RBFOX1

Researchers identify RBFox1 as a key intrinsic regulator of heart muscle cell maturation, overcoming a major limitation in cardiac regenerative therapy and disease modelling and demonstrating for the first time that RNA splicing control can significantly impact this process. Scientists led by Duke-NUS Medical School in Singapore and the University of California, Los Angeles, (UCLA) in the United States have discovered a new control mechanism that can drive the maturation of human stem cell-derived heart muscle cells, providing fresh insight into the maturation process of heart muscle cells from fetal to adult form. After birth, heart muscle cells undergo extensive changes to become fully mature adult cells, altering their form, function and physiology. However, the regulatory processes governing this maturation have been poorly understood thus far. For regenerative therapies in particular, this lack of understanding has proven a major limitation as efforts to grow stem cell-derived heart muscle cells have not been successful at producing mature adult cells, capable of restoring or improving heart function. Publishing in Circulation, the research team used transcriptomic analysis to pinpoint an RNA splicing regulator named RBFox1 that was highly elevated soon after birth in a newborn heart. Analyses of published single-cell data also showed dramatic RBFox1 increase in maturing heart cells. "This represents the first evidence that RNA splicing control contributes significantly to heart cell maturation," said lead author Dr Huang Jijun, who performed the preclinical study during his postdoctoral work at UCLA. "While RBFox1 alone may not be sufficient to mature fetal heart muscle cells all the way to fully matured adult cells, our findings uncover a new RNA-based internal network that can substantially drive this maturation process beyond other available approaches." By expressing RBFox1 in immature human stem cell-derived heart cells, the researchers saw enhancements in key indicators of maturation, including cell size, sarcomere structure, contraction, calcium handling and oxygen usage. RBFox1 expression also led to the development of characteristic electrical properties seen in adult cells. Further analyses showed RBFox1 regulated splicing of RNA transcripts linked to heart cell contraction and sarcomere components. "This work demonstrates for the first time that altering RNA splicing alone can stimulate significant maturation of human stem cell-derived heart cells," said senior author Professor Wang Yibin, Director of the Cardiovascular & Metabolic Disorders Programme at Duke-NUS. "Our results uncover a promising molecular approach to improve heart cell maturation, which could overcome a major limitation in cardiac regenerative therapy and disease modelling." While further research is needed to explore the mechanisms linking RBFox1-mediated RNA splicing with downstream maturation processes and phenotype, the study provides proof-of-concept that modulating RNA splicing can significantly impact heart muscle cell, or cardiomyocyte, maturation. This opens possibilities for regulating maturation that could eventually be translated to therapeutic strategies. The study brought together researchers from leading research institutions across Singapore and the US. Collaborating groups hail from the Agency for Science, Technology and Research (A*STAR)'s Institute of Molecular and Cell Biology in Singapore, and Baylor College of Medicine, Forcyte Biotechnologies, the Greater Los Angeles VA Healthcare System, Meharry Medical College, the Stanford Cardiovascular Institute, the University of Cincinnati, the University of North Carolina, and Vanderbilt University School of Medicine in the US. "Duke-NUS' partnerships with leading global institutions continue to foster impactful translational research that advances scientific knowledge and ultimately improves clinical outcomes for patients," said Professor Patrick Tan, Senior Vice-Dean for Research at Duke-NUS. "This study's findings provide a new understanding of the intrinsic regulatory network controlling heart cell maturation and reveal a promising molecular strategy that could potentially be harnessed to progress cell-based therapies and cardiac regenerative medicine." Moving forward, the researchers will investigate how RBFox1 coordinates splicing to direct the functional and morphological changes underlying maturation. Their long-term aim is to identify druggable targets that can boost heart cell maturation efficiency for regenerative medicine use.

Researchers have identified how three novel genes cause neurodevelopmental disorders. Researchers now have a better sense of the genes' roles in human brain development and function and their ability to serve as potential therapeutic targets in the future. An international study group led by researchers of Children's Hospital of Philadelphia (CHOP) have identified how three novel genes cause neurodevelopmental disorders. Researchers now have a better sense of the genes' roles in human brain development and function and their ability to serve as potential therapeutic targets in the future. The findings were recently published online by the Journal of Clinical Investigation. Over the last couple of decades, researchers have identified more than 1500 genes in different signaling pathways associated with neurodevelopmental disorders. On average, about one third of patients with neurodevelopmental disorders receive a genetic diagnosis. However, little is known about how these genes are networked and how their malfunction leads to these disorders. Prior research in other disorders has shown that issues related to gene splicing may be to blame. Before being turned into proteins, genes are transcribed into introns, or strands of RNA that do not code for proteins, and exons that code for proteins. Introns are removed in a process called splicing, which is carried out by a protein complex called the spliceosome. Variants impacting the spliceosome have rarely been implicated with neurodevelopmental disorders. However, through a series of complex testing, researchers in this study showed that malfunctions in the spliceosome are responsible for some neurodevelopmental disorders. "Using multiple techniques, including phenotyping, genomic sequencing and modeling in fly and stem cells, we were able to map the genetic architecture of three genes associated with neurodevelopmental disorders, particularly developmental delay, intellectual disability and autism," said Dong Li, Ph.D., a research faculty member in the Center for Applied Genomics and the Division of Human Genetics at CHOP and lead author on the study. "Combining fly and human genetics helped us understand the mechanisms of how variants of these genes affect the machinery of the spliceosome and cause these disorders." In this study, researchers utilized genomic and clinical data from unrelated patients with neurodevelopmental disorders. Among the cohort, 46 patients had missense variants of the gene U2AF2 and six patients had variants of the gene PRPF19. In human stem cell and fly models, the researchers noticed issues with the formation of neurites, or protrusions on neurons that give them their shape, as well as issues with splicing and social deficits in the fly models. Deeper profiling revealed that at third gene, RBFOX1, had missense variants that affected splicing and loss of proper neuron function. These findings were later compared with those of patients in the study, which confirmed that variants in the three genes can lead to neurodevelopmental disorders. "We used fruit flies to study the effects of losing the function of these three genes one at a time and found that two genes independently led to brain structural and functional abnormalities, highlighting the essentiality of these genes in development," said study co-author Yuanquan Song, Ph.D., an associate professor from the Department of Pathology & Laboratory Medicine at CHOP. "Apart from identifying patients with such variants in these genes for the first time, our extended translational modeling study efforts aimed to determine the underlying functions for these variants further elucidated their clinical relevance." "Not only does this study identify three causative genes associated with neurodevelopmental disorders, but it helps us understand how critical pre-mRNA splicing is to the development of the central nervous system," said senior study author Hakon Hakonarson, M.D., Ph.D., director of the Center for Applied Genomics at CHOP.

A team has identified an essential internal control mechanism that can promote the maturation of human stem cell-derived heart muscle cells, possibly leading to new therapies for heart disease and cardiac damage. A UCLA-led team has identified an essential internal control mechanism that can promote the maturation of human stem cell-derived heart muscle cells, offering a deeper understanding of how heart muscle cells develop from their immature fetal stage to their mature adult form. The findings, published in the peer-reviewed journal Circulation, could lead to new therapies for heart disease and cardiac damage. The collaborative effort with Duke-NUS Medical School in Singapore and other institutions identified an RNA splicing regulator named RBFox1, which was considerably more prevalent in adult heart cells than in newborns, based on a preclinical model. The sharp rise in RBFox1 during the maturation of heart cells was also confirmed through analyses of existing single-cell data. "This is the first piece of evidence suggesting that RNA splicing control plays a vital role in postnatal heart cell maturation," said study lead Jijun Huang, who conducted this research during his postdoctoral training in anesthesiology at UCLA. "While RBFox1 alone may not be sufficient to push mature fetal heart muscle cells all the way to fully matured adult cells, our findings uncover a new RNA-based internal network that can substantially drive this maturation process beyond other available approaches." The transformation of heart muscle cells from birth until they reach full maturity involves significant shifts in their structure, functionality, and physiological properties. The mechanisms overseeing this comprehensive maturation have been poorly understood thus far. Although the precise mechanics associating RBFox1-mediated RNA splicing with ensuing maturation procedures and characteristics still require further exploration, the study provides proof-of-concept that modulating RNA splicing can profoundly affect cardiomyocyte maturation. This newfound knowledge hints at future therapeutic applications, pending additional research to expand upon these initial findings. "For the first time, we've shown that by merely altering RNA splicing, we can encourage the significant maturation of heart cells derived from human stem cells," said senior author Yibin Wang, director of the Cardiovascular & Metabolic Disorders Program at Duke-NUS. "These findings present a potential molecular approach to enhance heart cell maturation, which could address a major challenge in the domains of cardiac regenerative therapy and disease modeling." The study was funded by an American Heart Association Postdoctoral Award (18POST33990469) the National Institutes of Health (R01 HL148714, R00 HL141626) and a Department of Defense Award (PR171540). Study co-authors are Josh Lee, Christoph Rau, Dr. Arash Pezhouman, Tomohiro Yokota, Hiromi Miwa, Tsz Kin Kong, Shreya Udani, Chen Gao, Linsey Stiles, Dr. Orian Shirihai, Dr. Reza Ardehali, and Dino Di Carlo of UCLA and others from Baylor College of Medicine, Vanderbilt University School of Medicine, Meharry Medical College, Forcyte Biotechnologies, the University of Cincinnati, the University of North Carolina, and the Agency for Science, Technology and Research (A*STAR) in Singapore.