Cloning and developmental expression analysis of the murine homolog of the spinocerebellar ataxia type 1 gene (Sca1)

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder caused by the expansion of a CAG trinucleotide repeat which encodes glutamine in the novel protein ataxin-1. In order to characterize the developmental expression pattern of SCA1 and to identify putative functional domains in ataxin-1, the murine homolog (Sca1) was isolated. Cloning and characterization of the murine Sca1 gene revealed that the gene organization is similar to that of the human gene. The murine and human ataxin-1 are highly homologous but the CAG repeat is virtually absent in the mouse sequence suggesting that the polyglutamine stretch is not essential for the normal function of ataxin-1 in mice. Cellular and developmental expression of the murine homolog was examined using RNA in situ hybridization. During cerebellar development, there is a transient burst of Sca1 expression at postnatal day 14 when the murine cerebellar cortex becomes physiologically functional. There is also marked expression of Sca1 in mesenchymal cells of the intervertebral discs during development of the spinal column. These results suggest that the normal Sca1 gene, has a role at specific stages of both cerebellar and vertebral column development.      

Delivery of a hammerhead ribozyme specifically down-regulates the production of fibrillin-1 by cultured dermal fibroblasts

The hammerhead ribozyme is a small catalytic RNA molecule. Potential hammerhead ribozymes that possess a catalytic domain and flanking sequence complementary to a target mRNA can cleave in trans at a putative cleavage site within the target molecule. We have investigated the potential of hammerhead ribozymes to down-regulate the product of the fibrillin-1 gene (FBN1). Fibrillin is a 347 kDa glycoprotein that is a major constituent of the elastin-associated microfibrils. Mutations in the FBN1 gene are responsible for Marfan syndrome (MFS), a common systemic disorder of the connective tissue. Many FBN1 mutations responsible for MFS appear to act in a dominant-negative fashion, raising the possibility that reduction of the amount of product from the mutant FBN1 allele might be a valid therapeutic approach for MFS. A trans-acting hammerhead ribozyme (FBN1-RZ1) targeted to the 5' end of the human FBN1 mRNA has been designed and synthesized, and shown to cleave its target efficiently in vitro. FBN1-RZ1 cleavage is magnesium dependent and efficient at both 37 and 50 degrees C. Delivery of the FBN1-RZ1 ribozyme into cultured dermal fibroblasts, by receptor- mediated endocytosis of a ribozyme-transferrin-polylysine complex, specifically reduces both cellular FBN1 mRNA and the deposition of fibrillin in the extracellular matrix. These results suggest that the use of hammerhead ribozymes is a valid approach to the study of fibrillin gene expression and possibly to the development of a therapeutic approach to MFS.      

Viral Persistence in Neurons Alters Synaptic Plasticity and Cognitive Functions without Destruction of Brain Cells

Neurons have a restricted expression of MHC heavy chain molecules which prevents presentation of antigens of infecting viruses. As a result, such infected cells escape immune surveillance and allow the establishment of noncytolytic persistent infection. Here we show that a chronic noncytolytic viral infection bothin vitroandin vivoselectively perturbed the expression of GAP-43, a protein that plays a central role in neuronal plasticity processes accompanying learning and memory. GAP-43 expression was greatly decreased in the hippocampus, an area of heightened viral replication, while synaptic density was preserved. Concurrently, the ability to learn tasks was significantly impaired in these persistently infected mice. Yet, infected neurons remained free from structural injury.     

Dorsal lunate tilt (DISI configuration): sign of scaphoid fracture displacement

Excessive dorsiflexion (dorsal tilting) of the lunate on a lateral wrist radiograph can be an important sign of carpal injury. Lunate dorsiflexion is a well-recognized sign of an intercarpal ligamentous injury pattern known as dorsal intercalated segment instability (DISI). It is less well recognized that excessive dorsal tilting of the lunate (DISI configuration) can also be produced by displacement of a scaphoid waist fracture. Since the management and prognosis of displaced scaphoid fractures may be quite different from those for nondisplaced fractures, radiologists can make an important contribution by recognizing dorsal tilting of the lunate and appreciating that it may be an important, indirect sign of scaphoid fracture displacement, which may not be directly visualized with standard wrist radiography. In this setting, computed tomography or complex motion tomography may be helpful for further evaluation of the scaphoid fracture.     

Evaluation of the In Vivo Activity of Different Concentrations of Clerodendrum Umbellatum Poir Against Schistosoma Mansoni Infection in Mice

Clerodendrum umbellatum Poir (Verbenaceae) is traditionally used in Cameroon for the treatment of many diseases including intestinal helminthiasis. This study was undertaken to assess the in vivo antischistosomal activity of its leaves aqueous extract on a Schistosoma mansoni mice model and to determine the most effective dose of this extract. Mice showing a patent infection of S. mansoni were daily treated with C. umbellatum leaves aqueous extract at the doses of 40, 80 or 160 mg/kg body weight for 14 days. Seven days after administration of the extract, schistosomicidal activity was evaluated on the liver and spleen weights, faecal eggs releasing, liver egg count and worm burden. Treatment using C. umbellatum leaves aqueous extract resulted in an important reduction in faecal egg output by 75.49 % and 85.14 % for 80 mg/kg and 160 mg/kg of the extract respectively. These reduction rates did not differ significantly from the 100 % obtained in the group of infected mice treated with 100 mg/kg of praziquantel. C. umbellatum leaves aqueous extract was lethal to S. mansoni worm. A 100 % reduction rate was recorded in the group of infected mice treated with 160 mg/kg of the extract, as well as in praziquantel-treated mice. An amelioration of the hepatosplenomegaly was noticed in both the extract-treated mice and the praziquantel-treated mice. From these results, we can conclude that C. umbellatum leaves aqueous extract demonstrated schistosomicidal properties in S. mansoni model at doses of at least 80 mg/kg body weight.     

bcl-2 transgene expression promotes survival and reduces proliferation of CD3-CD4-CD8- T cell progenitors

Proliferative expansion and apoptotic cell death play prominent roles in T cell development. The molecular control of cell cycle progression and apoptosis appear to be inter-connected since the Bcl-2 protein can inhibit apoptosis and slow cell cycle progression in cortical thymocytes and mature T cells, particularly during the transition from the quiescent state into the cell cycle. Here the impact of bcl-2 transgene expression on CD3-CD4-CD8- T cell progenitors was assessed. Bcl-2 enhanced the survival of these progenitors at all of the four major differentiation stages, CD25- CD44+ (pro-T1), CD25 + CD44+ (pro- T2), CD25 + CD44- (pro-T3) and CD25-CD44- (pro-T4). However, it reduced cell cycling and slowed turnover only in the pro-T4 subset. From an analysis of bcl-2 transgenic mice expressing a TCR transgene or bearing a mutation in the scid or rag-1 gene we conclude that Bcl-2 inhibits proliferation only of T cell progenitors that are activated via the pre- TCR, not those stimulated via c-Kit and the IL-7 receptor.      

Identification of MEN1 gene mutations in sporadic carcinoid tumors of the lung

Lung carcinoids occur sporadically and rarely in association with multiple endocrine neoplasia type 1 (MEN1). There are no well defined genetic abnormalities known to occur in these tumors. We studied 11 sporadic lung carcinoids for loss of heterozygosity (LOH) at the locus of the MEN1 gene on chromosome 11q13, and for mutations of the MEN1 gene using dideoxy fingerprinting. Additionally, a lung carcinoid from a MEN1 patient was studied. In four of 11 (36%) sporadic tumors, both copies of the MEN1 gene were inactivated. All four tumors showed the presence of a MEN1 gene mutation and loss of the other allele. Observed mutations included a 1 bp insertion, a 1 bp deletion, a 13 bp deletion and a single nucleotide substitution affecting a donor splice site. Each mutation predicts truncation or potentially complete loss of menin. The remaining seven tumors showed neither the presence of a MEN1 gene mutation nor 11q13 LOH. The tumor from the MEN1 patient showed LOH at chromosome 11q13 and a complex germline MEN1 gene mutation. The data implicate the MEN1 gene in the pathogenesis of sporadic lung carcinoids, representing the first defined genetic alteration in these tumors.      

High throughput parallel analysis of hundreds of patient samples for more than 100 mutations in multiple disease genes

As more mutations are identified in genes of known sequence, there is a crucial need in the areas of medical genetics and genome analysis for rapid, accurate and cost-effective methods of mutation detection. We have developed a multiplex allele-specific diagnostic assay (MASDA) for analysis of large numbers of samples (> 500) simultaneously for a large number of known mutations (> 100) in a single assay. MASDA utilizes oligonucleotide hybridization to interrogate DNA sequences. Multiplex DNA samples are immobilized on a solid support and a single hybridization is performed with a pool of allele-specific oligonucleotide (ASO) probes. Any probes complementary to specific mutations present in a given sample are in effect affinity purified from the pool by the target DNA. Sequence-specific band patterns (fingerprints), generated by chemical or enzymatic sequencing of the bound ASO(s), easily identify the specific mutation(s). Using this design, in a single diagnostic assay, we tested samples for 66 cystic fibrosis (CF) mutations, 14 beta-thalassemia mutations, two sickle cell anemia (SCA) mutations, three Tay-Sachs mutations, eight Gaucher mutations, four mutations in Canavan disease, four mutations in Fanconi anemia, and five mutations in BRCA1. Each mutation was correctly identified. Finally, in a blinded study of 106 of these mutations in > 500 patients, all mutations were properly identified. There were no false positives or false negatives. The MASDA assay is capable of detecting point mutations as well as small insertion or deletion mutations. This technology is amenable to automation and is suitable for immediate utilization for high-throughput genetic diagnostics in clinical and research laboratories.      

反复种植失败的相关对策新进展

辅助生殖技术的迅速发展使众多不孕症患者借助体外受精-胚胎移植(IVF-ET)及其衍生技术获得了后代。然而很大一部分妇女经历多次优质胚胎移植亦不能获得妊娠,反复种植失败(RIF)已经成为阻碍妊娠率进一步提高的瓶颈问题,且日益受到生殖医学界的广泛关注。就目前的条件而言,对RIF患者给予药物或者机械操作以提高子宫内膜容受性,行宫腹腔镜检查排除宫腔及盆腔病变以改善胚胎种植环境,通过辅助孵化、选择性囊胚移植、植入前胚胎遗传学筛查、共培养等技术提高胚胎着床能力都有可能改善和提高其种植率及妊娠率。RIF成为了我们亟待解决的问题,现综述近年有关反复种植失败的相关对策新进展。