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BACKGROUND: State-of-the-art genetic risk interpretation for a common complex disease such as coronary artery disease (CAD) requires assessment for both monogenic variants-such as those related to familial hypercholesterolemia-as well as the cumulative impact of many common variants, as quantified by a polygenic score. OBJECTIVES: The objective of the study was to describe a combined monogenic and polygenic CAD risk assessment program and examine its impact on patient understanding and changes to clinical management. METHODS: Study participants attended an initial visit in a preventive genomics clinic and a disclosure visit to discuss results and recommendations, primarily via telemedicine. Digital postdisclosure surveys and chart review evaluated the impact of disclosure. RESULTS: There were 60 participants (mean age 51 years, 37% women, 72% with no known CAD), including 30 (50%) referred by their cardiologists and 30 (50%) self-referred. Two (3%) participants had a monogenic variant pathogenic for familial hypercholesterolemia, and 19 (32%) had a high polygenic score in the top quintile of the population distribution. In a postdisclosure survey, both the genetic test report (in 80% of participants) and the discussion with the clinician (in 89% of participants) were ranked as very or extremely helpful in understanding the result. Of the 42 participants without CAD, 17 or 40% had a change in management, including statin initiation, statin intensification, or coronary imaging. CONCLUSIONS: Combined monogenic and polygenic assessments for CAD risk provided by preventive genomics clinics are beneficial for patients and result in changes in management in a significant portion of patients.
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BACKGROUND: The All of Us Research Program (AoURP, "the program") is an initiative, sponsored by the National Institutes of Health (NIH), that aims to enroll one million people (or more) across the USA. Through repeated engagement of participants, a research resource is being created to enable a variety of future observational and interventional studies. The program has also committed to genomic data generation and returning important health-related information to participants. METHODS: Whole-genome sequencing (WGS), variant calling processes, data interpretation, and return-of-results procedures had to be created and receive an Investigational Device Exemption (IDE) from the United States Food and Drug Administration (FDA). The performance of the entire workflow was assessed through the largest known cross-center, WGS-based, validation activity that was refined iteratively through interactions with the FDA over many months. RESULTS: The accuracy and precision of the WGS process as a device for the return of certain health-related genomic results was determined to be sufficient, and an IDE was granted. CONCLUSIONS: We present here both the process of navigating the IDE application process with the FDA and the results of the validation study as a guide to future projects which may need to follow a similar path. Changes to the program in the future will be covered in supplementary submissions to the IDE and will support additional variant classes, sample types, and any expansion to the reportable regions.
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Farmacogenética , Salud Poblacional , Genómica , Humanos , Estados Unidos , Secuenciación Completa del Genoma/métodosRESUMEN
Publicly available genetic databases promote data sharing and fuel scientific discoveries for the prevention, treatment and management of disease. In 2018, we built Color Data, a user-friendly, open access database containing genotypic and self-reported phenotypic information from 50 000 individuals who were sequenced for 30 genes associated with hereditary cancer. In a continued effort to promote access to these types of data, we launched Color Data v2, an updated version of the Color Data database. This new release includes additional clinical genetic testing results from more than 18 000 individuals who were sequenced for 30 genes associated with hereditary cardiovascular conditions as well as polygenic risk scores for breast cancer, coronary artery disease and atrial fibrillation. In addition, we used self-reported phenotypic information to implement the following four clinical risk models: Gail Model for 5-year risk of breast cancer, Claus Model for lifetime risk of breast cancer, simple office-based Framingham Coronary Heart Disease Risk Score for 10-year risk of coronary heart disease and CHARGE-AF simple score for 5-year risk of atrial fibrillation. These new features and capabilities are highlighted through two sample queries in the database. We hope that the broad dissemination of these data will help researchers continue to explore genotype-phenotype correlations and identify novel variants for functional analysis, enabling scientific discoveries in the field of population genomics. Database URL: https://data.color.com/.
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Neoplasias de la Mama , Predisposición Genética a la Enfermedad , Bases de Datos Factuales , Femenino , Estudios de Asociación Genética , Genotipo , HumanosRESUMEN
Genetic variation can predispose to disease both through (i) monogenic risk variants that disrupt a physiologic pathway with large effect on disease and (ii) polygenic risk that involves many variants of small effect in different pathways. Few studies have explored the interplay between monogenic and polygenic risk. Here, we study 80,928 individuals to examine whether polygenic background can modify penetrance of disease in tier 1 genomic conditions - familial hypercholesterolemia, hereditary breast and ovarian cancer, and Lynch syndrome. Among carriers of a monogenic risk variant, we estimate substantial gradients in disease risk based on polygenic background - the probability of disease by age 75 years ranged from 17% to 78% for coronary artery disease, 13% to 76% for breast cancer, and 11% to 80% for colon cancer. We propose that accounting for polygenic background is likely to increase accuracy of risk estimation for individuals who inherit a monogenic risk variant.
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Predisposición Genética a la Enfermedad , Herencia Multifactorial/genética , Penetrancia , Anciano , Neoplasias de la Mama/genética , Estudios de Casos y Controles , Neoplasias Colorrectales/genética , Enfermedad de la Arteria Coronaria/genética , Femenino , Genoma Humano , Humanos , Masculino , Persona de Mediana Edad , Oportunidad Relativa , Factores de RiesgoRESUMEN
BACKGROUND: Recent guidelines recommend consideration of germline testing for all newly diagnosed pancreatic ductal adenocarcinoma (PDAC). The primary aim of this study was to determine the burden of hereditary cancer susceptibility in PDAC. A secondary aim was to compare genetic testing uptake rates across different modes of genetic counselling. PATIENTS AND METHODS: All patients diagnosed with PDAC in the province of British Columbia, Canada referred to a population-based hereditary cancer program were eligible for multi-gene panel testing, irrespective of cancer family history. Any healthcare provider or patients themselves could refer. RESULTS: A total of 305 patients with PDAC were referred between July 2016 and January 2019. Two hundred thirty-five patients attended a consultation and 177 completed index germline genetic testing. 25/177 (14.1%) of unrelated patients had a pathogenic variant (PV); 19/25 PV were in known PDAC susceptibility genes with cancer screening or risk-reduction implications. PDAC was significantly associated with PV in ATM (OR, 7.73; 95% CI, 3.10 to 19.33, P = 6.14E-05) when comparing age and gender and ethnicity-matched controls tested on the same platform. The overall uptake rate for index testing was 59.2% and was significantly higher with 1-on-1 consultations and group consultations compared to telehealth consultations (88.9% vs 82.9% vs 61.8%, P < .001). CONCLUSION: In a prospective clinic-based cohort of patients with PDAC referred for testing irrespective of family history, germline PV were detected in 14.1%. PV in ATM accounted for half of all PVs and were significantly associated with PDAC. These findings support recent guidelines and will guide future service planning in this population.
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Biomarcadores de Tumor/genética , Carcinoma Ductal Pancreático/epidemiología , Costo de Enfermedad , Detección Precoz del Cáncer/métodos , Predisposición Genética a la Enfermedad , Mutación de Línea Germinal , Neoplasias Pancreáticas/epidemiología , Adulto , Anciano , Anciano de 80 o más Años , Colombia Británica/epidemiología , Carcinoma Ductal Pancreático/diagnóstico , Carcinoma Ductal Pancreático/genética , Estudios de Casos y Controles , Femenino , Estudios de Seguimiento , Pruebas Genéticas , Humanos , Masculino , Anamnesis , Persona de Mediana Edad , Neoplasias Pancreáticas/diagnóstico , Neoplasias Pancreáticas/genética , Pronóstico , Estudios Prospectivos , Estudios Retrospectivos , Factores de Riesgo , Neoplasias PancreáticasRESUMEN
BACKGROUND: Barriers to genetic testing and subsequent family cascade screening for familial hypercholesterolemia (FH) include cost, patient and provider awareness, privacy and discrimination concerns, need for a physician order, underutilization of genetic counselors, and family concerns about the implications of genetic testing for care. OBJECTIVES: The objective of the study was to determine the uptake of genetic testing with cost and privacy removed. METHODS: The FH Foundation offered free genetic testing and counseling to patients in the patient portal of the CASCADE FH Registry, who had not previously undergone genetic testing for 3 genes associated with FH (LDLR, APOB, and PCSK9). The free testing offer was extended to first-degree relatives of participants who had a positive genetic test result for cascade screening. RESULTS: Of 435 eligible patients, 147 opted in to participate, 122 consented, and 110 (68.2% female, median age: 52 years) received genetic testing. Of the participants, 64 had a positive genetic test result for a pathogenic variant in LDLR (59) or APOB (5); 11 had a variant of uncertain significance. Only 3 first-degrees relatives underwent genetic testing. CONCLUSIONS: Although there was substantial interest in genetic testing, uptake of family cascade screening was poor. Innovative approaches to increase family cascade screening should be explored.
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Pruebas Genéticas , Hiperlipoproteinemia Tipo II/diagnóstico , Hiperlipoproteinemia Tipo II/genética , Aceptación de la Atención de Salud/psicología , Aceptación de la Atención de Salud/estadística & datos numéricos , Sistema de Registros , Adulto , Anciano , Confidencialidad , Costos y Análisis de Costo , Femenino , Pruebas Genéticas/economía , Pruebas Genéticas/legislación & jurisprudencia , Humanos , Masculino , Persona de Mediana Edad , Adulto JovenRESUMEN
BACKGROUND: Inherited susceptibility to common, complex diseases may be caused by rare, pathogenic variants ("monogenic") or by the cumulative effect of numerous common variants ("polygenic"). Comprehensive genome interpretation should enable assessment for both monogenic and polygenic components of inherited risk. The traditional approach requires two distinct genetic testing technologies-high coverage sequencing of known genes to detect monogenic variants and a genome-wide genotyping array followed by imputation to calculate genome-wide polygenic scores (GPSs). We assessed the feasibility and accuracy of using low coverage whole genome sequencing (lcWGS) as an alternative to genotyping arrays to calculate GPSs. METHODS: First, we performed downsampling and imputation of WGS data from ten individuals to assess concordance with known genotypes. Second, we assessed the correlation between GPSs for 3 common diseases-coronary artery disease (CAD), breast cancer (BC), and atrial fibrillation (AF)-calculated using lcWGS and genotyping array in 184 samples. Third, we assessed concordance of lcWGS-based genotype calls and GPS calculation in 120 individuals with known genotypes, selected to reflect diverse ancestral backgrounds. Fourth, we assessed the relationship between GPSs calculated using lcWGS and disease phenotypes in a cohort of 11,502 individuals of European ancestry. RESULTS: We found imputation accuracy r2 values of greater than 0.90 for all ten samples-including those of African and Ashkenazi Jewish ancestry-with lcWGS data at 0.5×. GPSs calculated using lcWGS and genotyping array followed by imputation in 184 individuals were highly correlated for each of the 3 common diseases (r2 = 0.93-0.97) with similar score distributions. Using lcWGS data from 120 individuals of diverse ancestral backgrounds, we found similar results with respect to imputation accuracy and GPS correlations. Finally, we calculated GPSs for CAD, BC, and AF using lcWGS in 11,502 individuals of European ancestry, confirming odds ratios per standard deviation increment ranging 1.28 to 1.59, consistent with previous studies. CONCLUSIONS: lcWGS is an alternative technology to genotyping arrays for common genetic variant assessment and GPS calculation. lcWGS provides comparable imputation accuracy while also overcoming the ascertainment bias inherent to variant selection in genotyping array design.
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Variación Genética , Genoma Humano , Estudio de Asociación del Genoma Completo , Genómica , Predisposición Genética a la Enfermedad , Genética de Población , Genómica/métodos , Genotipo , Humanos , Reproducibilidad de los Resultados , Secuenciación Completa del GenomaRESUMEN
Recent advancements in next-generation sequencing have greatly expanded the use of multi-gene panel testing for hereditary cancer risk. Although genetic testing helps guide clinical diagnosis and management, testing recommendations are based on personal and family history of cancer and ethnicity, and many carriers are being missed. Herein, we report the results from 23,179 individuals who were referred for 30-gene next-generation sequencing panel testing for hereditary cancer risk, independent of current testing guidelines-38.7% of individuals would not have met National Comprehensive Cancer Network criteria for genetic testing. We identified a total of 2811 pathogenic variants in 2698 individuals for an overall pathogenic frequency of 11.6% (9.1%, excluding common low-penetrance alleles). Among individuals of Ashkenazi Jewish descent, three-quarters of pathogenic variants were outside of the three common BRCA1 and BRCA2 founder alleles. Across all ethnic groups, pathogenic variants in BRCA1 and BRCA2 occurred most frequently, but the contribution of pathogenic variants in other genes on the panel varied. Finally, we found that 21.7% of individuals with pathogenic variants in genes with well-established genetic testing recommendations did not meet corresponding National Comprehensive Cancer Network criteria. Taken together, the results indicate that more individuals are at genetic risk for hereditary cancer than are identified by current testing guidelines and/or use of single-gene or single-site testing.
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Biomarcadores de Tumor , Pruebas Genéticas , Heterocigoto , Síndromes Neoplásicos Hereditarios/diagnóstico , Síndromes Neoplásicos Hereditarios/genética , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Alelos , Femenino , Frecuencia de los Genes , Predisposición Genética a la Enfermedad , Pruebas Genéticas/métodos , Humanos , Masculino , Persona de Mediana Edad , Mutación , Síndromes Neoplásicos Hereditarios/mortalidad , Guías de Práctica Clínica como Asunto , Pronóstico , Adulto JovenRESUMEN
Deciphering how signaling pathways interact during development is necessary for understanding the etiopathogenesis of congenital malformations and disease. In several embryonic structures, components of the Hedgehog and retinoic acid pathways, two potent players in development and disease are expressed and operate in the same or adjacent tissues and cells. Yet whether and, if so, how these pathways interact during organogenesis is, to a large extent, unclear. Using genetic and experimental approaches in the mouse, we show that during development of ontogenetically different organs, including the tail, genital tubercle, and secondary palate, Sonic hedgehog (SHH) loss-of-function causes anomalies phenocopying those induced by enhanced retinoic acid signaling and that SHH is required to prevent supraphysiological activation of retinoic signaling through maintenance and reinforcement of expression of the Cyp26 genes. Furthermore, in other tissues and organs, disruptions of the Hedgehog or the retinoic acid pathways during development generate similar phenotypes. These findings reveal that rigidly calibrated Hedgehog and retinoic acid activities are required for normal organogenesis and tissue patterning.
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Familia 26 del Citocromo P450/genética , Desarrollo Embrionario/genética , Proteínas Hedgehog/genética , Ácido Retinoico 4-Hidroxilasa/genética , Animales , Apoptosis/genética , Diferenciación Celular/genética , Embrión de Mamíferos , Células Epiteliales/metabolismo , Regulación del Desarrollo de la Expresión Génica/genética , Ratones , Organogénesis/genética , Transducción de Señal/genética , Diente/crecimiento & desarrollo , Diente/metabolismo , Tretinoina/metabolismoRESUMEN
Next generation sequencing multi-gene panels have greatly improved the diagnostic yield and cost effectiveness of genetic testing and are rapidly being integrated into the clinic for hereditary cancer risk. With this technology comes a dramatic increase in the volume, type and complexity of data. This invaluable data though is too often buried or inaccessible to researchers, especially to those without strong analytical or programming skills. To effectively share comprehensive, integrated genotypic-phenotypic data, we built Color Data, a publicly available, cloud-based database that supports broad access and data literacy. The database is composed of 50 000 individuals who were sequenced for 30 genes associated with hereditary cancer risk and provides useful information on allele frequency and variant classification, as well as associated phenotypic information such as demographics and personal and family history. Our user-friendly interface allows researchers to easily execute their own queries with filtering, and the results of queries can be shared and/or downloaded. The rapid and broad dissemination of these research results will help increase the value of, and reduce the waste in, scientific resources and data. Furthermore, the database is able to quickly scale and support integration of additional genes and human hereditary conditions. We hope that this database will help researchers and scientists explore genotype-phenotype correlations in hereditary cancer, identify novel variants for functional analysis and enable data-driven drug discovery and development.
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Bases de Datos Genéticas , Variación Genética , Adulto , Alelos , Proteína BRCA1/genética , Proteína BRCA2/genética , Neoplasias Colorrectales Hereditarias sin Poliposis/genética , Femenino , Efecto Fundador , Genotipo , Humanos , Judíos/genética , Masculino , Persona de Mediana Edad , Fenotipo , Motor de Búsqueda , Interfaz Usuario-ComputadorRESUMEN
Precise regulation of the amplitude and duration of receptor tyrosine kinase (RTK) signaling is critical for the execution of cellular programs and behaviors. Understanding these control mechanisms has important implications for the field of developmental biology, and in recent years, the question of how augmentation or attenuation of RTK signaling via feedback loops modulates development has become of increasing interest. RTK feedback regulation is also important for human disease research; for example, germline mutations in genes that encode RTK signaling pathway components cause numerous human congenital syndromes, and somatic alterations contribute to the pathogenesis of diseases such as cancers. In this review, we survey regulators of RTK signaling that tune receptor activity and intracellular transduction cascades, with a focus on the roles of these genes in the developing embryo. We detail the diverse inhibitory mechanisms utilized by negative feedback regulators that, when lost or perturbed, lead to aberrant increases in RTK signaling. We also discuss recent biochemical and genetic insights into positive regulators of RTK signaling and how these proteins function in tandem with negative regulators to guide embryonic development.
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Embrión de Mamíferos/embriología , Desarrollo Embrionario , Regulación del Desarrollo de la Expresión Génica , Proteínas Tirosina Quinasas Receptoras/metabolismo , Transducción de Señal , Animales , Embrión de Mamíferos/patología , Humanos , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/patología , Proteínas Tirosina Quinasas Receptoras/genéticaRESUMEN
Li-Fraumeni syndrome (LFS) is an inherited, autosomal-dominant condition that predisposes individuals to a wide-spectrum of tumors at an early age. Approximately 70% of families with classic LFS have pathogenic variants in the tumor suppressor gene TP53 that disrupt protein function or stability. While more than 70% of pathogenic variants in TP53 are missense variants, the vast majority occur very infrequently, and thus their clinical significance is uncertain or conflicting. Here, we report an extremely rare TP53 missense variant, c.799C > T (p.Arg267Trp), identified in a 2-year-old Saudi proband diagnosed with choroid plexus carcinoma (CPC) and six of his first- and second-degree relatives. CPC is frequently found in families with LFS, and this is the first detailed report of a family with this variant. Intriguingly, the proband's father is homozygous for TP53 c.799C > T and phenotypically normal at 39 years of age. While loss of TP53 heterozygosity is often observed in tumors from individuals with LFS, homozygous germline TP53 pathogenic variants are rare. Based on our analysis of this single family, we hypothesize that TP53 c.799C > T has low or variable penetrance for LFS, with predisposition to the development of CPC. The observations from this family have furthered our understanding of the phenotypic variability that may be caused by one variant of TP53, even in the same family, and suggest that other factors (genetic and/or environmental) may play a role in mechanism of disease manifestation in LFS.
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Ribosome biogenesis is a global process required for growth and proliferation in all cells, but disruptions in this process surprisingly lead to tissue-specific phenotypic disorders termed ribosomopathies. Pathogenic variants in the RNA Polymerase (Pol) I subunit POLR1A cause Acrofacial Dysostosis-Cincinnati type, which is characterized by craniofacial and limb anomalies. In a zebrafish model of Acrofacial Dysostosis-Cincinnati type, we demonstrate that polr1a-/- mutants exhibit deficient 47S rRNA transcription, reduced monosomes and polysomes and, consequently, defects in protein translation. This results in Tp53-dependent neuroepithelial apoptosis, diminished neural crest cell proliferation and cranioskeletal anomalies. This indicates that POLR1A is critical for rRNA transcription, which is considered a rate limiting step in ribosome biogenesis, underpinning its requirement for neuroepithelial cell and neural crest cell proliferation and survival. To understand the contribution of the Tp53 pathway to the pathogenesis of Acrofacial Dysostosis-Cincinnati type, we genetically inhibited tp53 in polr1a-/- mutant embryos. Tp53 inhibition suppresses neuroepithelial apoptosis and partially ameliorates the polr1a mutant phenotype. However, complete rescue of cartilage development is not observed due to the failure to improve rDNA transcription and neural crest cell proliferation. Altogether, these data reveal specific functions for both Tp53-dependent and independent signaling downstream of polr1a in ribosome biogenesis during neural crest cell and craniofacial development, in the pathogenesis of Acrofacial Dysostosis-Cincinnati type. Furthermore, our work sets the stage for identifying Tp53-independent therapies to potentially prevent Acrofacial dysostosis-Cincinnati type and other similar ribosomopathies.
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Deformidades Congénitas de las Extremidades/metabolismo , Disostosis Mandibulofacial/metabolismo , Cresta Neural/patología , Proteína p53 Supresora de Tumor/metabolismo , Proteínas de Pez Cebra/metabolismo , Animales , Diferenciación Celular/genética , Proliferación Celular/genética , Modelos Animales de Enfermedad , Embrión no Mamífero , Regulación del Desarrollo de la Expresión Génica , Humanos , Deformidades Congénitas de las Extremidades/patología , Disostosis Mandibulofacial/patología , Mutación , ARN Polimerasa I/genética , ARN Polimerasa I/metabolismo , Transducción de Señal , Proteína p53 Supresora de Tumor/genética , Pez Cebra/embriología , Pez Cebra/genética , Proteínas de Pez Cebra/genéticaRESUMEN
The interaction between signaling pathways is a central question in the study of organogenesis. Using the developing murine tongue as a model, we uncovered unknown relationships between Sonic hedgehog (SHH) and retinoic acid (RA) signaling. Genetic loss of SHH signaling leads to enhanced RA activity subsequent to loss of SHH-dependent expression of Cyp26a1 and Cyp26c1. This causes a cell identity switch, prompting the epithelium of the tongue to form heterotopic minor salivary glands and to overproduce oversized taste buds. At developmental stages during which Wnt10b expression normally ceases and Shh becomes confined to taste bud cells, loss of SHH inputs causes the lingual epithelium to undergo an ectopic and anachronic expression of Shh and Wnt10b in the basal layer, specifying de novo taste placode induction. Surprisingly, in the absence of SHH signaling, lingual epithelial cells adopted a Merkel cell fate, but this was not caused by enhanced RA signaling. We show that RA promotes, whereas SHH, acting strictly within the lingual epithelium, inhibits taste placode and lingual gland formation by thwarting RA activity. These findings reveal key functions for SHH and RA in cell fate specification in the lingual epithelium and aid in deciphering the molecular mechanisms that assign cell identity.
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Diferenciación Celular/efectos de los fármacos , Epitelio/efectos de los fármacos , Proteínas Hedgehog/metabolismo , Tretinoina/farmacología , Alelos , Animales , Línea Celular , Familia 26 del Citocromo P450/genética , Familia 26 del Citocromo P450/metabolismo , Células Epiteliales/metabolismo , Epitelio/crecimiento & desarrollo , Femenino , Proteínas Hedgehog/genética , Masculino , Células de Merkel/efectos de los fármacos , Células de Merkel/metabolismo , Ratones , Ácido Retinoico 4-Hidroxilasa/genética , Ácido Retinoico 4-Hidroxilasa/metabolismo , Transducción de Señal , Papilas Gustativas/metabolismo , Lengua/crecimiento & desarrollo , Proteínas Wnt/genética , Proteínas Wnt/metabolismoRESUMEN
Fibroblast Growth Factor (FGF) signaling promotes self-renewal in progenitor cells by encouraging proliferation and inhibiting cellular senescence. Yet, these beneficial effects can be hijacked by disease-causing mutations in FGF receptor (FGFR) during embryogenesis. By studying dominant FGFR2 mutations that are germline in bent bone dysplasia syndrome (BBDS), we reveal a mechanistic connection between FGFR2, ribosome biogenesis, and cellular stress that links cell fate determination to disease pathology. We previously showed that FGFR2 mutations in BBDS, which amplify nucleolar targeting of FGFR2, activate ribosomal DNA (rDNA) transcription and delay differentiation in osteoprogenitor cells and patient-derived bone. Here we find that the BBDS mutations augment the ability of FGFR2 to recruit histone-remodeling factors that epigenetically activate transcriptionally silent rDNA. Nucleolar morphology is controlled by chromatin structure, and the high levels of euchromatic rDNA induced by the BBDS mutations direct nucleolar disorganization, alter ribosome biogenesis, and activate the Rpl11-Mdm2-p53 nucleolar stress response pathway. Inhibition of p53 in cells expressing the FGFR2 mutations in BBDS rescues delayed osteoblast differentiation, suggesting that p53 activation is an essential pathogenic factor in, and potential therapeutic target for, BBDS. This work establishes rDNA as developmentally regulated loci that receive direct input from FGF signaling to balance self-renewal and cell fate determination.
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Receptor Tipo 2 de Factor de Crecimiento de Fibroblastos/genética , Receptor Tipo 2 de Factor de Crecimiento de Fibroblastos/metabolismo , Enfermedades del Desarrollo Óseo/genética , Enfermedades del Desarrollo Óseo/metabolismo , Diferenciación Celular/fisiología , Proliferación Celular/genética , Proliferación Celular/fisiología , ADN Ribosómico/metabolismo , Humanos , Mutación , Osteoblastos/metabolismo , Osteogénesis/genética , Fragmentos de Péptidos/metabolismo , Proteínas Proto-Oncogénicas c-mdm2/metabolismo , Ribosomas/metabolismo , Transducción de Señal , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
Changes in ribosome biogenesis are tightly linked to cell growth, proliferation, and differentiation. The rate of ribosome biogenesis is established by RNA Pol I-mediated transcription of ribosomal RNA (rRNA). Thus, rRNA gene transcription is a key determinant of cell behavior. Here, we show that ribosome biogenesis is dynamically regulated during osteoblast differentiation. Upon osteoinduction, osteoprogenitor cells transiently silence a subset of rRNA genes through a reversible mechanism that is initiated through biphasic nucleolar depletion of UBF1 and then RNA Pol I. Nucleolar depletion of UBF1 is coincident with an increase in the number of silent but transcriptionally permissible rRNA genes. This increase in the number of silent rRNA genes reduces levels of ribosome biogenesis and subsequently, protein synthesis. Together these findings demonstrate that fluctuations in rRNA gene transcription are determined by nucleolar occupancy of UBF1 and closely coordinated with the early events necessary for acquisition of the osteoblast cell fate.
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Diferenciación Celular , Osteoblastos/citología , Ribosomas/metabolismo , Células 3T3 , Animales , Ratones , Biosíntesis de Proteínas , ARN Ribosómico/genética , Transcripción GenéticaRESUMEN
Ribosome biogenesis is a global process required for growth and proliferation of all cells, yet perturbation of ribosome biogenesis during human development often leads to tissue-specific defects termed ribosomopathies. Transcription of the ribosomal RNAs (rRNAs) by RNA polymerases (Pol) I and III, is considered a rate limiting step of ribosome biogenesis and mutations in the genes coding for RNA Pol I and III subunits, POLR1C and POLR1D cause Treacher Collins syndrome, a rare congenital craniofacial disorder. Our understanding of the functions of individual RNA polymerase subunits, however, remains poor. We discovered that polr1c and polr1d are dynamically expressed during zebrafish embryonic development, particularly in craniofacial tissues. Consistent with this pattern of activity, polr1c and polr1d homozygous mutant zebrafish exhibit cartilage hypoplasia and cranioskeletal anomalies characteristic of humans with Treacher Collins syndrome. Mechanistically, we discovered that polr1c and polr1d loss-of-function results in deficient ribosome biogenesis, Tp53-dependent neuroepithelial cell death and a deficiency of migrating neural crest cells, which are the primary progenitors of the craniofacial skeleton. More importantly, we show that genetic inhibition of tp53 can suppress neuroepithelial cell death and ameliorate the skeletal anomalies in polr1c and polr1d mutants, providing a potential avenue to prevent the pathogenesis of Treacher Collins syndrome. Our work therefore has uncovered tissue-specific roles for polr1c and polr1d in rRNA transcription, ribosome biogenesis, and neural crest and craniofacial development during embryogenesis. Furthermore, we have established polr1c and polr1d mutant zebrafish as models of Treacher Collins syndrome together with a unifying mechanism underlying its pathogenesis and possible prevention.
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Anomalías Craneofaciales/genética , ARN Polimerasas Dirigidas por ADN/genética , Disostosis Mandibulofacial/genética , Cresta Neural/crecimiento & desarrollo , Animales , Diferenciación Celular/genética , Anomalías Craneofaciales/fisiopatología , ARN Polimerasas Dirigidas por ADN/biosíntesis , Discapacidades del Desarrollo/genética , Discapacidades del Desarrollo/fisiopatología , Modelos Animales de Enfermedad , Desarrollo Embrionario/genética , Humanos , Disostosis Mandibulofacial/fisiopatología , Mutación , Proteína p53 Supresora de Tumor/genética , Pez Cebra/genética , Pez Cebra/crecimiento & desarrolloRESUMEN
Craniofacial development is an intricate process of patterning, morphogenesis, and growth that involves many tissues within the developing embryo. Genetic misregulation of these processes leads to craniofacial malformations, which comprise over one-third of all congenital birth defects. Significant advances have been made in the clinical management of craniofacial disorders, but currently very few treatments specifically target the underlying molecular causes. Here, we review recent studies in which modeling of craniofacial disorders in primary patient cells, patient-derived induced pluripotent stem cells (iPSCs), and mice have enhanced our understanding of the etiology and pathophysiology of these disorders while also advancing therapeutic avenues for their prevention.
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In the developing embryo, signaling pathways define how the mesenchymal precursors of bone form individual skeletal elements with the proper size, shape, orientation, and integration. Disruptions to these signaling processes lead to a large variety of congenital conditions categorized as skeletal dysplasias. While individually these skeletal disorders are rare, collectively they represent a significant cause of disability in the United States. Here, we discuss how the study of these rare events in human development reveal novel and unexpected insights into signaling mechanisms that regulate normal skeletal development and, in the process, advance novel molecular-based therapies for treatment of rare and common bone diseases alike.
Asunto(s)
Enfermedades del Desarrollo Óseo/embriología , Enfermedades Raras/embriología , Transducción de Señal , Cráneo/embriología , Animales , Enfermedades del Desarrollo Óseo/genética , Enfermedades del Desarrollo Óseo/terapia , Regulación del Desarrollo de la Expresión Génica , Predisposición Genética a la Enfermedad/genética , Humanos , Mutación , Enfermedades Raras/genética , Enfermedades Raras/terapia , Cráneo/metabolismoRESUMEN
Fibroblast growth factor receptor 2 (FGFR2) promotes osteoprogenitor proliferation and differentiation during bone development, yet how the receptor elicits these distinct cellular responses remains unclear. Analysis of the FGFR2-skeletal disorder bent bone dysplasia syndrome (BBDS) demonstrates that FGFR2, in addition to its canonical signaling activities at the plasma membrane, regulates bone formation from within the nucleolus. Previously, we showed that the unique FGFR2 mutations that cause BBDS reduce receptor levels at the plasma membrane and diminish responsiveness to extracellular FGF2. In this study, we find that these mutations, despite reducing canonical signaling, enhance nucleolar occupancy of FGFR2 at the ribosomal DNA (rDNA) promoter. Nucleolar FGFR2 activates rDNA transcription via interactions with FGF2 and UBF1 by de-repressing RUNX2. An increase in the nucleolar activity of FGFR2 in BBDS elevates levels of ribosomal RNA in the developing bone, consequently promoting osteoprogenitor cell proliferation and decreasing differentiation. Identifying FGFR2 as a transcriptional regulator of rDNA in bone unexpectedly reveals a nucleolar route for FGF signaling that allows for independent regulation of osteoprogenitor cell proliferation and differentiation.