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Heart failure has reached epidemic proportions in a progressively ageing population. The molecular mechanisms underlying heart failure remain elusive, but evidence indicates that DNA damage is enhanced in failing hearts. Here, we tested the hypothesis that endogenous DNA repair in cardiomyocytes is critical for maintaining normal cardiac function, so that perturbed repair of spontaneous DNA damage drives early onset of heart failure. To increase the burden of spontaneous DNA damage, we knocked out the DNA repair endonucleases xeroderma pigmentosum complementation group G (XPG) and excision repair cross-complementation group 1 (ERCC1), either systemically or cardiomyocyte-restricted, and studied the effects on cardiac function and structure. Loss of DNA repair permitted normal heart development but subsequently caused progressive deterioration of cardiac function, resulting in overt congestive heart failure and premature death within 6 months. Cardiac biopsies revealed increased oxidative stress associated with increased fibrosis and apoptosis. Moreover, gene set enrichment analysis showed enrichment of pathways associated with impaired DNA repair and apoptosis, and identified TP53 as one of the top active upstream transcription regulators. In support of the observed cardiac phenotype in mutant mice, several genetic variants in the ERCC1 and XPG gene in human GWAS data were found to be associated with cardiac remodelling and dysfunction. In conclusion, unrepaired spontaneous DNA damage in differentiated cardiomyocytes drives early onset of cardiac failure. These observations implicate DNA damage as a potential novel therapeutic target and highlight systemic and cardiomyocyte-restricted DNA repair-deficient mouse mutants as bona fide models of heart failure., (© 2023 The Authors. Aging Cell published by Anatomical Society and John Wiley & Sons Ltd.)

Aims: Impairment of the endothelial barrier leads to microvascular breakdown in cardiovascular disease and is involved in intraplaque haemorrhaging and the progression of advanced atherosclerotic lesions that are vulnerable to rupture. The exact mechanism that regulates vascular integrity requires further definition. Using a microarray screen for angiogenesis-associated genes during murine embryogenesis, we identified thrombospondin type I domain 1 (THSD1) as a new putative angiopotent factor with unknown biological function. We sought to characterize the role of THSD1 in endothelial cells during vascular development and cardiovascular disease., Methods and Results: Functional knockdown of Thsd1 in zebrafish embryos and in a murine retina vascularization model induced severe haemorrhaging without affecting neovascular growth. In human carotid endarterectomy specimens, THSD1 expression by endothelial cells was detected in advanced atherosclerotic lesions with intraplaque haemorrhaging, but was absent in stable lesions, implying involvement of THSD1 in neovascular bleeding. In vitro, stimulation with pro-atherogenic factors (3% O2 and TNFα) decreased THSD1 expression in human endothelial cells, whereas stimulation with an anti-atherogenic factor (IL10) showed opposite effect. Therapeutic evaluation in a murine advanced atherosclerosis model showed that Thsd1 overexpression decreased plaque vulnerability by attenuating intraplaque vascular leakage, subsequently reducing macrophage accumulation and necrotic core size. Mechanistic studies in human endothelial cells demonstrated that THSD1 activates FAK-PI3K, leading to Rac1-mediated actin cytoskeleton regulation of adherens junctions and focal adhesion assembly., Conclusion: THSD1 is a new regulator of endothelial barrier function during vascular development and protects intraplaque microvessels against haemorrhaging in advanced atherosclerotic lesions., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.)

Cardiac hypertrophy of the left ventricle (LV) in response to dynamic exercise-training (EX) is a beneficial adaptation to increased workload, and is thought to result from genetic reprogramming. We aimed to determine which transcription factors (TFs) are involved in this genetic reprogramming of the LV in swine induced by exercise-training. Swine underwent 3-6 weeks of dynamic EX, resulting in a 16% increase of LV weight/body weight ratio compared to sedentary animals (P=0.03). Hemodynamic analysis showed an increased stroke volume index (stroke volume/body weight +35%; P=0.02). Microarray-analysis of LV tissue identified 339 upregulated and 408 downregulated genes (false discovery rate<0.05). Of the human homologues of the differentially expressed genes, promoter regions were searched for TF consensus binding sites (TFBSs). For upregulated and downregulated genes, 17 and 24 TFBSs were overrepresented by >1.5-fold (P<0.01), respectively. In DNA-binding assays, using LV nuclear protein extracts and protein/DNA array, signal intensity changes >2-fold were observed for 23 TF-specific DNA probes. Matching results in TFBS and protein/DNA array analyses were obtained for transcription factors YY1 (Yin Yang 1), PAX6 (paired box 6) and GR (glucocorticoid receptor). Notably, PAX6 and GR show lower signals in TFBS and protein/DNA array analyses upon exercise-training, whereas we previously showed higher signals for these factors in the remodeled LV of swine post-myocardial infarction (MI). In conclusion, we have identified transcription factors that may drive the genetic reprogramming underlying exercise-training induced LV hypertrophy in swine. PAX6 and GR are among the transcription factors that are oppositely regulated in LV hypertrophy after exercise-training and MI. These proteins may be at the base of the differences between pathological and physiological hypertrophy., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Objective: In cardiovascular regulation, heme oxygenase-1 (HO-1) activity has been shown to inhibit vascular smooth muscle cell (VSMC) proliferation by promoting cell cycle arrest at the G1/S phase. However, the effect of HO-1 on VSMC migration remains unclear. We aim to elucidate the mechanism by which HO-1 regulates PDGFBB-induced VSMC migration., Methods and Results: Transduction of HO-1 cDNA adenoviral vector severely impeded human VSMC migration in a scratch, transmembrane, and directional migration assay in response to PDGFBB stimulation. Similarly, HO-1 overexpression in the remodeling process during murine retinal vasculature development attenuated VSMC coverage over the major arterial branches as compared with sham vector-transduced eyes. HO-1 expression in VSMCs significantly upregulated VEGFA and VEGFR2 expression, which subsequently promoted the formation of inactive PDGFRβ/VEGFR2 complexes. This compromised PDGFRβ phosphorylation and impeded the downstream cascade of FAK-p38 signaling. siRNA-mediated silencing of VEGFA or VEGFR2 could reverse the inhibitory effect of HO-1 on VSMC migration., Conclusions: These findings identify a potent antimigratory function of HO-1 in VSMCs, a mechanism that involves VEGFA and VEGFR2 upregulation, followed by assembly of inactive VEGFR2/PDGFRβ complexes that attenuates effective PDGFRβ signaling.

In this study we systematically assessed the sensitivity limits of fiber-FISH in model experiments. Exonic fragments and cDNAs with exon sizes of >/=200 bp could be mapped on their cognate cosmid. This positional fiber-FISH mapping was validated by long-range PCR. It is expected that these two independent mapping approaches will help to refine current available gene maps and show their applicability in fine mapping of sequence-tagged sites or expressed sequence tags. Also, they will be useful in resolving gene structures by mapping exon and intron locations.

Fluorescent in situ hybridization (FISH) is a powerful, direct and sensitive technique with a wide resolution range that enables the simultaneous study of multiple targets, labelled in different colours. Spreading techniques, denoted here as 'Fiber-FISH', increase FISH-resolution to the DNA fiber, using decondensed nuclear DNA as hybridization target. FISH could be a powerful analytical tool for thorough physical examination of yeast artificial chromosomes (YACs) which are often chimaeric or contain internal deletions. However, with one exception restricted to meiotic yeast chromosomes, FISH has not been used successfully on yeast/YAC DNA. We have developed a fast and simple method that can be applied routinely for compositional and structural analysis of cosmid and YAC DNA in yeast. It enables precise localization and ordering of clones, resolves overlaps and distances and gives a detailed picture of the integrity and colinearity of both probe and target. The combination of high resolution, signal abundance and short yeast cell cycle allows direct visualization of replicating DNA fibers. In a 400 kb region of the human dystrophin gene, we identified two replication origins, demonstrating that human DNA cloned in yeast is capable of initiating its own replication.

A 300-bp EcoRV polymorphism, detected with P20 (DXS269) in intron 44 of the human dystrophin gene, is due to an insertion or deletion. To make this restriction fragment length polymorphism (RFLP) available for polymerase chain reaction (PCR) analysis, we sequenced both alleles of this polymorphism and synthesized primers flanking the mutation site. The origin of the mutation is a single Alu repeat insertion. The 300-bp polymorphism can now be successfully detected by PCR and provides an excellent tool to detect female carriers in this deletion prone region of the dystrophin gene.

We have isolated 14 new DNA markers from the human Xpter-Xp21 region distal to the Duchenne muscular dystrophy gene by targeted cloning, employing two somatic cell hybrids containing this region as their sole human material. High-resolution physical localization of these markers within this region was obtained by hybridization to two mapping panels consisting of DNA from patients carrying various translocations and deletions in distal Xp. Five markers were assigned to the pseudoautosomal region where their position on the long-range map of this region was further determined by pulsed-field gel electrophoresis. The other nine markers map to the X-specific region. Informative TaqI restriction fragment length polymorphisms were observed for four loci. One of these represents a region-specific low-copy repeated element. These 14 new markers represent useful tools for the understanding of distal Xp deletion and translocation mechanisms and for the positional cloning of disease genes in the region.

McLeod syndrome, characterized by acanthocytosis and the absence of a red-blood-cell Kell antigen (Kx), is a multisystem disorder involving a late-onset myopathy, splenomegaly, and neurological defects. The locus for this syndrome has been mapped, by deletion analysis, to a region between the loci for Duchenne muscular dystrophy (DMD) and chronic granulomatous disease (CGD). In this study, we describe a new marker, 3BH/R 0.3 (DXS 709), isolated by cloning the deletion breakpoint of a DMD patient. A long-range restriction map of Xp21, encompassing the gene loci for McLeod and CGD, was constructed, and multiple CpG islands were found clustered in a 700-kb region. Using the new marker, we have limited the McLeod syndrome critical region to 150-380-kb. Within this interval, two CpG-rich islands which may represent candidate sites for the McLeod gene were identified.

Using whole cosmids as probes, we have mapped 242 DMD/BMD deletion breakpoints located in the major deletion hot spot of the DMD gene. Of these, 113 breakpoints were mapped more precisely to individual restriction enzyme fragments in the distal 80 kb of the 170-kb intron 44. An additional 12 breakpoints are distributed over the entire region, with no significant local variation in frequency. Furthermore, deletion sizes vary and are not influenced by the positions of the breakpoints. This argues against a predominant role of one or a few specific sequences in causing frequent rearrangements. It suggests that structural characteristics or a more widespread recombinogenic sequence makes this region so susceptible to deletion. Our study revealed several RFLPs, one of which is a 300-bp insertion/deletion polymorphism. Abnormally migrating junction fragments are found in 81% of the precisely mapped deletions and are highly valuable in the diagnosis of carrier females.

We have made a detailed study of a deletion hot spot in the distal half of the Duchenne muscular dystrophy (DMD) gene, using intragenic probe P20 (DXS269), isolated by a hybrid cell-mediated cloning procedure. P20 detects 16% deletions in patients suffering from either DMD or Becker muscular dystrophy (BMD), in sharp contrast to the adjacent intragenic markers JBir (7%) and J66 (less than 1%), mapping respectively 200-320 kb proximal and 380-500 kb distal to P20. Of the P20 deletions, 30% start within a region of 25-40 kb, the majority extending distally. P20 was confirmed to map internal to a distal intron of the DMD gene. This region was recently shown by both cDNA analysis (M. Koenig et al., 1987; Cell 50: 509-517), and field inversion electrophoresis studies (J.T. Den Dunnen et al., 1987, Nature (London) 329: 640-642) to be specifically prone to deletions. In addition, P20 detects MspI and EcoRV RFLPs, informative in 48% of the carrier females. Together, these properties make P20 useful for carrier detection, prenatal diagnosis, and the study of deletion induction in both DMD and BMD.

We have studied 34 Becker and 160 Duchenne muscular dystrophy (DMD) patients with the dystrophin cDNA, using conventional blots and FIGE analysis. One hundred twenty-eight mutations (65%) were found, 115 deletions and 13 duplications, of which 106 deletions and 11 duplications could be precisely mapped in relation to both the mRNA and the major and minor mutation hot spots. Junction fragments, ideal markers for carrier detection, were found in 23 (17%) of the 128 cases. We identified eight new cDNA RFLPs within the DMD gene. With the use of cDNA probes we have completed the long-range map of the DMD gene, by the identification of a 680-kb SfiI fragment containing the gene's 3' end. The size of the DMD gene is now determined to be about 2.3 million basepairs. The combination of cDNA hybridizations with long-range analysis of deletion and duplication patients yields a global picture of the exon spacing within the dystrophin gene. The gene shows a large variability of intron size, ranging from only a few kilobases to 160-180 kb for the P20 intron.

The locus DXS269 (P20) defines a deletion hotspot in the distal part of the Duchenne Muscular Dystrophy gene. We have cloned over 90 kilobase-pairs of genomic DNA from this region in overlapping cosmids. The use of whole cosmids as probes in a competitive DNA hybridization analysis proves a fast and convenient method for identifying rearrangements in this region. A rapid survey of P20-deletion patients is carried out to elucidate the nature of the propensity to deletions in this region. Using this technique, deletion breakpoints are pinpointed to individual restriction fragments in patient DNAs without the need for tedious isolation of single copy sequences. Simultaneously, the deletion data yield a consistent restriction map of the region and permit detection of several RFLPs. A 176 bp exon was identified within the cloned DNA, located 3' of an intron exceeding 150 Kb in length. Its deletion causes a frameshift in the dystrophin reading frame and produces the DMD phenotype. This exon is one of the most frequently deleted exons in BMD/DMD patients and its sequence is applied in a pilot study for diagnostic deletion screening using Polymerase Chain Reaction amplification.

About 60% of both Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) is due to deletions of the dystrophin gene. For cases with a deletion mutation, the "reading frame" hypothesis predicts that BMD patients produce a semifunctional, internally deleted dystrophin protein, whereas DMD patients produce a severely truncated protein that would be unstable. To test the validity of this theory, we analyzed 258 independent deletions at the DMD/BMD locus. The correlation between phenotype and type of deletion mutation is in agreement with the "reading frame" theory in 92% of cases and is of diagnostic and prognostic significance. The distribution and frequency of deletions spanning the entire locus suggests that many "in-frame" deletions of the dystrophin gene are not detected because the individuals bearing them are either asymptomatic or exhibit non-DMD/non-BMD clinical features.

Choroideremia (tapeto-choroidal dystrophy, TCD), an X chromosome-linked disorder of retina and choroid, causes progressive nightblindness and central blindness in affected males by the third to fourth decade of life. Recently, we have been able to map the TCD gene to a small region of overlap between five different, male-viable Xq21 deletions that were found in patients with TCD and other clinical features. Two families were identified in which classical, nonsyndromic TCD is associated with small interstitial deletions that are only detectable with probe p1bD5 (DXS165). To characterize these and two other deletions that were identified more recently, we have used the chromosome walking and jumping techniques to generate a set of five chromosomal-jumping clones flanking the DXS165 locus at various distances. With these clones, we could localize four of the eight deletion endpoints and the breakpoint on the X chromosome of a female with a de novo X/13 translocation and choroideremia. These studies assign the TCD gene, or part of it, to a DNA segment of only 15-20 kilobases.