Conditional inactivation of the Cacna1a gene in transgenic mice

Ca(v)2.1 (P/Q-type) voltage-gated calcium channels play an important role in neurotransmitter release at many brain synapses and at the neuromuscular junction. Mutations in the CACNA1A gene, encoding the pore forming alpha(1) subunit of Ca(v)2.1 channels, are associated with a wide spectrum of neurological disorders. Here we generated mice with a conditional, floxed, Cacna1a allele without any overt phenotype. Deletion of the floxed Cacna1a allele resulted in ataxia, dystonia, and lethality during the fourth week, a severe phenotype similar to conventional Ca(v)2.1 knockout mice. Although neurotransmitter release at the neuromuscular junction was not affected in the conditional mice, homozygous deletion of the floxed allele caused an ablation of Ca(v)2.1 channel-mediated neurotransmission that was accompanied by a compensatory upregulation of Ca(v)2.3 (R-type) channels at this synapse. Pharmacological inhibition of Ca(v)2.1 channels is possible, but the contributing cell-types and time windows relevant to the different Ca(v)2.1-related neurological disorders can only be reliably determined using Cacna1a conditional mice.     

混酸法降解植物纤维素技术研究

以单酸正交试验结果为基础,对二酸混合法和三酸混合法降解植物纤维素的最佳工艺条件进行了探讨。二酸混合法的结果表明,酸的添加顺序严重影响纤维素向葡萄糖的转化。强酸与弱酸同时混用均使葡萄糖的转化率降低。但盐酸与乙酸的混用效果则因所选最佳条件的不同而不同,虽然硫酸与盐酸均为无机强酸,与乙酸混用时添加的顺序亦一样即先弱酸后强酸,但其结果差别甚大,前者使葡萄糖的转化率降低,后者则使葡萄糖的转化率由40.9%锰增到62.7%。三酸混合法的结果表明,在本研究所选用的四种酸中,无论是哪三种酸同时混用,均使葡萄糖的转化率降低;当按一定顺序添加时,其结果亦不如二酸混合法,结论：在用多种酸降解植物纤维素时,一定要按一定的顺序添加,最好用两种酸即可。     

Modulating skeletal muscle mass by postnatal,muscle-specific inactivation of the myostatin gene

By using a conditional gene targeting approach exploiting the cre-lox system, we show that postnatal inactivation of the myostatin gene in striated muscle is sufficient to cause a generalized muscular hypertrophy of the same magnitude as that observed for constitutive myostatin knockout mice. This formally demonstrates that striated muscle is the production site of functional myostatin and that this member of the TGFbeta family of growth and differentiation factors regulates muscle mass not only during early embryogenesis but throughout development. It indicates that myostatin antagonist could be used to treat muscle wasting and to promote muscle growth in man and animals.     

Tup1突变对转录抑制局部网络中基因表达的非线性影响

研究基因网络的非线性行为特征是研制基因网络技术的基础。Tup1基因是酵母中作用最为广泛的转录抑制因子之一,利用酵母生物信息学数据库中蛋白相互作用关系,构建一个以Tup1为中心,4个层次741个基因的局部基因网络。统计分析六张Tup1不同突变的基因表达芯片数据,将局部基因网络中的全部基因按照3个网络特征进行统计分析：必需、非必需基因、网络层次和网络节点,并研究这些特征与基因表达之间的关系。初步发现基因表达变化的强度与节点数目成一定的反比关系,必需基因的平均变化程度较非必需基因为低,且由Tup1突变引发的其他基因的表达变化在以Tup1为中心的局部基因网络中近层次网络变化程度较大,远层次网络变化程度较低。     

Conditional gene knockout using cre recombinase

Cre recombinase has become an important instrument for achieving precise genetic manipulation in mice. Many of these desired genetic manipulations rely on Cre’s ability to direct spatially and temporally specified excision of a predesignated DNA sequence that has been flanked by directly repeated copies of the loxP recombination site. Success in achieving such conditional mutagenesis in mice depends both on the careful design of conditional alleles and on reliable detection of cre gene expression. These procedures include PCR, immunohistochemistry and the use of a recombination-proficient GFP-tagged Cre protein.     

Conditional inactivation of nicastrin restricts amyloid deposition in an Alzheimer's disease mouse model

Production of Aβ by γ‐secretase is a key event in Alzheimer's disease (AD). The γ‐secretase complex consists of presenilin (PS) 1 or 2, nicastrin (ncstn), Pen‐2, and Aph‐1 and cleaves type I transmembrane proteins, including the amyloid precursor protein (APP). Although ncstn is widely accepted as an essential component of the complex required for γ‐secretase activity, recent in vitro studies have suggested that ncstn is dispensable for APP processing and Aβ production. The focus of this study was to answer this controversy and evaluate the role of ncstn in Aβ generation and the development of the amyloid‐related phenotype in the mouse brain. To eliminate ncstn expression in the mouse brain, we used a ncstn conditional knockout mouse that we mated with an established AD transgenic mouse model (5XFAD) and a neuronal Cre‐expressing transgenic mouse (CamKIIα‐iCre), to generate AD mice (5XFAD/CamKIIα‐iCre/ncstn^f/f mice) where ncstn was conditionally inactivated in the brain. 5XFAD/CamKIIα‐iCre/ncstn^f/f mice at 10 week of age developed a neurodegenerative phenotype with a significant reduction in Aβ production and formation of Aβ aggregates and the absence of amyloid plaques. Inactivation of nctsn resulted in substantial accumulation of APP‐CTFs and altered PS1 expression. These results reveal a key role for ncstn in modulating Aβ production and amyloid plaque formation in vivo and suggest ncstn as a target in AD therapeutics.     

Ubiquitin-independent proteasomal degradation driven by C-degron pathways

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