A genetic model of substrate deprivation therapy for a glycosphingolipid storage disorder.
Inherited defects in the degradation of glycosphingolipids (GSLs) cause a group of severe diseases known as GSL storage disorders. There are currently no effective treatments for the majority of these disorders. We have explored a new treatment paradigm, substrate deprivation therapy, by constructing a genetic model in mice. Sandhoff's disease mice, which abnormally accumulate GSLs, were bred with mice that were blocked in their synthesis of GSLs. The mice with simultaneous defects in GSL synthesis and degradation no longer accumulated GSLs, had improved neurologic function, and had a much longer life span. However, these mice eventually developed a late-onset neurologic disease because of accumulation of another class of substrate, oligosaccharides. The results support the validity of the substrate deprivation therapy and also highlight some limitations. (+info)
A computational screen for methylation guide snoRNAs in yeast.
Small nucleolar RNAs (snoRNAs) are required for ribose 2'-O-methylation of eukaryotic ribosomal RNA. Many of the genes for this snoRNA family have remained unidentified in Saccharomyces cerevisiae, despite the availability of a complete genome sequence. Probabilistic modeling methods akin to those used in speech recognition and computational linguistics were used to computationally screen the yeast genome and identify 22 methylation guide snoRNAs, snR50 to snR71. Gene disruptions and other experimental characterization confirmed their methylation guide function. In total, 51 of the 55 ribose methylated sites in yeast ribosomal RNA were assigned to 41 different guide snoRNAs. (+info)
Familial antiphospholipid antibody syndrome: criteria for disease and evidence for autosomal dominant inheritance.
OBJECTIVE: To develop diagnostic criteria for a familial form of antiphospholipid antibody syndrome (APS), identify families with >1 affected member, examine possible modes of inheritance, and determine linkage to potential candidate genes. METHODS: Family members of probands with primary APS were analyzed for clinical and laboratory abnormalities associated with APS. Families with > or =2 affected members were analyzed by segregation analysis and typed for candidate genetic markers. RESULTS: Seven families were identified. Thirty of 101 family members met diagnostic criteria for APS. Segregation studies rejected both environmental and autosomal recessive models, and the data were best fit by either a dominant or codominant model. Linkage analysis showed independent segregation of APS and several candidate genes. CONCLUSION: Clinical and laboratory criteria are essential to identify the spectrum of disease associated with APS. We believe a set of criteria was developed that can precisely define affected family members with APS. Modeling studies utilizing these criteria strongly support a genetic basis for disease in families with APS and suggest that a susceptibility gene is inherited in an autosomal dominant pattern. However, in these families, APS was not linked with HLA, Fas, or other candidate genes, including beta2-glycoprotein 1, HLA, T cell receptor beta chain, Ig heavy chain, antithrombin III, Fas ligand, factor V, complement factor H, IgK, and Fas. (+info)
Telomere length dynamics and chromosomal instability in cells derived from telomerase null mice.
To study the effect of continued telomere shortening on chromosome stability, we have analyzed the telomere length of two individual chromosomes (chromosomes 2 and 11) in fibroblasts derived from wild-type mice and from mice lacking the mouse telomerase RNA (mTER) gene using quantitative fluorescence in situ hybridization. Telomere length at both chromosomes decreased with increasing generations of mTER-/- mice. At the 6th mouse generation, this telomere shortening resulted in significantly shorter chromosome 2 telomeres than the average telomere length of all chromosomes. Interestingly, the most frequent fusions found in mTER-/- cells were homologous fusions involving chromosome 2. Immortal cultures derived from the primary mTER-/- cells showed a dramatic accumulation of fusions and translocations, revealing that continued growth in the absence of telomerase is a potent inducer of chromosomal instability. Chromosomes 2 and 11 were frequently involved in these abnormalities suggesting that, in the absence of telomerase, chromosomal instability is determined in part by chromosome-specific telomere length. At various points during the growth of the immortal mTER-/- cells, telomere length was stabilized in a chromosome-specific man-ner. This telomere-maintenance in the absence of telomerase could provide the basis for the ability of mTER-/- cells to grow indefinitely and form tumors. (+info)
Plasmid replication initiator protein RepD increases the processivity of PcrA DNA helicase.
The replication initiator protein RepD encoded by the Staphylococcus chloramphenicol resistance plasmid pC221 stimulates the helicase activity of the Bacillus stearothermophilus PcrA DNA helicase in vitro. This stimulatory effect seems to be specific for PcrA and differs from the stimulatory effect of the Escherichia coli ribosomal protein L3. Whereas L3 stimulates the PcrA helicase activity by promoting co-operative PcrA binding onto its DNA substrate, RepD stimulates the PcrA helicase activity by increasing the processivity of the enzyme and enables PcrA to displace DNA from a nicked substrate. The implication of these results is that PcrA is the helicase recruited into the replisome by RepD during rolling circle replication of plasmids of the pT181 family. (+info)
Transplacement mutagenesis: a novel in situ mutagenesis system using phage-plasmid recombination.
Site-specific mutagenesis provides the ability to alter DNA with precision so that the function of any given gene can be more fully understood. Several methods of in vitro mutagenesis are time-consuming and imprecise, requiring the subcloning and sequencing of products. Here we describe a rapid, high fidelity method of in situ mutagenesis in bacteriophage lambda using transplacement. Using this method, mutations are transferred from oligonucleotides to target phages using a plasmid interface. A small (50 bp) homology region bearing a centred point mutation is generated from oligonucleotides and subcloned into a transplacement plasmid bearing positive and negative phage selectable markers. Following a positive/negative selection cycle of integrative recombination and excision, the point mutation is transferred precisely from plasmid to phage in a subset ( approximately 25-50%) of recombinants. As the fidelity of both oligonucleotide synthesis and phage-plasmid recombination is great, this approach is extremely reliable. Using transplacement, point mutations can be accurately deposited within large phage clones and we demonstrate the utility of this technique in the construction of gene targeting vectors in bacteriophages. (+info)
Rapid modification of bacterial artificial chromosomes by ET-recombination.
We present a method to modify bacterial artificial chromosomes (BACs) resident in their host strain. The method is based on homologous recombination by ET-cloning. We have successfully modified BACs at two distinct loci by recombination with a PCR product containing homology arms of 50 nt. The procedure we describe here is rapid, was found to work with high efficiency and should be applicable to any BAC modification desired. (+info)
Amplification of cDNA ends based on template-switching effect and step-out PCR.
A new method for amplifying cDNA ends is described which requires only first-strand cDNA synthesis and a single PCR to generate a correct product with very low or no background. The method can be successfully applied to total RNA as well as poly A+ RNA. The same first-strand cDNA can be used to amplify flanking sequences of any cDNA species present in the sample. (+info)