A Chinese patient with Rothmund-Thomson syndrome.

INTRODUCTION: Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder that has been reported in all ethnicities, with several identifiable pathogenic variants. There have been reported cases indicating that RTS may lead to low birth weight in fetuses, but specific data on the fetal period are lacking. Genetic testing for RTS II is currently carried out by identifying pathogenic variants in RECQL4. METHODS: In order to determine the cause, we performed whole-genome sequencing (WGS) analysis on the patient and his parents. Variants detected by WGS were confirmed by Sanger sequencing and examined in family members. RESULTS: After analyzing the WGS data, we found a heterozygous nonsense mutation c.2752G>T (p.Glu918Ter) and a novel frameshift insertion mutation c.1547dupC (p.Leu517AlafsTer23) of RECQL4, which is a known pathogenic/disease-causing variant of RTS. Further validation indicated these were compound heterozygous mutations from parents. CONCLUSION: Our study expands the mutational spectrum of the RECQL4 gene and enriches the phenotype spectrum of Chinese RTS patients. Our information can assist the patient's parents in making informed decisions regarding their future pregnancies. This case offers a new perspective for clinicians to consider whether to perform prenatal diagnosis.

Biallelic variants in CRIPT cause a Rothmund-Thomson-like syndrome with increased cellular senescence.

PURPOSE: Rothmund-Thomson syndrome (RTS) is characterized by poikiloderma, sparse hair, small stature, skeletal defects, cancer, and cataracts, resembling features of premature aging. RECQL4 and ANAPC1 are the 2 known disease genes associated with RTS in >70% of cases. We describe RTS-like features in 5 individuals with biallelic variants in CRIPT (OMIM 615789). METHODS: Two newly identified and 4 published individuals with CRIPT variants were systematically compared with those with RTS using clinical data, computational analysis of photographs, histologic analysis of skin, and cellular studies on fibroblasts. RESULTS: All CRIPT individuals fulfilled the diagnostic criteria for RTS and additionally had neurodevelopmental delay and seizures. Using computational gestalt analysis, CRIPT individuals showed greatest facial similarity with individuals with RTS. Skin biopsies revealed a high expression of senescence markers (p53/p16/p21) and the senescence-associated ß-galactosidase activity was elevated in CRIPT-deficient fibroblasts. RECQL4- and CRIPT-deficient fibroblasts showed an unremarkable mitotic progression and unremarkable number of mitotic errors and no or only mild sensitivity to genotoxic stress by ionizing radiation, mitomycin C, hydroxyurea, etoposide, and potassium bromate. CONCLUSION: CRIPT causes an RTS-like syndrome associated with neurodevelopmental delay and epilepsy. At the cellular level, RECQL4- and CRIPT-deficient cells display increased senescence, suggesting shared molecular mechanisms leading to the clinical phenotypes.

Precocious puberty and anal stenosis in an African patient with Rothmund-Thomson syndrome.

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder characterized by a rash that progresses to poikiloderma. Other common features include sparse hair, eyelashes and eyebrows, short stature, variable skeletal abnormalities, dental defects, cataracts, hypogonadism, and an increased risk for cancer, especially osteosarcoma and skin cancer. RTS is caused by biallelic pathogenic variants in ANAPC1 (Type 1 RTS) or RECQL4 (Type 2 RTS). We present an African girl with Type 2 RTS caused by a nonsense variant and an intronic variant in RECQL4. The patient presented precocious puberty, which has not been previously reported in RTS and that was treated with a GnRH analog, and anal stenosis, which has only been reported once. This case highlights the need to consider deep intronic variants in patients with RTS when pathogenic variants in the coding regions and exon/intron boundaries are not identified and expands the phenotypic spectrum of this disorder.

Cancer risk among RECQL4 heterozygotes.

Rothmund-Thomson syndrome (RTS) is an autosomal recessive cancer-predisposition disorder characterized by the presence of a wide range of clinical features including poikiloderma, sparse hair, growth deficiency, cataracts, and skeletal abnormalities. Importantly, two-thirds of individuals with RTS have a significant risk of developing osteosarcoma due to the presence of biallelic pathogenic variants in RECQL4, a critical gene involved in DNA repair and replication. It is unknown whether individuals who are heterozygous for a RECQL4 pathogenic variant also have an increased risk of cancer. To address this question, we examined the largest international RTS registry and analyzed 123 RECQL4 heterozygous family members of RTS probands. Overall, the prevalence of cancer among RECQL4 heterozygous family members was 2.4% (3/123). We found that compared to the age-adjusted population estimate of 5.6% from the Surveillance, Epidemiology, and End Results program, the prevalence of cancer was not significantly different in this cohort of RECQL4 heterozygotes (Fisher's exact test, P = 0.2). Given that the biological parents of individuals with RTS are obligate heterozygotes and that siblings have a fifty-percent chance of being asymptomatic heterozygotes, these findings provide valuable information to help guide clinicians in counseling RTS family members regarding the likelihood of developing cancer.

Rothmund-Thomson syndrome: a case series from a tertiary pediatric hospital in Mexico.

BACKGROUND: Rothmund-Thomson syndrome, also known as congenital poikiloderma, is a rare autosomal recessive genodermatosis with onset in early childhood that affects at a multisystem level. CASE REPORTS: Case 1. A 4-year-old male patient, consanguineous parents, 26-year-old brother with a probable diagnosis of Rothmund-Thompson syndrome. He presented with adactyly of the right thumb, hypoplasia of the left thumb, delayed growth and psychomotor development. At 3 months, he presented rough, dry, sparse hair and erythematous lesions on the face, leaving hyperpigmented and hypopigmented spots with a reticulated pattern. We detected hypoacusis, skeletal alterations, narrow chin, short stature, severe malnutrition, and chronic and asymptomatic hypodontia. Genetic sequencing showed a mutation for the RECQL4 gene, for which a multidisciplinary follow-up was provided by the genetics, gastroenterology, nutrition, endocrinology, stomatology, audiology, orthopedics, rehabilitation, ophthalmology and oncology services. Case 2. A 2-year-old female patient presented facial erythema that spread to the arms and legs at 3 months; skin biopsy showed poikiloderma. She was evaluated by the endocrinology service and followed up for short stature and hypogonadism. A genetic study was not performed. CONCLUSIONS: Rothmund-Thomson syndrome is characterized by atrophy. Only a few cases are reported in the literature. We present two cases of Rothmund-Thomson syndrome, emphasizing its clinical and dermatological characteristics.

INTRODUCCIÓN: El síndrome de Rothmund-Thomson, también conocido como poiquilodermia congénita, es una rara genodermatosis autosómica recesiva de inicio en la infancia temprana y afectación multisistémica. CASOS CLÍNICOS: Se describen dos casos de pacientes con síndrome de Rothmund-Thomson. Caso 1. Paciente de sexo masculino de 4 años de edad, padres consanguíneos, hermano de 26 años con diagnóstico probable de síndrome de Rothmund-Thompson. Presentó adactilia del pulgar derecho, hipoplasia de pulgar izquierdo, retraso en el crecimiento y retraso del desarrollo psicomotor. A los 3 meses de edad mostraba pelo áspero, seco y escaso, y lesiones eritematosas en la cara, las cuales dejaron manchas hiperpigmentadas e hipopigmentadas con patrón reticulado. Se detectaron hipoacusia, alteraciones esqueléticas, mentón estrecho, talla baja, desnutrición grave e hipodontia crónica y asintomática. La secuenciación genética resultó con mutación para el gen RECQL4, por lo que se dio seguimiento multidisciplinario por los servicios de genética, gastroenterología, nutrición, endocrinología, estomatología, audiología, ortopedia, rehabilitación, oftalmología y oncología. Caso 2. Paciente de sexo femenino de 2 años de edad que a los 3 meses de vida inició con eritema facial que se diseminó a los brazos y la piernas; la biopsia de piel reportó poiquilodermia. Se encuentra en seguimiento por el servicio de endocrinología por talla baja e hipogonadismo. No se realizó estudio genético. CONCLUSIONES: El síndrome de Rothmund-Thomson se caracteriza por atrofia. Existen pocos casos reportados en la literatura. Se presentan dos casos de síndrome de Rothmund-Thomson, enfatizando sus características clínicas y dermatológicas.

Patient-derived iPSCs link elevated mitochondrial respiratory complex I function to osteosarcoma in Rothmund-Thomson syndrome.

Rothmund-Thomson syndrome (RTS) is an autosomal recessive genetic disorder characterized by poikiloderma, small stature, skeletal anomalies, sparse brows/lashes, cataracts, and predisposition to cancer. Type 2 RTS patients with biallelic RECQL4 pathogenic variants have multiple skeletal anomalies and a significantly increased incidence of osteosarcoma. Here, we generated RTS patient-derived induced pluripotent stem cells (iPSCs) to dissect the pathological signaling leading to RTS patient-associated osteosarcoma. RTS iPSC-derived osteoblasts showed defective osteogenic differentiation and gain of in vitro tumorigenic ability. Transcriptome analysis of RTS osteoblasts validated decreased bone morphogenesis while revealing aberrantly upregulated mitochondrial respiratory complex I gene expression. RTS osteoblast metabolic assays demonstrated elevated mitochondrial respiratory complex I function, increased oxidative phosphorylation (OXPHOS), and increased ATP production. Inhibition of mitochondrial respiratory complex I activity by IACS-010759 selectively suppressed cellular respiration and cell proliferation of RTS osteoblasts. Furthermore, systems analysis of IACS-010759-induced changes in RTS osteoblasts revealed that chemical inhibition of mitochondrial respiratory complex I impaired cell proliferation, induced senescence, and decreased MAPK signaling and cell cycle associated genes, but increased H19 and ribosomal protein genes. In summary, our study suggests that mitochondrial respiratory complex I is a potential therapeutic target for RTS-associated osteosarcoma and provides future insights for clinical treatment strategies.

Skin Abnormalities in Disorders with DNA Repair Defects, Premature Aging, and Mitochondrial Dysfunction.

Defects in DNA repair pathways and alterations of mitochondrial energy metabolism have been reported in multiple skin disorders. More than 10% of patients with primary mitochondrial dysfunction exhibit dermatological features including rashes and hair and pigmentation abnormalities. Accumulation of oxidative DNA damage and dysfunctional mitochondria affect cellular homeostasis leading to increased apoptosis. Emerging evidence demonstrates that genetic disorders of premature aging that alter DNA repair pathways and cause mitochondrial dysfunction, such as Rothmund-Thomson syndrome, Werner syndrome, and Cockayne syndrome, also exhibit skin disease. This article summarizes recent advances in the research pertaining to these syndromes and molecular mechanisms underlying their skin pathologies.

ATM activation is impaired in human cells defective in RecQL4 helicase activity.

RecQL4 has been shown to be involved in DNA replication and repair, but its role in DNA damage checkpoint pathway has not been reported. Here, we show that RecQL4 plays an important role in the activation of ataxia telangiectasia mutated (ATM)-dependent checkpoint pathway in human cells. Cells depleted with RecQL4 or Rothmund-Thomson syndrome cells showed significant impairment in the activation of ATM and the downstream effector proteins such as checkpoint kinase 2 and p53 after DNA damage. This defect was recovered with the expression of wild type RecQL4 but not any mutant RecQL4 proteins with defective helicase activities. While RecQL4 failed to show any direct interaction with ATM, it stably interacted with the Mre11-Rad50-Nbs1 complex that is essential for the activation of ATM and was localized on the DNA damage foci. Thus, our results suggest that the helicase activity of RecQL4 plays an important role in the activation of ATM-dependent checkpoint pathway against DNA double strand breaks in human cells.

Rothmund-Thomson Syndrome: Insights from New Patients on the Genetic Variability Underpinning Clinical Presentation and Cancer Outcome.

Biallelic mutations in RECQL4 gene, a caretaker of the genome, cause Rothmund-Thomson type-II syndrome (RTS-II) and confer increased cancer risk if they damage the helicase domain. We describe five families exemplifying clinical and allelic heterogeneity of RTS-II, and report the effect of pathogenic RECQL4 variants by in silico predictions and transcripts analyses. Complete phenotype of patients #39 and #42 whose affected siblings developed osteosarcoma correlates with their c.[1048_1049del], c.[1878+32_1878+55del] and c.[1568G>C;1573delT], c.[3021_3022del] variants which damage the helicase domain. Literature survey highlights enrichment of these variants affecting the helicase domain in patients with cancer outcome raising the issue of strict oncological surveillance. Conversely, patients #29 and #19 have a mild phenotype and carry, respectively, the unreported homozygous c.3265G>T and c.3054A>G variants, both sparing the helicase domain. Finally, despite matching several criteria for RTS clinical diagnosis, patient #38 is heterozygous for c.2412_2414del; no pathogenic CNVs out of those evidenced by high-resolution CGH-array, emerged as contributors to her phenotype.

Generalized metabolic bone disease and fracture risk in Rothmund-Thomson syndrome.

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder characterized by poikiloderma, small stature, sparse hair, skeletal abnormalities, increased risk of osteosarcoma, and decreased bone mass. To date, there has not been a comprehensive evaluation of the prevalence and extent of metabolic bone disease in RTS. Furthermore, the mechanisms that result in this phenotype are largely unknown. In this report, we provide a detailed evaluation of 29 individuals with RTS with respect to their metabolic bone status including bone mineral density, calcium kinetics studies, and markers of bone remodeling. We show that individuals with RTS have decreased areal bone mineral density. Additionally, we demonstrate that the presence of pathogenic variants in RECQL4 and low bone mineral density correlate with the history of increased risk of fractures. Using a RECQL4-deficient mouse model that recapitulates skeletal abnormalities seen in individuals with RTS, we demonstrate that generalized skeletal involvement is likely due to decreased osteogenesis. Our findings are clinically relevant as they may help in the risk stratification of patients with RTS and also in the identification of individuals who may benefit from additional surveillance and management of metabolic bone disease.

Rothmund-Thomson syndrome and ocular surface findings: case reports and review of the literature.

Rothmund-Thomson syndrome (RTS) is a rare dermatosis with about 300 cases reported to date. The authors describe two siblings with RTS and inflammatory conjunctival disease featuring fornix shortening and symblepharon as well as palpebral disease with sparse eyelashes. These cases demonstrate RTS ocular surface findings different to those usually described.

Rothmund-Thomson syndrome and ocular surface findings: case reports and review of the literature / Síndrome de Rothmund-Thomson e achados da superfície ocular: casos clínicos e revisão da literatura

ABSTRACT Rothmund-Thomson syndrome (RTS) is a rare dermatosis with about 300 cases reported to date. The authors describe two siblings with RTS and inflammatory conjunctival disease featuring fornix shortening and symblepharon as well as palpebral disease with sparse eyelashes. These cases demonstrate RTS ocular surface findings different to those usually described.

RESUMO A síndrome de Rothmund-Thomson (SRT) é uma dermatose rara com cerca de 300 casos reportados. Os autores descrevem dois irmãos com síndrome de Rothmund-Thomson e doença inflamatória conjuntival com encurtamento do fundo de saco e simbléfaro, assim como doença palpebral com escassez de cilíos. Ambos os casos demonstram achados da superfície ocular diferentes dos habitualmente descritos.

Síndrome de Rothmund / Rothmund syndrome

RESUMO A síndrome de Rothmund (RTS) é uma rara genodermatose, de herança autossômica recessiva. Sua incidência é desconhecida, com aproximadamente 300 casos descritos na literatura. A síndrome é determinada por eritema facial (poiquilodermia), seu marco diagnóstico, além de alterações esqueléticas, alopecia, catarata juvenil e predisposição a osteossarcoma. Neste relato, descrevemos uma paciente com esta síndrome, que foi referida ao serviço de oftalmologia por baixa visão e hiperemia ocular.

ABSTRACT Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive genodermatosis. While its incidence is unknown, approximately 300 cases have been reported in the literature. The syndrome typically presents with a characteristic facial rash (poikiloderma), its diagnostic hallmark, and heterogeneous clinical features including congenital skeletal abnormalities, sparse hair distribution, juvenile cataracts, and a predisposition to osteosarcoma. This is a report describing a patient diagnosed with RTS referred to us because of low vision and red eyes.

RECQL4 Regulates p53 Function In Vivo During Skeletogenesis.

RECQ DNA helicases play critical roles in maintaining genomic stability, but their role in development has been less well studied. Rothmund-Thomson syndrome, RAPADILINO, and Baller-Gerold syndrome are rare genetic disorders caused by mutations in the RECQL4 gene. These patients have significant skeletal developmental abnormalities including radial ray, limb and craniofacial defects. To investigate the role of Recql4 in the developing skeletal system, we generated Recql4 conditional knockout mice targeting the skeletal lineage. Inactivation of Recql4 using the Prx1-Cre transgene led to limb abnormalities and craniosynostosis mimicking the major bone findings in human RECQL4 patients. These Prx1-Cre(+) ;Recql4(fl/fl) mice as well as Col2a1-Cre(+) ;Recql4(fl/fl) mice exhibited growth plate defects and an increased p53 response in affected tissues. Inactivation of Trp53 in these Recql4 mutants resulted in genetic rescue of the skeletal phenotypes, indicating an in vivo interaction between Recql4 and Trp53, and p53 activation as an underlying mechanism for the developmental bone abnormalities in RECQL4 disorders. Our findings show that RECQL4 is critical for skeletal development by modulating p53 activity in vivo.

RECQ helicase RECQL4 participates in non-homologous end joining and interacts with the Ku complex.

RECQL4, a member of the RecQ helicase family, is a multifunctional participant in DNA metabolism. RECQL4 protein participates in several functions both in the nucleus and in the cytoplasm of the cell, and mutations in human RECQL4 are associated with three genetic disorders: Rothmund-Thomson, RAPADILINO and Baller-Gerold syndromes. We previously reported that RECQL4 is recruited to laser-induced DNA double-strand breaks (DSB). Here, we have characterized the functional roles of RECQL4 in the non-homologous end joining (NHEJ) pathway of DSB repair. In an in vitro NHEJ assay that depends on the activity of DNA-dependent protein kinase (DNA-PK), extracts from RECQL4 knockdown cells display reduced end-joining activity on DNA substrates with cohesive and non-cohesive ends. Depletion of RECQL4 also reduced the end joining activity on a GFP reporter plasmid in vivo. Knockdown of RECQL4 increased the sensitivity of cells to γ-irradiation and resulted in accumulation of 53BP1 foci after irradiation, indicating defects in the processing of DSB. We find that RECQL4 interacts with the Ku70/Ku80 heterodimer, part of the DNA-PK complex, via its N-terminal domain. Further, RECQL4 stimulates higher order DNA binding of Ku70/Ku80 to a blunt end DNA substrate. Taken together, these results implicate that RECQL4 participates in the NHEJ pathway of DSB repair via a functional interaction with the Ku70/Ku80 complex. This is the first study to provide both in vitro and in vivo evidence for a role of a RecQ helicase in NHEJ.

RECQ DNA helicases and osteosarcoma.

The RECQ family of DNA helicases is a conserved group of enzymes that are important for maintaining genomic integrity. In humans, there are five RECQ helicase genes, and mutations in three of them-BLM, WRN, and RECQL4-are associated with the genetic disorders Bloom syndrome, Werner syndrome, and Rothmund-Thomson syndrome (RTS), respectively. Importantly all three diseases are cancer predisposition syndromes. Patients with RTS are highly and uniquely susceptible to developing osteosarcoma; thus, RTS provides a good model to study the pathogenesis of osteosarcoma. The "tumor suppressor" role of RECQL4 and the other RECQ helicases is an area of active investigation. This chapter reviews what is currently known about the cellular functions of RECQL4 and how these may relate to tumorigenesis, as well as ongoing efforts to understand RECQL4's functions in vivo using animal models. Understanding the RECQ pathways may provide insight into avenues for novel cancer therapies in the future.

Senescence induced by RECQL4 dysfunction contributes to Rothmund-Thomson syndrome features in mice.

Cellular senescence refers to irreversible growth arrest of primary eukaryotic cells, a process thought to contribute to aging-related degeneration and disease. Deficiency of RecQ helicase RECQL4 leads to Rothmund-Thomson syndrome (RTS), and we have investigated whether senescence is involved using cellular approaches and a mouse model. We first systematically investigated whether depletion of RECQL4 and the other four human RecQ helicases, BLM, WRN, RECQL1 and RECQL5, impacts the proliferative potential of human primary fibroblasts. BLM-, WRN- and RECQL4-depleted cells display increased staining of senescence-associated ß-galactosidase (SA-ß-gal), higher expression of p16(INK4a) or/and p21(WAF1) and accumulated persistent DNA damage foci. These features were less frequent in RECQL1- and RECQL5-depleted cells. We have mapped the region in RECQL4 that prevents cellular senescence to its N-terminal region and helicase domain. We further investigated senescence features in an RTS mouse model, Recql4-deficient mice (Recql4(HD)). Tail fibroblasts from Recql4(HD) showed increased SA-ß-gal staining and increased DNA damage foci. We also identified sparser tail hair and fewer blood cells in Recql4(HD) mice accompanied with increased senescence in tail hair follicles and in bone marrow cells. In conclusion, dysfunction of RECQL4 increases DNA damage and triggers premature senescence in both human and mouse cells, which may contribute to symptoms in RTS patients.