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Biochemical Genetics (v.36, #9-10)
Characterization of Lethal Drosophila melanogaster alpha-Actinin Mutants by Christine Fyrberg; Andrew Ketchum; Elizabeth Ball; Eric Fyrberg (pp. 299-310).
We have partially characterized four Drosophilamelanogaster alpha-actinin gene mutants,I(1)2Cb1, I(1)2Cb2,I(1)2Cb4, and I(1)2Cb5. Wedemonstrate that in each case the mutation is caused bya chromosomal rearrangement that precludes normal proteinsynthesis. In the absence of alpha-actinin, fliescomplete embryogenesis and develop into flaccid larvaethat die within approximately 24 hr. These larvae have noticeable muscle dysfunction at hatching,although they, nevertheless, are capable of escapingfrom the egg membranes and of subsequent crawlingmovements. During larval development muscles degenerate, progressively limiting mobility and ultimatelycausing death. Electron microscopy of mutant musclefibers reveals that myofibrils are grossly disrupted inone day old larvae and that electron-dense structures reminiscent of those seen in human nemalinemyopathies are present throughout larval life. Our workrigorously demonstrates that alpha-actinin deficienciesare the cause of I(1)2Cb muscle defects. We anticipate that the alpha-actinin mutants described hereinwill facilitate in vivo tests of spectrin superfamilyprotein domain functions using a combination of directedmutagenesis and germline transformation.
Keywords: ALPHA-ACTININ; DROSOPHILA DEVELOPMENT ; MUSCLE PATHOLOGY; SPECTRIN PROTEIN SUPERFAMILY
Characterization and Expression of the Mx1 Gene in Wild Mouse Species by Hee Kyung Jin; Tadashi Yamashita; Kenji Ochiai; Otto Haller; Tomomasa Watanabe (pp. 311-322).
The mouse Mx1 gene encodes an interferon(IFN)-inducible nuclear protein and confers resistanceto influenza virus infection. The standard laboratorymouse strains all carry the Mx1- allele andare susceptible to influenza virus. In this study, severalmouse strains established from wild mice were tested todetermine their Mx1+ or Mx1-allele status with polymerase chain reaction-restrictionfragment length variation (PCR-RFLV), sequence analysis, reversetranscription (RT)-PCR, and immunofluorescence staining.All of the mouse strains originating from wild mice werefound uniformly to carry the Mx1+ allele.Therefore, it is conceivable that the Mx1+allele in wild populations serves a function againstsome pathogens related to orthomyxoviruses. The PCR-RFLVand sequence analysis allowed us to classify theMx1+ alleles of the laboratory and wild-origin mouse strainsinto distinct classes. RT-PCR and immunofluorescencestaining demonstrated that the Mx1 transcripts andproteins were induced by IFN-alpha/beta in macrophages from wild mouse species.
Keywords: MX1 GENE; WILD MICE; IFN-ALPHA/BETA; INFLUENZA VIRUS; DNA SEQUENCE; PCR-RFLV
Expansion of a (GA) Dinucleotide at a Microsatellite Locus Associated with Domestication in Rice by W. Ramakrishna; A. P. Davierwala; V. S. Gupta; P. K. Ranjekar (pp. 323-327).
Microsatellites undergo rapid changes over shortevolutionary time periods which can be phylogeneticallyinformative in related species. Here we show the repeatunit expansion of a (GA)n-type microsatellite in the process of cultivation of rice from itswild ancestors. We amplified a microsatellite locusharboring (GA)n repeats from several wild andcultivated rices. Sequencing revealed an increase inrepeat number from 14 in distantly related wild ricespecies to 24 in the widely grown present-day indicarice cultivars.
Keywords: RICE; MICROSATELLITE; REPEAT EXPANSION; DOMESTICATION EVOLUTION
Regulation of the Expression of the sn-Glycerol-3-Phosphate Dehydrogenase Gene in Drosophila melanogaster by Slawek Bartoszewski; John B. Gibson (pp. 329-350).
P element-mediated transformation has been usedto investigate the regulation of expression of thesn-glycerol-3-phosphate dehydrogenase gene ofDrosophila melanogaster. A 13-kb constructcontaining the eight exons and associated introns, 5 kb of the5′ region, and 3 kb downstream from the structuralgene produced normal levels of enzyme activity andrescued the poor viability of flies lacking the enzyme. All the regulatory elements essential fornormal enzyme expression were located in a fragment thatincluded the exons and introns and 1-kb upstreamnoncoding sequence. Deletions of the 1.6-kb secondintron reduced activity to 25%. Transformants withfusion constructs between the sn-glycerol-3-phosphatedehydrogenase gene and the beta-galactosidase gene fromE. coli revealed three elements that affectedexpression. A (CT)9 repeat element at the5′ end of the second intron increased expressionin both larvae and adults, particularly at emergence. Asecond regulatory element, which includes a(CT)7 repeat, was located 5′ to the TATA box and had similareffects on the gene's expression. A third, undefined,enhancer was located in the second intron, between 0.5and 1.8 kb downstream of the translation initiationcodon. This element increases enzyme activity to asimilar extent in larvae and adults but has littleeffect when the enhancer at the 5′ end of theintron is present.
Keywords: DROSOPHILA ; SN-GLYCEROL-3-PHOSPHATE DEHYDROGENASE; ENHANCER; GPDH
PCR Amplification of a Locus with RFLP Alleles Specific to African Honey Bees by H. Glenn Hall (pp. 351-361).
An anonymous honey bee locus, detectedpreviously with a cloned probe, has HhaI RFLP allelesspecific to African bees or common to both African andEuropean bees. To facilitate identification of thesealleles, this region, 1231, was made analyzable with thePCR. The two halves of the region, excluding thetermini, were amplified as two overlapping segments.Restriction sites were mapped, and the site differences responsible for the allelic RFLP patterns weredetermined. In the first half of the region, twopolymorphic HhaI sites are present in the commonalleles, whereas one, the other, or both of the sitesare absent in the African alleles. In the secondhalf, a third polymorphic HhaI site is present or absentin both common and African alleles. A short part of thesecond half of the region, including more of the terminus, was amplified as a third segment.Within this segment, close to this terminus, a fourthpolymorphic HhaI site is absent in some Africanalleles.
Keywords: AFRICAN HONEY BEES; POLYMERASE CHAIN REACTION; RESTRICTION FRAGMENT LENGTH POLYMORPHISM