Neuron-specific expression of mutant superoxide dismutase 1 in transgenic mice does not lead to motor impairment.

Mutations were identified in the Cu/Zn superoxide dismutase gene (SOD1) in approximately 15% of patients with familial amyotrophic lateral sclerosis. Transgenic animals expressing mutant SOD1 in all tissues develop an ALS-like phenotype. To determine whether neuron-specific expression of mutant SOD1 is sufficient to produce such a phenotype, we generated transgenic animals carrying the G37R mutation that is associated with the familial form of ALS (FALS), which is driven by the neurofilament light chain promoter. The transgenic animals express high levels of the human SOD1 protein in neuronal tissues, especially in the large motor neurons of the spinal cord, but they show no apparent motor deficit at up to 1.5 years of age. Our animal model suggests that neuron-specific expression of ALS-associated mutant human SOD1 may not be sufficient for the development of the disease in mice.

SOD1 mutation is associated with accumulation of neurofilaments in amyotrophic lateral sclerosis.

Mutations in the Cu/Zn superoxide dismutase (SOD1) gene are found in 15 to 20% of patients with familial amyotrophic lateral sclerosis (FALS). Increased levels of neurofilament subunits in transgenic mouse models of ALS also suggests a key role for these proteins in the pathogenesis of the disease. We report the coexistence of an Ile113-->Thr substitution in exon 4 of the SOD1 gene and marked neurofilamentous pathology in the same FALS patient. These observations suggest that two mechanisms, SOD1-induced toxicity and neurofilament disruption, are acting together.

Identification of new mutations in the Cu/Zn superoxide dismutase gene of patients with familial amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder affecting motor neurons. Although most cases of ALS are sporadic, approximately 10% are inherited as an autosomal dominant trait. Mutations in the Cu/Zn superoxide dismutase gene (SOD 1) are responsible for a fraction of familial ALS (FALS). Screening our FALS kindreds by SSCP, we have identified mutations in 15 families, of which 9 have not been previously reported. Two of the new mutations alter amino acids that have never been implicated in FALS. One of them affects a highly conserved amino acid involved in dimer contact, and the other one affects the active-site loop of the enzyme. These two mutations reduce significantly SOD 1 enzyme activity in lymphoblasts. Our results suggest that SOD 1 mutations are responsible for > or = 13% of FALS cases.

Efficient recovery of cloned human cytomegalovirus DNA fragments from agarose gels.

A simple and efficient method for the recovery of DNA fragments from agarose gels is described. After electrophoresis, bands of interest are cut out of the gel and agarose slices pushed through the opening of a syringe needle. The resulting gel slurry is frozen and thawed three times and then centrifuged. DNA in the supernatant is precipitated, resuspended in a small volume of buffer and, finally, desalted. A recombinant pAT153 plasmid carrying the BamHI-P fragment of the human cytomegalovirus (HCMV) genome was detected using purified viral HindIII-E DNA fragment as a probe. Restriction endonuclease analysis was used to confirm the identity of the cloned fragment. Experiments performed with the recombinant pLCR127 plasmid indicate that our freeze/thaw method, with about 80% recovery and very little DNA degradation, is more advantageous than the well known electroelution and NaI/glass methods.

Electrophoresis of small DNA molecules in agaroses with different electroendosmotic properties.

The migration rate of DNA standards in agaroses with different electroendosmotic (EEO) properties was compared in order to find an alternative to polyacrylamide slab gels for the separation of small restriction fragments by electrophoresis. Slower migration of DNA molecules only a few hundred of base pairs in length was observed after raising the concentration of unmodified low EEO agarose in gels up to 6%. Resolution of low-molecular-weight DNA fragments was best achieved, however, with hydroxyethylated agaroses showing high or low EEO properties. An immediate application of the above results was to confirm the presence of the human cytomegalovirus BamH I-P subgenomic fragment (7.2 kb) in a recombinant pAT153 plasmid by restriction endonuclease analysis.

Electrophoretic transfer of DNA from gels to filters by using a homemade apparatus.

Electroblotting is a rapid and high-efficiency method of transferring DNA from gels to the variety of membranes available, in very short time frames when compared with capillary-blotting techniques and with much less preparation required. A simple apparatus made of two food savers, one dialysis membrane, one sponge, and two removable electrodes was used to transfer DNA molecules up to 21 kb, from agarose gels to nitrocellulose filters, in less than 30 min. A recombinant pAT153 plasmid carrying the human cytomegalovirus BamH I-P fragment (7.2 kb) was rapidly identified by hybridization, using our simplified transfer procedure.

Restriction endonuclease patterns of herpes simplex virus DNA: subtyping of HSV-1 and HSV-2 strains from genital and nongenital lesions.

Herpes simplex type 1 (HSV-1) and type 2 (HSV-2) isolates from genital and nongenital infections were submitted to restriction endonuclease analysis for possible genomic changes in relation with the adaptation of the virus to a new site on the body. HSV-1 and HSV-2 strains were successfully divided into two subgroups using the Hin c II restriction enzyme. No correlation was found, however, between the proposed genomic subtypes H1A, H1B, H2A and H2B, and the genital or nongenital origin of the HSV strains.

Low tumorigenicity of canine cells transformed by the human cytomegalovirus.

Dog embryo kidney cells transformed by the human cytomegalovirus (HCMV) were obtained after non-permissive infection or transfection with viral DNA digested by restriction endonuclease EcoR I. The transformed cells, growing rapidly and showing an unlimited division potential, could use medium with only 2% serum for growth, contained nuclear virus antigens, and formed small colonies (less than 0.2 mm) in agarose. From 40 mice inoculated with transformed canine cells, only one eventually developed a tumor. Results indicate that dog cells are immortalized but not tumorigenically transformed by the human cytomegalovirus.