Genetic analysis of a spontaneous mutation in a rat with a novel hind limb defect

新型后肢缺陷大鼠自发突变的遗传分析

• 批准号: 7658476
• 负责人: DEBASISH SINHA
• 金额: $ 24.6万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-05-01 至 2011-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7658476
• 关键词: Accounting; Action Potentials; Affect; Afferent Neurons; Age; Animal Model; Animals; Apoptosis; Appearance; Atrophic; Axon; Birth; Body Weight; Brain; Breeding; Bromodeoxyuridine; Candidate Disease Gene; Cell Communication; Cell Nucleolus; Cerebral Ventricles; Chromosome Mapping; Chromosomes; Chromosomes, Human, Pair 1; Chromosomes, Human, Pair 10; Comorbidity; Crystallins; Cytoplasm; Data; Databases; Defect; Denervation; Development; Disease; Dorsal; Electron Microscopy; Evaluation; Exhibits; Exons; Eye; Female; Fibroblast Growth Factor Receptor 2; Gait; Gene Mutation; Genes; Genetic; Genome; Genotype; Health; Heterozygote; Homozygote; Human; In Situ Nick-End Labeling; Inherited; Label; Laboratories; Limb structure; Lod Score; Maps; Measures; Molecular; Motor; Motor Neurons; Muscle; Mutation; Names; Nature; Neural Conduction; Neurodevelopmental Disorder; Neuroglia; Neurologic; Neurons; Newborn Infant; Online Mendelian Inheritance In Man; Parents; Partner in relationship; Pathology; Pattern; Peripheral Nervous System Diseases; Phenotype; Poly-A Addition Site; RNA Splicing; Rana; Rattus; Relative (related person); Reverse Transcriptase Polymerase Chain Reaction; Rodent; Rotation; Schwann Cells; Site; Sprague-Dawley Rats; Structure of phrenic nerve; Study models; Techniques; Ventral Roots; Weight; Work; autosomal recessive trait; base; disability; gene function; genetic analysis; genetic linkage analysis; genome wide association study; interest; juvenile animal; mRNA Expression; male; mouse genome; mutant; novel; public health relevance; rat genome; sciatic nerve; spinal nerve posterior root; sural; sural nerve; tool

DESCRIPTION (provided by applicant): We describe here a novel rat mutant that arose spontaneously from a mating of two Sprague Dawley rats in a colony that we maintain to study another mutation, Nuc1. Nuc1 is an eye-specific phenotype with developmental abnormalities that we have been investigating for several years. Hind limbs of the new mutant animals are extended and abducted so severely that they do not effectively support the animal's weight. Because of this unusual appearance and gait anomaly, we have named the mutant strain frogleg. The brain of a frogleg rat is smaller in size and weight relative to normal littermates; however body weight, which is typically lower in the affected newborn rats, does catch up to normal after several months. Histological analysis of frogleg sciatic nerve revealed some abnormal changes in Schwann cells. Neurometric studies also showed that sciatic compound muscle action potential is significantly reduced in frogleg rats. Attempts to breed frogleg animals with each other or with phenotypically normal males and females were unsuccessful. Carrying the line was complicated by the absence of a heterozygote phenotype. We were able to perpetuate the frogleg line by breeding unaffected littermates of frogleg rats in random combination until specific matings produced frogleg progeny, thereby identifying the parents as heterozygotes. We have established that the condition is inherited in a Mendelian fashion as a single autosomal recessive trait, and have used genetic linkage analysis to map the gene to rat chromosome 1q36-37. This disease interval has been reduced to a chromosomal region of 2.7 Mbp. Based on the Reference Sequence annotation database for the most current rat genome assembly, there are 8 potential frogleg gene candidates. However, augmentation of this number by alignment with syntenic portions of the human and mouse genomes increases the total number of genes in the interval to approximately 19. In the current application, we seek to identify the gene and the specific mutation responsible for the frogleg phenotype. In addition we will better characterize the neurological abnormalities of frogleg rats. Knowing the gene's identity and the nature of the mutation will help us to further understand the molecular and cellular mechanisms responsible for this interesting phenotype. Our working hypothesis is that identification of the mutation and the gene responsible for the frogleg phenotype will provide a novel model for studying cellular and molecular mechanisms of neurodevelopmental disorders. Therefore, we propose the following aims: SPECIFIC AIM 1: To refine the linkage map of the frogleg locus. SPECIFIC AIM 2: To identify the frogleg gene and mutation. SPECIFIC AIM 3: To characterize the pathology that underlies the phenotype of the frogleg rat. The identification of the gene responsible for frogleg would be a major step toward defining the potential value of the model for the study of mechanisms involved in neurodevelopmental disorders. PUBLIC HEALTH RELEVANCE: The frogleg rat is a novel spontaneous mutant with a well-defined hind limb disability. This defect is neurological in origin. With the identification of the gene and specific mutation, the frogleg rat will become a valuable animal model for the study of neurodevelopmental disorders.

描述（由申请人提供）：我们在这里描述了一种新的大鼠突变，它是由两只斯普拉格·道利大鼠在一个群体中的交配自发产生的，我们维持这个群体来研究另一个突变，Nuc1。Nuc1是一种具有发育异常的眼睛特异性表型，我们已经研究了好几年。新突变动物的后肢被严重地拉长和绑架，以至于它们不能有效地支撑动物的体重。由于这种不寻常的外观和步态异常，我们将这种突变株命名为蛙腿。蛙腿鼠的大脑在体积和重量上都比正常的同伴要小；然而，体重，在受影响的新生大鼠中通常较低，在几个月后确实赶上了正常水平。蛙腿坐骨神经的组织学分析显示雪旺细胞有一些异常变化。神经测量学研究还表明，蛙腿大鼠坐骨复合肌动作电位明显降低。蛙腿动物相互交配或与正常雌雄交配的尝试都不成功。由于缺乏杂合子表型，携带该系变得复杂。我们能够通过随机组合繁殖未受影响的蛙腿鼠的后代，直到特定的交配产生蛙腿后代，从而将父母确定为杂合子，从而使蛙腿系得以延续。我们已经确定这种情况以孟德尔方式遗传为单一常染色体隐性性状，并使用遗传连锁分析将该基因定位到大鼠染色体1q36-37上。该疾病间隔已缩小到染色体区域2.7 Mbp。基于最新的大鼠基因组汇编的参考序列注释数据库，有8个潜在的青蛙腿基因候选。然而，通过与人类和小鼠基因组的同源部分比对，增加了这个数字，使间隔内的基因总数增加到大约19个。在目前的应用中，我们试图确定导致蛙腿表型的基因和特定突变。此外，我们将更好地描述蛙腿大鼠的神经异常。了解基因的身份和突变的性质将有助于我们进一步了解导致这种有趣表型的分子和细胞机制。我们的工作假设是，鉴定突变和负责蛙腿表型的基因将为研究神经发育障碍的细胞和分子机制提供一个新的模型。因此，我们提出以下目标：具体目标1：完善蛙腿基因座的连锁图谱。特异性目的2：鉴定蛙腿基因及其突变。具体目的3：表征蛙腿大鼠表型的病理特征。鉴定导致青蛙腿的基因将是确定该模型在神经发育障碍机制研究中的潜在价值的重要一步。