Distinct polymorphisms in a single herpesvirus gene are capable of enhancing virulence and mediating vaccinal resistance

Modified-live herpesvirus vaccines are widely used in humans and animals, but field strains can emerge that have a higher virulence and break vaccinal protection. Since the introduction of the first vaccine in the 1970s, Marek’s disease virus overcame the vaccine barrier by the acquisition of numerous genomic mutations. However, the evolutionary adaptations in the herpesvirus genome responsible for the vaccine breaks have remained elusive. Here, we demonstrate that point mutations in the multifunctional meq gene acquired during evolution can significantly alter virulence. Defined mutations found in highly virulent strains also allowed the virus to overcome innate cellular responses and vaccinal protection. Concomitantly, the adaptations in meq enhanced virus shedding into the environment, likely providing a selective advantage for the virus. Our study provides the first experimental evidence that few point mutations in a single herpesviral gene result in drastically increased virulence, enhanced shedding, and escape from vaccinal protection.     

Cloning, mRNA Expression, and Chromosomal Mapping of Mouse and Human Preprocortistatin

Cortistatin is a 14-residue putative neuropeptide with strong structural similarity to somatostatin and is expressed predominantly in cortical GABAergic interneurons of rats. Administration of cortistatin into the brain ventricles specifically enhances slow-wave sleep, presumably by antagonizing the effects of acetylcholine on cortical excitability. Here we report the identification of cDNAs corresponding to mouse and human preprocortistatin and the mRNA distribution and gene mapping of mouse cortistatin. Analysis of the nucleotide and predicted amino acid sequences from rat and mouse reveals that the 14 C-terminal residues of preprocortistatin, which make up the sequence that is most similar to somatostatin, are conserved between species. Lack of conservation of other dibasic amino acid residues whose cleavage by prohormone convertases would give rise to additional peptides suggests that cortistatin-14 is the only active peptide derived from the precursor. As in the rat, mouse preprocortistatin mRNA is present in GABAergic interneurons in the cerebral cortex and hippocampus. The preprocortistatin gene maps to mouse chromosome 4, in a region showing conserved synteny with human 1p36. The human putative cortistatin peptide has an arginine for lysine substitution, compared to the rat and mouse products, and is N-terminally extended by 3 amino acids.     

Chromosomal Mapping of Mouse Genes Expressed Selectively within the Central Nervous System

We have used RFLP analysis on DNA from a panel of interspecific (C57BL/6J × Mus spretus) F₁ × M. spretus backcross offspring to assign the genes encoding 10 neuron-specific mRNAs and 2 loci corresponding to cyclophilin 2-related sequences to the mouse chromosomal map. The Pss1 locus encoding the forebrain-enriched protein kinase C substrate RC3, a component of dendritic spines, mapped to proximal Chr 9. The Camkl locus encoding the calmodulin-binding protein kinase-like vesicle protein 1G5 mapped to distal Chr 9. The Gng7 locus encoding the γ7 G-protein subunit, highly enriched in the striatum and presumptively coupled to dopamine receptors, mapped to mid-Chr 10. The Htr1f, Htr5a, Htr5b, and Htr7 loci, encoding four serotonin receptors, mapped to Chr 16.5, 1, and 19, respectively. The Peplb locus, encoding a CD26 ectopeptidase-like neuronal membrane protein activated by kainate and long-term potentiation, mapped to Chr 5. The D2Sut1e and Cpu3 loci, encoding neural proteins of unknown functions, mapped to Chrs 2 and 9, respectively. Two cyclophilin 2-related loci, Cphn2-r1 and Cphn2-r2, mapped to different regions of Chr 9. Comparison of these 12 newly mapped loci with the existing mouse map and known regions of syntenic homology with the human map, along with the known features and expression profiles of the products of these genes, suggests a few candidates for mouse mutations and human neurological and immunological deficits, including the Tourette syndrome and Bloom syndrome genes.     

Heterogeneous expression of the triggering receptor expressed on myeloid cells-2 on adult murine microglia

Microglial activation is an early and common feature of almost all neuropathologies, including multiple sclerosis, Alzheimer's disease and mechanical injury. To better understand the relative contributions microglia make toward neurodegeneration and neuroprotection, we used TOGA(R) to identify molecules expressed by microglia and regulated by inflammatory signals. Triggering receptor expressed on myeloid cells-2 (TREM-2) was among the mRNAs identified as being expressed by unactivated microglia, but down-regulated by lipopolysaccharide/interferon gamma. In the healthy CNS, not all microglia expressed TREM-2. Microglial expression of TREM-2 varied not only between brain regions but also within each brain region. Brain regions with an incomplete blood-brain barrier had the lowest percentages of TREM-2- expressing microglia, whereas the lateral entorhinal and cingulate cortex had the highest percentages. A novel form of TREM-2b that lacked a transmembrane domain was detected, perhaps indicating a soluble form of the protein. Taken together, these data suggest that (1) subsets of microglia are specialized to respond to defined extracellular signals; and (2) regional variations in TREM-2 expression may contribute to the varying sensitivities of different brain regions to similar pathological signals.