2'-O-methylation (Nm) in RNA: progress, challenges, and future directions.

RNA 2'-O-methylation (Nm) is highly abundant in noncoding RNAs including ribosomal RNA (rRNA), transfer RNA (tRNA), and small nuclear RNA (snRNA), and occurs in the 5' cap of virtually all messenger RNAs (mRNAs) in higher eukaryotes. More recently, Nm has also been reported to occur at internal sites in mRNA. High-throughput methods have been developed for the transcriptome-wide detection of Nm. However, these methods have mostly been applied to abundant RNAs such as rRNA, and the validity of the internal mRNA Nm sites detected with these approaches remains controversial. Nonetheless, Nm in both coding and noncoding RNAs has been demonstrated to impact cellular processes, including translation and splicing. In addition, Nm modifications at the 5' cap and possibly at internal sites in mRNA serve to prevent the binding of nucleic acid sensors, thus preventing the activation of the innate immune response by self-mRNAs. Finally, Nm has been implicated in a variety of diseases including cancer, cardiovascular diseases, and neurologic syndromes. In this review, we discuss current challenges in determining the distribution, regulation, function, and disease relevance of Nm, as well as potential future directions for the field.

Programmable protein expression using a genetically encoded m6A sensor.

The N6-methyladenosine (m6A) modification is found in thousands of cellular mRNAs and is a critical regulator of gene expression and cellular physiology. m6A dysregulation contributes to several human diseases, and the m6A methyltransferase machinery has emerged as a promising therapeutic target. However, current methods for studying m6A require RNA isolation and do not provide a real-time readout of mRNA methylation in living cells. Here we present a genetically encoded m6A sensor (GEMS) technology, which couples a fluorescent signal with cellular mRNA methylation. GEMS detects changes in m6A caused by pharmacological inhibition of the m6A methyltransferase, giving it potential utility for drug discovery efforts. Additionally, GEMS can be programmed to achieve m6A-dependent delivery of custom protein payloads in cells. Thus, GEMS is a versatile platform for m6A sensing that provides both a simple readout for m6A methylation and a system for m6A-coupled protein expression.

Early Outcomes in Patients With LVAD Undergoing Heart Transplant via Use of the SherpaPak Cardiac Transport System.

BACKGROUND: Heart transplant (HT) in recipients with left ventricular assist devices (LVADs) is associated with poor early post-HT outcomes, including primary graft dysfunction (PGD). As complicated heart explants in recipients with LVADs may produce longer ischemic times, innovations in donor heart preservation may yield improved post-HT outcomes. The SherpaPak Cardiac Transport System is an organ preservation technology that maintains donor heart temperatures between 4 °C and 8 °C, which may minimize ischemic and cold-induced graft injuries. This analysis sought to identify whether the use of SherpaPak versus traditional cold storage was associated with differential outcomes among patients with durable LVAD undergoing HT. METHODS: Global Utilization and Registry Database for Improved Heart Preservation-Heart (NCT04141605) is a multicenter registry assessing post-HT outcomes comparing 2 methods of donor heart preservation: SherpaPak versus traditional cold storage. A retrospective review of all patients with durable LVAD who underwent HT was performed. Outcomes assessed included rates of PGD, post-HT mechanical circulatory support use, and 30-day and 1-year survival. RESULTS: SherpaPak (n=149) and traditional cold storage (n=178) patients had similar baseline characteristics. SherpaPak use was associated with reduced PGD (adjusted odds ratio, 0.56 [95% CI, 0.32-0.99]; P=0.045) and severe PGD (adjusted odds ratio, 0.31 [95% CI, 0.13-0.75]; P=0.009), despite an increased total ischemic time in the SherpaPak group. Propensity matched analysis also noted a trend toward reduced intensive care unit (SherpaPak 7.5±6.4 days versus traditional cold storage 11.3±18.8 days; P=0.09) and hospital (SherpaPak 20.5±11.9 days versus traditional cold storage 28.7±37.0 days; P=0.06) lengths of stay. The 30-day and 1-year survival was similar between groups. CONCLUSIONS: SherpaPak use was associated with improved early post-HT outcomes among patients with LVAD undergoing HT. This innovation in preservation technology may be an option for HT candidates at increased risk for PGD. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04141605.