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To identify bipolar disorder (BD) genetic susceptibility factors, we conducted two genome-wide association (GWA) studies: one involving a sample of individuals of European ancestry (EA; n=1001 cases; n=1033 controls), and one involving a sample of individuals of African ancestry (AA; n=345 cases; n=670 controls). For the EA sample, single-nucleotide polymorphisms (SNPs) with the strongest statistical evidence for association included rs5907577 in an intergenic region at Xq27.1 (P=1.6 x 10(-6)) and rs10193871 in NAP5 at 2q21.2 (P=9.8 x 10(-6)). For the AA sample, SNPs with the strongest statistical evidence for association included rs2111504 in DPY19L3 at 19q13.11 (P=1.5 x 10(-6)) and rs2769605 in NTRK2 at 9q21.33 (P=4.5 x 10(-5)). We also investigated whether we could provide support for three regions previously associated with BD, and we showed that the ANK3 region replicates in our sample, along with some support for C15Orf53; other evidence implicates BD candidate genes such as SLITRK2. We also tested the hypothesis that BD susceptibility variants exhibit genetic background-dependent effects. SNPs with the strongest statistical evidence for genetic background effects included rs11208285 in ROR1 at 1p31.3 (P=1.4 x 10(-6)), rs4657247 in RGS5 at 1q23.3 (P=4.1 x 10(-6)), and rs7078071 in BTBD16 at 10q26.13 (P=4.5 x 10(-6)). This study is the first to conduct GWA of BD in individuals of AA and suggests that genetic variations that contribute to BD may vary as a function of ancestry.

The ς D regulon of Bacillus subtilis is composed of genes encoding proteins for flagellar synthesis, motility, and chemotaxis. Concurrent analyses of ς D protein levels and flagellin mRNA demonstrate that sigD expression and ς D activity are tightly coupled during growth in both complex and minimal media, although they exhibit different patterns of expression. We therefore used the ς D -dependent flagellin gene ( hag ) as a model gene to study the effects of different nutritional environments on ς D -dependent gene expression. In complex medium, the level of expression of a hag-lacZ fusion increased exponentially during the exponential growth phase and peaked early in the transition state. In contrast, the level of expression of this reporter remained constant and high throughout growth in minimal medium. These results suggest the existence of a nutritional signal(s) that affects sigD expression and/or ς D activity. This signal(s) allows for nutritional repression early in growth and, based on reconstitution studies, resides in the complex components of sporulation medium, as well as in a mixture of mono-amino acids. However, the addition of Casamino Acids to minimal medium results in a dose-dependent decrease in hag-lacZ expression throughout growth and the postexponential growth phase. In work by others, CodY has been implicated in the nutritional repression of several genes. Analysis of a codY mutant bearing a hag-lacZ reporter revealed that flagellin expression is released from nutritional repression in this strain, whereas mutations in the transition state preventor genes abrB , hpr , and sinR failed to elicit a similar effect during growth in complex medium. Therefore, the CodY protein appears to be the physiologically relevant regulator of hag nutritional repression in B. subtilis.

The sigma D form of RNA polymerase from Bacillus subtilis has been shown previously to direct the synthesis of several transcription units bearing genes for flagellin, motility proteins, and autolysins. In this report, we describe an operon of genes transcribed from the sigma D-dependent promoter PD-1. We have identified three complete open reading frames and one partial one downstream of this promoter; immediately upstream is the previously identified comF locus. The PD-1 operon encodes the presumptive B. subtilis homologs of two Salmonella typhimurium late flagellar genes, flgM and flgK. Also present in this operon are two genes of unknown function, orf139 and orf160, whose products show similarities to the eukaryotic cytoskeletal proteins myosin and vimentin, respectively. orf139 and orf160 may encode proteins that form extended alpha-helical secondary structures and coiled-coil quaternary structures which may be filamentous components of the gram-positive bacterial flagellum. We have characterized the B. subtilis flgM gene further by constructing an in-frame deletion mutation, flgM delta 80, and creating strains of B. subtilis in which this allele has replaced the wild-type copy. By primer extension analysis of cellular RNA, we have shown that the flgM delta 80 mutation relieves the block to transcription of two other sigma D-dependent operons imposed by an unlinked mutation in a gene directing early flagellar synthesis. We conclude that, as in the case of S. typhimurium, early flagellar synthesis in B. subtilis is coupled to late flagellar synthesis through repression of sigma D-dependent transcription by the flgM gene product.

Two genes controlling motility functions in Bacillus subtilis were identified by DNA sequence analysis of a chromosomal fragment containing a strong promoter for sigma D RNA polymerase. Previous studies had shown that this sigma D-dependent promoter controls synthesis of a 1.6-kb transcript in vivo and in vitro. Sequence analysis revealed that the 1.6-kb transcript contains two open reading frames coding for protein sequences homologous to the Escherichia coli motA and motB gene products, respectively, and ends in a rho-independent termination site. Direct evidence linking these genes to motility functions in B. subtilis was obtained by precise localization by polymerase chain reaction of Tn917 transposon insertion mutations of Mot- strains, isolated by Zuberi et al. (A. R. Zuberi, C. Ying, H. M. Parker, and G. W. Ordal, J. Bacteriol. 172:6841-6848, 1990), to within this mot. operon. Replacement of each wild-type gene by in-frame deletion mutations yielded strains possessing paralyzed flagella and confirmed that both motA and motB are required for the motility of B. subtilis. These current findings support our earlier suggestions that sigma D in B. subtilis plays a central role in the control of gene expression for flagellar assembly, chemotaxis, and motility functions. Sigma F, the enteric homolog of sigma D, controls similar functions in E. coli and Salmonella typhimurium, and these factors appear to be representative of a family of factors implicated in flagellar synthesis in many bacterial species, which we propose to designate the sigma 28 family.

The Bacillus subtilis gene hag, which codes for the flagellin structural protein, was identified by DNA sequence analysis in a collection of DNA fragments bearing in vitro promoters for the sigma 28 form of RNA polymerase. The hag gene and adjacent regions of the B. subtilis chromosome were restriction mapped, and the nucleotide sequence was determined. The hag gene was transcribed at all stages of growth from a single promoter that had sequences in the promoter recognition region characteristic of the consensus sequence for the sigma 28 holoenzyme. Transcription of hag was eliminated by insertion mutations that blocked synthesis of the sigma 28 protein. These findings provide strong support for the previous proposal that the sigma 28 form of RNA polymerase controls transcription of a regulon specifying flagellar, chemotaxis, and motility functions in B. subtilis (J. D. Helmann and M. J. Chamberlin, Proc. Natl. Acad. Sci. USA 84:6422-6424, 1987). The steady-state levels of hag mRNA increased during exponential growth and peaked as the B. subtilis cells entered the stationary phase. The transcript levels then decreased to zero within 4 h after the onset of sporulation. Hence, sigma 28 RNA polymerase function is temporally regulated.