Genomic Imprinting in Development and Disease

发育和疾病中的基因组印记

• 批准号: 7592680
• 负责人: COLIN STEWART
• 金额: $ 28.17万
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7592680
• 关键词: Alleles; Animals; Area; Arousal; Birth; Brain; Breathing; Cell Cycle; Cell Cycle Regulation; Cell Proliferation; Cell Survival; Cells; Chromatin; Chromosomes; Chromosomes, Human, Pair 15; Chromosomes, Human, Pair 7; Circadian Rhythms; Clinical; Condition; Count; Cyclin-Dependent Kinases; Darkness; Defect; Derivation procedure; Desire for food; Development; Disease; Disruption; Dissection; Eating; Eating Disorders; Embryo; Epigenetic Process; Exhibits; Feeding behaviors; Fibroblasts; Food; Gene Expression; Gene Expression Regulation; Gene Targeting; Genes; Genetic; Genome; Genomic Imprinting; Growth; Growth and Development function; Hormones; Human; Hyperphagia; Individual; Inherited; Insulin-Like Growth Factor II; Knockout Mice; Life; Link; Malignant Neoplasms; Mammals; Membrane; Modeling; Molecular; Molecular Analysis; Mus; Muscle hypotonia; Neurons; Neuropeptides; Newborn Infant; Nuclear Receptors; Obesity; Pathology; Pattern; Periodicity; Prader-Willi Syndrome; Pregnancy; Purpose; Regulation; Regulator Genes; Respiratory physiology; Screening procedure; Staging; Time; Transact; Tumor Suppressor Genes; Vertebrates; Week; cofactor; density; design; epsilon Sarcoglycan; fetal; gene function; ghrelin; hypocretin; imprint; inhibitor/antagonist; insight; interest; mouse model; necdin; nervous system disorder; novel; receptor; respiratory; size; tumor

Unlike the majority of genes expressed in mammals, imprinted genes are expressed from only one parental allele- which allele depends on the particular gene. Thus the Insulin like growth factor 2 (Igf2) is expressed almost exclusively from the paternal allele, whereas p57Kip2, a CDK inhibitor is expressed from the maternal allele. This form of gene regulation is, among vertebrates, unique to mammals. Why it exists is still unclear. Much evidence has suggested that imprinted genes are involved in regulating cell proliferation and viability. Androgenetic embryos, in which the entire genome is paternal in origin, exhibit overgrowth of the extraembryonic membranes and in increase in fetal size at mid gestation. Parthenogenetic embryos, where the entire genome is maternal in origin show retarded embryonic growth. To facilitate an understanding of imprinting and to identify novel imprinted genes, we established fibroblast lines which are either exclusively androgenetic or parthenogenetic in origin. The lines show diametrically opposite patterns of growth with the androgenetic cells having a shorter cell cycle time, reaching a higher saturation density and forming tumors, whereas the parthenotes senesced and died. Using mouse lines deficient for imprinted genes such as Igf2, one of its receptors, the Igf2r, and p57Kip2 revealed that Igf2 was a major determinant regulating proliferation and viability of these cells. In addition to these growth studies, we have used these lines to identify novel imprinted genes. Using a suppressive subtractive screen we identified the nuclear receptor cofactor repressor/activator Zac1 and epsilon sarcoglycan as being imprinted genes expressed from the paternal allele, as well as an Est that is strongly expressed in the brain, and is transcribed from the maternal allele. Current studies are centered on determining the function of these genes in development and growth regulation. We have developed several mouse models for a human congenital disease associated with a defect in imprinting called Prader-Willi syndrome. In this condition, newborns are featured by hypotonia, have disrupted breathing patterns and often fail to thrive past the first year of their lives. Those that survive develop an eating disorder and hyperphagia (excessive food intake) frequently resulting in obesity. The disease is associated with loss of part of the paternal chromosome 15. A homologous region is found on mouse chromosome 7. We recently described the derivation of mice lacking the paternal allele of a gene Necdin located in the Prader-Willi region. Such mice die shortly after birth due to respiratory problems and have mimicked one aspect of Prader-Willi syndrome. Their respiratory physiology is being studied in greater detail to determine the function of Necdin. We have also analyzed in gene targeting mouse model the function of another closely linked gene to Necdin, Magel2, that is also expressed from the paternal allele specifically in several key areas in the brain known to regulate the circadina rhythm and the appetite. We were able to demonstrate that the heterozygous animals bearing a disrupted Magel2 allele inherited paternally show severe disruption of circadian rhythmicity. All KO mice became severely arrhythmic within a short time period when subject to entraining in the constant darkness, whereas the control wild-type littermates displayed the robust circadian rhythm after several weeks of the same regime. We moreover were able to identify disrupted feeding behavior in Magel2 null mice, although contrary to teh human PWS individuals Magel2 KO animals appeared to consume on the average less food than their wild-type littermates, and displayed the collinear supression in the appetite-regulating hormone ghrelin. On the neuro-anatomical level we found that in Magel2 null mice the count of neurons expressing arousal and appetite regulating neuropeptide orexin is almost twice reduced as compared to the wild-type animals. In summary, we conclude that our Magel2 deficient mouse line provides a satisfactory model for the second stage of PWS pathology. Overall, a molecular analysis of imprinting will provide insights into the epigenetic control of gene expression, an aspect that is of increasing relevance to understanding the regulation of certain tumor suppressor genes in cancer formation

与哺乳动物中表达的大多数基因不同，印记基因只表达于一个亲代等位基因--该等位基因取决于特定的基因。因此，胰岛素样生长因子2(IGF2)几乎完全来自父亲的等位基因，而CDK抑制因子p57Kip2则来自母亲的等位基因。在脊椎动物中，这种形式的基因调控是哺乳动物独有的。它为什么会存在仍不清楚。许多证据表明，印记基因参与调节细胞的增殖和活性。雄核发育胚胎的整个基因组起源于父系，在怀孕中期表现出胚胎外膜的过度生长和胎儿尺寸的增加。孤雌生殖胚胎，其中整个基因组是母体起源的，表现出胚胎发育迟缓。为了促进对印记的理解和鉴定新的印记基因，我们建立了起源于雄性或孤雌生殖的成纤维细胞系。这些品系表现出截然相反的生长模式，雄核发育细胞的细胞周期时间较短，达到较高的饱和密度并形成肿瘤，而孤雌生殖细胞衰老和死亡。使用缺乏印记基因的小鼠株系，如其受体之一Igf2r和p57Kip2，揭示了Igf2是调节这些细胞的增殖和活性的主要决定因素。除了这些生长研究，我们还使用这些品系来鉴定新的印记基因。使用抑制性消减筛选，我们鉴定了核受体辅因子抑制/激活子Zac1和epsilon肌聚糖是从父亲的等位基因表达的印迹基因，以及在大脑中强烈表达的EST，是从母亲的等位基因转录而来的。目前的研究集中在确定这些基因在发育和生长调节中的功能。我们已经为一种与印记缺陷相关的人类先天性疾病建立了几个小鼠模型，称为Prader-Willi综合征。在这种情况下，新生儿的特点是低眼压，呼吸模式中断，通常在出生第一年后无法茁壮成长。那些幸存下来的人会出现进食障碍和吞噬过度(过量进食)，经常导致肥胖。这种疾病与父系15号染色体的部分缺失有关。在小鼠7号染色体上发现了一个同源区域。我们最近描述了一种缺乏位于Prader-Willi区的Necdin基因的小鼠的起源。这些小鼠出生后不久就会死于呼吸问题，并模仿了Prader-Willi综合征的一个方面。正在对它们的呼吸生理学进行更详细的研究，以确定Necdin的功能。我们还在基因打靶的小鼠模型中分析了另一个与Necdin紧密连锁的基因Magel2的功能，该基因也从父亲的等位基因中特异地表达在大脑中几个已知的调节昼夜节律和食欲的关键区域。我们能够证明，携带父系遗传的中断的Magel2等位基因的杂合子动物表现出严重的昼夜节律中断。所有KO小鼠在持续黑暗中的短时间内都出现了严重的心律失常，而对照野生型小鼠在相同的条件下几周后表现出强烈的昼夜节律。此外，我们还能够识别Magel2基因缺失小鼠的摄食行为中断，尽管与人类PWS个体相反，Magel2 KO动物似乎平均消耗的食物比它们的野生型小鼠更少，并显示出食欲调节激素Ghrelin的共线抑制。在神经解剖学水平上，我们发现在Magel2基因缺失的小鼠中，表达觉醒和食欲调节神经肽的神经元数量几乎是野生型动物的两倍。总之，我们得出的结论是，我们的Magel2缺陷小鼠系为PWS病理的第二阶段提供了一个令人满意的模型。总体而言，印迹的分子分析将提供对基因表达的表观遗传控制的洞察，这一方面对理解某些肿瘤抑制基因在癌症形成中的调控越来越重要。

项目成果

Absence of Ndn, encoding the Prader-Willi syndrome-deleted gene necdin, results in congenital deficiency of central respiratory drive in neonatal mice.

Ndn（编码普瑞德-威利综合征缺失基因necdin）的缺失，会导致新生小鼠中枢呼吸驱动先天性缺陷。

• DOI: 10.1523/jneurosci.23-05-01569.2003
• 发表时间: 2003
• 期刊: The Journal of neuroscience : the official journal of the Society for Neuroscience
• 作者: Ren,Jun;Lee,Syann;Pagliardini,Silvia;Gerard,Matthieu;Stewart,ColinL;Greer,JohnJ;Wevrick,Rachel
• 通讯作者: Wevrick,Rachel