Monteiro João P, Saha Diptarka, Spiroski Ana-Mishel, Mahesh Saiba, Kaltzis Peter, Nadavallil Abhijit, Janbandhu Vaibhao, Murray Nicholas J, Severi Francesco, De Pace Azzurra Laura, Sánchez-Esteban Sandra, Rodor Julie, Beqqali Abdelaziz, Bennett Matthew, Stewart Kevin, Thomson Adrian, Hadoke Patrick W F, Markose Dyana, Wilson-Kanamori John R, Henderson Neil C, O'Carroll Dónal, Quertermous Thomas, Harvey Richard P, Del Monte-Nieto Gonzalo, Baker Andrew H
Centre for Cardiovascular Science, Queen's Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, UK.
Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
Cardiovasc Res. 2025 Jul 8;121(7):988-991. doi: 10.1093/cvr/cvaf043.
The highly conserved long non-coding RNA (lncRNA) MIR505HG has been primarily recognized as a precursor for microRNAs (miR)-424 and miR-503. However, studies have since demonstrated that MIR503HG has distinct functions from its associated miRNAs, playing important roles in cell proliferation, invasion, apoptosis, and differentiation. While these miRNAs are known to influence cardiomyocyte differentiation, the specific role of MIR503HG in heart development remains unexplored. We seek to determine how MIR503HG deletion impacts ventricular chamber development and to identify underlying molecular mechanisms.
To study the role of the lncRNA in vivo, we generated a functional MIR503HG knockout mouse model (MIR503HG-/-) using a synthetic polyadenylation signal to terminate MIR503HG transcription without affecting miR-424/503 expression. We performed morphological analyses on embryonic and adult hearts using microCT along with cardiac functional analysis via transthoracic echocardiography. We further apply single-nuclei RNA sequencing (snRNA-seq) on adult hearts to identify potential molecular mechanisms underlying the observed phenotypes. Functional deletion of MIR503HG alone was associated with reduced compact myocardium thickness and increased trabecular myocardium in the left ventricle (LV) at embryonic day 17.5 compared to wild-type mice, indicating a LV non-compaction (LVNC) phenotype. Moreover, adult MIR503HG-/- mutant hearts showed increased trabecular complexity, impaired LV relaxation, and mitral valve regurgitation. SnRNA-seq further revealed altered expression of several genes associated with cardiomyocyte function and LVNC, including Actc1, Mib1, Mybpc3, and Myh7. Lastly, Notch1 activity was also significantly increased in mutant hearts which has been previously associated with LVNC.
MIR503HG plays a role in ventricular chamber development, and its deletion leads to an LVNC phenotype independent of the miRNA cluster within its locus, highlighting its importance in cardiac development and disease. We further suggest that abnormal Notch1 activity may underpin the LVNC phenotype presented.
高度保守的长链非编码RNA（lncRNA）MIR505HG最初主要被认为是微小RNA（miR）-424和miR-503的前体。然而，此后的研究表明，MIR503HG与其相关的微小RNA具有不同的功能，在细胞增殖、侵袭、凋亡和分化中发挥重要作用。虽然已知这些微小RNA会影响心肌细胞分化，但MIR503HG在心脏发育中的具体作用仍未被探索。我们试图确定MIR503HG缺失如何影响心室腔发育，并确定潜在的分子机制。
为了研究lncRNA在体内的作用，我们使用合成聚腺苷酸化信号生成了一个功能性MIR503HG基因敲除小鼠模型（MIR503HG-/-），以终止MIR503HG转录，而不影响miR-424/503的表达。我们使用微型计算机断层扫描（microCT）对胚胎和成年心脏进行形态学分析，并通过经胸超声心动图进行心脏功能分析。我们进一步对成年心脏应用单核RNA测序（snRNA-seq），以确定观察到的表型背后的潜在分子机制。与野生型小鼠相比，在胚胎第17.5天，单独功能性缺失MIR503HG与左心室（LV）致密心肌厚度降低和小梁心肌增加有关，表明存在左心室心肌致密化不全（LVNC）表型。此外，成年MIR503HG-/-突变心脏显示小梁复杂性增加、左心室舒张功能受损和二尖瓣反流。snRNA-seq进一步揭示了几个与心肌细胞功能和LVNC相关的基因表达改变，包括Actc1、Mib1、Mybpc3和Myh7。最后，Notch1活性在突变心脏中也显著增加，这与LVNC有关。
MIR503HG在心室腔发育中起作用，其缺失导致独立于其基因座内微小RNA簇的LVNC表型，突出了其在心脏发育和疾病中的重要性。我们进一步表明，异常的Notch1活性可能是所呈现的LVNC表型的基础。
