Autism spectrum disorder (ASD) is a neurodevelopmental syndrome marked by impairments in social interactive functioning and communication skills, and the presence of repetitive and restrictive behaviors. Twin and linkage studies provide evidence that ASD is heritable and genetically complex. Genetic analyses of familial quantitative traits in those with ASD may help to reveal underlying risk genes. We report a quantitative trait locus (QTL) analysis of nonverbal communication (NVC) in 228 families from the autism genetics resource exchange (AGRE) ascertained for at least two siblings with ASD. QTL at 1p13-q12, 4q21-25, 7q35, 8q23-24, and 16p12-13 indicate that genes at these loci may contribute to the variation in NVC among those with ASD. Using the criteria of Lander and Kruglyak, the QTL at 1p13-q12 is 'suggestive', while the other four are 'possible'. To assess whether these QTL are likely to harbor genes contributing specifically to the deficits in NVC, linkage analysis of ASD sibships with the most severe NVC scores was conducted. The sibships were identified by ordered-subset analyses (OSA), and families with the most severe NVC scores displayed lod scores of 3.4 at 8q23-24 and 3.8 at 16p12-13, indicating that these two regions are likely to harbor gene(s) contributing to ASD by predisposing to deficits in NVC.
Single-step selection with vinblastine was performed in populations of the human sarcoma cell line MES-SA, to assess cellular mechanisms of resistance to the drug and mutation rates via fluctuation analysis. At a stringent selection with 20 nM vinblastine, resulting in 5–6 logs of cell killing, the mutation rate was 7 × 10–7per cell generation. Analysis of variance supported the hypothesis of spontaneous mutations conferring vinblastine resistance, rather than induction of adaptive response elements. Surviving clones displayed a stable multidrug resistance phenotype over a 3-month period. All propagated clones demonstrated high levels of resistance to vinblastine and paclitaxel, and lower cross-resistance to doxorubicin and etoposide. Activation of MDR 1 gene expression and P-glycoprotein function was demonstrable in all clones. No elevation was found in the expression of the mrp gene, the LRP-56 major vault protein and β-tubulin isotypes (M40, β4, 5β, and β9) in these mutants. We conclude that initial-step resistant mechanism in these vinblastine-selected mutants commonly arises from a stochastic mutation event with activation of the MDR 1 gene. © 2000 Cancer Research Campaign
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