Selenium, a trace element that is fundamental to human health, is incorporated into some proteins as selenocysteine (Sec), generating a family of selenoproteins. Sec incorporation is mediated by a multiprotein complex that includes Sec insertion sequence-binding protein 2 (SECISBP2; also known as SBP2). Here, we describe subjects with compound heterozygous defects in the SECISBP2 gene. These individuals have reduced synthesis of most of the 25 known human selenoproteins, resulting in a complex phenotype. Azoospermia, with failure of the latter stages of spermatogenesis, was associated with a lack of testis-enriched selenoproteins. An axial muscular dystrophy was also present, with features similar to myopathies caused by mutations in selenoprotein N (SEPN1). Cutaneous deficiencies of antioxidant selenoenzymes, increased cellular ROS, and susceptibility to ultraviolet radiation-induced oxidative damage may mediate the observed photosensitivity. Reduced levels of selenoproteins in peripheral blood cells were associated with impaired T lymphocyte proliferation, abnormal mononuclear cell cytokine secretion, and telomere shortening. Paradoxically, raised ROS in affected subjects was associated with enhanced systemic and cellular insulin sensitivity, similar to findings in mice lacking the antioxidant selenoenzyme glutathione peroxidase 1 (GPx1). Thus, mutation of SECISBP2 is associated with a multisystem disorder with defective biosynthesis of many selenoproteins, highlighting their role in diverse biological processes.

The L1014F (kdr) mutation, known to confer pyrethroid resistance in many insect pests, has been identified for the first time in S. avenae. Clonal lines heterozygous for the mutation showed 35-40-fold resistance to lambda-cyhalothrin in laboratory bioassays, consistent with the reported effect of this mutation on pyrethroid sensitivity in other aphid species.

This study describes a rapid and sensitive assay that very effectively detects the R81T mutation in individual aphids. The results also have practical significance for the control of M. persicae in southern France and provide contemporary data to inform current resistance management strategies.

Recombination experiments were performed to assess the affect of amber mutations in 12 genes of T4D bacteriophage on genetic recombination. Crosses were performed in various suppressor-containing bacterial hosts to permit the production of progeny phage. Amber mutations in genes 32, 46, and 47 caused decreased recombination, amber mutations in genes 30, 41, 42, 43, 56, 61, and 62 caused increased recombination, whereas mutations in genes 63 and 37 showed no demonstrable effect on recombination.

Complementation tests were performed between pairs of independently isolated aggregation defective mutants of P. violaceum. Analysis of the results suggests that the approximate number of genes controlling aggregation in this organism is 50.Aggregation in cellular slime molds such as Polysphondylium violaceum and Dictyostelium discoideum is a chemotactic process in which previously independent amebae come together to form a multicellular mass which differentiates into a fruiting body. After depletion of the food supply, scattered amebae release an attractant (acrasin). Neighboring amebae respond by moving toward the acrasin source and releasing acrasin, thus relaying the aggregation signal. As the amebae move toward aggregation centers, they adhere to each other, forming streams (2-6).Here we report on studies designed to assess the genetic complexity of aggregation in P. violaceum. Our approach was to isolate many independent aggregation defective (ag-) mutants after oguanidine treaent and to perform complementation tests between pairs of these mutants. Enough mutants were isolated so that noncomplementing pairs were found and a statistical estimate of the number of complementation units involved in aggregation (ag genes) could be made.The method of diploid selection used by Loomis (7) and Katz and Sussman (8) in D. discoideum was employed in doing complementation tests with P. violaceum. Ag-mutants isolated in a cycloheximide resistant growth temperature sensitive strain (t8119_CyR) were grown in pairwise combinations at a permissive temperature (210) with ag-mutants isolated in a second temperature sensitive strain (tsl52).Diploid heterozygotes (tsll9/+,ts152/+,'cyR/CyS) formed by fusion of haploid t8119_CyR and tsW52 cells were selected at a nonpermissive temperature (30°) and their aggregation phenotypes observed. Diploidy was confirmed by spore size and analysis of cycloheximide-resistant (haploid) segregants (6,8).Using 17 tsW5M ag-mutants and 24 t8119_cyR ag-mutants, we isolated 380 of 408 possible diploids (Fig. 1). Thirty-two of these showed defective aggregation and were considered to