Antley-Bixler syndrome (ABS) represents a group of heterogeneous disorders characterized by skeletal, cardiac and urogenital abnormalities that have frequently been associated with mutations in fibroblast growth factor receptor 2 or cytochrome P450 reductase genes. In some ABS patients, reduced activity of the cholesterogenic cytochrome P450 CYP51A1, an ortholog of the mouse CYP51, and accumulation of lanosterol and 24,25-dihydrolanosterol has been reported, but the role of CYP51A1 in the ABS etiology has remained obscure. To test whether Cyp51 could be involved in generating an ABS-like phenotype, a mouse knockout model was developed that exhibited several prenatal ABS-like features leading to lethality at embryonic day 15. Cyp51(-/-) mice had no functional Cyp51 mRNA and no immunodetectable CYP51 protein. The two CYP51 enzyme substrates (lanosterol and 24,25-dihydrolanosterol) were markedly accumulated. Cholesterol precursors downstream of the CYP51 enzymatic step were not detected, indicating that the targeting in this study blocked de novo cholesterol synthesis. This was reflected in the up-regulation of 10 cholesterol synthesis genes, with the exception of 7-dehydrocholesterol reductase. Lethality was ascribed to heart failure due to hypoplasia, ventricle septum, epicardial and vasculogenesis defects, suggesting that Cyp51 deficiency was involved in heart development and coronary vessel formation. As the most likely downstream molecular mechanisms, alterations were identified in the sonic hedgehog and retinoic acid signaling pathways. Cyp51 knockout mice provide evidence that Cyp51 is essential for embryogenesis and present a potential animal model for studying ABS syndrome in humans. THIS IS THE FIRST TRANSGENIC MOUSE ENTIRELY CONSTRUCTED IN SLOVENIA.
Cytochromes P450 (CYPs) catalyse diverse reactions and are key enzymes in fungal primary and secondary metabolism, and xenobiotic detoxification. CYP enzymatic properties and substrate specificity determine the reaction outcome. However, CYP-mediated reactions may also be influenced by their redox partners. Filamentous fungi with numerous CYPs often possess multiple microsomal redox partners, cytochrome P450 reductases (CPRs). In the plant pathogenic ascomycete Cochliobolus lunatus we recently identified two CPR paralogues, CPR1 and CPR2. Our objective was to functionally characterize two endogenous fungal cytochrome P450 systems and elucidate the putative physiological roles of CPR1 and CPR2. We reconstituted both CPRs with CYP53A15, or benzoate 4-hydroxylase from C. lunatus, which is crucial in the detoxification of phenolic plant defence compounds. Biochemical characterization using RP-HPLC shows that both redox partners support CYP activity, but with different product specificities. When reconstituted with CPR1, CYP53A15 converts benzoic acid to 4-hydroxybenzoic acid, and 3-methoxybenzoic acid to 3-hydroxybenzoic acid. However, when the redox partner is CPR2, both substrates are converted to 3,4-dihydroxybenzoic acid. Deletion mutants and gene expression in mycelia grown on media with inhibitors indicate that CPR1 is important in primary metabolism, whereas CPR2 plays a role in xenobiotic detoxification.
One of the candidate genes for suicide is also a gene in the pathway for catecholamine degradation encoding an enzyme catehol-O-methyl-transferase (COMT). It harbors a common functional polymorphism, a G to A nucleotide transition resulting in amino acid substitution from valine (Val) to methionine (Met) at position 158 (COMT Val(108/158)Met; rs4680) that has been associated with psychiatric disorders characterized with an increased risk of suicidal behavior. We have performed the first study on Caucasian population examining the association between completed suicide and the COMT Val(108/158)Met polymorphism. The study population consisted of 356 suicide victims and 198 control subjects. Significant difference in COMT Val(108/158)Met variants (genotypes, alleles and Val carriers) distribution was found only in male groups, between controls and suicide victims (p = 0.018; p = 0.031; p = 0.005), and between controls and violent suicide victims (p = 0.026; p = 0.042; p = 0.010). The R value from the standardized residuals revealed that the Met/Met genotype (R = 2.03) in the control group contributed to these significant differences. In contrast to male subjects, no significant differences in the frequency of the COMT Val(108/158)Met variants were detected between female control and female suicide groups; however the POC (range 0.161-0.680) was below the desired 0.800. In addition, the logistic regression analysis confirmed these significant differences. In conclusion, our results showed the over-presentation of the Met/Met genotype in male control subjects compared to male suicide victims, suggesting that this genotype of the COMT Val(108/158) Met might be a protective factor against suicide.