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We present an overview of the gene content and organization of the mitochondrial genome of Dictyostelium discoideum. The mitochondria genome consists of 55,564 bp with an A + T content of 72.6%. The identi®ed genes include those for two ribosomal RNAs (rnl and rns), 18 tRNAs, ten subunits of the NADH dehydrogenase complex (nad1, 2, 3, 4, 4L, 5, 6, 7, 9 and 11), apocytochrome b (cytb), three subunits of the cytochrome oxidase (cox1/2 and 3), four subunits of the ATP synthase complex (atp1, 6, 8 and 9), 15 ribosomal proteins, and ®ve other ORFs, excluding intronic ORFs. Notable features of D. discoideum mtDNA include the following. (1) All genes are encoded on the same strand of the DNA and a universal genetic code is used.(2) The cox1 gene has no termination codon and is fused to the downstream cox2 gene. The 13 genes for ribosomal proteins and four ORF genes form a cluster 15.4 kb long with several gene overlaps. (3) The number of tRNAs encoded in the genome is not sucient to support the synthesis of mitochondrial protein. (4) In total, ®ve group I introns reside in rnl and cox1/2, and three of those in cox1/2 contain four free-standing ORFs. We compare the genome to other sequenced mitochondrial genomes, particularly that of Acanthamoeba castellanii.

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Background: Peroxisome proliferator activated receptor-c coactivator-1b (PGC-1b) is a recently identified homologue of the tissue specific coactivator PGC-1a, a coactivator of transcription factors such as the peroxisome proliferators activated receptors and nuclear respiratory factors. PGC-1a is involved in adipogenesis, mitochondrial biogenesis, fatty acid b oxidation, and hepatic gluconeogenesis. Methods: We studied variation in the coding region of human PPARGC1B in Danish whites and related these variations to the prevalence of obesity and type 2 diabetes in population based samples. Results: Twenty nucleotide variants were identified. In a study of 525 glucose tolerant subjects, the Ala203Pro and Val279Ile variants were in almost complete linkage disequilibrium (R 2 = 0.958). In a casecontrol study of obesity involving a total of 7790 subjects, the 203Pro allele was significantly less frequent among obese participants (p = 0.004; minor allele frequencies: normal weight subjects 8.1% (95% confidence interval: 7.5 to 8.8), overweight subjects 7.6% (7.0 to 8.3), obese subjects 6.5% (5.6 to 7.3)). In a case-control study involving 1433 patients with type 2 diabetes and 4935 glucose tolerant control subjects, none of the examined variants were associated with type 2 diabetes. Conclusions: Variation of PGC-1b may contribute to the pathogenesis of obesity, with a widespread Ala203 allele being a risk factor for the development of this common disorder.

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