RESUMEN
BACKGROUND: The DNA-repair enzyme Artemis is essential for rearrangement of T- and B-cell receptors. Mutations in DCLRE1C, which encodes Artemis, cause Artemis-deficient severe combined immunodeficiency (ART-SCID), which is poorly responsive to allogeneic hematopoietic-cell transplantation. METHODS: We carried out a phase 1-2 clinical study of the transfusion of autologous CD34+ cells, transfected with a lentiviral vector containing DCLRE1C, in 10 infants with newly diagnosed ART-SCID. We followed them for a median of 31.2 months. RESULTS: Marrow harvest, busulfan conditioning, and lentiviral-transduced CD34+ cell infusion produced the expected grade 3 or 4 adverse events. All the procedures met prespecified criteria for feasibility at 42 days after infusion. Gene-marked T cells were detected at 6 to 16 weeks after infusion in all the patients. Five of 6 patients who were followed for at least 24 months had T-cell immune reconstitution at a median of 12 months. The diversity of T-cell receptor ß chains normalized by 6 to 12 months. Four patients who were followed for at least 24 months had sufficient B-cell numbers, IgM concentration, or IgM isohemagglutinin titers to permit discontinuation of IgG infusions. Three of these 4 patients had normal immunization responses, and the fourth has started immunizations. Vector insertion sites showed no evidence of clonal expansion. One patient who presented with cytomegalovirus infection received a second infusion of gene-corrected cells to achieve T-cell immunity sufficient for viral clearance. Autoimmune hemolytic anemia developed in 4 patients 4 to 11 months after infusion; this condition resolved after reconstitution of T-cell immunity. All 10 patients were healthy at the time of this report. CONCLUSIONS: Infusion of lentiviral gene-corrected autologous CD34+ cells, preceded by pharmacologically targeted low-exposure busulfan, in infants with newly diagnosed ART-SCID resulted in genetically corrected and functional T and B cells. (Funded by the California Institute for Regenerative Medicine and the National Institute of Allergy and Infectious Diseases; ClinicalTrials.gov number, NCT03538899.).
Asunto(s)
Terapia Genética , Inmunodeficiencia Combinada Grave , Humanos , Lactante , Busulfano/uso terapéutico , Terapia Genética/efectos adversos , Terapia Genética/métodos , Inmunoglobulina M , Inmunodeficiencia Combinada Grave/genética , Inmunodeficiencia Combinada Grave/inmunología , Inmunodeficiencia Combinada Grave/terapia , Enzimas Reparadoras del ADN/deficiencia , Enzimas Reparadoras del ADN/genética , Antígenos CD34/administración & dosificación , Antígenos CD34/inmunología , Trasplante Autólogo/efectos adversos , Trasplante Autólogo/métodos , Lentivirus , Vectores Genéticos/administración & dosificación , Vectores Genéticos/efectos adversos , Vectores Genéticos/uso terapéutico , Linfocitos T/inmunología , Linfocitos B/inmunologíaRESUMEN
The perception of multisensory emotion cues is affected by culture. For example, East Asians rely more on vocal, as compared to facial, affective cues compared to Westerners. However, it is unknown whether these cultural differences exist in childhood, and if not, which processing style is exhibited in children. The present study tested East Asian and Western children, as well as adults from both cultural backgrounds, to probe cross-cultural similarities and differences at different ages, and to establish the weighting of each modality at different ages. Participants were simultaneously shown a face and a voice expressing either congruent or incongruent emotions, and were asked to judge whether the person was happy or angry. Replicating previous research, East Asian adults relied more on vocal cues than did Western adults. Young children from both cultural groups, however, behaved like Western adults, relying primarily on visual information. The proportion of responses based on vocal cues increased with age in East Asian, but not Western, participants. These results suggest that culture is an important factor in developmental changes in the perception of facial and vocal affective information.
Asunto(s)
Expresión Facial , Voz , Adulto , Ira , Niño , Preescolar , Emociones , Humanos , PercepciónRESUMEN
Rapid phosphorylation of histone variant H2AX proximal to DNA breaks is an initiating event and a hallmark of eukaryotic DNA damage responses. Three mammalian kinases are known to phosphorylate H2AX in response to DNA damage. However, the mechanism(s) for damage-localized phosphorylation remains incompletely understood. The DNA-dependent protein kinase (DNA-PK) is the most abundant H2AX-modifying kinases and uniquely activated by binding DNA termini. Here, we have developed a novel approach to examine enzyme activity and substrate properties by executing biochemical assays on intact cellular structures. We apply this approach to examine the mechanisms of localized protein modification in chromatin within fixed cells. DNA-PK retains substrate specificity and independently generates break-localized γH2AX foci in chromatin. In situ DNA-PK activity recapitulates localization and intensity of in vivo H2AX phosphorylation and requires no active cellular processes. Nuclease treatments or addition of exogenous DNA resulted in genome-wide H2AX phosphorylation, showing that DNA termini dictated the locality of H2AX phosphorylation in situ. DNA-PK also reconstituted focal phosphorylation of structural maintenance of chromatin protein 1, but not activating transcription factor 2. Allosteric regulation of DNA-PK by DNA termini protruding from chromatin constitutes an autonomous mechanism for break-localized protein phosphorylation that generates sub-nuclear foci. We discuss generalized implications of this mechanism in localizing mammalian DNA damage responses.
Asunto(s)
Cromatina/metabolismo , Daño del ADN , Proteína Quinasa Activada por ADN/metabolismo , Procesamiento Proteico-Postraduccional , Factor de Transcripción Activador 2/metabolismo , Regulación Alostérica , Proteínas de Ciclo Celular/metabolismo , Línea Celular , Cromatina/genética , Proteínas Cromosómicas no Histona/metabolismo , Proteína Quinasa Activada por ADN/fisiología , Activación Enzimática , Histonas/metabolismo , Humanos , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Microscopía Fluorescente , Fosforilación , Proteínas Proto-Oncogénicas c-akt/metabolismo , Transducción de Señal , Especificidad por Sustrato , Proteína 1 de Unión al Supresor Tumoral P53RESUMEN
Deficiency in Artemis is associated with lack of V(D)J recombination, sensitivity to radiation and radiomimetic drugs, and failure to repair a subset of DNA double-strand breaks (DSBs). Artemis harbors an endonuclease activity that trims both 5'- and 3'-ends of DSBs. To examine whether endonucleolytic trimming of terminally blocked DSBs by Artemis is a biologically relevant function, Artemis-deficient fibroblasts were stably complemented with either wild-type Artemis or an endonuclease-deficient D165N mutant. Wild-type Artemis completely restored resistance to γ-rays, bleomycin and neocarzinostatin, and also restored DSB-repair proficiency in G0/G1 phase as measured by pulsed-field gel electrophoresis and repair focus resolution. In contrast, cells expressing the D165N mutant, even at very high levels, remained as chemo/radiosensitive and repair deficient as the parental cells, as evidenced by persistent γ-H2AX, 53BP1 and Mre11 foci that slowly increased in size and ultimately became juxtaposed with promyelocytic leukemia protein nuclear bodies. In normal fibroblasts, overexpression of wild-type Artemis increased radioresistance, while D165N overexpression conferred partial repair deficiency following high-dose radiation. Restoration of chemo/radioresistance by wild-type, but not D165N Artemis suggests that the lack of endonucleolytic trimming of DNA ends is the principal cause of sensitivity to double-strand cleaving agents in Artemis-deficient cells.
Asunto(s)
Roturas del ADN de Doble Cadena , Reparación del ADN , Endodesoxirribonucleasas/genética , Proteínas Nucleares/genética , Tolerancia a Radiación , Bleomicina/toxicidad , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/efectos de la radiación , Proteínas de Unión al ADN , Endodesoxirribonucleasas/deficiencia , Endodesoxirribonucleasas/metabolismo , Endonucleasas , Fase G1 , Humanos , Mutación , Proteínas Nucleares/análisis , Proteínas Nucleares/deficiencia , Proteínas Nucleares/metabolismo , Proteína de la Leucemia Promielocítica , Factores de Transcripción/análisis , Proteínas Supresoras de Tumor/análisis , Cinostatina/toxicidadRESUMEN
Historically, there has been a great deal of confusion in the literature regarding cross-cultural differences in attitudes towards artificial agents and preferences for their physical appearance. Previous studies have almost exclusively assessed attitudes using self-report measures (i.e., questionnaires). In the present study, we sought to expand our knowledge on the influence of cultural background on explicit and implicit attitudes towards robots and avatars. Using the Negative Attitudes Towards Robots Scale and the Implicit Association Test in a Japanese and Dutch sample, we investigated the effect of culture and robots' body types on explicit and implicit attitudes across two experiments (total n = 669). Partly overlapping with our hypothesis, we found that Japanese individuals had a more positive explicit attitude towards robots compared to Dutch individuals, but no evidence of such a difference was found at the implicit level. As predicted, the implicit preference towards humans was moderate in both cultural groups, but in contrast to what we expected, neither culture nor robot embodiment influenced this preference. These results suggest that only at the explicit but not implicit level, cultural differences appear in attitudes towards robots. Supplementary Information: The online version contains supplementary material available at 10.1007/s12369-022-00917-7.
RESUMEN
Due to the COVID-19 pandemic, the significance of online research has been rising in the field of psychology. However, online experiments with child participants are rare compared to those with adults. In this study, we investigated the validity of web-based experiments with child participants 4-12 years old and adult participants. They performed simple emotional perception tasks in an experiment designed and conducted on the Gorilla Experiment Builder platform. After short communication with each participant via Zoom videoconferencing software, participants performed the auditory task (judging emotion from vocal expression) and the visual task (judging emotion from facial expression). The data collected were compared with data collected in our previous similar laboratory experiment, and similar tendencies were found. For the auditory task in particular, we replicated differences in accuracy perceiving vocal expressions between age groups and also found the same native language advantage. Furthermore, we discuss the possibility of using online cognitive studies for future developmental studies.
RESUMEN
The inhibitor of basic helix-loop-helix transcription factors, Id-1, is an important gene whose expression increases during prostate cancer progression and that upregulates proliferation, migration and invasion. We used microarray analysis to identify the downstream genes whose transcriptional expression is modulated by Id-1 protein. We compared gene expression in control LNCaP cells and Id-1-transduced LNCaP cells, which become significantly more aggressive after Id-1 overexpression, thus mimicking the high levels of Id-1 detected in metastatic cell lines. We used the Affy HTA U133A Expression Arrays with 45,000 probe sets representing more than 39,000 transcripts. We found that one of the most significantly downregulated genes on Id-1 expression was kallikrein 3 [also called prostate specific antigen (PSA)], the most commonly used biomarker of prostate cancer. Here, we show that the reduction in PSA mRNA and protein expression associated with high-grade prostate cancers, which generally express high levels of Id-1, could be the consequence of Id-1 overexpression.
Asunto(s)
Biomarcadores de Tumor/metabolismo , Carcinoma/metabolismo , Proteína 1 Inhibidora de la Diferenciación/metabolismo , Antígeno Prostático Específico/metabolismo , Neoplasias de la Próstata/metabolismo , Western Blotting , Carcinoma/inmunología , Línea Celular Tumoral , Progresión de la Enfermedad , Regulación hacia Abajo , Regulación Neoplásica de la Expresión Génica , Secuencias Hélice-Asa-Hélice/efectos de los fármacos , Humanos , Proteína 1 Inhibidora de la Diferenciación/farmacología , Masculino , Análisis de Secuencia por Matrices de Oligonucleótidos , Reacción en Cadena de la Polimerasa , Antígeno Prostático Específico/efectos de los fármacos , Neoplasias de la Próstata/inmunología , ARN Interferente Pequeño/metabolismo , Regulación hacia ArribaRESUMEN
This study investigated the developmental paths in the use of audiovisual information for the perception of emotions and phonemes by Japanese speakers. Children aged 5 to 12 years and adults aged 30 to 39 years engaged in an emotion perception task in which speakers expressed their emotions through their faces and voices, and a phoneme perception task using phonemic information in speakers' lip movements and speech sounds. Results indicated that Japanese children's judgement of emotions by using auditory information increased with increasing age, whereas the use of audiovisual information for judging phonemes remained constant with increasing age. Moreover, adults were affected by visual information more than children. We discuss whether these differences in developmental patterns are due to differential integration processes for information indicative of emotions and phonemes, as well as possible cultural / linguistic reasons for these differences.
Asunto(s)
Desarrollo Infantil , Emociones , Fonética , Percepción del Habla , Percepción Visual , Adulto , Pueblo Asiatico , Niño , Femenino , Humanos , Japón , Juicio , Lectura de los Labios , Percepción Sonora , Masculino , Acústica del LenguajeRESUMEN
Cellular senescence is a tumor suppressive mechanism that can paradoxically contribute to aging pathologies. Despite evidence of immune clearance in mouse models, it is not known how senescent cells (SnCs) persist and accumulate with age or in tumors in individuals. Here, we identify cooperative mechanisms that orchestrate the immunoevasion and persistence of normal and cancer human SnCs through extracellular targeting of natural killer receptor signaling. Damaged SnCs avoid immune recognition through MMPs-dependent shedding of NKG2D-ligands reinforced via paracrine suppression of NKG2D receptor-mediated immunosurveillance. These coordinated immunoediting processes are evident in residual, drug-resistant tumors from cohorts of >700 prostate and breast cancer patients treated with senescence-inducing genotoxic chemotherapies. Unlike in mice, these reversible senescence-subversion mechanisms are independent of p53/p16 and exacerbated in oncogenic RAS-induced senescence. Critically, the p16INK4A tumor suppressor can disengage the senescence growth arrest from the damage-associated immune senescence program, which is manifest in benign nevi lesions where indolent SnCs accumulate over time and preserve a non-pro-inflammatory tissue microenvironment maintaining NKG2D-mediated immunosurveillance. Our study shows how subpopulations of SnCs elude immunosurveillance, and reveals secretome-targeted therapeutic strategies to selectively eliminate -and restore the clearance of- the detrimental SnCs that actively persist after chemotherapy and accumulate at sites of aging pathologies.
Asunto(s)
Envejecimiento/inmunología , Antineoplásicos/farmacología , Neoplasias de la Mama/tratamiento farmacológico , Senescencia Celular/inmunología , Resistencia a Antineoplásicos/inmunología , Neoplasias de la Próstata/tratamiento farmacológico , Escape del Tumor/inmunología , Envejecimiento/patología , Animales , Antineoplásicos/uso terapéutico , Biopsia , Mama/patología , Neoplasias de la Mama/inmunología , Neoplasias de la Mama/patología , Línea Celular Tumoral , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , Daño del ADN/efectos de los fármacos , Conjuntos de Datos como Asunto , Femenino , Perfilación de la Expresión Génica , Regulación Neoplásica de la Expresión Génica/inmunología , Humanos , Vigilancia Inmunológica/efectos de los fármacos , Vigilancia Inmunológica/inmunología , Masculino , Metaloendopeptidasas/metabolismo , Ratones , Subfamilia K de Receptores Similares a Lectina de Células NK/antagonistas & inhibidores , Subfamilia K de Receptores Similares a Lectina de Células NK/inmunología , Subfamilia K de Receptores Similares a Lectina de Células NK/metabolismo , Próstata/patología , Neoplasias de la Próstata/inmunología , Neoplasias de la Próstata/patología , Análisis de Matrices Tisulares , Escape del Tumor/efectos de los fármacos , Microambiente Tumoral/genética , Microambiente Tumoral/inmunologíaRESUMEN
DNA ligase 4 deficiency (LIG4-SCID) causes lymphopenia (T-B-NK+) and a radiosensitive SCID (RS-SCID) phenotype. We demonstrate, for the first time, flow cytometric-based kinetic analysis of phosphorylated H2AX (γH2AX) in lymphocyte subsets, especially NK cells, for the assessment of LIG4-SCID. Measurement of phosphorylated (p) ATM, SMC1, and H2AX (γH2AX) was performed by flow cytometry to assess DNA repair defects in a 3-year-old girl. Functional assessment (phosphorylation) was measured in T and NK cells (B cells were absent) before irradiation (background control) or after low-dose (2Gy) irradiation (1 and 24 hours). We observed maximal γH2AX at 1 hour postirradiation, with dephosphorylation at 24 hours postirradiation in healthy control patients. The patient showed normal frequencies (percentage) of T cells and NK cells for γH2AX, but increased levels of γH2AX compared with control patients at 1 hour postirradiation. At 24 hours postirradiation, there was a lack of dephosphorylation in a substantial proportion of lymphocytes (with differences observed between T and NK cells) compared with healthy control patients. Although there was dephosphorylation of γH2AX at 24 hours in patient lymphocytes compared with 1 hour, the amount remained elevated at 24 hours compared with in control patients. The data from pATM and pSMC1 were uninformative. Flow-based kinetic analysis of γH2AX is a useful marker for the diagnosis of LIG4-SCID.
Asunto(s)
ADN Ligasa (ATP)/deficiencia , Rayos gamma , Histonas/inmunología , Células Asesinas Naturales , Inmunodeficiencia Combinada Grave , Linfocitos T , Biomarcadores , ADN Ligasa (ATP)/inmunología , Femenino , Citometría de Flujo , Humanos , Células Asesinas Naturales/inmunología , Células Asesinas Naturales/patología , Fosforilación/inmunología , Tolerancia a Radiación/genética , Tolerancia a Radiación/inmunología , Inmunodeficiencia Combinada Grave/diagnóstico , Inmunodeficiencia Combinada Grave/genética , Inmunodeficiencia Combinada Grave/inmunología , Inmunodeficiencia Combinada Grave/patología , Linfocitos T/inmunología , Linfocitos T/patologíaRESUMEN
During B and T lymphocyte maturation, V(D)J recombination is initiated by creation of DNA double-strand breaks. Artemis is an exonuclease essential for their subsequent repair by nonhomologous end-joining. Mutations in DCLRE1C, the gene encoding Artemis, cause T-B-NK+ severe combined immunodeficiency (ART-SCID) and also confer heightened sensitivity to ionizing radiation and alkylating chemotherapy. Although allogeneic hematopoietic cell transplantation can treat ART-SCID, conditioning regimens are poorly tolerated, leading to early mortality and/or late complications, including short stature, endocrinopathies, and dental aplasia. However, without alkylating chemotherapy as preconditioning, patients usually have graft rejection or limited T cell and no B cell recovery. Thus, addition of normal DCLRE1C cDNA to autologous hematopoietic stem cells is an attractive strategy to treat ART-SCID. We designed a self-inactivating lentivirus vector containing human Artemis cDNA under transcriptional regulation of the human endogenous Artemis promoter (AProArt). Fibroblasts from ART-SCID patients transduced with AProArt lentivirus showed correction of radiosensitivity. Mobilized peripheral blood CD34+ cells from an ART-SCID patient as well as hematopoietic stem cells from Artemis-deficient mice demonstrated restored T and B cell development following AProArt transduction. Murine hematopoietic cells transduced with AProArt exhibited no increase in replating potential in an in vitro immortalization assay, and analysis of AProArt lentivirus insertions showed no predilection for sites that could activate oncogenes. These efficacy and safety findings support institution of a clinical trial of gene addition therapy for ART-SCID.
Asunto(s)
Endonucleasas/genética , Terapia Genética , Vectores Genéticos/administración & dosificación , Lentivirus/genética , Proteínas Nucleares/genética , Inmunodeficiencia Combinada Grave/terapia , Animales , Linfocitos B/citología , Linfocitos B/metabolismo , Linfocitos B/efectos de la radiación , Células Cultivadas , Terapia Combinada , Reparación del ADN/efectos de la radiación , Proteínas de Unión al ADN , Modelos Animales de Enfermedad , Endonucleasas/deficiencia , Fibroblastos/citología , Fibroblastos/metabolismo , Fibroblastos/efectos de la radiación , Rayos gamma , Trasplante de Células Madre Hematopoyéticas , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/metabolismo , Células Madre Hematopoyéticas/efectos de la radiación , Humanos , Ratones , Ratones Noqueados , Ratones SCID , Proteínas Nucleares/deficiencia , Tolerancia a Radiación/genética , Inmunodeficiencia Combinada Grave/genética , Linfocitos T/citología , Linfocitos T/metabolismo , Linfocitos T/efectos de la radiaciónRESUMEN
Cellular senescence irreversibly arrests proliferation in response to potentially oncogenic stress. Senescent cells also secrete inflammatory cytokines such as IL-6, which promote age-associated inflammation and pathology. HMGB1 (high mobility group box 1) modulates gene expression in the nucleus, but certain immune cells secrete HMGB1 as an extracellular Alarmin to signal tissue damage. We show that nuclear HMGB1 relocalized to the extracellular milieu in senescent human and mouse cells in culture and in vivo. In contrast to cytokine secretion, HMGB1 redistribution required the p53 tumor suppressor, but not its activator ATM. Moreover, altered HMGB1 expression induced a p53-dependent senescent growth arrest. Senescent fibroblasts secreted oxidized HMGB1, which stimulated cytokine secretion through TLR-4 signaling. HMGB1 depletion, HMGB1 blocking antibody, or TLR-4 inhibition attenuated senescence-associated IL-6 secretion, and exogenous HMGB1 stimulated NF-κB activity and restored IL-6 secretion to HMGB1-depleted cells. Our findings identify senescence as a novel biological setting in which HMGB1 functions and link HMGB1 redistribution to p53 activity and senescence-associated inflammation.
Asunto(s)
Regulación de la Expresión Génica , Proteína HMGB1/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Animales , Proteínas de la Ataxia Telangiectasia Mutada , Proteínas de Ciclo Celular/metabolismo , Núcleo Celular/metabolismo , Proliferación Celular , Senescencia Celular , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , Citocinas/metabolismo , Proteínas de Unión al ADN/metabolismo , Fibroblastos/metabolismo , Humanos , Inflamación , Interleucina-6/metabolismo , Ratones , Ratones Endogámicos C57BL , FN-kappa B/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal , Receptor Toll-Like 4/metabolismo , Proteínas Supresoras de Tumor/metabolismoRESUMEN
BACKGROUND: Artemis has a defined role in V(D)J recombination and has been implicated in the repair of radiation induced double-strand breaks. However the exact function(s) of Artemis in DNA repair and its preferred substrate(s) in vivo remain undefined. Our previous work suggests that Artemis is important for the repair of complex DNA damage like that inflicted by high Linear Energy Transfer (LET) radiation. To establish the contribution of Artemis in repairing DNA damage caused by various radiation qualities, we evaluated the effect of over-expressing Artemis on cell survival, DNA repair, and cell cycle arrest after exposure to high and low LET radiation. RESULTS: Our data reveal that Artemis over-expression confers marked radioprotection against both types of radiation, although the radioprotective effect was greater following high LET radiation. Inhibitor studies reveal that the radioprotection imparted by Artemis is primarily dependent on DNA-PK activity, and to a lesser extent on ATM kinase activity. Together, these data suggest a DNA-PK dependent role for Artemis in the repair of complex DNA damage. CONCLUSIONS: These findings indicate that Artemis levels significantly influence radiation toxicity in human cells and suggest that Artemis inhibition could be a practical target for adjuvant cancer therapies.
Asunto(s)
Ciclo Celular/efectos de la radiación , Supervivencia Celular/efectos de la radiación , Roturas del ADN de Doble Cadena/efectos de la radiación , Reparación del ADN , Transferencia Lineal de Energía , Proteínas Nucleares/fisiología , Proteínas de la Ataxia Telangiectasia Mutada , Proteínas de Ciclo Celular/metabolismo , Proliferación Celular , Proteínas de Unión al ADN/metabolismo , Endonucleasas , Citometría de Flujo , Células HEK293 , Humanos , Cinética , Proteínas Nucleares/metabolismo , Fosforilación , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal , Factores de Tiempo , Proteínas Supresoras de Tumor/metabolismoRESUMEN
Females with germline mutations in BRCA1 are predisposed to develop breast and ovarian cancers. A previous report indicated that BRCA1 colocalizes with and is necessary for the correct localization of XIST, a noncoding RNA that coats the inactive X chromosome (Xi) to mediate formation of facultative heterochromatin. A model emerged from this study suggesting that loss of BRCA1 in female cells could reactivate genes on the Xi through loss of the XIST RNA. However, our independent studies of BRCA1 and XIST RNA revealed little evidence to support this model. We report that BRCA1 is not enriched on XIST RNA-coated chromatin of the Xi. Neither mutation nor depletion of BRCA1 causes significant changes in XIST RNA localization or X-linked gene expression. Together, these results do not support a role for BRCA1 in promoting XIST RNA localization to the Xi or regulating XIST-dependent functions in maintaining the stability of facultative heterochromatin.