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

与大多数在哺乳动物中表达的基因不同，印记基因仅从一个亲本等位基因表达-哪个等位基因取决于特定的基因。因此，胰岛素样生长因子2（Igf 2）几乎完全由父本等位基因表达，而p57 Kip 2（CDK抑制剂）由母本等位基因表达。在脊椎动物中，这种形式的基因调控是哺乳动物所独有的。它为什么存在还不清楚。许多证据表明，印记基因参与调节细胞增殖和活力。雄激素胚胎，其中整个基因组是父系起源，表现出过度生长的胚外膜和增加胎儿的大小在中期妊娠。单性生殖胚胎，其中整个基因组都是母系起源，表现出胚胎生长迟缓。为了便于理解印迹和识别新的印迹基因，我们建立了成纤维细胞系，这是完全雄激素或孤雌生殖的起源。这些细胞系显示出完全相反的生长模式，雄激素细胞具有较短的细胞周期时间，达到较高的饱和密度并形成肿瘤，而单性生殖细胞衰老并死亡。使用缺乏印迹基因如Igf 2、其受体之一Igf 2 r和p57 Kip 2的小鼠品系，发现Igf 2是调节这些细胞增殖和活力的主要决定因素。除了这些生长研究之外，我们还使用这些品系来鉴定新的印迹基因。使用抑制性消减筛选，我们确定了核受体辅因子阻遏物/激活剂Zac 1和β-肌聚糖作为从父亲等位基因表达的印记基因，以及在大脑中强烈表达的Est，并从母亲等位基因转录。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。我们已经开发了几种与印记缺陷相关的人类先天性疾病（称为Prader-Willi综合征）的小鼠模型。在这种情况下，新生儿的特点是张力减退，呼吸模式中断，往往无法茁壮成长过去的第一年的生活。那些幸存下来的人会发展成饮食失调和暴食症（过量的食物摄入），经常导致肥胖。这种疾病与父亲15号染色体的部分丢失有关。在小鼠7号染色体上发现一个同源区域。我们最近描述了小鼠的起源缺乏位于Prader-Willi区域的基因Necdin的父系等位基因。这些小鼠在出生后不久就死于呼吸系统疾病，并模仿了普拉德-威利综合征的一个方面。他们的呼吸生理学正在进行更详细的研究，以确定Necdin的功能。我们还在基因靶向小鼠模型中分析了另一个与Necdin密切相关的基因Magel 2的功能，该基因也在已知调节circadina节律和食欲的大脑中的几个关键区域中从父系等位基因特异性表达。我们能够证明，携带破坏的Magel 2等位基因父系遗传的杂合子动物表现出严重的昼夜节律破坏。所有KO小鼠在经历持续黑暗的夹带时在短时间内变得严重抑郁，而对照野生型同窝小鼠在相同方案的几周后显示出稳健的昼夜节律。此外，我们能够鉴定Magel 2敲除小鼠的进食行为中断，尽管与人类PWS个体相反，Magel 2敲除小鼠似乎平均消耗比野生型同窝小鼠更少的食物，并且在食欲调节激素ghrelin中显示出共线抑制。在神经解剖学水平上，我们发现在Magel 2缺失小鼠中，表达唤醒和食欲调节神经肽食欲素的神经元的计数与野生型动物相比几乎减少了两倍。总之，我们得出结论，我们的Magel 2缺陷型小鼠系为PWS病理学的第二阶段提供了令人满意的模型。总的来说，印迹的分子分析将提供对基因表达的表观遗传控制的见解，这一方面与理解某些肿瘤抑制基因在癌症形成中的调节越来越相关

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