SummaryDehalogenases are environmentally important enzymes that detoxify organohalogens by cleaving their carbon‐halogen bonds. Many microbial genomes harbour enzyme families containing dehalogenases, but a sequence‐based identification of genuine dehalogenases with high confidence is challenging because of the low sequence conservation among these enzymes. Furthermore, these protein families harbour a rich diversity of other enzymes including esterases and phosphatases. Reliable sequence determinants are necessary to harness genome sequencing‐efforts for accelerating the discovery of novel dehalogenases with improved or modified activities. In an attempt to extract dehalogenase sequence fingerprints, 103 uncharacterized potential dehalogenase candidates belonging to the α/β hydrolase (ABH) and haloacid dehalogenase‐like hydrolase (HAD) superfamilies were screened for dehalogenase, esterase and phosphatase activity. In this first biochemical screen, 1 haloalkane dehalogenase, 1 fluoroacetate dehalogenase and 5 l‐2‐haloacid dehalogenases were found (success rate 7%), as well as 19 esterases and 31 phosphatases. Using this functional data, we refined the sequence‐based dehalogenase selection criteria and applied them to a second functional screen, which identified novel dehalogenase activity in 13 out of only 24 proteins (54%), increasing the success rate eightfold. Four new l‐2‐haloacid dehalogenases from the HAD superfamily were found to hydrolyse fluoroacetate, an activity never previously ascribed to enzymes in this superfamily.
Although the genetic contribution to schizophrenia is substantial, positive findings in wholegenome linkage scans have not been consistently replicated. We analyzed gene expression in various rat conditions to identify novel candidate genes for schizophrenia. Suppression subtraction hybridization (SSH), with polyA mRNA from temporal and frontal cortex of rats, was used to identify differentially expressed genes. Expression of mRNA was compared between adult Lewis and Fischer 344 (F344) rats, adult and postnatal day 6 (d6) F344, and adult F344 treated with haloperidol or control vehicle. These groups were chosen because each highlights a particular aspect of schizophrenia: differences in strain vulnerability to behavioral analogs of psychosis; factors that may relate to disease onset in relation to CNS development; and improvement of symptoms by haloperidol. The 14-3-3 gene family, as represented by 14-3-3c and 14-3-3f isoforms in the SSH study, and SNAP-25 were among the candidate genes. Genetic association between schizophrenia and the 14-3-3g gene, positioned close to a genomic locus implicated in schizophrenia, and SNAP-25 genes was analyzed in 168 schizophrenia probands and their families. These findings address three different genes in the 14-3-3 family. We find a significant association with schizophrenia for two polymorphisms in the 14-3-3g gene: a 7 bp variable number of tandem repeats in the 5 0 noncoding region (P ¼ 0.036, 1 df), and a 3 0 untranslated region SNP (753G/A) that is an RFLP visualized with Ava II (P ¼ 0.028). There was no significant genetic association with SNAP-25. The candidate genes identified may be of functional importance in the etiology, pathophysiology or treatment response of schizophrenia or psychotic symptoms. This is to our knowledge the first report of a significant association between the 14-3-3g-chain gene and schizophrenia in a family-based sample, strengthening prior association reports in case-control studies and microarray gene expression studies.
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