Targeted expression of Bcl-2 in mouse oocytes inhibits ovarian follicle atresia and prevents spontaneous and chemotherapy-induced oocyte apoptosis in vitro.

Members of the Bcl-2 family serve as central checkpoints for cell death regulation, and overexpression of Bcl-2 is known to inhibit apoptosis in many cell types. To determine whether targeted expression of Bcl-2 could be used to protect female germ cells from apoptosis, we generated transgenic mice expressing fully functional human Bcl-2 protein only in oocytes. Transgenic mice were produced using a previously characterized 480-bp fragment of the mouse zona pellucida protein-3 (ZP3) gene 5'-flanking region to direct oocyte-specific expression of a human bcl-2 complementary DNA. Immunohistochemical analyses using a human Bcl-2-specific antibody showed that transgene expression was restricted to growing oocytes and was not observed in the surrounding ovarian somatic cells or in any other nonovarian tissues. Histomorphometric analyses revealed that ovaries collected from transgenic female mice possessed significantly fewer atretic small preantral follicles compared with wild-type sisters, resulting in a larger population of healthy maturing follicles per ovary. However, the number of oocytes ovulated in response to exogenous gonadotropin priming and the number of pups per litter were not significantly different among wild-type vs. transgenic female mice. Nonetheless, oocytes obtained from transgenic mice and cultured in vitro were found to be resistant to spontaneous and anticancer drug-induced apoptosis. We conclude that targeted expression of Bcl-2 only in oocytes can be achieved as a means to convey resistance of the female germ line to naturally occurring and chemotherapy-induced apoptosis.     

A nanoformulation of siRNA and its role in cancer therapy: In vitro and in vivo evaluation

Overexpression of anti-apoptotic Bcl-2 is often observed in a wide variety of human cancers. It prevents the induction of apoptosis in neoplastic cells and contributes to resistance to chemotherapy. RNA interference has emerged as an efficient and selective technique for gene silencing. The potential to use small interfering RNA (siRNA) as a therapeutic agent for the treatment of cancer has elicited a great deal of interest. However, insufficient cellular uptake and poor stability have limited its therapeutic applications. The purpose of this study was to prepare chitosan nanoparticles via ionic gelation of chitosan by tripolyphosphate for effective delivery of siRNA to silence the anti-apoptotic Bcl-2 gene in neoplastic cells. Chitosan nanoparticles loaded with siRNA were in the size range 190 to 340 nm with a polydispersive index ranging from 0.04 to 0.2. They were able to completely bind with siRNA, provide protection against nuclease degradation, and enhance the transfection. Cell culture studies revealed that nanoparticles with entrapped siRNA could efficiently silence the antiapoptotic Bcl-2 gene. Studies on Swiss albino mice showed that siRNA could be effectively delivered through nanoparticles. There was significant decrease in the tumor volume. Blocking the expression of anti-apoptotic Bcl-2 can enhance the sensitivity of cancerous cells to anti-cancer drugs and the apoptosis rate. Therefore, nanoformulations with siRNA can be promoted as an adjuvant therapy in combination with anti-cancer drugs.     

Protection against murine leukemia virus-induced spongiform myeloencephalopathy in mice overexpressing Bcl-2 but not in mice deficient for interleukin-6, inducible nitric oxide synthetase, ICE, Fas, Fas ligand, or TNF-R1 genes

Some murine leukemia viruses (MuLVs), among them Cas-Br-E and ts-1 MuLVs, are neurovirulent, inducing spongiform myeloencephalopathy and hind limb paralysis in susceptible mice. It has been shown that the env gene of these viruses harbors the determinant of neurovirulence. It appears that neuronal loss occurs by an indirect mechanism, since the target motor neurons have not been found to be infected. However, the pathogenesis of the disease remains unclear. Several lymphokines, cytokines, and other cellular effectors have been found to be aberrantly expressed in the brains of infected mice, but whether these are required for the development of the neurodegenerative lesions is not known. In an effort to identify the specific effectors which are indeed required for the initiation and/or development of spongiform myeloencephalopathy, we inoculated gene-deficient (knockout [KO]) mice with ts-1 MuLV. We show here that interleukin-6 (IL-6), inducible nitric oxide synthetase (iNOS), ICE, Fas, Fas ligand (FasL), and TNF-R1 KO mice still develop signs of disease. However, transgenic mice overexpressing Bcl-2 in neurons (NSE/Bcl-2) were largely protected from hind limb paralysis and had less-severe spongiform lesions. These results indicate that motor neuron death occurs in this disease at least in part by a Bcl-2-inhibitable pathway not requiring the ICE, iNOS, Fas/FasL, TNF-R1, and IL-6 gene products.     

Overexpression of Bcl-2 in transgenic mice decreases apoptosis and improves survival in sepsis

In sepsis there is extensive apoptosis of lymphocytes, which may be beneficial by down-regulating the accompanying inflammation. Alternatively, apoptosis may be detrimental by impairing host defense. We studied whether Bcl-2, a potent antiapoptotic protein, could prevent lymphocyte apoptosis in a clinically relevant model of sepsis. Transgenic mice in which Bcl-2 was overexpressed in T cells had complete protection against sepsis-induced T lymphocyte apoptosis in thymus and spleen. Surprisingly, there was also a decrease in splenic B cell apoptosis in septic Bcl-2 overexpressors compared with septic HeJ and HeOuJ mice. There were marked increases in TNF-alpha, IL-1beta, and IL-10 in thymic tissue in sepsis in the three species of mice, and the increase in TNF-alpha and IL-10 in HeOuJ mice was greater than that in Bcl-2 mice. Mitotracker, a mitochondrial membrane potential indicator, demonstrated a sepsis-induced loss of membrane potential in T cells in HeJ and HeOuJ mice but not in Bcl-2 mice. Importantly, Bcl-2 overexpressors also had improved survival in sepsis. To investigate the potential impact of loss of lymphocytes on survival in sepsis, Rag-1-/- mice, which are totally deficient in mature T and B cells, were also studied. Rag-1-/- mice had decreased survival compared with immunologically normal mice with sepsis. We conclude that overexpression of Bcl-2 provides protection against cell death in sepsis. Lymphocyte death may be detrimental in sepsis by compromising host defense.     

Production of transgenic mice carrying the Thanatin gene by intratesticular injection

Transgenic animals have potential applications in medicine, life sciences, and biopharmacy. In this study, we developed a convenient, economic, and efficient method for gene transfer by transfection of male spermatogonial stem cells. Three fragments of the Thanatin gene, encoding an antibacterial peptide, were synthesized and amplified by overlap extension polymerase chain reaction (PCR). They were inserted into vector pIRES2-EGFP. The pIRES2-EGFP-Thanatin plasmid was mixed with liposomes and injected into the testes of male mice by a minimally invasive operation. Six weeks after injection, male mice were mated with normal female mice to produce an F1 generation. PCR and Southern blotting were performed to analyze F1 mice. Among those 52 F1 mice produced, 38.46% were found to be positive for the Thanatin gene by PCR and 30.77% by Southern blotting. Six positive mice were selected from the F1 generation and mated with normal females to an F2 generation, in which 36.36% were found to be positive for the Thanatin gene. Expression of the green fluorescence protein in the transgenic mice was confirmed by fluorescence imaging. These results showed that the Thanatin gene was integrated into the mouse genome. The study provides a useful method for the future development of disease-resistant animals and production of antibacterial peptides through transgenic animals.     

A Bcl-2 transgene expressed in hepatocytes does not protect mice from fulminant liver destruction induced by Fas ligand

We compared the biological mechanism of cell death during hepatotoxicity induced by ligation of the Fas receptor in wild-type and liver-specific bcl-2 transgenic mice. Transgenic overexpression of Bcl-2 in mouse hepatocytes can prevent lethal hepatitis induced by agonistic anti-Fas antibodies. In contrast, Fas ligand (FasL)-induced death cannot be overcome in bcl-2 transgenic mice, indicating that anti-Fas antibodies do not reliably mimic the more physiological ligand. Different apoptotic parameters, viz. caspase activation, cytochrome c release and nuclear DNA degradation were analysed. No differences, however, could be observed between wild-type and bcl-2 transgenic mice after injection with a lethal dose of soluble FasL, indicating that apoptosis by FasL-dependent ligation is not modulated by Bcl-2 in vivo. These results demonstrate that the stimulus determines the outcome between type I mitochondria-independent apoptosis, in the case of FasL, or type II mitochondria-dependent and Bcl-2-inhibitable apoptosis, in the case of anti-Fas antibodies.     

大蒜多糖对中毒性心肌炎心肌细胞凋亡的影响

目的:研究大蒜多糖 (GP)对中毒性心肌炎心肌细胞凋亡及Bcl -2、Bax蛋白表达的影响,探讨GP抑制心肌细胞凋亡的可能机制。方法:建立小鼠阿霉素 (ADR)中毒性心肌炎模型,利用缺口末端标记法检测心肌凋亡细胞;免疫组化法检测心肌细胞bcl 2、bax基因的蛋白表达情况,并利用电镜观察心肌结构变化。结果:ADR( 3mgkg-1ip,qod× 7)可致小鼠心肌细胞凋亡数明显升高,心肌细胞线粒体水肿,促进心肌细胞凋亡蛋白bax和抑制细胞凋亡蛋白bcl 2含量均明显升高,但bax/ bcl- 2的比值同时升高明显,与正常组比较有显著差异性 (P <0 . 0 1 )。GP可逆转ADR所致的上述改变,表现为剂量依赖性抑制细胞凋亡,降低bax蛋白表达同时增加bcl 2表达,使bcl- 2/ bax的比值增加 (P <0 .0 5或P <0 . 0 1 )。结论:GP能拮抗阿霉素所致的小鼠中毒性心肌炎心肌细胞凋亡作用,其作用机制可能与抑制Bax基因的蛋白表达,使Bcl -2基因表达的蛋白功能相对增强,Bcl -2 /Bax比值升高有关。     

Optimizing the production of animal models for target and lead validation

The need for genetically engineered animals for drug target discovery, development and validation is growing. Transgenic animals, including mice and rats, and knockout and knock-in animals, provide useful animal models on which to test hypotheses and therapies. Tosk, Inc. has developed two gene delivery vectors based on the Drosophila P element transposon: StealthGene™ and a targeted gene delivery (TGD) vector that works via homologous recombination. The promise of these new vectors will be assessed for applications ranging from replacing current transgenic and knockout technologies, to creating large transgenic animals such as goats, pigs, sheep and chickens, to human gene therapy.     

Targeted expression of Cre recombinase to adipose tissue of transgenic mice directs adipose-specific excision of loxP-flanked gene segments.

Functional analysis of mammalian genes relies, in part, on targeted mutations generated by homologous recombination in mice. We have developed a strategy for adipose-specific inactivation of loxP-floxed gene segments. Transgenic mice have been established that express Cre recombinase under the control of the adipose-specific aP2 enhancer/promoter. Crossing of the aP2/ Cre mice with any loxP-floxed gene will facilitate its functional analysis in adipose tissue.     

Gene Targeting Approaches to Neuroendocrinology: Oxytocin, Maternal Behavior, and Affiliation

Transgenic technology affords exciting new opportunities in the field of behavioral neuroendocrinology. We have extended our research into the behavioral function of oxytocin in maternal and social behavior using two transgenic approaches: (i) targeted deletion of the oxytocin gene in mice and (ii) augmented oxytocin receptor expression in the brain. Mice genetically deficient in oxytocin can mate, give birth, and display normal maternal behavior; however, milk ejection and certain aspects of social behavior are affected. Comparative studies of oxytocin receptors have led to the observation that species differences in social organization are associated with differences in receptor distribution. Specifically, monogamous prairie voles and nonmonogamous, asocial montane voles exhibit different patterns of OT receptor expression in the brain. Transgenic mice have been created with a reporter gene driven by the prairie vole oxytocin receptor gene promoter. Analysis of the expression pattern suggests that it should be possible to manipulate receptor expression in the vole brain in order to examine the effects of receptor distribution on behavior.     

Promoting Optic Nerve Regeneration in Adult Mice with Pharmaceutical Approach

Our previous research has suggested that lack of Bcl-2-supported axonal growth mechanisms and the presence of glial scarring following injury are major impediments of optic nerve regeneration in postnatal mice. Mice overexpressing Bcl-2 and simultaneously carrying impairment in glial scar formation supported robust optic nerve regeneration in the postnatal stage. To develop a therapeutic strategy for optic nerve damage, the combined effects of chemicals that induce Bcl-2 expression and selectively eliminate mature astrocytes—scar forming cells—were examined in mice. Mood-stabilizer, lithium, has been shown to induce Bcl-2 expression and stimulate axonal outgrowth in retinal ganglion cells in culture and in vivo. Moreover, astrotoxin (alpha-aminoadipate), a glutamate analogue, selectively kills astrocytes while has minimal effects on surrounding neurons. In the present study, we sought to determine whether concurrent applications of lithium and astrotoxin were sufficient to induce optic nerve regeneration in mice. Induction of Bcl-2 expression was detected in the ganglion cell layer (GCL) of mice that received a lithium diet in compared with control-treated group. Moreover, efficient elimination of astrocytes and glial scarring was observed in the optic nerve of mice treated with astrotoxin. Simultaneous application of lithium and astrotoxin, but not any of the drugs alone, induced robust optic nerve regeneration in adult mice. These findings further support that a combinatorial approach of concurrent activation of Bcl-2-supported growth mechanism and suppression of glial scarring is required for successful regeneration of the severed optic nerve in adult mice. They suggest a potential therapeutic strategy for treating optic nerve and CNS damage. Special issue article in honor of Dr. Ji-Sheng Han.     

白细胞介素22对T细胞介导的小鼠肝损伤的治疗作用及初步机制探讨

目的研究人白介素22（IL-22）对T细胞介导的肝损伤小鼠的治疗作用。方法利用刀豆蛋白A（ConA）建立T细胞介导的肝损伤小鼠模型,检测静脉注射IL-22对肝损伤小鼠血清丙氨酸转氨酶（ALT）、天门冬氨酸转氨酶（AST）活性的影响,同时取小鼠肝组织进行病理学检查。并采用半定量RT-PCR方法检测IL-22刺激HepG2和LO2细胞后,对c-myc及Bcl-2基因转录表达水平的影响。结果IL-22明显降低ConA致小鼠急性肝损伤血清ALT、AST值的升高,减轻ConA对肝组织的病理损伤。体外检测IL-22对HepG2和LO2细胞表达c-myc及Bcl-2基因转录水平有促进作用。结论IL-22对T细胞介导的肝损伤小鼠模型具有治疗作用,该作用可能是通过IL-22促进肝细胞的抗凋亡因子的表达实现的。     

Bax and Bcl-2 interaction in a transgenic mouse model of familial amyotrophic lateral sclerosis

It has been proposed that mutations in copper/zinc-superoxide dismutase (SOD1), the only proven cause of amyotrophic lateral sclerosis (ALS), induce the disease by a toxic property that promotes apoptosis. Consistent with this, we have demonstrated that overexpression of Bcl-2, a protein that inhibits apoptosis, attenuates neurodegeneration produced by the familial ALS-linked SOD1 mutant G93A (mSOD1). Herein, we assessed the status of key members of the Bcl-2 family in the spinal cord of transgenic mSOD1 mice at different stages of the disease. In asymptomatic transgenic mSOD1 mice, expression of Bcl-2, Bcl-XL, Bad, and Bax does not differ from that in nontransgenic mice. In contrast, in symptomatic mice, expression of Bcl-2 and Bcl-XL, which inhibit apoptosis, is reduced, whereas expression of Bad and Bax, which stimulate apoptosis, is increased. These alterations are specific to affected brain regions and are caused by the mutant and not by the normal SOD1 enzyme. Relevant to the neuroprotective effects of Bcl-2 in transgenic mSOD1 mice, overexpression of Bcl-2 increases the formation of Bcl-2:Bax heterodimers, which abolish the Bax proapoptotic property. This study demonstrates significant alterations in the expression of key members of the Bcl-2 family associated with mSOD1 deleterious effects. That these changes contribute to the neurodegenerative process in this model of ALS is supported by our observations in double transgenic mSOD1/Bcl-2 mice in which the pernicious increase of Bax is tempered by an increase in formation of Bcl-2:Bax heterodimers. Based on these findings, it may be concluded that Bcl-2 family members appear as invaluable targets for the development of new neuroprotective therapies in ALS.     

低密度脂蛋白受体相关蛋白2结合蛋白在心脏特异转基因小鼠中引起的心脏功能代偿

目的建立心脏特异表达的低密度脂蛋白受体相关蛋白2结合蛋白(Lrp2bp)转基因小鼠,研究该基因在心肌病发病中的作用。方法克隆鼠源Lrp2bp基因入α-MHC启动子下游,构建a-MHC-Lrp2bp表达载体,显微注射法建立Lrp2bp转基因小鼠。PCR鉴定转基因首建鼠的基因型。Westernblotting鉴定Lrp2bp在心脏中的表达,心脏超声检测转基因鼠及野生型小鼠心脏结构和功能,透射电镜观察心肌细胞的超微结构改变。结果得到了4个Lrp2bp转基因品系,其中3个品系心脏Lrp2bp蛋白表达量与同龄野生型鼠相比明显增加。1M龄转基因小鼠与同窝阴性对照小鼠相比,心壁变厚,心腔变大,射血分数和短轴缩短率下降。结论心脏特异表达的Lrp2bp基因能引起心肌肥厚表型,可能是参与心肌代偿性肥厚的基因之一。     

神经组织特异表达CTF1转基因小鼠的建立

目的建立神经组织特异表达CTF1的转基因模型小鼠,为研究CTF1生物学功能及与老年痴呆等疾病发病机制的关系提供工具动物。方法把CTF1基因插入神经组织特异的启动子PDGF下游,构建转基因表达载体,显微注射法建立C57BL/6J CTF1转基因小鼠。PCR鉴定转基因小鼠基因型,采用Western Blot方法鉴定CTF1在脑组织中的表达,对转基因小鼠脑组织进行石蜡切片,HE染色,显微镜观察组织结构形态的改变。结果建立了2个不同表达水平的CTF1转基因小鼠品系。转入的CTF1基因在脑组织的表达水平均高于同龄对照小鼠。组织学分析显示CTF1转基因小鼠大小脑组织基本结构形态未见异常。结论成功建立了稳定遗传的神经组织特异表达CTF1转基因小鼠品系,为CTF1的生物学功能及与老年痴呆等疾病发病机制关系的研究提供了有力的模型工具。     

Molecular manipulations of the multidrug transporter: a new role for transgenic mice

Multidrug resistance in human cancer is associated with overexpression of the MDR1 gene which encodes a 170,000 molecular weight membrane glycoprotein that transports cytotoxic drugs out of cancer cells. The MDR1 gene is normally expressed in intestine, kidney, liver, and adrenal glands, and in tumors derived from these tissues, but it is not expressed in normal bone marrow. Transgenic mice that express the MDR1 gene in their bone marrow have been developed, and because of this expression these mice are resistant to the bone marrow-suppressive effects of daunomycin, doxorubicin, taxol, and several other anticancer drugs. These mice can be used in several different ways to develop new types of drugs to treat human cancer.--Pastan, I.; Willingham, M. C.; Gottesman, M. Molecular manipulations of the multidrug transporter: a new role for transgenic mice.     

Mouse models for methylmalonic aciduria

Methylmalonic aciduria (MMA) is a disorder of organic acid metabolism resulting from a functional defect of methylmalonyl-CoA mutase (MCM). MMA is associated with significant morbidity and mortality, thus therapies are necessary to help improve quality of life and prevent renal and neurological complications. Transgenic mice carrying an intact human MCM locus have been produced. Four separate transgenic lines were established and characterised as carrying two, four, five or six copies of the transgene in a single integration site. Transgenic mice from the 2-copy line were crossed with heterozygous knockout MCM mice to generate mice hemizygous for the human transgene on a homozygous knockout background. Partial rescue of the uniform neonatal lethality seen in homozygous knockout mice was observed. These rescued mice were significantly smaller than control littermates (mice with mouse MCM gene). Biochemically, these partial rescue mice exhibited elevated methylmalonic acid levels in urine, plasma, kidney, liver and brain tissue. Acylcarnitine analysis of blood spots revealed elevated propionylcarnitine levels. Analysis of mRNA expression confirms the human transgene is expressed at higher levels than observed for the wild type, with highest expression in the kidney followed closely by brain and liver. Partial rescue mouse fibroblast cultures had only 20% of the wild type MCM enzyme activity. It is anticipated that this humanised partial rescue mouse model of MMA will enable evaluation of long-term pathophysiological effects of elevated methylmalonic acid levels and be a valuable model for the investigation of therapeutic strategies, such as cell transplantation.