SignificanceWe present identification of the luciferase and enzymes of the biosynthesis of a eukaryotic luciferin from fungi. Fungi possess a simple bioluminescent system, with luciferin being only two enzymatic steps from well-known metabolic pathways. The expression of genes from the fungal bioluminescent pathway is not toxic to eukaryotic cells, and the luciferase can be easily co-opted to bioimaging applications. With the fungal system being a genetically encodable bioluminescent system from eukaryotes, it is now possible to create artificially bioluminescent eukaryotes by expression of three genes. The fungal bioluminescent system represents an example of molecular evolution of a complex ecological trait and with molecular details reported in the paper, will allow additional research into ecological significance of fungal bioluminescence.

Using a systematic, whole-genome analysis of enhancer activity of human-specific endogenous retroviral inserts (hsERVs), we identified an element, hsERV PRODH , that acts as a tissue-specific enhancer for the PRODH gene, which is required for proper CNS functioning. PRODH is one of the candidate genes for susceptibility to schizophrenia and other neurological disorders. It codes for a proline dehydrogenase enzyme, which catalyses the first step of proline catabolism and most likely is involved in neuromediator synthesis in the CNS. We investigated the mechanisms that regulate hsERV PRODH enhancer activity. We showed that the hsERV PRODH enhancer and the internal CpG island of PRODH synergistically activate its promoter. The enhancer activity of hsERV PRODH is regulated by methylation, and in an undermethylated state it can up-regulate PRODH expression in the hippocampus. The mechanism of hsERV PRODH enhancer activity involves the binding of the transcription factor SOX2, whch is preferentially expressed in hippocampus. We propose that the interaction of hsERV PRODH and PRODH may have contributed to human CNS evolution.human-specific endogenous retrovirus | DNA methylation | central nervous system | human speciation | retroelement U nderstanding the molecular basis of phenotypic differences between humans and chimpanzees can provide important clues to human-specific behavioral peculiarities and neurological disorders. For this purpose we conducted a genome-wide analysis of human-specific endogenous retroviral (hsERV) inserts that may induce new regulatory pathways by acting as promoters and enhancers (1, 2). HsERVs of the HERV-K(HML-2) group are one of the four families of transposable elements that were able to transpose at the time of the radiation of human lineage from the lineage of its most closely related species, chimpanzee (3). At least 50% of all hsERV elements exhibit promoter activity in human tissues (4). We found only six hsERV inserts in the upstream regions of known human genes, close to transcription start sites. Three of them displayed strong enhancer activity in transient transfection experiments; of these three, only one-near the PRODH gene-matched the transcriptional activity pattern of its endogenous genomic copy. This copy of hsERV is a full-length, almost intact betaretrovirus belonging to the HERV-K(HML-2) group. PRODH encodes a mitochondrial enzyme proline, dehydrogenase (oxidase), that converts proline to D-1-pyrroline-5-carboxylate (5). PRODH regulates proline catabolism, which is vital for normal CNS functioning. Several PRODH mutations are associated with neuropsychiatric disorders, such as schizophrenia (6). Gene knockouts in mice cause severe changes in the executive functioning of the brain (7). Given the potential importance of PRODH in brain functioning and disease, we attempted to characterize its newly recognized hsERV PRODH enhancer. We showed that hsERV PRODH enhancer activity is regulated by methylation and that the hsERV PRODH enhancer and PRODH internal CpG island act syne...

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SUMMARYThe secreted protein Noggin1 is an embryonic inducer that can sequester TGF cytokines of the BMP family with extremely high affinity. Owing to this function, ectopic Noggin1 can induce formation of the headless secondary body axis in Xenopus embryos. Here, we show that Noggin1 and its homolog Noggin2 can also bind, albeit less effectively, to ActivinB, Nodal/Xnrs and XWnt8, inactivation of which, together with BMP, is essential for the head induction. In support of this, we show that both Noggin proteins, if ectopically produced in sufficient concentrations in Xenopus embryo, can induce a secondary head, including the forebrain. During normal development, however, Noggin1 mRNA is translated in the presumptive forebrain with low efficiency, which provides the sufficient protein concentration for only its BMP-antagonizing function. By contrast, Noggin2, which is produced in cells of the anterior margin of the neural plate at a higher concentration, also protects the developing forebrain from inhibition by ActivinB and XWnt8 signaling. Thus, besides revealing of novel functions of Noggin proteins, our findings demonstrate that specification of the forebrain requires isolation of its cells from BMP, Activin/Nodal and Wnt signaling not only during gastrulation but also at post-gastrulation stages.

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