Rothmund-Thomson Syndrome Research Articles

Update on Recommendations for Cancer Screening and Surveillance in Children with Genomic Instability Disorders.

Genomic instability disorders are characterized by DNA or chromosomal instability resulting in various clinical manifestations including developmental anomalies, immunodeficiency, and increased risk to develop cancers beginning in childhood. Many of these genomic instability disorders also present with exquisite sensitivity to anticancer treatments such as ionizing radiation and chemotherapy, which may further increase the risk of second cancers. In July 2023, the American Association of Cancer Research held the second Childhood Cancer Predisposition Workshop where multidisciplinary international experts discussed, reviewed, and updated recommendations for children with cancer predisposition syndromes. This article will discuss childhood cancer risks and surveillance recommendations for the group of genomic instability disorders with predominantly recessive inheritance, including the DNA repair disorders ataxia telangiectasia, Nijmegen breakage syndrome, Fanconi anemia, Xeroderma Pigmentosum, Bloom syndrome, and Rothmund-Thomson syndrome, as well as the telomere biology disorders and mosaic variegated aneuploidy. Recognition of children with genomic instability disorders is important in order to make the proper diagnosis, enable genetic counseling, and inform cancer screening, cancer risk reduction, and choice of anti-cancer therapy.

Atypical presentations of RECQL4-related syndromes.

RECQL4-related syndromes are a group of rare cancer-predisposition syndromes caused by biallelic pathogenic/likely pathogenic variants (PV/LPV) in the DNA helicase gene, RECQL4. Genetic testing is typically prompted by the presence of one or more hallmark clinical features, and in the absence of such manifestations, diagnosis may be delayed or even missed. We describe five patients with biallelic germline mutations in RECQL4 who presented atypically, without the hallmark clinical manifestations of this syndrome. Three of these patients developed osteosarcoma, underscoring the importance of recognizing atypical presentations of Rothmund-Thomson syndrome (RTS) to allow for early awareness and surveillance for cancer.

Rothmund Thomson syndrome with late onset and good preventive control of non-melanoma cancer with acitretin: case report

Rothmund-Thomson syndrome is a rare autosomal recessive disease that presents with poikiloderma, short stature, alopecia, juvenile cataracts, skeletal abnormalities, and premature skin aging. The manifestation of the disease can begin in the first years of life and people with the syndrome have a greater chance of developing non-melanoma skin cancer. We report a case of late manifestation of the syndrome, treated with acitretin as a preventive measure for skin cancer.

A case of Rothmund-Thomson syndrome and genetic variation analysis

A case of Rothmund-Thomson syndrome and genetic variation analysis

Comprehensive Review of Rothmund-Thomson Syndrome: Clinical Manifestations, Molecular Pathogenesis, and Therapeutic Approaches

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive genodermatosis characterized by a spectrum of clinical manifestations, including poikiloderma, sparse hair, short stature, skeletal abnormalities, and an increased predisposition to malignancies, particularly osteosarcoma. This syndrome is primarily associated with mutations in the RECQL4 gene, a critical player in DNA repair and genomic stability. This review provides an in-depth analysis of the clinical presentation, underlying molecular mechanisms, and current therapeutic strategies for RTS. We aim to elucidate the genetic and cellular pathways implicated in RTS, highlight the challenges in clinical management, and explore potential future directions in research and therapy.

Skin cancer-associated genodermatoses in skin of color patients: a review.

Skin cancers are associated with a large number of genodermatoses. Existing knowledge and guidelines on the presentations of these genodermatoses focus disproportionately on White patients. Our goal is to identify notable characteristics in location, frequency, and severity of cutaneous findings along with the median age of skin cancers in skin-of-color (SOC) patients with skin-cancer-associated genodermatoses to improve diagnosis rates. We searched for genodermatoses on six databases. Each case report or case series was reviewed, including reports, published in English, containing adult patient descriptions. Duplicate manuscripts were removed using EndNote. The following case-level data were collected from the manuscripts: age, gender, patient country or region of origin, author country/continent of residence, skin cancer-related, and other key dermatologic features. 381 published articles, with a total of 578 SOC patients, met criteria for inclusion. SOC patients can present with fewer classic findings, such as a lower incidence of basal cell carcinomas (44%) in SOC Gorlin syndrome patients than palmar pits (66%) and mandibular cysts (66%). Differences between SOC populations were also noted, such as leukoplakia being more common in Asian dyskeratosis congenita patients (80%) in comparison to African dyskeratosis congenita patients (44%). SOC patients also have varying onset of skin cancer depending on the genodermatosis, from a median of 25years of age in Rothmund-Thomson syndrome to 53 in Muir-Torre syndrome. In this review, SOC patients with genodermatoses can have varying presentations. Being cognizant of these characteristics may lead to earlier diagnosis and interventions to mitigate skin-cancer-related morbidity in SOC patients.

Rothmund-Thomson syndrome: Unpacking a rare diagnosis

Rothmund-Thomson syndrome (RTS), also known as congenital poikiloderma, is a genodermatosis that appears in infancy and is characterized by poikilodermatous changes in the skin. It is a very rare and complex genetic disorder that can present with a wide range of symptoms and affect multiple systems in the body. The syndrome is inherited in an autosomal recessive manner. A 21-year-old female patient presented to our rheumatology outpatient clinic with swelling of the hands, sclerodactyly, and stiffness of the fingers with preliminary diagnosis of systemic sclerosis. She has had deformities in her feet and hands since the age of one year. Physical examination revealed poikiloderma and extremity deformities. She also had neutropenia in her bloodstream. She was diagnosed with Rothmund Thomson syndrome after genetic test results, prescribed colchicine and followed up regularly every three months. After two years of follow-up, she was diagnosed with ovarian cancer.

Abstract 6376: Establishment of the Consortium for Childhood Cancer Predisposition and the Childhood Cancer Predisposition Study

Abstract Background: Genetic predisposition contributes to a much higher proportion of cancer in children than previously appreciated. This creates a unique opportunity to develop improved methods to identify children at increased risk for cancer, enable early detection or prevention of tumors, and improve cure rates with decreased morbidity. However, several challenges have impeded successful research and systematic approaches to the care of children with cancer predisposition. Methods: We established the Consortium for Childhood Cancer Predisposition (C3P), currently comprised of seven large pediatric institutions in North America. The long-term goal of C3P is to improve outcomes for children with genetic susceptibility to cancer through collaborative research and data sharing. To this end, we have developed the Childhood Cancer Predisposition Study (CCPS), a multicenter registry and biorepository, to achieve three main aims: 1) Establish and maintain the infrastructure for recruitment, participation, collection and sharing of clinical data and biological samples for children with cancer predisposition syndromes (CPS); 2) Define the spectrum of disease in children with CPS and explore the unique characteristics and management approaches of CPS-related tumors compared to their sporadic counterparts; and 3) Evaluate the clinical impact and effectiveness of standard and emerging tumor surveillance strategies. Results: The CCPS opened to enrollment in May, 2021 and is currently recruiting at 3 member sites. To date, 276 primary subjects and 44 family members have been enrolled, 211 in the last year. In total, 37 different cancer predisposition diagnoses are represented among participants, including those that are more prevalent, e.g., Li-Fraumeni syndrome (n=42), DICER1 syndrome (n=27), and PTEN Hamartoma Syndrome (n=21), and those which are very rare, e.g., Rothmund-Thomson syndrome (n=2). There is excellent uptake on obtaining samples, with the CCPS Biorepository at Emory University receiving biospecimens from 261 subjects to date, including constitutional DNA (n=261), frozen peripheral blood mononuclear cells (n=32), and plasma samples for ctDNA analysis (n= 26). Conclusions: C3P has established the infrastructure to facilitate comprehensive collaborative work to improve outcomes for children with cancer predisposition, which represent a wide variety of disorders. Future efforts will include the development of innovative strategies to promote recruitment beyond the primary C3P sites and the support of additional clinical and biological studies of specific CPS. Citation Format: Anita Villani, Garrett M. Brodeur, Lisa R. Diller, Chloe Edgerton, Junne Kamihara, Wendy Kohlmann, Suzanne P. MacFarland, Luke Maese, David Malkin, Kim E. Nichols, Melissa R. Perrino, Sharon E. Plon, Surya Rednam, Christopher C. Porter. Establishment of the Consortium for Childhood Cancer Predisposition and the Childhood Cancer Predisposition Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6376.

Abstract B010: DNA-PKcs-dependent phosphorylation of RECQL4 promotes NHEJ by stabilizing the NHEJ machinery at DNA double-strand breaks

Abstract RECQL4, one of the five RecQ helicases in mammalian cells, guards the genome by promoting DNA replication, DNA repair, and telomere maintenance. Mutations in human RECQL4 are associated with three genetic disorders, Rothmund-Thomson syndrome (RTS), Baller-Gerold syndrome (BGS), and RAPADILINO syndrome, which display accelerated aging, developmental abnormalities, and a predisposition to cancer. It is believed that accumulation of DNA damage contributes to the clinical features observed in patients with RECQL4 mutations. Previously, RECQL4 was implicated in promoting the DNA double strand break repair pathway non-homologous end joining (NHEJ), but its role in the pathway remains unresolved. In this study, we report that RECQL4 stabilizes the NHEJ machinery at DSBs to promote repair. Specifically, we find that RECQL4 interacts with the NHEJ core factor DNA-PKcs and the interaction is increased following IR. RECQL4 promotes DNA end bridging mediated by DNA-PKcs and Ku70/80 in vitro and the accumulation/retention of NHEJ factors at DSBs in vivo. Moreover, interaction between DNA-PKcs and the other core NHEJ proteins following IR treatment is attenuated in the absence of RECQL4. These data indicate that RECQL4 promotes the stabilization of the NHEJ factors at DSBs to support formation of the NHEJ long-range synaptic complex. In addition, we observed that the kinase activity of DNA-PKcs is required for accumulation of RECQL4 to DSBs and that DNA-PKcs phosphorylates RECQL4 at six serine/threonine residues. Blocking phosphorylation at these sites reduced the recruitment of RECQL4 to DSBs, attenuated the interaction between RECQL4 and NHEJ factors, destabilized interactions between the NHEJ machinery, and resulted in decreased NHEJ. Collectively, these data illustrate reciprocal regulation between RECQL4 and DNA-PKcs in NHEJ and the potential that dysfunctional NHEJ may play a role in RECQL4-associated genetic disorders and tumorigenesis. Citation Format: Anthony J. Davis. DNA-PKcs-dependent phosphorylation of RECQL4 promotes NHEJ by stabilizing the NHEJ machinery at DNA double-strand breaks [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Damage Repair: From Basic Science to Future Clinical Application; 2024 Jan 9-11; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2024;84(1 Suppl):Abstract nr B010.

DONSON: Slding in 2 the limelight

For over a decade, it has been known that yeast Sld2, Dpb11, GINS and Polε form the pre-loading complex (pre-LC), which is recruited to a CDC45-bound MCM2–7 complex by the Sld3/Sld7 heterodimer in a phospho-dependent manner. Whilst functional orthologs of Dbp11 (TOPBP1), Sld3 (TICRR) and Sld7 (MTBP) have been identified in metazoans, controversy has surrounded the identity of the Sld2 ortholog. It was originally proposed that the RECQ helicase, RECQL4, which is mutated in Rothmund-Thomson syndrome, represented the closest vertebrate ortholog of Sld2 due to a small region of sequence homology at its N-Terminus. However, there is no clear evidence that RECQL4 is required for CMG loading. Recently, new findings suggest that the functional ortholog of Sld2 is actually DONSON, a replication fork stability factor mutated in a range of neurodevelopmental disorders characterised by microcephaly, short stature and limb abnormalities. These studies show that DONSON forms a complex with TOPBP1, GINS and Polε analogous to the pre-LC in yeast, which is required to position the GINS complex on the MCM complex and initiate DNA replication. Taken together with previously published functions for DONSON, these observations indicate that DONSON plays two roles in regulating DNA replication, one in promoting replication initiation and one in stabilising the fork during elongation. Combined, these findings may help to uncover why DONSON mutations are associated with such a wide range of clinical deficits.

A Chinese patient with Rothmund-Thomson syndrome.

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. 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. 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. 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.

Rothmund-Thomson syndrome, a disorder far from solved.

Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder characterized by a range of clinical symptoms, including poikiloderma, juvenile cataracts, short stature, sparse hair, eyebrows/eyelashes, nail dysplasia, and skeletal abnormalities. While classically associated with mutations in the RECQL4 gene, which encodes a DNA helicase involved in DNA replication and repair, three additional genes have been recently identified in RTS: ANAPC1, encoding a subunit of the APC/C complex; DNA2, which encodes a nuclease/helicase involved in DNA repair; and CRIPT, encoding a poorly characterized protein implicated in excitatory synapse formation and splicing. Here, we review the clinical spectrum of RTS patients, analyze the genetic basis of the disease, and discuss molecular functions of the affected genes, drawing some novel genotype-phenotype correlations and proposing avenues for future studies into this enigmatic disorder.

Roles of poly(ADP-ribose) polymerase 1 and mitophagy in progeroid syndromes as well as physiological ageing

Progeroid syndromes are characterized by clinical signs of premature ageing, which may contain several diseases such as Werner syndrome, Bloom syndrome, Rothmund-Thomson syndrome, Hutchinson-Gilford progeria syndrome, and Cockayne syndrome. These disorders may also exhibit some pathological involvements reminiscent of primary mitochondrial diseases. Emerging evidence has linked mitochondria even to physiological ageing. In addition, alterations in the maintenance pathway of mitochondria have been also deliberated as relevant in age-related diseases. In particular, mitophagy and its regulatory pathway might be key process for the homeostasis of mitochondria. Therefore, chronic DNA damage and/or the activation of poly[adenosine diphosphate (ADP)-ribose] polymerase 1 (PARP1) could be a threat to the mitochondrial alterations. The PARP1 is an enzyme responding to the DNA damage, which might be also involved in the mitophagy. Interestingly, the PARP1 has been reported to play an important role in the longevity of lifespan, which has attracted growing attention with the social development. This review may provide a rationalized overview of the involvement of mitochondrial oxidative stresses in genetically defined accelerated ageing, progeroid syndromes, physiological ageing, and/or age-related diseases for the innovative therapeutic approaches.

Hyperubiquitylation of DNA helicase RECQL4 by E3 ligase MITOL prevents mitochondrial entry and potentiates mitophagy

Mutations in the DNA helicase RECQL4 lead to Rothmund-Thomson Syndrome (RTS), a disorder characterized by mitochondrial dysfunctions, premature aging, and genomic instability. However, the mechanisms by which these mutations lead to pathology are unclear. Here we report that RECQL4 is ubiquitylated by a mitochondrial E3 ligase, MITOL, at two lysine residues (K1101, K1154) via K6 linkage. This ubiquitylation hampers the interaction of RECQL4 with mitochondrial importer Tom20, thereby restricting its own entry into mitochondria. We show the RECQL4 2K mutant (where both K1101 and K1154 are mutated) has increased entry into mitochondria and demonstrates enhanced mtDNA replication. We observed that the three tested RTS patient mutants were unable to enter the mitochondria and showed decreased mtDNA replication. Furthermore, we found that RECQL4 in RTS patient mutants are hyper-ubiquitylated by MITOL and form insoluble aggregate-like structures on the outer mitochondrial surface. However, depletion of MITOL allows RECQL4 expressed in these RTS mutants to enter mitochondria and rescue mtDNA replication. Finally, we show increased accumulation of hyper-ubiquitylated RECQL4 outside the mitochondria leads to the cells being potentiated to increased mitophagy. Hence, we conclude regulating the turnover of RECQL4 by MITOL may have a therapeutic effect in RTS patients.

DNA replication initiation factor RECQ4 possesses a role in antagonizing DNA replication initiation

Deletion of the conserved C-terminus of the Rothmund-Thomson syndrome helicase RECQ4 is highly tumorigenic. However, while the RECQ4 N-terminus is known to facilitate DNA replication initiation, the function of its C-terminus remains unclear. Using an unbiased proteomic approach, we identify an interaction between the RECQ4 N-terminus and the anaphase-promoting complex/cyclosome (APC/C) on human chromatin. We further show that this interaction stabilizes APC/C co-activator CDH1 and enhances APC/C-dependent degradation of the replication inhibitor Geminin, allowing replication factors to accumulate on chromatin. In contrast, the function is blocked by the RECQ4 C-terminus, which binds to protein inhibitors of APC/C. A cancer-prone, C-terminal-deleted RECQ4 mutation increases origin firing frequency, accelerates G1/S transition, and supports abnormally high DNA content. Our study reveals a role of the human RECQ4 C-terminus in antagonizing its N-terminus, thereby suppressing replication initiation, and this suppression is impaired by oncogenic mutations.

De novo myelodysplastic syndrome in a Rothmund-Thomson Syndrome patient with novel pathogenic RECQL4 variants.

Rothmund-Thomson syndrome (RTS) is a rare autosomal-recessive disorder with clinical features consisting of rash, poikiloderma, sparse hair, short stature, juvenile cataracts, skeletal abnormalities, and cancer predisposition. Genetic studies involving detection of pathogenic RECQL4 variants provide the diagnostic certitude. Osteosarcoma was found in two-thirds RECQL4-mutated RTS patients, while hematological malignancies were rarely reported. The variant diversity of RECQL4 gene has not been fully identified and mutations associated with hematologic malignancies are not well described. In this study, we presented a pedigree of RTS from a Chinese family, among which the proband was diagnosed with de novo myelodysplastic syndrome (MDS). Comprehensive medical examination and chromosome karyotyping were performed on the proband. Whole exome sequencing (WES) was performed on the proband, his sister and his mother. The familial cosegregation of sequence variants derived from WES was conducted by polymerase chain reaction-based Sanger sequencing. Structures of candidate RECQL4 mutants were done by in silico analysis to assess pathogenicity. Three novel RECQL4 germline variants, including c.T274C, c.G3014A, and c.G801C, were identified by WES and validated by Sanger sequencing. Prediction of conformation indicated that the structural stability of human RECQL4 protein was largely affected with these variants. The co-occurring U2AF1 p.S34F and TP53 p.Y220C mutations might contribute to the development of MDS. Our study expands the mutational spectrum of RECQL4 and provides underlying molecular mechanism for the development of MDS in RTS patients.

Molecular and Cellular Responses to Ionization Radiation in Untransformed Fibroblasts from the Rothmund–Thomson Syndrome: Influence of the Nucleo-Shuttling of the ATM Protein Kinase

The Rothmund–Thomson syndrome (RTS) is a rare autosomal recessive disease associated with poikiloderma, telangiectasias, sun-sensitive rash, hair growth problems, juvenile cataracts and, for a subset of some RTS patients, a high risk of cancer, especially osteosarcoma. Most of the RTS cases are caused by biallelic mutations of the RECQL4 gene, coding for the RECQL4 DNA helicase that belongs to the RecQ family. Cellular and post-radiotherapy radiosensitivity was reported in RTS cells and patients since the 1980s. However, the molecular basis of this particular phenotype has not been documented to reliably link the biological and clinical responses to the ionizing radiation (IR) of cells from RTS patients. The aim of this study was therefore to document the specificities of the radiosensitivity associated with RTS by examining the radiation-induced nucleo-shuttling of ATM (RIANS) and the recognition and repair of the DNA double-strand breaks (DSB) in three skin fibroblasts cell lines derived from RTS patients and two derived from RTS patients’ parents. The results showed that the RTS fibroblasts tested were associated with moderate but significant radiosensitivity, a high yield of micronuclei, and impaired DSB recognition but normal DSB repair at 24 h likely caused by a delayed RIANS, supported by the sequestration of ATM by some RTS proteins overexpressed in the cytoplasm. To our knowledge, this report is the first radiobiological characterization of cells from RTS patients at both molecular and cellular scales.

Perioperative Management in Rothmund–Thomson Syndrome

Rothmund-Thomson Syndrome (RTS) is a rare, multisystem disease accompanied by many anomalies that require careful attention from preoperative evaluation to discharge regarding anesthesia preparation and management. Due to craniofacial deformities accompanying facial abnormalities, maintaining the airway becomes a complete struggle with a race against time for survival. This case report presents the preoperative preparation and perioperative management, the risks that may be encountered, and the detailed preparation for a 7-year-old patient diagnosed with RTS and multiple system involvement. General anesthesia was administered to this patient, who had intrauterine growth retardation, nail streaking, redness of the bullae and legs, and a history of somatotropin treatment and antinuclear antibody (ANA) positivity under optimum conditions. Thanks to successful and detailed preoperative preparation and perioperative management, the patient was followed up and discharged without any complications. Although RTS is rare, the need for general anesthesia often arises due to juvenile cataracts, dental anomalies, syndactyly and other extremity anomalies in these patients whose airway management is complex. Furthermore, this increases the current risk in the population of these patients. Managing these patients with a multidisciplinary approach will reduce complications, morbidity, mortality, and length of stay.

The Diagnostic Dilemma of Rothmund-Thomson Syndrome Type II: A Rare Disorder with a Novel Mutation in the RECQL4 Gene in an Indian Boy

Abstract Rothmund-Thomson syndrome (RTS) is a rare autosomal recessive disorder caused by homozygous or compound heterozygous mutations in RECQL4 gene and has characteristic clinical features of poikiloderma, congenital bone defects, gastrointestinal disturbances such as chronic diarrhea and vomiting, and an increased susceptibility to malignancy. A 2½-year-old Indian boy presented with reticulate hyperpigmented erythema with superimposed hypopigmented atrophic macular lesions over the cheeks and diffuse background hyperpigmentation with multiple discrete atrophic hypopigmented macules of variable size over the abdomen and extensor aspects of the forearms. X-rays suggested metaphyseal irregularity around knee joint and radioulnar synostosis. Whole-exome sequencing was suggestive of a de novo novel RECQL4 gene mutation causing RTS Type II. There is an overlapping of clinical features of the group of syndrome associated with skin lesions, skeletal, and gastric manifestations. All these conditions present a challenge to the clinician. Thus, molecular diagnosis is the only way to resolve these phenotypically similar conditions. This report expands the RECQL4 gene pathogenic mutations spectrum.

Abstract 3779: Patient-derived iPSCs reveal pharmacologic targeting mitochondrial respiratory complex I for treating Rothmund-Thomson syndrome associated osteosarcoma

Abstract Background: Rothmund-Thomson syndrome (RTS) is an autosomal recessive genetic disorder characterized by a rash that progresses to poikiloderma; small stature; skeletal anomalies; sparse hair, eyelashes, and/or eyebrows, juvenile cataracts, and an increased risk to cancer. Type 2 RTS patients with biallelic RECQL4 pathogenic variants have a significantly increased incidence of osteosarcoma. However, there is currently no available RTS model that recapitulates the bone malignancy phenotype in this disease, severely limiting the ability of researchers to explore new treatment avenues. Here, we generated RTS patient-derived induced pluripotent stem cells (iPSCs) to dissect the pathological signaling leading to RTS patient-associated osteosarcoma. Methods: iPSCs were reprogrammed from fibroblasts of four individuals from two RTS families, each with one affected RTS proband with RECQL4 mutations and one unaffected parent. These patient iPSCs were differentiated to mesenchymal stem cells (MSCs) and then to osteoblasts, the cell-of-origin of osteosarcoma. All of these MSCs and osteoblasts were subjected to transcriptome analysis by RNA-seq. Based on enriched mitochondrial respiratory gene signatures, we also systematically analyzed the enzymatic activities of the major mitochondrial respiratory protein complexes including complex I/II/III and citrate synthase enzyme activity in RTS osteoblasts by Seahorse assay. Finally, we tested the potential therapeutic effect of clinical oxidative phosphorylation complex I inhibitor IACS-010759 to treat RTS cells and dissect the pharmacological mechanisms involved. Results: RTS iPSC-derived osteoblasts showed defective osteogenic differentiation and a gain of in vitro tumorigenic ability. Transcriptome analysis of RTS osteoblasts revealed decreased bone morphogenesis gene expression but aberrantly upregulated mitochondrial complex I gene expression. Metabolic assays of RTS osteoblasts demonstrated elevated mitochondrial respiratory complex I function, increased oxidative phosphorylation, but decreased ATP production. Inhibition of mitochondrial respiratory complex I activity by IACS-010759 selectively suppressed cellular respiration and cell viability of RTS osteoblasts. Furthermore, systems analysis of IACS-010759-induced changes to RTS osteoblasts suggested that inhibition of mitochondrial complex I in RTS osteoblasts leads to enhanced cell senescence, decreased MAPK signaling and cell cycle associated genes. Conclusion: In summary, we established an RTS iPSC disease platform to dissect the pathological mechanisms involved in RTS-associated osteosarcoma. Our data suggested that mitochondrial complex I is a potential therapeutic target for RTS-associated osteosarcoma and provides future insights for clinical treatment strategies. Citation Format: An Xu, Brittany E. Jewell, Dandan Zhu, Mo-Fan Huang, Yi-Hung Chen, Linchao Lu, Ruiying Zhao, Lisa L. Wang, Dung-Fang Lee. Patient-derived iPSCs reveal pharmacologic targeting mitochondrial respiratory complex I for treating Rothmund-Thomson syndrome associated osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3779.