Family-based association study of 76 candidate genes in bipolar disorder: BDNF is a potential risk locus. Brain-derived neutrophic factor.

Identification of the genetic bases for bipolar disorder remains a challenge for the understanding of this disease. Association between 76 candidate genes and bipolar disorder was tested by genotyping 90 single-nucleotide polymorphisms (SNPs) in these genes in 136 parent-proband trios. In this preliminary analysis, SNPs in two genes, brain-derived neurotrophic factor (BDNF) and the alpha subunit of the voltage-dependent calcium channel were associated with bipolar disorder at the P<0.05 level. In view of the large number of hypotheses tested, the two nominally positive associations were then tested in independent populations of bipolar patients and only BDNF remains a potential risk gene. In the replication samples, excess transmission of the valine allele of amino acid 66 of BDNF was observed in the direction of the original result in an additional sample of 334 parent-proband trios (T/U=108/87, P=0.066). Resequencing of 29 kb surrounding the BDNF gene identified 44 additional SNPs. Genotyping eight common SNPs identified three additional markers transmitted to bipolar probands at the P < 0.05 level. Strong LD was observed across this region and all adjacent pairwise haplotypes showed excess transmission to the bipolar proband. Analysis of these haplotypes using TRANSMIT revealed a global P value of 0.03. A single haplotype was identified that is shared by both the original dataset and the replication sample that is uniquely marked by both the rare A allele of the original SNP and a novel allele 11.5 kb 3'. Therefore, this study of 76 candidate genes has identified BDNF as a potential risk allele that will require additional study to confirm.

Surfactant inhibits cationic liposome-mediated gene transfer.

We have demonstrated that tracheal insufflation of recombinant plasmid DNA results in transfection of rat lungs to the same extent as insufflation of plasmid-cationic liposome complex. To understand this observation better, we investigated the in vitro gene transfer of plasmid DNA in the presence and absence of cationic liposome and the effect of surfactant on gene transfer. The chloramphenicol acetyltransferase (CAT) expression plasmids pBL-CAT and pSV-CAT were studied in three cell types: rat fetal lung fibroblast (RFL-6), calf pulmonary artery endothelial cell (CPAE), and rat type II alveolar epithelial cell (type II AE). Three cationic liposomes were tested: DDAB (dimethyl-dioctadecyl ammonium bromide)-liposome, DOTAP (dioleoyltrimethyl ammonium propane)-liposome, and lipofectin. The results revealed that (i) plasmid DNA alone caused a dose-dependent, low-level transfection, most efficiently in RFL-6 followed by CPAE and type II AE, (ii) DDAB-liposome markedly enhanced gene transfer, most efficiently in RFL-6 followed by CPAE and type II AE, (iii) Survanta, a naturally derived surfactant preparation, and Exosurf, a synthetic surfactant, while having no effect on in vitro gene transfer by plasmid DNA alone, markedly inhibited cationic liposome-mediated gene transfer, (iv) dipalmitoyl phosphatidylcholine was responsible for the inhibitory effect of Exosurf, and (v) inhibition of cationic liposome-mediated gene transfer by Exosurf was not due to inhibition of plasmid DNA-cationic liposome complex uptake or interference with the promoter and enhancer. The observed inhibition of cationic liposome-mediated gene transfer by surfactant may in part explain our previous observation that tracheal insufflation of plasmid DNA and plasmid-cationic liposome complex results in equal lung gene transfer.