Project description:Gene expression profiling in homozygous LMNA-/- mouse model with cardiomyopathy phenotype unraveled novel LMNA-mediated alterations of signaling pathways leading to dilated cardiomyopathy
Project description:Changes in the gene expression in the heart of knock-in mouse model of dilated cardiomyopathy caused by delK210 mutation in cardiac troponin T.
Project description:Truncating variants in titin can cause dilated cardiomyopathy, however, the role of missense titin variants is less clear. In humans the heterozygous titin A178D variant is associated with dilated cardiomyopathy with left ventricular non-compaction. Using CRISPR-Cas9 mediated homology-directed repair the A178D titin variant was introduced into a mouse model. Homozygous A178D mice showed features of dilated cardiomyopathy. Total RNA was extracted from the left ventricles of WT and homozygous A178D littermate control mice and RNA-sequencing performed. Different patterns of gene expression were identified in wildtype and homozygous A178D left ventricles.
Project description:PURPOSE: To provide a detailed gene expression profile of the normal postnatal mouse cornea. METHODS: Serial analysis of gene expression (SAGE) was performed on postnatal day (PN)9 and adult mouse (6 week) total corneas. The expression of selected genes was analyzed by in situ hybridization. RESULTS: A total of 64,272 PN9 and 62,206 adult tags were sequenced. Mouse corneal transcriptomes are composed of at least 19,544 and 18,509 unique mRNAs, respectively. One third of the unique tags were expressed at both stages, whereas a third was identified exclusively in PN9 or adult corneas. Three hundred thirty-four PN9 and 339 adult tags were enriched more than fivefold over other published nonocular libraries. Abundant transcripts were associated with metabolic functions, redox activities, and barrier integrity. Three members of the Ly-6/uPAR family whose functions are unknown in the cornea constitute more than 1% of the total mRNA. Aquaporin 5, epithelial membrane protein and glutathione-S-transferase (GST) omega-1, and GST alpha-4 mRNAs were preferentially expressed in distinct corneal epithelial layers, providing new markers for stratification. More than 200 tags were differentially expressed, of which 25 mediate transcription. CONCLUSIONS: In addition to providing a detailed profile of expressed genes in the PN9 and mature mouse cornea, the present SAGE data demonstrate dynamic changes in gene expression after eye opening and provide new probes for exploring corneal epithelial cell stratification, development, and function and for exploring the intricate relationship between programmed and environmentally induced gene expression in the cornea. Keywords: other
Project description:Aims: Pathogenic truncating variants in the largest human protein TITIN are a leading cause of dilated cardiomyopathy. Because of the size of the gene encoding TITIN, many missense variations are identified. These are difficult to evaluate in genetic testing, as even individually rare variants are common in aggregate in normal populations. While the majority will be benign, a small subset is pathogenic, but distinction is challenging. Here, we describe the generation of a mouse model to investigate the underlying disease mechanism of a previously reported TITIN A178D missense variant identified in a family with non-compaction and dilated cardiomyopathy. Methods and Results: Heterozygous and homozygous mice carrying the TITIN A178D missense variant were characterised in vivo. Heterozygous mice had no detectable phenotype at any time point observed (up to 1 year). By contrast, homozygous mice developed dilated cardiomyopathy from 3 months. Chronic adrenergic stimulation aggravated the phenotype. Targeted transcript profiling revealed induction of the fetal gene programme and hypertrophic signalling pathways in homozygous mice, and these were confirmed at the protein level. Unsupervised proteomics identified down-regulation of TELETHONIN and FOUR-AND-A-HALF LIM DOMAIN 2, as well as the up-regulation of heat shock proteins and MYELOID LEUKEMIA FACTOR 1. Loss of TELETHONIN from the cardiac Z-disc was accompanied by proteasomal degradation; however, TELETHONIN also accumulated in the cytoplasm. In parallel, a proteo-toxic response was observed in the mice. Conclusions: We have shown that the TITIN A178D missense variant is pathogenic in homozygous mice, resulting in cardiomyopathy. We also provide evidence of the disease mechanism. Because the TITIN A178D variant abolishes binding of TELETHONIN, this leads to its abnormal cytoplasmic accumulation. Subsequent degradation of TELETHONIN by the proteasome results in proteasomal overload, and activation of a proteo-toxic response. The latter appears to be a driving factor for the cardiomyopathy observed in the mouse model.
Project description:Cardiac metabolism is deranged in heart failure, but underlying mechanisms remain unclear. Lysine demethylase 8 (Kdm8) represses gene expression in the embryo and controls metabolism in cancer. However, its function in cardiac homeostasis is unknown. We show that Kdm8 maintains a mitochondrial gene network active by repressing Tbx15 to prevent dilated cardiomyopathy leading to lethal heart failure. Deletion of Kdm8 in mouse cardiomyocytes increased H3K36me2 with activation of Tbx15 and repression of target genes in the NAD+ pathway before dilated cardiomyopathy initiates. Moreover, NAD+ supplementation prevented dilated cardiomyopathy in Kdm8 mutant mice and TBX15 overexpression blunted NAD+-activated cardiomyocyte respiration. Furthermore, KDM8 was downregulated in human hearts affected by dilated cardiomyopathy and higher TBX15 expression defines a subgroup of affected hearts with the strongest downregulation of genes encoding mitochondrial proteins. Thus, KDM8 represses TBX15 to maintain cardiac metabolism. Our results suggest that epigenetic dysregulation of metabolic gene networks initiates myocardium deterioration towards heart failure and could underlie heterogeneity of dilated cardiomyopathy.