No Evidence for a Difference in Neuropsychological Profile among Carriers and Noncarriers of the FMR1 Premutation in Adults under the Age of 50

The 5′ untranslated region of the fragile X mental retardation gene, FMR1, contains a polymorphic CGG repeat. Expansions of this repeat are associated with a spectrum of disorders. Full mutation alleles, repeats ≥ 200, are associated with fragile X syndrome. Premutation alleles, repeats of ~55–199, are associated with a tremor-ataxia syndrome most commonly in older males and primary ovarian insufficiency in females. However, the neuropsychological impact of carrying a premutation allele is presently unclear in younger adults. In this study, we analyzed neuropsychological scores for 138 males and 506 females ascertained from the general population and from families with a history of fragile X syndrome. Subjects were age 18–50 years and had varying repeat lengths. Neuropsychological scores were obtained from measures of general intelligence, memory, and executive functioning, including attention. Principal component analysis followed by varimax rotation was used to create independent factors for analysis. These factors were modeled for males and females separately via a general linear model that accounted for correlation among related subjects. All models were adjusted for potential confounders, including age at testing, ethnicity, and household income. Among males, no repeat length associations were detected for any factor. Among females, only a significant association with repeat length and self-report attention (p < 0.01) was detected, with premutation carriers self-reporting significantly more attention-related problems compared to noncarriers. No significant interactions between repeat length and age were detected. Overall, these results indicate the lack of a global neuropsychological impact of carrying a premutation allele among adults under the age of 50.     

The budding yeast Msh4 protein functions in chromosome synapsis and the regulation of crossover distribution.

The budding yeast MSH4 gene encodes a MutS homolog produced specifically in meiotic cells. Msh4 is not required for meiotic mismatch repair or gene conversion, but it is required for wild-type levels of crossing over. Here, we show that a msh4 null mutation substantially decreases crossover interference. With respect to the defect in interference and the level of crossing over, msh4 is similar to the zip1 mutant, which lacks a structural component of the synaptonemal complex (SC). Furthermore, epistasis tests indicate that msh4 and zip1 affect the same subset of meiotic crossovers. In the msh4 mutant, SC formation is delayed compared to wild type, and full synapsis is achieved in only about half of all nuclei. The simultaneous defects in synapsis and interference observed in msh4 (and also zip1 and ndj1/tam1) suggest a role for the SC in mediating interference. The Msh4 protein localizes to discrete foci on meiotic chromosomes and colocalizes with Zip2, a protein involved in the initiation of chromosome synapsis. Both Zip2 and Zip1 are required for the normal localization of Msh4 to chromosomes, raising the possibility that the zip1 and zip2 defects in crossing over are indirect, resulting from the failure to localize Msh4 properly.     

T cell selection and differential activation on structurally related HLA-DR4 ligands.

Plasticity of TCR interactions during CD4(+) T cell activation by an MHC-peptide complex accommodates variation in the peptide or MHC contact sites in which recognition of an altered ligand by the T cell can modify the T cell response. To explore the contribution of this form of TCR cross-recognition in the context of T cell selection on disease-associated HLA molecules, we have analyzed the relationship between TCR recognition of the DRB1*0401- and DRB1*0404-encoded HLA class II molecules associated with rheumatoid arthritis. Thymic reaggregation cultures demonstrated that CD4(+) T cells selected on either DRB1*0401 or DRB1*0404 could be subsequently activated by the other MHC molecule. Using HLA tetramer technology we identify hemagglutinin residue 307-319-specific T cells restricted by DRB1*0401, but activated by hemagglutinin residues 307-319, in the context of DRB1*0404. One such clone exhibits an altered cytokine profile upon activation with the alternative MHC ligand. This altered phenotype persists when both class II molecules are present. These findings directly demonstrate that T cells selected on an MHC class II molecule carry the potential for activation on altered self ligands when encountering Ags presented on a related class II molecule. In individuals heterozygous for these alleles the possibility of TCR cross-recognition could lead to an aberrant immune response.     

Inhibition of adriamycin-stimulated microsomal lipid peroxidation by mitoxantrone and ametantrone,two new anthracenedione antineoplastic agents

Ametantrone and mitoxantrone, two new anthracenedione antineoplastic agents, produced a concentration-dependent inhibition of hepatic microsomal lipid peroxidation. Malondialdehyde production was diminished from 10.6 nmoles/mg/60 min to 3.3 and 5.4 nmoles/mg/60 min, in the presence of 100 μM mitoxantrone and ametantrone, respectively. Under similar conditions, Adriamycin stimulated lipid peroxidation over twofold. In addition, both mitoxantrone and ametantrone inhibited Adriamycin-stimulated lipid peroxidation, with 50% inhibition occurring at concentrations of 4 and 6 μM, respectively. Microsomal superoxide production was not significantly inhibited at anthracenedione concentrations which markedly decreased lipid peroxidation, suggesting that inhibition of lipid peroxidation was not the result of inhibition of superoxide generation. These results correlate with the lack of anthracenedione cardiotoxicity and also demonstrate anthracenedione inhibition of lipid peroxidation at micromolar concentrations; an observation with potential therapeutic significance.