A Role for RE-1-Silencing Transcription Factor in Embryonic Stem Cells Cardiac Lineage Specification

Congenital heart defects in CTNNB1 syndrome: Raising clinical awareness

CTNNB1 [OMIM *116806] encodes β-catenin, an integral part of the cadherin/catenin complex, which functions as effector of Wnt signaling. CTNNB1 is highly expressed in brain as well as in other tissues, including heart. Heterozygous CTNNB1 pathogenic variations are associated with a neurodevelopmental disorder characterized by spastic diplegia and visual defects (NEDSDV) [OMIM #615075], featuring psychomotor delay, intellectual disability, behavioral disturbances, movement disorders, visual defects and subtle facial and somatic features. We report on a new series of 19 NEDSDV patients (mean age 10.3 years), nine of whom bearing novel CTNNB1 variants. Notably, five patients showed congenital heart anomalies including absent pulmonary valve with intact ventricular septum, atrioventricular canal with hypoplastic aortic arch, tetralogy of Fallot, and mitral valve prolapse. We focused on the cardiac phenotype characterizing such cases and reviewed the congenital heart defects in previously reported NEDSDV patients. While congenital heart defects had occasionally been reported so far, the present findings configure a higher rate of cardiac anomalies, suggesting dedicated heart examination to NEDSDV clinical management.

Replication of genetic associations of chemotherapy-related cardiotoxicity in the adjuvant NSABP B-31 clinical trial

Background

The cardiotoxic effects of doxorubicin, trastuzumab, and other anticancer agents are well known, but molecular genetic testing is lacking for the early identification of patients at risk for therapy-related cardiac toxicity.

Methods

Using the Agena Bioscience MassARRAY system, we genotyped TRPC6 rs77679196, BRINP1 rs62568637, LDB2 rs55756123, RAB22A rs707557, intergenic rs4305714, LINC01060 rs7698718, and CBR3 rs1056892 (V244M) (previously associated with either doxorubicin or trastuzumab-related cardiotoxicity in the NCCTG N9831 trial of anthracycline-based chemotherapy ± trastuzumab) in 993 patients with HER2+ early breast cancer from the NSABP B-31 trial of adjuvant anthracycline-based chemotherapy ± trastuzumab. Association analyses were performed with outcomes of congestive heart failure (N = 29) and maximum decline in left ventricular ejection fraction (LVEF) using logistic and linear regression models, respectively, under an additive model with age, baseline LVEF, and previous use of hypertensive medications as covariates.

Results

Associations of maximum decline in LVEF in the NCCTG N9831 patients did not replicate in the NSABP B-31 patients. However, TRPC6 rs77679196 and CBR3 rs1056892 were significantly associated with congestive heart failure, p < 0.05, with stronger associations observed in patients treated with chemotherapy only (no trastuzumab) or in the combined analysis of all patients relative to those patients treated with chemotherapy + trastuzumab.

Conclusions

TRPC6 rs77679196 and CBR3 rs1056892 (V244M) are associated with doxorubicin-induced cardiac events in both NCCTG N9831 and NSABP B-31. Other variants previously associated with trastuzumab-related decline in LVEF failed to replicate between these studies.

β-actin dependent chromatin remodeling mediates compartment level changes in 3D genome architecture

β-actin is a crucial component of several chromatin remodeling complexes that control chromatin structure and accessibility. The mammalian Brahma-associated factor (BAF) is one such complex that plays essential roles in development and differentiation by regulating the chromatin state of critical genes and opposing the repressive activity of polycomb repressive complexes (PRCs). While previous work has shown that β-actin loss can lead to extensive changes in gene expression and heterochromatin organization, it is not known if changes in β-actin levels can directly influence chromatin remodeling activities of BAF and polycomb proteins. Here we conduct a comprehensive genomic analysis of β-actin knockout mouse embryonic fibroblasts (MEFs) using ATAC-Seq, HiC-seq, RNA-Seq and ChIP-Seq of various epigenetic marks. We demonstrate that β-actin levels can induce changes in chromatin structure by affecting the complex interplay between chromatin remodelers such as BAF/BRG1 and EZH2. Our results show that changes in β-actin levels and associated chromatin remodeling activities can not only impact local chromatin accessibility but also induce reversible changes in 3D genome architecture. Our findings reveal that β-actin-dependent chromatin remodeling plays a role in shaping the chromatin landscape and influences the regulation of genes involved in development and differentiation.

MicroRNA-124a inhibits endoderm lineage commitment by targeting Sox17 and Gata6 in mouse embryonic stem cells

The role of microRNAs (miRNAs) during mouse early development, especially in endoderm germ layer formation, is largely unknown. Here, via miRNA profiling during endoderm differentiation, we discovered that miR‐124a negatively regulates endoderm lineage commitment in mouse embryonic stem cells (mESCs). To further investigate the functional role of miR‐124a in early stages of differentiation, transfection of embryoid bodies with miR‐124a mimic was performed. We showed that overexpression of miR‐124a inhibits endoderm differentiation in vitro through targeting the 3′‐untranslated region (UTR) of Sox17 and Gata6, revealing the existence of interplay between miR‐124a and the Sox17/Gata6 transcription factors in hepato‐specific gene regulation. In addition, we presented a feasible in vivo system that utilizes teratoma and gene expression profiling from microarray to quantitatively evaluate the functional role of miRNA in lineage specification. We demonstrated that ectopic expression of miR‐124a in teratomas by intratumor delivery of miR‐124a mimic and Atelocollagen, significantly suppressed endoderm and mesoderm lineage differentiation while augmenting the differentiation into ectoderm lineage. Collectively, our findings suggest that miR‐124a plays a significant role in mESCs lineage commitment.

miR-218 Involvement in Cardiomyocyte Hypertrophy Is Likely through Targeting REST

MicroRNAs (miRNAs) have been identified as key players in cardiomyocyte hypertrophy, which is associated with significant risks of heart failure. However, many microRNAs are still not recognized for their functions in pathophysiological processes. In this study, we evaluated effects of miR-218 in cardiomyocyte hypertrophy using both in vitro and in vivo models. We found that miR-218 was evidently downregulated in a transverse aortic constriction (TAC) mouse model. Overexpression of miR-218 is sufficient to reduce hypertrophy, whereas the suppression of miR-218 aggravates hypertrophy in primary cardiomyocytes induced by isoprenaline (ISO). In addition, we identified RE1-silencing transcription factor (REST) as a novel target of miR-218; it negatively regulated the expression of REST in hypertrophic cardiomyocytes and the TAC model. These results showed that miR-218 plays a crucial role in cardiomyocyte hypertrophy, likely via targeting REST, suggesting a potential candidate target for interfering hypertrophy.