Biology subjects

Akerberg, A. A.

Publications and source records attributed to Akerberg, A. A..

3 recordsLinked to original sources

bioRxiv2025

Dosage-sensitive RBFOX2 autoregulation promotes cardiomyocyte differentiation through transcriptome maturation

Haploinsufficiency of the RNA splicing regulator, RBFOX2, is linked to congenital heart disease (CHD), yet its pathogenic mechanisms remain unclear. Here, we demonstrate that RBFOX2 is essential for progressing cardiomyocyte (CM) differentiation by shifting exon usage profiles to more mature patterns in sarcomere, cytoskeletal, and focal adhesion genes, including alpha-actinin-2 (ACTN2). This maturation program is initiated by critical levels of RBFOX2 that facilitate autoregulatory splicing at mutually exclusive exons encoding early and late isoforms with distinct functional roles. In heterozygous CMs, autoregulation is disrupted, which skews isoform ratios and generates a dominant-negative product caused by exon co-inclusion. Finally, we demonstrate that overexpression of ACTN2 rescues heterozygous, but not null, phenotypes by restoring contractility, which triggers a mechanosensing feedback loop involving upregulation of RBFOX2 from the wildtype allele and transcriptome maturation. Our data suggest that decreased RBFOX2 dosage and autoregulation impair CM differentiation, contributing to CHD pathogenesis and heart failure susceptibility.

developmental biology↗

bioRxiv2025

A genetically engineered vertebrate animal model of NAA15-related heart disease uncovers myocardial growth, contractility, and mitochondrial defects

Delineating the genetic and environmental instigators of congenital heart disease (CHD), affecting up to 1% of newborns, will improve preventative, diagnostic, and therapeutic efforts to mitigate disease outcomes. Although mutations in NAA15, which encodes the auxiliary subunit of N-alpha-acetyltransferase A (NatA), are associated with CHD in humans, vertebrate animal models of NAA15-related heart disease have yet to be described. Therefore, we isolated zebrafish strains carrying null mutations in paralogs naa15a and naa15b, which we co-localized to the early larval myocardium. Double knockout (DKO) naa15-deficient larvae exhibited diminutive, lowly contractile, and bradycardic ventricles composed of fewer and smaller cardiomyocytes (CMs) incapable of proliferation. On a subcellular level, mutant CMs exhibited moderately disorganized myofibrils. CM-specific re-expression of naa15a partially rescued the contractility and growth deficits, revealing an indispensable myocardial function. Ubiquitous mis-expression of human NAA15 achieved complete rescue, enabling functional testing of human NAA15 variants. Animals with a reduced dosage (RD) of naa15 survived to adulthood and shared phenotypes with DKO larvae, including smaller ventricular chambers and CMs, which exhibited mosaic myofibril disarray. Deep quantitative proteomic profiling of WT and naa15RD adult hearts revealed differential expression of multiple protein classes, including several subunits of mitochondrial respiratory complex I, a component of the electron transport chain. Accordingly, we documented reduced mitochondrial content and function in the myocardium of naa15-deficient larvae. Taken together, our data reveal myocardial functional and structural abnormalities associated with mitochondrial dysfunction in a vertebrate animal model of NAA15-related heart disease.

developmental biology↗

bioRxiv2021

RBPMS2 is a conserved regulator of alternative splicing that promotes myofibrillar organization and optimal calcium handling in cardiomyocytes

RationaleThe identification of novel cardiomyocyte-intrinsic factors that support heart function will expand the number of candidate genes and therapeutic options for heart failure, a leading cause of death worldwide. ObjectiveTo identify and characterize conserved regulators of cardiomyocyte function. Methods and ResultsWe report that the RNA-binding protein RBPMS2 is required for myofibril organization and the regulation of intracellular calcium dynamics in both zebrafish embryos and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). A differential expression screen in zebrafish uncovered enrichment of rbpms2 paralogs, rbpms2a and rbpms2b, in the myocardium. Double knock-out (rbpms2-null) embryos suffer from compromised ventricular filling during the relaxation phase of the cardiac cycle, which significantly reduces cardiac output. Whole transcriptome sequencing and validation studies revealed differential alternative splicing of several genes linked to cardiomyopathies in humans, including myosin binding protein C3 (mybpc3) and phospholamban (pln), consistent with a role in causing the observed ventricular deficiencies. Further, RBPMS2-null hiPSC-CMs exhibit myofibril and calcium handling defects that are highly analogous to those observed in the rbpms2-null zebrafish ventricle. ConclusionsTaken together, our data identify RBPMS2 as a conserved and essential regulator of alternative splicing that is required for myofibrillar organization and optimal calcium handling from zebrafish to humans.

developmental biology↗