Expression data of regenerating embryonic mouse hearts

We have recently shown a remarkable regenerative capacity of the prenatal heart using a genetic model of mosaic mitochondrial dysfunction in mice. This model is based on inactivation of the X-linked gene encoding holocytochrome c synthase (Hccs) specifically in the developing heart. Loss of HCCS activity results in respiratory chain dysfunction, disturbed cardiomyocyte differentiation and reduced cell cycle activity. The Hccs gene is subjected to X chromosome inactivation, such that in females heterozygous for the heart conditional Hccs knockout approximately 50% of cardiac cells keep the defective X chromosome active and develop mitochondrial dysfunction while the other 50% remain healthy. During heart development, however, the contribution of HCCS deficient cells to the cardiac tissue decreases from 50% at midgestation to 10% at birth. This regeneration of the prenatal heart is mediated by increased proliferation of the healthy cardiac cell population, which compensate for the defective cells and allow the formation of a fully functional heart at birth. Here we performed microarray expression ananlyses on 13.5 dpc control and heterozygous Hccs knockout hearts to identify molecular mechanisms that drive embryonic heart regeneration. 13.5 dpc hearts of heterozygous heart conditional Hccs knockout and littermate control female embryos were dissected, RNA was isolated and hybridized to Affymetrix arrays. At this developmental stage the most dramatic changes in tissue composition occur in the knockouts, as hyperproliferation of healthy cardiomyocytes is readily detectable while a substantial contribution of HCCS deficient cells is still present. 5 biological replicates per genotyp each containing 4-5 pooled hearts were analyzed.本团队近期利用小鼠嵌合型线粒体功能障碍遗传模型，证实了产前心脏具备显著的再生能力。该模型通过特异性灭活发育中心脏内编码全细胞色素c合酶（holocytochrome c synthase, HCCS）的X连锁基因构建而成。HCCS活性缺失会引发呼吸链功能障碍、心肌细胞分化紊乱以及细胞周期活性降低。Hccs基因受X染色体失活（X chromosome inactivation）调控，因此在心脏条件性敲除（conditional knockout）的杂合雌性小鼠中，约50%的心肌细胞会保留活跃的缺陷型X染色体，进而出现线粒体功能障碍，剩余50%则保持健康状态。但在心脏发育过程中，HCCS缺陷细胞在心脏组织中的占比从妊娠中期的50%降至出生时的10%。这种产前心脏再生是通过健康心肌细胞群体的增殖增强介导的，后者可代偿缺陷细胞，最终在出生时形成功能完整的心脏。本研究针对胚胎发育第13.5天（13.5 dpc）的野生型与杂合Hccs条件性敲除心脏开展基因芯片表达谱分析（microarray expression analyses），以阐明驱动胚胎心脏再生的分子机制。我们解剖了杂合心脏条件性敲除雌性胚胎及其同窝野生型对照胚胎的13.5 dpc心脏，提取RNA并与Affymetrix基因芯片进行杂交。在该发育阶段，敲除组的组织组成发生最为显著的变化：健康心肌细胞的过度增殖已可被检测到，同时仍存在相当比例的HCCS缺陷细胞贡献。每个基因型设置5个生物学重复样本，每个样本包含4~5个混合的心脏组织。