LRRK2 G2019S Promotes Colon Cancer Potentially via LRRK2-GSDMD Axis-Mediated Gut Inflammation.

Leucine-rich repeat kinase 2 (LRRK2) is a serine-threonine protein kinase belonging to the ROCO protein family. Within the kinase domain of LRRK2, a point mutation known as LRRK2 G2019S has emerged as the most prevalent variant associated with Parkinson's disease. Recent clinical studies have indicated that G2019S carriers have an elevated risk of cancers, including colon cancer. Despite this observation, the underlying mechanisms linking LRRK2 G2019S to colon cancer remain elusive. In this study, employing a colitis-associated cancer (CAC) model and LRRK2 G2019S knock-in (KI) mouse model, we demonstrate that LRRK2 G2019S promotes the pathogenesis of colon cancer, characterized by increased tumor number and size in KI mice. Furthermore, LRRK2 G2019S enhances intestinal epithelial cell proliferation and inflammation within the tumor microenvironment. Mechanistically, KI mice exhibit heightened susceptibility to DSS-induced colitis, with inhibition of LRRK2 kinase activity ameliorating colitis severity and CAC progression. Our investigation also reveals that LRRK2 G2019S promotes inflammasome activation and exacerbates gut epithelium necrosis in the colitis model. Notably, GSDMD inhibitors attenuate colitis in LRRK2 G2019S KI mice. Taken together, our findings offer experimental evidence indicating that the gain-of-kinase activity in LRRK2 promotes colorectal tumorigenesis, suggesting LRRK2 as a potential therapeutic target in colon cancer patients exhibiting hyper LRRK2 kinase activity.

Rice ins(3)P synthase1 (RINO1) participates in embryonic development by regulating inositol-associated changes in auxin synthesis and its distribution.

The breeding of low phytic acid (LPA) crops is widely considered an effective strategy to improve crop nutrition, but the LPA crops usually have inferior seed germination performance. To clarify the reason for the suboptimal seed performance of LPA rice, this study investigated the impact of reduced seed phytic acid (InsP6) content in rice ins(3)P synthase1 (EC 5.5.1.4, RINO1), one of the key targets for engineering LPA rice, knockouton cellular differentiation in seed embryos and its relation to myo-inositol metabolism and auxin signalling during embryogenesis. The results indicated that the homozygotes of RINO1 knockout could initiate differentiation at the early stage of embryogenesis but failed to form normal differentiation of plumule and radicle primordia. The loss of RINO1 function disrupted vesicle trafficking and auxin signalling due to the significantly lowered phosphatidylinositides (PIs) concentration in seed embryos, thereby leading to the defects of seed embryos without the recognizable differentiation of shoot apex meristem (SAM) and radicle apex meristem (RAM) for the homozygotes of RINO1 knockout. The abnormal embryo phenotype of RINO1 homozygotes was partially rescued by exogenous spraying of inositol and indole-3-acetic acid (IAA) in rice panicle. Thus, RINO1 is crucial for both seed InsP6 biosynthesis and embryonic development. The lower phosphatidylinositol (4,5)-bisphosphate (PI (4,5) P2) concentration and the disorder auxin distribution induced by insufficient inositol supply in seed embryos were among the regulatory switch steps leading to aberrant embryogenesis and failure of seed germination in RINO1 knockout.

Keratinocyte FABP5-VCP complex mediates recruitment of neutrophils in psoriasis.

One of the hallmarks of intractable psoriasis is neutrophil infiltration in skin lesions. However, detailed molecular mechanisms of neutrophil chemotaxis and activation remain unclear. Here, we demonstrate a significant upregulation of epidermal fatty acid binding protein (E-FABP, FABP5) in the skin of human psoriasis and psoriatic mouse models. Genetic deletion of FABP5 in mice by global knockout and keratinocyte conditional (Krt6a-Cre) knockout, but not myeloid cell conditional (LysM-Cre) knockout, attenuates psoriatic symptoms. Immunophenotypic analysis shows that FABP5 deficiency specifically reduces skin recruitment of Ly6G+ neutrophils. Mechanistically, activated keratinocytes produce chemokines and cytokines that trigger neutrophil chemotaxis and activation in an FABP5-dependent manner. Proteomic analysis further identifies that FABP5 interacts with valosin-containing protein (VCP), a key player in NF-κB signaling activation. Silencing of FABP5, VCP, or both inhibits NF-κB/neutrophil chemotaxis signaling. Collectively, these data demonstrate dysregulated FABP5 as a molecular mechanism promoting NF-κB signaling and neutrophil infiltration in psoriasis pathogenesis.

LRRK2 G2019S promotes the development of colon cancer via modulating intestinal inflammation.

LRRK2 G2019S is the most prevalent variant associated with Parkinson's disease (PD), found in 1-3% of sporadic and 4-8% of familial PD cases. Intriguingly, emerging clinical studies have suggested that LRRK2 G2019S carriers have an increased risk of cancers including colorectal cancer. However, the underlying mechanisms of the positive correlation between LRRK2-G2019S and colorectal cancer remain unknown. Using a mouse model of colitis-associated cancer (CAC) and LRRK2 G2019S knockin (KI) mice, here we report that LRRK2 G2019S promotes the pathogenesis of colon cancer as evidenced by increased tumor number and tumor size in LRRK2 G2019S KI mice. LRRK2 G2019S promoted intestinal epithelial cell proliferation and inflammation within the tumor microenvironment. Mechanistically, we found that LRRK2 G2019S KI mice are more susceptible to dextran sulfate sodium (DSS)-induced colitis. Suppressing the kinase activity of LRRK2 ameliorated the severity of colitis in both LRRK2 G2019S KI and WT mice. At the molecular level, our investigation unveiled that LRRK2 G2019S promotes the production of reactive oxygen species, triggers inflammasome activation, and induces cell necrosis in the gut epithelium in a mouse model of colitis. Collectively, our data provide direct evidence that gain-of-kinase activity in LRRK2 promotes colorectal tumorigenesis, implicating LRRK2 as a potential target in colon cancer patients with hyper LRRK2 kinase activity.

Histology and clinical correlations in autoimmune hepatitis, primary biliary cholangitis, and autoimmune hepatitis-primary biliary cholangitis overlap syndrome.

OBJECTIVES: The diagnosis of autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and AIH-PBC overlap syndrome (OS) relies on their histologic features and clinical findings. In this study, we aimed to identify specific morphologic features of these diseases and evaluate their clinical correlation. METHODS: We included initial biopsies from untreated patients with AIH (n = 14), PBC (n = 10), and OS (n = 7). Histologic features of the portal tract, portal-lobular interface, and hepatic lobule, fibrosis, as well as clinical data including serology, autoantibodies, treatment, and prognosis were reviewed and analyzed. RESULTS: Our results showed that several histologic features differed significantly between AIH and PBC (p < 0.05). Among these features, OS cases were more likely to present with bile duct-centered processes (presence of bile duct damage while absence of inflammation gradient from bile duct to interface, plasma cell cluster and pericentral inflammation) unlike those seen in AIH (p < 0.05), and interface-centered processes (unequivocal interface hepatitis, ductular reaction, and periportal fibrosis) which were not seen in PBC (p < 0.05). We observed a significant correlation between transaminase levels and lobular inflammation, including numbers of lymphocyte, plasma cell and eosinophil. Our study also found that anti-smooth muscle antibody positivity was associated with interface hepatitis (p < 0.01), while antimitochondrial antibody positivity was associated with duct damage (including ductopenia) and granulomas (p < 0.05). CONCLUSION: Our results highlight distinctive morphological features between AIH and PBC. The possibility of overlap syndrome should be considered when encountering AIH with bile duct-centered processes or PBC with interface-centered processes in morphology and correlation with autoantibodies.

MYC overexpression in inflammatory bowel disease-associated conventional dysplasia and association of subsequent low-grade dysplasia in follow-up biopsies.

OBJECTIVE: Diagnosis of inflammatory bowel disease (IBD)-associated dysplastic lesions can be challenging. This study aims to evaluate MYC immunohistochemistry (IHC) as a potential biomarker for IBD-associated dysplasia and compare its effectiveness with p53 IHC. METHODS: The study cohort included resections from 12 IBD patients with carcinoma and concurrent conventional low-grade dysplasia (LGD), as well as biopsies from 21 patients with visible conventional LGD, which were followed up for 2 years with subsequent endoscopic examination. MYC and p53 IHC and MYC-FISH analysis were performed. RESULTS: Sensitivity for LGD detection was 67% (8/12) and 50% (6/12) for MYC and p53, respectively, but the difference was not statistically significant (p = 0.2207). MYC and p53 overexpression were not always mutually exclusive, nor were they always present simultaneously. Patients who presented dysplasia in subsequent biopsies (7/21) were found to be more likely present with multiple LGD polyps and MYC-overexpressed LGD in the initial biopsies, compared to those without subsequent dysplasia (p < 0.05). These dysplastic lesions were commonly associated with chronic colitis (p = 0.0614). The distribution of LGD sites did not show a significant difference between patients with and without subsequent LGD. In MYC overexpressed cases, homogeneously strong nuclear expression was not identified in all dysplastic epithelial cells, and no MYC amplification was found in these cases by FISH. CONCLUSION: MYC IHC can complement p53 IHC as an adjunct biomarker for diagnosing IBD-associated conventional LGD and can be used for the prediction of subsequent LGD in the follow-up biopsies combined with endoscopic features.

Further prognostic stratification of intestinal type of gastric adenocarcinoma by CDX2 expression pattern.

Gastric cancer is one of the most deadly malignancies worldwide. It is routinely divided into 2 common histologic subtypes by the Lauren classification, intestinal type and diffuse type. In recent years, the intestinal type of gastric cancer has been found to represent a heterogeneous disease with divergent prognosis. Our objective was to investigate the CDX2/CK7 immunohistochemical pattern and its role in further stratifying this type of gastric cancer. Gastrectomy cases with a diagnosis of the intestinal type of gastric adenocarcinoma from a single large institution between 2008 and 2022 were collected. Forty-four cases with available blocks and enough tumor tissue were included in this study. Four different immunohistochemical patterns were identified: CDX2+/CK7+ (40.9%), CDX2-/CK7+ (34.1%), CDX2+/CK7- (18.2%), and CDX2-/CK7- (6.8%). Compared to CDX2-negative cases, CDX2-positive ones are more likely to present better prognostic histopathological features including early stage, less perineural and lymphovascular invasion, and lower nodal metastasis. In addition, CDX2 expression was associated with specific molecular features like HER2 overexpression and genetic alterations of receptor tyrosine kinase (TRK) genes including EGFR, ERBB2, ERBB3, DDR2, and MET. In conclusion, according to the CDX2 expression pattern, the intestinal type of gastric cancer could be further divided into 2 subgroups, which have different histopathological and molecular features and different prognosis.

Refractory Pediatric Fibrostenotic Eosinophilic Esophagitis Treated With Dupilumab.

Eosinophilic esophagitis (EoE) is a progressive inflammatory disease of the esophagus. Untreated or uncontrolled disease over time can lead to the development of fibrosis and formation of strictures. Once the patient develops strictures, it is difficult to treat with the available medical therapies and will often require esophageal dilations. The Food and Drug Administration recently approved dupilumab for the treatment of EoE in patients older than 12 years. The clinical trials excluded patients with esophageal strictures. We describe a case of EoE with fibrostenotic stricture who had stricture resolution while on dupilumab therapy.

Polyclonal PAX8 expression in carcinomas of the biliary tract - Frequent non-specific staining represents a potential diagnostic pitfall.

Paired box protein 8 (PAX8) is a transcription factor that is considered a relatively specific marker of carcinomas of the thyroid, kidney, and Müllerian/Wolffian duct derivatives. Unexpected PAX8 immunoreactivity has occasionally been reported in other tumors. The frequency of PAX8 expression in carcinomas of the biliary tract is not well studied. We evaluated the immunohistochemical expression of PAX8 in 73 cases of biliary tract carcinoma. We found that 28 of 73 (38%) biliary tract carcinomas had variable immunoreactivity for PAX8, assessed by a widely used polyclonal antibody (ProteinTech Group, Chicago, IL). This included 3 (4%) of cases with strong diffuse, and 14 (19%) of cases with strong focal staining. Strong PAX8 expression was more frequent in distal bile duct carcinomas than other biliary sites (p = 0.015), and showed a weak association with advanced T stage (T3-T4 versus T1-T2; p = 0.09). No correlation was observed between PAX8 positivity and age at diagnosis, gender, or lymph node metastasis. The 28 polyclonal PAX8-positive cases were largely negative for monoclonal PAX8 and PAX6 immunostains, with only rare tumor cells with weak immunoreactivity being present in a subset of cases. We show that a substantial fraction of biliary tract carcinomas exhibit immunoreactivity with a widely used polyclonal PAX8 antibody. Pathologists should be aware of this potential pitfall during the diagnostic workup of hepatobiliary lesions to avoid misdiagnosis as a metastasis from a PAX8-positive tumor.

Frequent TLE1 Expression in Cutaneous Neoplasms.

TLE1 immunohistochemistry is widely used as a biomarker for synovial sarcoma. Recently, we identified TLE1 expression in a subset of melanomas and noted staining in sebaceous glands and follicular epithelium. TLE1 immunohistochemistry has not been well studied in cutaneous tumors. The aim was to investigate TLE1 expression in sebaceous neoplasms, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC) to determine whether the staining patterns may aid in the diagnosis or classification of these neoplasms. TLE1 immunohistochemistry was performed on sebaceous adenoma (n = 26), sebaceoma (n = 10), sebaceous carcinoma (n = 19), BCC (n = 20), and SCC (n = 19). Positivity was defined as dark-brown nuclear staining and graded as 3+ (strong staining of >50% of cells at 4×), 2+ (moderate staining of 10-50% of cells at 4× or >50% of cells staining at 10×), and 1+ (weak staining of <50% of cells at 10×). No staining was scored as 0. A score of 2-3+ was considered positive and 0-1+ negative. Nuclear TLE1 expression was identified in 25/26 (96%) sebaceous adenomas, 8/10 (80%) sebaceomas, and 17/19 (90%) sebaceous carcinomas. TLE1 also labeled 19/20 (95%) BCCs and 12/19 (63%) SCCs. TLE1 immunohistochemistry frequently highlights sebaceous neoplasms, BCC, and SCC with a fairly high sensitivity (63%-96%). Therefore, TLE1 is not a specific biomarker for synovial sarcoma and should be evaluated with caution, particularly in cases in which the differential diagnosis may include other cutaneous tumors. In addition, TLE1 does not seem to be useful in the diagnosis or classification of these neoplasms.

Expression of TLE1 in Malignant Melanoma With Spindle Cell Morphology: A Potential Diagnostic Pitfall.

OBJECTIVES: Transducer-like enhancer of split 1 (TLE1) immunohistochemistry is widely used as a biomarker of synovial sarcoma. Spindle cell or desmoplastic melanoma can morphologically mimic synovial sarcoma. The aim of this study was to investigate the expression of TLE1 in melanomas with a spindle cell morphology. METHODS: A search of the surgical pathology files resulted in 57 cases of melanomas diagnosed with a spindle cell or desmoplastic component. After review, 8 cases had no definitive dermal spindle cell component and 7 cases had insufficient tissue remaining and were excluded from the study. A total of 42 melanomas were examined for TLE1 immunohistochemistry using a mouse monoclonal antibody (Cell Marque, clone 1F5). Strength and percentage of nuclear TLE1 positivity was graded on a scale from 0 to 3+. Staining for TLE1 was considered positive for 2 to 3+ and negative for 0 to 1+. RESULTS: Nuclear TLE1 expression was identified in 24 (57%) of the 42 melanoma cases with spindle cell morphology (2+, n = 14; 3+, n = 10). TLE1 was considered negative in 18 cases (43%), of which most contained weak staining (1+, n = 14 [33%]) and only a small subset did not show any staining (0, n = 4 [10%]). CONCLUSION: TLE1 frequently highlights melanomas with spindle cell morphology and is a potential diagnostic pitfall. Therefore, when evaluating spindle cell tumors in which the differential may include both a melanoma and synovial sarcoma, TLE1 expression should be interpreted with caution and in conjunction with an immunohistochemical panel.

Development of a Commercial Reference Laboratory Elective Rotation for Residents in Clinical Pathology.

OBJECTIVES: To develop a curriculum for a commercial reference laboratory clinical pathology training elective. METHODS: A 4-day elective at Quest Diagnostics was developed. The elective included 32 sessions composed of interactive didactic sessions and laboratory tours/demonstrations. Ten residents who attended the elective completed a written evaluation and scored each component of the curriculum. RESULTS: Written comments were very positive and demonstrated the goals of the elective were achieved. Laboratory tours and one-on-one sessions with the medical directors were especially well received. Most of the residents stated that the rotation gave them exposure to an area of laboratory medicine that they were not familiar with. CONCLUSIONS: The elective provided a resident training experience that was highly regarded and exposed residents to an area of laboratory medicine not encountered in most pathology training programs. Our curriculum could serve as a model for establishing a similar elective in other training programs.

Immunohistochemical expression and prognostic value of PD-L1 in Extrapulmonary small cell carcinoma: a single institution experience.

BACKGROUND: Extrapulmonary small cell carcinomas (ESCC) are rare but aggressive tumors. Relapses are common despite treatment with chemotherapy and/or radiotherapy. Prospective data for treatment of ESCC are lacking; treatment of these cancers usually incorporates lung small cell carcinoma treatment recommendations. Cancer staging remains the most important prognostic factor. Cancer immunotherapy targeting the PD-1/PD-L1 pathway has shown efficacy in multiple tumor types, and could be an appealing treatment strategy for these rare tumors. METHODS: We investigated PD-L1 expression by immunochemistry (IHC) in ESCCs diagnosed at University of Massachusetts Medical Center, from 1999 to 2016. 34 cases with sufficient material were selected for PD-L1 IHC analysis using clone E1L3N. PD-L1 expression was evaluated using the combined positive score (CPS). Retrospective chart review was performed. We evaluated the incidence and prognostic value of PD-L1 expression in ESCC at our institution. RESULTS: Twelve out 34 cases (35%) had PD-L1 CPS scores ≥1. Ten cases had CPS scores ranging 1-5, whereas 2 cases had CPS scores > 80. The overall response rate to the standard chemotherapy with/without radiotherapy in the PD-L1 positive group was 80% versus 67% for the PDL-1 negative group (p-value 0.67). The median overall survival for the PD-L1 positive group, regardless of stage, was 11.5 months versus 7 months for PD-L1 negative group (p-value 0.34). Patients with limited stage disease with positive PD-L1 had a median survival of 53 months compared to 15 months for patients with PD-L1 negative limited stage (p-value 0.80). CONCLUSIONS: This study showed that at least one third of our ESCC tissue samples expressed PD-L1. There was a trend for higher response rates to the standard chemotherapy with/without radiotherapy and improved survival in PD-L1 positive patients. Further studies are required to understand the implications of immune dysregulation in these aggressive tumors. PD-L1/PD-1 inhibitors should be investigated in this group of patients.

Epigenetic response to environmental stress: Assembly of BRG1-G9a/GLP-DNMT3 repressive chromatin complex on Myh6 promoter in pathologically stressed hearts.

Chromatin structure is determined by nucleosome positioning, histone modifications, and DNA methylation. How chromatin modifications are coordinately altered under pathological conditions remains elusive. Here we describe a stress-activated mechanism of concerted chromatin modification in the heart. In mice, pathological stress activates cardiomyocytes to express Brg1 (nucleosome-remodeling factor), G9a/Glp (histone methyltransferase), and Dnmt3 (DNA methyltransferase). Once activated, Brg1 recruits G9a and then Dnmt3 to sequentially assemble repressive chromatin-marked by H3K9 and CpG methylation-on a key molecular motor gene (Myh6), thereby silencing Myh6 and impairing cardiac contraction. Disruption of Brg1, G9a or Dnmt3 erases repressive chromatin marks and de-represses Myh6, reducing stress-induced cardiac dysfunction. In human hypertrophic hearts, BRG1-G9a/GLP-DNMT3 complex is also activated; its level correlates with H3K9/CpG methylation, Myh6 repression, and cardiomyopathy. Our studies demonstrate a new mechanism of chromatin assembly in stressed hearts and novel therapeutic targets for restoring Myh6 and ventricular function. The stress-induced Brg1-G9a-Dnmt3 interactions and sequence of repressive chromatin assembly on Myh6 illustrates a molecular mechanism by which the heart epigenetically responds to environmental signals. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.

The phylogenetic analysis of Acrossocheilus paradoxus among the acrossocheilus base on complete mitochondrial DNA sequence.

In our research, we used 17 sets of primers to amplify the complete mitochondrial DNA (mtDNA) of Acrossocheilus paradoxus. The total length of the mitochondrial genome is 16 597 bp and deposited in the GenBank with accession numbers KT751364. The gene arrangement and transcriptional direction were similar to other bony fishes which contained 37 genes (13 protein-coding genes, 2 ribosomal RNA and 22 transfer RNAs) and a major non-coding control region. Most genes were encoded on the H-strand, except for the ND6 and 8 tRNA genes, encoding on the L-strand. The nucleotide skewness for the coding strands of A. Paradoxus (GC-skew= -0.24, AT-skew = 0.07) is biased toward A and C. The negative GC-skew ranges from -0.35(ND6) to -0.21(CO1) and the AT-skew showed more positive varying from -0.23(ND4L) to 0.42(ND6). The phylogenetic analysis demonstrated that Acrossocheilus clustal together as one group.

Coronary Artery Disease Associated Transcription Factor TCF21 Regulates Smooth Muscle Precursor Cells That Contribute to the Fibrous Cap.

Recent genome wide association studies have identified a number of genes that contribute to the risk for coronary heart disease. One such gene, TCF21, encodes a basic-helix-loop-helix transcription factor believed to serve a critical role in the development of epicardial progenitor cells that give rise to coronary artery smooth muscle cells (SMC) and cardiac fibroblasts. Using reporter gene and immunolocalization studies with mouse and human tissues we have found that vascular TCF21 expression in the adult is restricted primarily to adventitial cells associated with coronary arteries and also medial SMC in the proximal aorta of mouse. Genome wide RNA-Seq studies in human coronary artery SMC (HCASMC) with siRNA knockdown found a number of putative TCF21 downstream pathways identified by enrichment of terms related to CAD, including "vascular disease," "disorder of artery," and "occlusion of artery," as well as disease-related cellular functions including "cellular movement" and "cellular growth and proliferation." In vitro studies in HCASMC demonstrated that TCF21 expression promotes proliferation and migration and inhibits SMC lineage marker expression. Detailed in situ expression studies with reporter gene and lineage tracing revealed that vascular wall cells expressing Tcf21 before disease initiation migrate into vascular lesions of ApoE-/- and Ldlr-/- mice. While Tcf21 lineage traced cells are distributed throughout the early lesions, in mature lesions they contribute to the formation of a subcapsular layer of cells, and others become associated with the fibrous cap. The lineage traced fibrous cap cells activate expression of SMC markers and growth factor receptor genes. Taken together, these data suggest that TCF21 may have a role regulating the differentiation state of SMC precursor cells that migrate into vascular lesions and contribute to the fibrous cap and more broadly, in view of the association of this gene with human CAD, provide evidence that these processes may be a mechanism for CAD risk attributable to the vascular wall.

A long noncoding RNA protects the heart from pathological hypertrophy.

The role of long noncoding RNA (lncRNA) in adult hearts is unknown; also unclear is how lncRNA modulates nucleosome remodelling. An estimated 70% of mouse genes undergo antisense transcription, including myosin heavy chain 7 (Myh7), which encodes molecular motor proteins for heart contraction. Here we identify a cluster of lncRNA transcripts from Myh7 loci and demonstrate a new lncRNA-chromatin mechanism for heart failure. In mice, these transcripts, which we named myosin heavy-chain-associated RNA transcripts (Myheart, or Mhrt), are cardiac-specific and abundant in adult hearts. Pathological stress activates the Brg1-Hdac-Parp chromatin repressor complex to inhibit Mhrt transcription in the heart. Such stress-induced Mhrt repression is essential for cardiomyopathy to develop: restoring Mhrt to the pre-stress level protects the heart from hypertrophy and failure. Mhrt antagonizes the function of Brg1, a chromatin-remodelling factor that is activated by stress to trigger aberrant gene expression and cardiac myopathy. Mhrt prevents Brg1 from recognizing its genomic DNA targets, thus inhibiting chromatin targeting and gene regulation by Brg1. It does so by binding to the helicase domain of Brg1, a domain that is crucial for tethering Brg1 to chromatinized DNA targets. Brg1 helicase has dual nucleic-acid-binding specificities: it is capable of binding lncRNA (Mhrt) and chromatinized--but not naked--DNA. This dual-binding feature of helicase enables a competitive inhibition mechanism by which Mhrt sequesters Brg1 from its genomic DNA targets to prevent chromatin remodelling. A Mhrt-Brg1 feedback circuit is thus crucial for heart function. Human MHRT also originates from MYH7 loci and is repressed in various types of myopathic hearts, suggesting a conserved lncRNA mechanism in human cardiomyopathy. Our studies identify a cardioprotective lncRNA, define a new targeting mechanism for ATP-dependent chromatin-remodelling factors, and establish a new paradigm for lncRNA-chromatin interaction.