A high-throughput approach to identify BRCA1-downregulating compounds to enhance PARP inhibitor sensitivity.

PARP inhibitors (PARPi) are efficacious in BRCA1-null tumors; however, their utility is limited in tumors with functional BRCA1. We hypothesized that pharmacologically reducing BRCA1 protein levels could enhance PARPi effectiveness in BRCA1 wild-type tumors. To identify BRCA1 downregulating agents, we generated reporter cell lines using CRISPR-mediated editing to tag endogenous BRCA1 protein with HiBiT. These reporter lines enable the sensitive measurement of BRCA1 protein levels by luminescence. Validated reporter cells were used in a pilot screen of epigenetic-modifying probes and a larger screen of more than 6,000 compounds. We identified 7 compounds that could downregulate BRCA1-HiBiT expression and synergize with olaparib. Three compounds, N-acetyl-N-acetoxy chlorobenzenesulfonamide (NANAC), A-443654, and CHIR-124, were validated to reduce BRCA1 protein levels and sensitize breast cancer cells to the toxic effects of olaparib. These results suggest that BRCA1-HiBiT reporter cells hold promise in developing agents to improve the clinical utility of PARPi.

Adult-onset obstructive sleep apnea and pediatric pharyngoplasty in 22q11.2 deletion syndrome.

OBJECTIVE/BACKGROUND: We aimed to evaluate adult-onset obstructive sleep apnea (OSA) and related risk factors, including history of pediatric palatal/pharyngeal surgery to remediate velopharyngeal dysfunction, in 22q11.2 deletion syndrome (22q11.2DS). PATIENTS/METHODS: Using a retrospective cohort design and standard sleep study-based criteria, we determined presence of adult-onset OSA (age ≥16 years) and relevant variables through comprehensive chart review in a well-characterized cohort of 387 adults with typical 22q11.2 microdeletions (51.4% female, median age 32.3, interquartile range 25.0-42.5, years). We used multivariate logistic regression to identify independent risk factors for OSA. RESULTS: Of the 73 adults with sleep study data, 39 (53.4%) met criteria for OSA at median age 33.6 (interquartile range 24.0-40.7) years, indicating a minimum OSA prevalence of 10.1% in this 22q11.2DS cohort. History of pediatric pharyngoplasty (odds ratio 2.56, 95% confidence interval 1.15-5.70) was a significant independent predictor of adult-onset OSA, while accounting for other significant independent predictors (asthma, higher body mass index, older age), and for male sex. An estimated 65.5% of those prescribed continuous positive airway pressure therapy were reported as adherent. CONCLUSIONS: In addition to factors of known importance in the general population, delayed effects of pediatric pharyngoplasty may contribute to risk of adult-onset OSA in individuals with 22q11.2DS. The results support increased index of suspicion for OSA in adults with a 22q11.2 microdeletion. Future research with this and other homogeneous genetic models may help to improve outcomes and to better understand genetic and modifiable risk factors for OSA.

Hypertriglyceridemia in young adults with a 22q11.2 microdeletion.

Objective: Mild to moderate hypertriglyceridemia is a condition often associated with obesity and diabetes, with as yet incomplete knowledge of underlying genetic architecture. The 22q11.2 microdeletion is associated with multimorbidity, including increased risk of obesity and diabetes. In this study, we sought to investigate whether the 22q11.2 microdeletion was associated with mild to moderate hypertriglyceridemia (1.7-10 mmol/L). Design: This was a cohort study comparing 6793 population-based adults and 267 with a 22q11.2 microdeletion aged 17-69 years, excluding those with diabetes or on statins. Methods: We used binomial logistic regression modeling to identify predictors of hypertriglyceridemia, accounting for the 22q11.2 microdeletion, male sex, BMI, ethnicity, age, and antipsychotic medications. Results: The 22q11.2 microdeletion was a significant independent predictor of mild to moderate hypertriglyceridemia (odds ratio (OR): 2.35, 95% CI: 1.70-3.26). All other factors examined were also significant predictors (OR: 1.23-2.10), except for antipsychotic medication use. Within the 22q11.2 microdeletion subgroup, only male sex (OR: 3.10, 95% CI: 1.77-5.44) and BMI (OR: 1.63, 95% CI: 1.14-1.98) were significant predictors of hypertriglyceridemia, evident at mean age 31.2 years. Conclusions: The 22q11.2 microdeletion is associated with hypertriglyceridemia even when accounting for other known risk factors for elevated triglycerides. This effect is seen in young adulthood (76.6% were <40 years), in the absence of diabetes, and irrespective of antipsychotics, suggesting that the 22q11.2 microdeletion may represent an unrecognized genetic risk factor for hypertriglyceridemia, providing novel opportunities for animal and cellular models. Early dyslipidemia screening and management strategies would appear prudent for individuals with 22q11.2 microdeletions.

lncRNA DIGIT and BRD3 protein form phase-separated condensates to regulate endoderm differentiation.

Cooperation between DNA, RNA and protein regulates gene expression and controls differentiation through interactions that connect regions of nucleic acids and protein domains and through the assembly of biomolecular condensates. Here, we report that endoderm differentiation is regulated by the interaction between the long non-coding RNA (lncRNA) DIGIT and the bromodomain and extraterminal domain protein BRD3. BRD3 forms phase-separated condensates of which the formation is promoted by DIGIT, occupies enhancers of endoderm transcription factors and is required for endoderm differentiation. BRD3 binds to histone H3 acetylated at lysine 18 (H3K18ac) in vitro and co-occupies the genome with H3K18ac. DIGIT is also enriched in regions of H3K18ac, and the depletion of DIGIT results in decreased recruitment of BRD3 to these regions. Our findings show that cooperation between DIGIT and BRD3 at regions of H3K18ac regulates the transcription factors that drive endoderm differentiation and suggest that protein-lncRNA phase-separated condensates have a broader role as regulators of transcription.