Carleton Jennifer L, Halabi Rami R, Willson Jessica A, Plageman Timothy F, Bridgewater Darren, Feng Qingping, Drysda E Thomas A
Children's Health Research Institute, Victoria Research Labs, London, Ontario, Canada.
Department of Physiology & Pharmacology, The University of Western Ontario, London, Ontario, Canada.
PLoS One. 2025 Sep 8;20(9):e0331583. doi: 10.1371/journal.pone.0331583. eCollection 2025.
Loss of actin cytoskeleton control can hinder integral developmental and physiological processes and can be the basis for a subset of developmental defects. SHROOM3 is an actin binding protein, best characterized as being essential for neural tube closure in vertebrates. Shroom3 expression has also been identified in the developing heart, with some associated congenital heart defects. Here we show that the expression pattern of Shroom3 in the developing and adult mouse heart is specific to the myocardium. Using a gene trap line, we show that embryos with homozygous full-body Shroom3 loss die at birth due to exencephaly but also show congenital heart defects. This includes ventricular septal defects, semilunar valve abnormalities, and ventricle wall thinning. Adult mice heterozygous for Shroom3 loss also show ventricular thinning due to decreased cardiomyocyte size. To explore if SHROOM3 is operating in a cell autonomous manner in the cardiomyocytes, we utilized a floxed Shroom3 mouse line, allowing for spatial and temporal control of Shroom3 loss. Using an Nkx2-5-Cre recombinase, we targeted Shroom3 loss to the myocardium of the developing heart. Neonate pups with myocardial specific Shroom3 loss showed no significant impact on heart development, including no septal or valve defects, no ventricular thinning, and no change in viability into adulthood. Adult mice with myocardial specific Shroom3 loss showed no ventricular thinning and no change in cardiomyocyte size. These results show that the heart defects seen in full-body Shroom3 loss do not arise from myocardial specific loss. Rather, other cell types expressing Shroom3, such as the cardiac neural crest cells, may be directly contributing to cardiac development.
肌动蛋白细胞骨架控制的丧失会阻碍整体发育和生理过程，并可能成为一部分发育缺陷的基础。SHROOM3是一种肌动蛋白结合蛋白，其最显著的特征是对脊椎动物的神经管闭合至关重要。在发育中的心脏中也发现了Shroom3的表达，且与一些相关的先天性心脏缺陷有关。在这里，我们表明Shroom3在发育中和成年小鼠心脏中的表达模式是心肌特异性的。利用一个基因陷阱品系，我们发现全身Shroom3纯合缺失的胚胎在出生时因无脑畸形而死亡，但也表现出先天性心脏缺陷。这包括室间隔缺损、半月瓣异常和心室壁变薄。Shroom3缺失的成年杂合小鼠也因心肌细胞大小减小而出现心室变薄。为了探究SHROOM3是否在心肌细胞中以细胞自主方式发挥作用，我们利用了一个floxed Shroom3小鼠品系，从而实现对Shroom3缺失的时空控制。使用Nkx2-5-Cre重组酶，我们将Shroom3的缺失靶向到发育中心脏的心肌。心肌特异性Shroom3缺失的新生幼崽对心脏发育没有显著影响，包括没有间隔或瓣膜缺陷、没有心室变薄，以及成年后的存活率没有变化。心肌特异性Shroom3缺失的成年小鼠没有出现心室变薄，心肌细胞大小也没有变化。这些结果表明，全身Shroom3缺失时出现的心脏缺陷并非源于心肌特异性缺失。相反，其他表达Shroom3的细胞类型，如心脏神经嵴细胞，可能直接参与心脏发育。
