Improved in Planta Expression of the Human Islet Autoantigen Glutamic Acid Decarboxylase (GAD65)

The smaller isoform of the enzyme glutamic acid decarboxylase (GAD65) is a major islet autoantigen in autoimmune type 1 diabetes mellitus (T1DM). Transgenic plants expressing human GAD65 (hGAD65) are a potential means of direct oral administration of the islet autoantigen in order to induce tolerance and prevent clinical onset of disease. We have previously reported the successful generation of transgenic tobacco and carrot that express immunoreactive, full-length hGAD65. In the present study, we tested the hypothesis that the expression levels of recombinant hGAD65 in transgenic plants can be increased by targeting the enzyme to the plant cell cytosol and by mediating expression through the potato virus X (PVX) vector. By substituting the NH₂-terminal region of hGAD65 with a homologous region of rat GAD67, a chimeric GAD67_1-87/GAD65_88-585 molecule was expressed in transgenic tobacco plants. Immunolocalization analysis showed that immunoreactive GAD67/65 was found in the plant cell cytosol. By using a radio-immuno assay with human serum from a GAD65 autoantibody-positive T1DM patient, the highest expression level of the recombinant GAD67/65 protein was estimated to be 0.19% of the total soluble protein, compared to only 0.04% of wild-type hGAD65. Transient expression of wild-type, full-length hGAD65 in N. benthamiana mediated by PVX infection was associated with expression levels of immunoreactive protein as high as 2.2% of total soluble protein. This substantial improvement of the expression of hGAD65 in plants paves the way for immunoprevention studies of oral administration of GAD65-containing transgenic plant material in animal models of spontaneous autoimmune diabetes.     

Sperm mediated gene transfer in pig: Selection of donor boars and optimization of DNA uptake

Transgenic animals are produced primarily by microinjecting exogenous DNA into the male pronuclei of a zygote. Microinjection is successful in mice but not efficient in farm animals, limiting its general utility. We have pursued an alternative technology for producing transgenic animals: Sperm Mediated Gene Transfer (SMGT). Based on our finding that sperm cells bind and internalize exogenous DNA, we used sperm as a vector for transmitting, not only their own DNA, but also, the exogenously-introduced gene of interest to the zygote. SMGT is highly efficient (up to greater than 80%) and relatively inexpensive; it can be used in species refractory to microinjection, whenever reproduction is mediated by gametes. In this report, we describe the procedure for selection of sperm donors and optimization of DNA uptake that are the key steps for the successful outcome of SMGT. We found that the nominal parameters that boar sperm should possess to serve as a good vector for exogenous DNA are the quality of semen based on standard parameters used in conventional animal breeding programs (volume, concentration, presence of abnormal sperm cells, motility at time of collection, and high progressive motility after 2 hr) and the ability of the sperm cells to take up and internalize exogenous DNA. The results described provide significant advances in SMGT technology applied to pigs, so that transgenic pigs can be efficiently obtained. Mol.     

A peptide from heat shock protein 60 is the dominant peptide bound to Qa-1 in the absence of the MHC class Ia leader sequence peptide Qdm

The MHC class Ib molecule Qa-1 binds specifically and predominantly to a single 9-aa peptide (AMAPRTLLL) derived from the leader sequence of many MHC class Ia proteins. This peptide is referred to as Qdm. In this study, we report the isolation and sequencing of a heat shock protein 60-derived peptide (GMKFDRGYI) from Qa-1. This peptide is the dominant peptide bound to Qa-1 in the absence of Qdm. A Qa-1-restricted CTL clone recognizes this heat shock protein 60 peptide, further verifying that it binds to Qa-1 and a peptide from the homologous Salmonella typhimurium protein GroEL (GMQFDRGYL). These observations have implications for how Qa-1 can influence NK cell and T cell effector function via the TCR and CD94/NKG2 family members, and how this effect can change under conditions that cause the peptides bound to Qa-1 to change.     

Protection by herpes simplex virus glycoprotein D against Fas-mediated apoptosis: role of nuclear factor kappaB

Signals involved in protection against apoptosis by herpes simplex virus 1 (HSV-1) were investigated. Using U937 monocytoid cells as an experimental model, we have demonstrated that HSV-1 rendered these cells resistant to Fas-induced apoptosis promptly after infection. UV-inactivated virus as well as the envelope glycoprotein D (gD) of HSV-1, by itself, exerted a protective effect on Fas-induced apoptosis. NF-kappaB was activated by gD, and protection against Fas-mediated apoptosis by gD was abolished in cells stably transfected with a dominant negative mutant I-kappaBalpha, indicating that NF-kappaB activation plays a role in the antiapoptotic activity of gD in our experimental model. Moreover, NF-kappaB-dependent protection against Fas-mediated apoptosis was associated with decreased levels of caspase-8 activity and with the up-regulation of intracellular antiapoptotic proteins.     

UV-induced apoptosis is mediated independent of caspase-9 in MCF-7 cells: a model for cytochrome c resistance

The importance of the mitochondria in UV-induced apoptosis has become increasingly apparent. Following DNA damage cytochrome c and other pro-apoptotic factors are released from the mitochondria, allowing for formation of the apoptosome and subsequent cleavage and activation of caspase-9. Active caspase-9 then activates downstream caspases-3 and/or -7, which in turn cleave poly(ADP)-ribose polymerase (PARP) and other down-stream targets, resulting in apoptosis. In an effort to understand the mechanisms of Akt-mediated cell survival in breast cancer, we studied the effects of insulin-like growth factor (IGF)-I treatment on UV-treated MCF-7 human breast cancer cells. Apoptosis was induced in MCF-7 cells after UV treatment, as measured by caspase-7 and PARP cleavage, and IGF-I co-treatment protected against this response. Surprisingly caspase-9 cleavage was unchanged with UV and/or IGF-I treatment. Using MCF-7 cells overexpressing caspase-3 we have shown that resistance of caspase-9 to cleavage was not altered by the expression of caspase-3. Furthermore, overexpression of caspase-9 did not enhance PARP or caspase-7 cleavage after UV treatment. Because caspase-8 was activated with UV treatment alone, we believe that UV-induced apoptosis in MCF-7 cells occurs independently of cytochrome c and caspase-9, supporting the existence of a cytoplasmic inhibitor of cytochrome c in MCF-7 cells. We anticipate that such inhibitors may be overexpressed in cancer cells, allowing for treatment resistance.     

Reaction and substrate specificity of recombinant pig kidney Dopa decarboxylase under aerobic and anaerobic conditions

Dopa decarboxylase (DDC) catalyzes as main reaction the stereospecific CO(2) abstraction from L-Dopa and L-5-hydroxytryptophan (5-HTP), generating the corresponding aromatic amines, dopamine and serotonin, respectively. Side reactions with turnover time of minutes are also catalyzed by the enzyme. In particular, DDC exhibits half-transaminase activity toward D-aromatic amino acids and oxidative deaminase activity toward aromatic amines. The latter reaction could represent a new activity for this class of enzymes. Studies on the effect exerted by O(2) on reaction specificity of DDC revealed that under anaerobic conditions decarboxylation of L-aromatic amino acids takes place with a k(cat) approximately half of that measured in the presence of O(2), and is accompanied by a decarboxylation-dependent transamination, whereas oxidative deamination of aromatic amines is replaced by half-transamination. Half-transamination of D-aromatic amino acids is unaffected by the presence or absence of O(2). Some structural elements relevant for the control of reaction and substrate specificity of DDC have been identified by means of limited tryptic digestion and site-directed mutagenesis studies. All together, the data indicate that the chemical nature of the substrate, the presence of O(2), the integrity of a mobile loop, the absence of perturbation in the coenzyme-binding cleft and pH are important requirements for the achievement of a closed conformational state where the highest level of reaction specificity is reached.     

Kinetic properties of the glucose 6-phosphatase of the liver from arthritic rats

According to previous reports, adjuvant-induced arthritic rats present reduced activities of the hepatic glucose 6-phosphatase. A kinetic study was done in order to characterize this phenomenon. Microsomes were isolated from livers of arthritic and control rats (Holtzman strain) and the glucose 6-phosphatase was measured at various temperatures (13-37 degrees C) and glucose 6-phosphate concentrations. Irrespective of the temperature, the enzyme from arthritic rats presented a reduction of both V(max) and K(M). Detergent treatment of liver microsomes from control rats increased the activity, but no increase was found when microsomes from arthritic rats were treated in the same way. The mannose 6-phosphatase activity of detergent-treated microsomes from arthritic rats was only 25% of the activity found with detergent-treated microsomes from control rats. Without detergent treatment, the mannose 6-phosphatase activities of both control and arthritic rats were minimal. The activation energy, derived from V(max), was not changed by arthritis. In vivo arthritic rats presented higher hepatic glucose 6-phosphate concentrations, a phenomenon that is consistent with a reduced activity of glucose 6-phosphatase. It was concluded that in arthritic rats, the hydrolase is probably reduced, without a similar change in the translocase activity.     

Association of specific language impairment (SLI) to the region of 7q31

FOXP2 (forkhead box P2) was the first gene characterized in which a mutation affects human speech and language abilities. A common developmental language disorder, specific language impairment (SLI), affects 6%-7% of children with normal nonverbal intelligence and has evidence of a genetic basis in familial and twin studies. FOXP2 is located on chromosome 7q31, and studies of other disorders with speech and language impairment, including autism, have found linkage to this region. In the present study, samples from children with SLI and their family members were used to study linkage and association of SLI to markers within and around FOXP2, and samples from 96 probands with SLI were directly sequenced for the mutation in exon 14 of FOXP2. No mutations were found in exon 14 of FOXP2, but strong association was found to a marker within the CFTR gene and another marker on 7q31, D7S3052, both adjacent to FOXP2, suggesting that genetic factors for regulation of common language impairment reside in the vicinity of FOXP2.     

Evolution of additive and nonadditive genetic variance in development time along a cline in Drosophila serrata

Abstract. Latitudinal clines provide natural systems that may allow the effect of natural selection on the genetic variance to be determined. Ten clinal populations of Drosophila serrata collected from the eastern coast of Australia were used to examine clinal patterns in the trait mean and genetic variance of the life-history trait egg-to-adult development time. Development time significantly lengthened from tropical areas to temperate areas. The additive genetic variance for development time in each population was not associated with latitude but was associated with the population mean development time. Additive genetic variance tended to be larger in populations with more extreme development times and appeared to be consistent with allele frequency change. In contrast, the nonadditive genetic variance was not associated with the population mean but was associated with latitude. Levels of nonadditive genetic variance were greatest in the region of the cline where the gradient in the change in mean was greatest, consistent with Barton's (1999) conjecture that the generation of linkage disequilibrium may become an important component of the genetic variance in systems with a spatially varying optimum.