The -514C>T polymorphism in the LIPC gene modifies type 2 diabetes risk through modulation of HDL-cholesterol levels in Mexicans.

PURPOSE: Both type 2 diabetes (T2D) and low levels of high-density lipoprotein cholesterol (HDL-C) are very prevalent conditions among Mexicans. Genetic variants in the LIPC gene have been associated with both conditions. This study aimed to evaluate the association of the -514C < T (rs1800588) LIPC gene polymorphism with different metabolic traits, particularly the effects of this polymorphism on HDL-C plasma levels and T2D risk. METHODS: Mediation analysis was used to assess the direct and indirect effects of the -514C>T LIPC gene variant on HDL-C levels, T2D risk, and body mass index (BMI), in 2105 Mexican mestizo participants. We also assessed the functional effect of the -514C>T LIPC variant on the promoter activity of a reporter gene in the HepG2 cell line. RESULTS: Direct effects show that the -514C>T LIPC polymorphism is significantly associated with increased HDL-C plasma levels (ß = 0.03; p < 0.001). The -514C>T variant resulted in an indirect protective effect on T2D risk through increasing HDL-C levels (ß = - 0.03; p < 0.001). Marginal direct association between -514C>T and T2D was found (ß = 0.08; p = 0.06). Variables directly influencing T2D status were European ethnicity (ß = - 7.20; p < 0.001), age (ß = 0.04; p < 0.001), gender (ß = - 0.15; p = 0.017) and HDL-C (ß = - 1.07; p < 0.001). In addition, we found that the -514C>T variant decreases the activity of LIPC promoter by 90% (p < 0.001). CONCLUSIONS: The -514C>T polymorphism was not directly associated with T2D risk. HDL-C acts as a mediator between -514C>T LIPC gene variant and T2D risk in the Mexican population.

Inheritance of organelle DNA sequences in a citrus-poncirus intergeneric cross.

Many land plants deviate from the maternal pattern of organelle inheritance. In this study, heterologous mitochondrial and chloroplast probes were used to investigate the inheritance of organelle genomes in the progeny of an intergeneric cross. The seed parent was LB 1-18 (a hybrid of Citrus reticulata Blanco cv. Clementine x C. paradisi Macf. cv. Duncan) and the pollen parent was the cross-compatible species Poncirus trifoliata (L.) Raf. All 26 progeny examined exhibited maternal inheritance of plastid petA and petD loci. However, 17 of the 26 progeny exhibited an apparent biparental inheritance of mitochondrial atpA, cob, coxII, and coxIII restriction fragment length polymorphisms (RFLPs) and maternal inheritance of mitochondrial rrn26 and coxI RFLPs. The remaining nine progeny inherited only maternal mitochondrial DNA (mtDNA) configurations. Investigations of plant mitochondrial genome inheritance are complicated by the multipartite structure of this genome, nuclear gene control over mitochondrial genome organization, and transfer of mitochondrial sequences to the nucleus. In this study, paternal mtDNA configurations were not detected in purified mtDNA of progeny plants, but were present in progeny DNA preparations enriched for nuclear genome sequences. MtDNA sequences in the nuclear genome therefore produced an inheritance pattern that mimics biparental inheritance of mtDNA.

The tobacco apocytochrome b gene predicts sensitivity to the respiratory inhibitors antimycin A and myxothiazol.

The potential for use of the cytochrome-pathway electron-transfer inhibitors antimycin A and myxothiazol in the selection of plant mitochondrial genome transformants was investigated. The net growth of Nicotiana tabacum L. (tobacco) suspension-culture cells was reduced by these inhibitors, but complete repression of cell growth occurred only in the presence of both cytochrome and alternative electron-transfer-pathway inhibitors. Antimycin A and myxothiazol bind to and block electron transfer through different sites in the cytochrome b (COB) subunit of the mitochondrial bc1 respiratory complex (complex III). The nucleotide sequence of the tobacco cob gene was determined and found to predict highly conserved glycine and phenylalanine residues that are associated with sensitivity to antimycin A and myxothiazol, respectively. These residues are altered by mutations that confer resistance to antimycin A or myxothiazol in diverse organisms. Tobacco cob cDNA clones were constructed and sequenced, revealing eight full and 11 partial RNA-editing sites. RNA editing did not, however, alter codons for the conserved glycine and phenylalanine residues associated with sensitivity to the respiratory inhibitors. Antimycin A or myxothiazol, in conjunction with a modified cob gene, may therefore be useful in the selection of tobacco cells carrying a genetically transformed mitochondrial genome.

Organization of ATPA coding and 3' flanking sequences associated with cytoplasmic male sterility in Phaseolus vulgaris L.

A region of the mitochondrial genome associated with cytoplasmic male sterility (CMS) in Phaseolus vulgaris was flanked by two different repeated sequences designated x and y. The DNA sequence of the CMS-unique region and a portion of each flanking repeat was determined. Repeat x contained a complete coding copy of the F1 ATPase subunit A (atpA) gene, as well as an open reading frame (orf) predicting a protein of 209 amino acids. The TGA termination codon of the atpA gene and the ATG initiation codon of orf209 were overlapping. These reading frames were oriented with their 3' ends proximal to the CMS-unique region. The CMS-unique region of 3736 nucleotides contained numerous orfs. The longest of these predicted proteins being of 239, 98 and 97 amino acids. The 3' coding and 3' flanking regions of orf98 were derived from an internal region of the higher plant chloroplast tRNA alanine intron. The region of repeat y immediately adjacent to the CMS-unique region contained the 111 carboxy-terminal coding residues of the apocytochrome b (cob) gene. This segment was oriented with its 5' end proximal to the CMS-unique region, but cob gene sequences were not fused to an initiation codon within the unique region.

DNA restriction fragment length polymorphisms correlate with isozyme diversity in Phaseolus vulgaris L.

Genetic variation in Phaseolus vulgaris L. (P. vulgaris) was investigated at the isozyme and DNA levels. We constructed a library of size-selected Pst I clones of P. vulgaris nuclear DNA. Clones from this library were used to examine 14 P. vulgaris accessions for restriction fragment length polymorphisms (RFLPs). DNAs from each accession were analyzed with three restriction enzymes and 18 single copy probes. The same accessions were also examined for variability at 16 isozyme loci. Accessions included four representatives of the T phaseolin group and five representatives each of the C and S phaseolin groups. One member of the S group (the breeding line XR-235-1-1) was derived from a cross between P. vulgaris and P. coccineus. Isozymes and RFLPs revealed very similar patterns of genetic variation. Little variation was observed among accessions with C and T phaseolin types or among those with the S phaseolin type. However, both isozyme and RFLP data grouped accessions with S phaseolin separately from those accessions with C or T phaseolin. The highest degree of polymorphism was observed between XR-235-1-1 and members of the C/T group. RFLP markers will supplement isozymes, increasing the number of polymorphic loci that can be analyzed in breeding, genetic, and evolutionary studies of Phaseolus.