Frataxin deficiency alters gene expression in Friedreich ataxia derived IPSC-neurons and cardiomyocytes.

BACKGROUND: Friedreich's ataxia (FRDA) is an autosomal recessive disease, whereby homozygous inheritance of an expanded GAA trinucleotide repeat expansion in the first intron of the FXN gene leads to transcriptional repression of the encoded protein frataxin. FRDA is a progressive neurodegenerative disorder, but the primary cause of death is heart disease which occurs in 60% of the patients. Several functions of frataxin have been proposed, but none of them fully explain why its deficiency causes the FRDA phenotypes nor why the most affected cell types are neurons and cardiomyocytes. METHODS: To investigate, we generated iPSC-derived neurons (iNs) and cardiomyocytes (iCMs) from an FRDA patient and upregulated FXN expression via lentivirus without altering genomic GAA repeats at the FXN locus. RESULTS: RNA-seq and differential gene expression enrichment analyses demonstrated that frataxin deficiency affected the expression of glycolytic pathway genes in neurons and extracellular matrix pathway genes in cardiomyocytes. Genes in these pathways were differentially expressed when compared to a control and restored to control levels when FRDA cells were supplemented with frataxin. CONCLUSIONS: These results offer novel insight into specific roles of frataxin deficiency pathogenesis in neurons and cardiomyocytes.

Corrigendum: Phenotypic variability in iPSC-induced cardiomyocytes and cardiac fibroblasts carrying diverse LMNA mutations.

[This corrects the article DOI: 10.3389/fphys.2021.778982.].

Generation of a heterozygous FLNC mutation-carrying human iPSC line, USFi002-A, for modeling dilated cardiomyopathy.

Dilated Cardiomyopathy (DCM) is one of the main causes of sudden cardiac death and heart failure and is the leading indication for cardiac transplantation worldwide. Mutations in different genes including TTN, MYH7, and LMNA, have been linked to the development of DCM. Here, we generated a human induced pluripotent stem cell (IPSC) line from a DCM patient with a familial history that carries a frameshift mutation in Filamin C (FLNC). The IPSCs show typical morphology of pluripotent cells, expression of pluripotency markers, normal karyotype, and in vitro capacity to differentiate into all three germ layers.

Generation of a Friedreich's Ataxia patient-derived iPSC line USFi001-A.

Friedreich's Ataxia (FA) is an autosomal recessive disorder with an incidence of 1 in 50,000 in Caucasians. Most cases are caused by a biallelic GAA expansion in the first intron of the Frataxin (FXN) gene. FA is a neurodegenerative disease, but the leading cause of death is hypertrophic cardiomyopathy (HCM) that develops in 60% of the patients. We generated an induced pluripotent stem cell (iPSC) line from an FA patient with a homozygous GAA expansion in intron 1 of the FXN gene. The IPSCs display pluripotent cell morphology, expression of pluripotency markers, normal karyotype, and the capability to differentiate into all three germ layers.

Generation of an iPSC cell line (USFi003-A) from a patient with dilated cardiomyopathy carrying a heterozygous mutation in LMNA (p.R541C).

Mutations in the gene that encodes the nuclear envelope proteins lamin A/C (LMNA) are considered to be a prominent cause of Dilated cardiomyopathy (DCM), a leading cause of heart failure and a prevalent indication for heart transplant. Here we described the generation of induced pluripotent stem cells (iPSCs) from a 53-year-old female with DCM plus progressive conduction disease who carry a heterozygous mutation in LMNA (c.1621C > T, p.R541C). PBMCs isolated from the patient were reprogrammed with Yamanaka factors KOS, KLF4, and c-MYC by the non-integrating sendai virus vector system. The obtained iPSC lines demonstrated normal karyotype and pluripotent identity.

Phenotypic Variability in iPSC-Induced Cardiomyocytes and Cardiac Fibroblasts Carrying Diverse LMNA Mutations.

Mutations in the LMNA gene (encoding lamin A/C) are a significant cause of familial arrhythmogenic cardiomyopathy. Although the penetrance is high, there is considerable phenotypic variability in disease onset, rate of progression, arrhythmias, and severity of myopathy. To begin to address whether this variability stems from specific LMNA mutation sites and types, we generated seven patient-specific induced pluripotent stem cell (iPSC) lines with various LMNA mutations. IPSC-derived cardiomyocytes (iCMs) and cardiac fibroblasts (iCFs) were differentiated from each line for phenotypic analyses. LMNA expression and extracellular signal-regulated kinase pathway activation were perturbed to differing degrees in both iCMs and iCFs from the different lines. Enhanced apoptosis was observed in iCMs but not in iCFs. Markedly diverse irregularities of nuclear membrane morphology were present in iCFs but not iCMs, while iCMs demonstrated variable sarcomere disarray. Heterogenous electrophysiological aberrations assayed by calcium indicator imaging and multi-electrode array suggest differing substrates for arrhythmia that were accompanied by variable ion channel gene expression in the iCMs. Coculture studies suggest enhancement of the LMNA mutation effects on electrophysiological function exerted by iCFs. This study supports the utility of patient-specific iPSC experimental platform in the exploration of mechanistic and phenotypic heterogeneity of different mutations within a cardiac disease-associated gene. The addition of genetically defined coculture of cardiac-constituent non-myocytes further expands the capabilities of this approach.

Transcriptional changes associated with advancing stages of heart failure underlie atrial and ventricular arrhythmogenesis.

BACKGROUND: Heart failure (HF) is a leading cause of mortality and is associated with cardiac remodeling. Vulnerability to atrial fibrillation (AF) has been shown to be greater in the early stages of HF, whereas ventricular tachycardia/fibrillation develop during late stages. Here, we explore changes in gene expression that underlie the differential development of fibrosis and structural alterations that predispose to atrial and ventricular arrhythmias. OBJECTIVE: To study transcriptomic changes associated with the development of cardiac arrhythmias in early and late stages of heart failure. METHODS: Dogs were tachy-paced from right ventricle (RV) for 2-3 or 5-6 weeks (early and late HF). We performed transcriptomic analysis of right atria (RA) and RV isolated from control dogs and those in early and late HF. Transcripts with mean relative log2-fold change ≥2 were included in the differential analysis with significance threshold adjusted to p<0.05. RESULTS: Early HF remodeling was more prominent in RA with enrichment of extracellular matrix, circulatory system, wound healing and immune response pathways; many of these processes were not present in RA in late HF. RV showed no signs of remodeling in early HF but enrichment of extracellular matrix and wound healing in late HF. CONCLUSION: Our transcriptomic data indicate significant fibrosis-associated transcriptional changes in RA in early HF and in RV in late HF, with strong atrial predominance. These alterations in gene expression are consistent with the development of arrhythmogenesis in atria in early but not late HF and in the ventricle in late but not early HF.

Toxoplasma gondii infection induces suppression in a mouse model of allergic airway inflammation.

Allergic asthma is an inflammatory disorder characterized by infiltration of the airway wall with inflammatory cells driven mostly by activation of Th2-lymphocytes, eosinophils and mast cells. There is a link between increased allergy and a reduction of some infections in Western countries. Epidemiological data also show that respiratory allergy is less frequent in people exposed to orofecal and foodborne microbes such as Toxoplasma gondii. We previously showed that both acute and chronic parasite T. gondii infection substantially blocked development of airway inflammation in adult BALB/c mice. Based on the high levels of IFN-γ along with the reduction of Th2 phenotype, we hypothesized that the protective effect might be related to the strong Th1 immune response elicited against the parasite. However, other mechanisms could also be implicated. The possibility that regulatory T cells inhibit allergic diseases has received growing support from both animal and human studies. Here we investigated the cellular mechanisms involved in T. gondii induced protection against allergy. Our results show for the first time that thoracic lymph node cells from mice sensitized during chronic T. gondii infection have suppressor activity. Suppression was detected both in vitro, on allergen specific T cell proliferation and in vivo, on allergic lung inflammation after adoptive transference from infected/sensitized mice to previously sensitized animals. This ability was found to be contact-independent and correlated with high levels of TGF-ß and CD4(+)FoxP3(+) cells.