity. Mutations of CSA or CSB responsible for impaired transcription-coupled repair cause Cockayne syndrome (CS). Its characteristics are (1) profound growth deficiency affecting all tissues, including the brain, (2) premature aging marked by cachexia, vascular disease, exocrine deficiency, and osteopenia, but not cancer, and (3) a selective degenerative disorder of central and peripheral myelin and by neuronal loss in the retina and inner ear, and in the cerebellum and basal ganglia where it is associated with calcification. Xeroderma pigmentosum (XP) can arise from mutations of at least eight genes involved in global genomic repair. Severe XPA and XPC cause innumerable carcinomas and melanomas in light-exposed eyes and skin, and enhanced risk of visceral cancers. XPA and XPD and others can cause childhood XP neurological disease with widespread neuronal loss, axonal sensorimotor neuropathy, and dwarfing. Four genes, including XPD, can cause trichothiodystrophy (TTD) with sulfur-deficient, brittle, tiger-tail hair, and growth and developmental inadequacy. CSB or XPD can cause the severe congenital cerebro-oculofacioskeletal (COFS) CS-like syndrome with joint contractures, cataracts, and early death. Three XP genes can also cause XP/CS complex. Much more needs to be learned about these and other disorders of DNA repair to enable prevention and treatment.

Cockayne syndrome b maintains neural precursor function

Neurodevelopmental defects are observed in the hereditary disorder Cockayne syndrome (CS). The gene most frequently mutated in CS, Cockayne Syndrome B (CSB), is required for the repair of bulky DNA adducts in transcribed genes during transcription-coupled nucleotide excision repair. CSB also plays a role in chromatin remodeling and mitochondrial function. The role of CSB in neural development is poorly understood. Here we report that the abundance of neural progenitors is normal in Csb(-/-) mice and the frequency of apoptotic cells in the neurogenic niche of the adult subependymal zone is similar in Csb(-/-) and wild type mice. Both embryonic and adult Csb(-/-) neural precursors exhibited defective self-renewal in the neurosphere assay. In Csb(-/-) neural precursors, self-renewal progressively decreased in serially passaged neurospheres. The data also indicate that Csb and the nucleotide excision repair protein Xpa preserve embryonic neural stem cell self-renewal after UV DNA damage. Although Csb(-/-) neural precursors do not exhibit altered neuronal lineage commitment after low-dose UV (1J/m(2)) in vitro, neurons differentiated in vitro from Csb(-/-) neural precursors that had been irradiated with 1J/m(2) UV exhibited defective neurite outgrowth. These findings identify a function for Csb in neural precursors.

Cholestasis in patients with Cockayne syndrome and suggested modified criteria for clinical diagnosis

BACKGROUND

Cockayne syndrome is a rare autosomal recessive neurodegenerative disease characterized by low-to-normal birth weight; growth failure; brain dysmyelination with calcium deposits, cutaneous photosensitivity; pigmentary retinopathy, cataract, and sensorineural hearing loss. To the best of our knowledge, cholestatic liver disease was not previously reported in these patients.

AIM

To highlight the presence of cholestasis and liver dysfunction in this group of patients and to suggest modified criteria for clinical diagnosis.

METHODS

The study included nine patients with Cockayne from four different families (five males and four females) in which Cockayne was suspected clinically. In all patients chromosomal breakage studies revealed mild (45%) to moderate (60%) increase in frequency of chromatid and chromosome gaps and breaks versus 25% in normal controls. Diagnosis was confirmed by DNA repair assay.

RESULTS

During routine follow up of these patients, seven of them had evident liver affection ranging from mild elevation in liver enzymes to cholestatic liver disease and liver cell failure. The attacks were recurrent in two patients and were sometimes preceded by infection. The attack may lead to deterioration of neurological and/or liver condition. It may end in liver cell failure that either recovers completely or may lead to death.

CONCLUSIONS

liver disease could be considered common in Egyptian patients with Cockayne with the cholestatic form being the most evident. The syndrome should be included in the list of causes of cholestatic liver disease. Chromosomal breakage study and positive family history should be included as major criteria for clinical diagnosis of Cockayne especially in a population like ours where consanguineous marriage is very high and molecular testing and UV sensitivity tests are considered unaffordable.

Skeletal phenotype of mandibuloacral dysplasia associated with mutations in ZMPSTE24

Mandibuloacral dysplasia (MAD) is a rare recessively inherited premature aging disease characterized by skeletal and metabolic anomalies. It is part of the spectrum of diseases called laminopathies and results from mutations in genes regulating the synthesis of the nuclear laminar protein, lamin A. Homozygous or compound heterozygous mutations in the LMNA gene, which encodes both the precursor protein prelamin A and lamin C, are the commonest cause of MAD type A. In a few cases of MAD type B, mutations have been identified in the ZMPSTE24 gene encoding a zinc metalloproteinase important in the post-translational modification of lamin A. Here we describe a new case of MAD resulting from compound heterozygote mutations in ZMPSTE24 (p.N256S/p.Y70fs). The patient had typical skeletal changes of MAD, but in addition a number of unusual skeletal features including neonatal tooth eruption, amorphous calcific deposits, submetaphyseal erosions, vertebral beaking, severe cortical osteoporosis and delayed fracture healing. Treatment with conventional doses of pamidronate improved estimated volumetric bone density in the spine but did not arrest cortical bone loss. We reviewed the literature on cases of MAD associated with proven LMNA and ZMPSTE24 mutations and found that the unusual features described above were all substantially more prevalent in patients with mutations in ZMPSTE24 than in those with LMNA mutations. We conclude that MAD associated with ZMPSTE24 mutations has a more severe phenotype than that associated with LMNA mutations--probably reflecting the greater retention of unprocessed farnesylated prelamin A in the nucleus, which is toxic to cells.

Neuropathology of Cockayne syndrome: Evidence for impaired development, premature aging, and neurodegeneration

Global growth and development failure, premature, accelerated, pathologic aging, and neurodegeneration characterize Cockayne syndrome (CS) and the cerebro-oculo-facial-skeletal and xeroderma pigmentosum/CS syndromes which overlap CS partially in their genetic, somatic, and neuropathologic features. Mutations of CSA or CSB genes jeopardize transcription-coupled repair of damaged nuclear and mitochondrial DNA and resumption of replication and transcription. Resultant defective proteins or gene silencing eventuate in profound dwarfism and micrencephaly, cachexia, vasculopathy, and neurodegeneration. Cellular effects are highly selective. Purkinje cells may die by apoptosis and have grossly dystrophic dendrites. Neuronal death and axonal spheroids indexing neuronal pathology predominate in, but are not limited to, the cerebellum. Progressive loss of retinal, cochlear, and vestibular sensory receptors foster degeneration of ganglion cells and transneuronal brain degeneration. Some proliferating astrocytes are multinucleated and bizarre. Primary damage of oligodendrocytes and Schwann cells may - or may not - explain severe patchy myelin loss ("tigroid leukodystrophy") and segmental demyelinating peripheral neuropathy. Age-related changes are minor in the brain, although precocious severe athero- and arteriolosclerosis are responsible for occasional strokes. Vasculopathology may contribute to myelin loss and to dystrophic mineralization of neurons and vessels, especially in basal ganglia and cerebellum. Understanding the genetics, biochemical, and cellular pathophysiology of these disorders remains fragmentary.

Prenatal diagnosis of Cockayne syndrome type A based on the identification of two novel mutations in the ERCC8 gene

Back Cockayne syndrome (CS; MIM 133540-216400) is a rare autosomal recessive neurodegenerative disorder characterized by progressive growth failure, microcephaly, mental retardation, retinal pigmentary degeneration, deafness, photosensitivity, accelerated systemic degeneration of somatic tissue, and premature death. Complementation assays have defined Cockayne syndrome group A (CSA) and Cockayne syndrome group B (CSB), caused by mutations in ERCC8 and ERCC6. The aim of this work was to perform a molecular analysis in a family with an affected son, who died at the age of 12, presenting clinical features typical of CSA. Molecular analysis of ERCC8 allowed us to characterize two novel mutations: a maternally inherited deletion encompassing exons 5 and 6, and a nonsense mutation located in exon 4, segregating from the father. Based on this molecular characterization, we successively performed a prenatal diagnosis on chorionic villus sampling, at 11th week of pregnancy. Molecular prenatal analysis of the ERCC8 was done by analyzing fetal DNA and RNA, looking for both mutations identified in the proband. A linkage analysis was performed using microsatellite markers located on chromosome 5q11 with the purpose to follow the segregation of the mutated alleles within the family. The fetal genotype at CSA locus resulted wild type and was confirmed at birth on biological material isolated from placenta. This study documents for the first time a molecular prenatal diagnosis of CSA, which results in the preferred approach if the mutation within the family is identified in a timely manner.

Blepharokeratoconjunctivitis in Cockayne syndrome

Cockayne syndrome is a multisystemic, autosomal recessive disease resulting from abnormalities of DNA repair. Ocular manifestations are common, particularly congenital cataract and retinal dystrophy. This study describes a previously unreported association of blepharokeratoconjunctivitis (BKC) in Cockayne syndrome. The authors conducted a retrospective case review of patients with Cockayne syndrome between 1997 and 2006. The ocular manifestations were documented. All cases were bilaterally aphakic from congenital cataract surgery. Four cases of BKC with resultant corneal changes were identified. Two other cases of BKC without corneal changes were also noted. There were no cases of corneal ulceration or visually significant scarring. These findings are clinically important because many patients with Cockayne syndrome wear contact lenses for the refractive correction of aphakia with a resultant risk of corneal ulceration.

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. UV(S)S is genetically heterogeneous, in that it appears in individuals with mutations in CSB or in a still-unidentified gene. We report the identification of a UV(S)S patient (UV(S)S1VI) with a novel mutation in the CSA gene (p.trp361cys) that confers hypersensitivity to UV light, but not to inducers of oxidative damage that are notably cytotoxic in cells from CS patients. The defect in UV(S)S1VI cells is corrected by expression of the WT CSA gene. Expression of the p.trp361cys-mutated CSA cDNA increases the resistance of cells from a CS-A patient to oxidative stress, but does not correct their UV hypersensitivity. These findings imply that some mutations in the CSA gene may interfere with the TC-NER-dependent removal of UV-induced damage without affecting its role in the oxidative stress response. The differential sensitivity toward oxidative stress might explain the difference between the range and severity of symptoms in CS and the mild manifestations in UV(s)S patients that are limited to skin photosensitivity without precocious aging or neurodegeneration.

Non-traumatic enophthalmos: a review

Enophthalmos can be defined as a relative, posterior displacement of a normal-sized globe in relation to the bony orbital margin. Non-traumatic enophthalmos has a wide variety of clinical presentations and may be the first manifestation of a number of local or systemic conditions. It may present with cosmetic problems such as deep superior sulcus, pseudoptosis or eyelid retraction; or functional problems such as diplopia or exposure keratopathy. There are three main pathogenic mechanisms: structural alterations in the bony orbit; orbital fat atrophy; and retraction. Evaluation of enophthalmos patients includes orbital imaging and a thorough ophthalmic and systemic examination. In this review, we discuss the presenting features of non-traumatic enophthalmos and include a brief description of the more important causes. An approach to the clinical evaluation of these patients is also discussed together with a brief overview of the principles of management.

An abundant evolutionarily conserved CSB-PiggyBac fusion protein expressed in Cockayne syndrome

Cockayne syndrome (CS) is a devastating progeria most often caused by mutations in the CSB gene encoding a SWI/SNF family chromatin remodeling protein. Although all CSB mutations that cause CS are recessive, the complete absence of CSB protein does not cause CS. In addition, most CSB mutations are located beyond exon 5 and are thought to generate only C-terminally truncated protein fragments. We now show that a domesticated PiggyBac-like transposon PGBD3, residing within intron 5 of the CSB gene, functions as an alternative 3′ terminal exon. The alternatively spliced mRNA encodes a novel chimeric protein in which CSB exons 1–5 are joined in frame to the PiggyBac transposase. The resulting CSB-transposase fusion protein is as abundant as CSB protein itself in a variety of human cell lines, and continues to be expressed by primary CS cells in which functional CSB is lost due to mutations beyond exon 5. The CSB-transposase fusion protein has been highly conserved for at least 43 Myr since the divergence of humans and marmoset, and appears to be subject to selective pressure. The human genome contains over 600 nonautonomous PGBD3-related MER85 elements that were dispersed when the PGBD3 transposase was last active at least 37 Mya. Many of these MER85 elements are associated with genes which are involved in neuronal development, and are known to be regulated by CSB. We speculate that the CSB-transposase fusion protein has been conserved for host antitransposon defense, or to modulate gene regulation by MER85 elements, but may cause CS in the absence of functional CSB protein.

For reasons that are still unclear, genetic defects in DNA repair can cause diseases that resemble aspects of premature ageing (“segmental progerias”). Cockayne syndrome (CS) is a particularly devastating progeria most commonly caused by mutations in the CSB chromatin remodeling gene. About 43 million years ago, before humans diverged from marmosets, one of the last PiggyBac transposable elements to invade the human lineage landed within intron 5 of the 21 exon CSB gene. As a result, the CSB locus now encodes two equally abundant proteins generated by alternative mRNA splicing: the original full length CSB protein, and a novel CSB-PiggyBac fusion protein in which the N-terminus of CSB is fused to the complete PiggyBac transposase. Conservation of the CSB-PiggyBac fusion protein since marmoset suggests that it is normally beneficial, demonstrating once again that “selfish” transposable elements can be exploited or “domesticated” by the host. More importantly, almost all CSB mutations that cause CS continue to make the CSB-PiggyBac fusion protein, whereas a mutation that compromises both does not cause CS. Thus the fusion protein which is beneficial in the presence of functional CSB may be harmful in its absence. This may help clarify the cause of CS and other progerias.

Aortic dilatation in Cockayne syndrome

Cockayne syndrome is a rare growth failure and premature aging disorder featuring abnormal ultraviolet sensitivity and impaired transcription-coupled DNA repair. Cardiac involvement has not been described in Cockayne patients except for one recently described case of dilated cardiomyopathy. We describe one patient in whom marked ascending aorta dilatation was observed together with mild aortic regurgitation. Ascending aorta dilatation might be another feature of premature aging in Cockayne syndrome and may require cardiovascular investigation and monitoring.

The current evidence for defective repair of oxidatively damaged DNA in Cockayne syndrome

Cockayne syndrome (CS) is a rare recessive disorder characterized by a number of developmental abnormalities and premature aging. Two complementation groups (A and B) have been identified so far in CS cases. Defective transcription-coupled nucleotide excision repair is the hallmark of these patients, but in recent years evidence has been presented for a possible defect in the base excision repair pathway that removes oxidized bases. Recent results indicate that both A and B complementation groups are involved but the phenotypical consequences of this flaw remain undetermined.

Alström syndrome: progressive deafness and blindness

Alström syndrome is a very rare, genetically transmitted disorder that affects special sense functions, resulting in progressive visual and auditory impairment. The diagnostic criteria for this disorder are presented, and the differential issues between it and other, similar syndromal forms of sensory and multisystem dysfunction are discussed. A report of 2 siblings so involved is summarized. The disability of other organs is considered, namely, the kidney, the heart, and the metabolic and endocrine systems.

A novel splice site mutation in the Cockayne syndrome group A gene in two siblings with Cockayne syndrome

Cockayne syndrome (CS) is mainly caused by mutations in the Cockayne syndrome group A or B (CSA or CSB) genes which are required for a sub-pathway of nucleotide excision repair entitled transcription coupled repair. Approximately 20% of the CS patients have mutations in CSA, which encodes a 44 kDa tryptophane (Trp, W) and aspartic acid (Asp, D) amino acids (WD) repeat protein. Up to now, nine different CSA mutations have been identified. We examined two Somali siblings 9 and 12 years old with clinical features typical of CS including skin photosensitivity, progressive ataxia, spasticity, hearing loss, central and peripheral demyelination and intracranial calcifications. Molecular analysis showed a novel splice acceptor site mutation, a G to A transition in the -1 position of intervening sequence 6 (g.IVS6-1G>A), in the CSA (excision repair cross-complementing 8 (ERCC8)) gene. IVS6-1G>A results in a new 28 amino acid C-terminus and premature termination of the CSA protein (G184DFs28X). A review of the CSA protein and the 10 known CSA mutations is also presented.

New insights for understanding the transcription-coupled repair pathway

Transcription-coupled repair (TCR) is a sub-pathway of nucleotide excision repair (NER) able to remove bulky DNA lesions located on the transcribed strands of active genes more rapidly than those located on the non-transcribed genomic DNA. Two recently published reports try to dissect the molecular mechanisms of TCR using simplified in vitro assays. A third report shows in vivo data that confirmed the in vitro ones and extends them to the role of other TCR factors such as those involved in chromatin remodeling. These approaches shed light on the interplay between stalled RNA polymerase II and NER factors necessary for efficient repair. Because severe diseases, such as Cockayne syndrome, are associated with defects or mutations in proteins required for transcription-coupled nucleotide excision repair, complete understanding of this pathway should allow us to understand this disease better and eventually to propose adequate therapies.

Retinitis pigmentosa, pigmentary retinopathies, and neurologic diseases

Retinitis pigmentosa (RP) refers to a group of inherited retinal diseases with phenotypic and genetic heterogeneity. The pathophysiologic basis of the progressive visual loss in patients with RP is not completely understood but is felt to be due to a primary retinal photoreceptor cell degenerative process mainly affecting the rods of the peripheral retina. In most cases RP is seen in isolation (nonsyndromic), but in some other cases it may be a part of a genetic, metabolic, or neurologic syndrome or disorder. Nyctalopia, or night blindness, is the most common symptom of RP. The classic fundus appearance of RP includes retinal pigment epithelial cell changes resulting in retinal hypo- or hyperpigmentation ("salt-and-pepper"), retinal granularity, and bone spicule formation. The retinal vessels are often narrowed or attenuated and there is a waxy pallor appearance of the optic nerve head. Electroretinography will demonstrate rod and cone photoreceptor cell dysfunction and is a helpful test in the diagnosis and monitoring of patients with RP. A detailed history with pedigree analysis, a complete ocular examination, and the appropriate paraclinical testing should be performed in patients complaining of visual difficulties at night or in dim light. This review discusses the clinical manifestations of RP as well as describing the various systemic diseases, with a special emphasis on neurologic diseases, associated with a pigmentary retinopathy.