Open housing drives the expression of immune response genes in the nasal mucosa, but not the olfactory bulb.

Nasal mucosa and olfactory bulb are separated by the cribriform plate which is perforated by olfactory nerves. We have previously demonstrated that the cribriform plate is permissive for T cells and monocytes and that viruses can enter the bulb upon intranasal injection by axonal transportation. Therefore, we hypothesized that nasal mucosa and olfactory bulb are equipped to deal with constant infectious threats. To detect genes involved in this process, we compared gene expression in nasal mucosa and bulb of mice kept under specific pathogen free (SPF) conditions to gene expression of mice kept on non-SPF conditions using RNA deep sequencing. We found massive alterations in the expression of immune-related genes of the nasal mucosa, while the bulb did not respond immunologically. The absence of induction of immune-related genes in the olfactory bulb suggests effective defence mechanisms hindering entrance of environmental pathogens beyond the outer arachnoid layer. The genes detected in this study may include candidates conferring susceptibility to meningitis

Investigating the prehistory of Tungusic peoples of Siberia and the Amur-Ussuri region with complete mtDNA genome sequences and Y-chromosomal markers.

Evenks and Evens, Tungusic-speaking reindeer herders and hunter-gatherers, are spread over a wide area of northern Asia, whereas their linguistic relatives the Udegey, sedentary fishermen and hunter-gatherers, are settled to the south of the lower Amur River. The prehistory and relationships of these Tungusic peoples are as yet poorly investigated, especially with respect to their interactions with neighbouring populations. In this study, we analyse over 500 complete mtDNA genome sequences from nine different Evenk and even subgroups as well as their geographic neighbours from Siberia and their linguistic relatives the Udegey from the Amur-Ussuri region in order to investigate the prehistory of the Tungusic populations. These data are supplemented with analyses of Y-chromosomal haplogroups and STR haplotypes in the Evenks, Evens, and neighbouring Siberian populations. We demonstrate that whereas the North Tungusic Evenks and Evens show evidence of shared ancestry both in the maternal and in the paternal line, this signal has been attenuated by genetic drift and differential gene flow with neighbouring populations, with isolation by distance further shaping the maternal genepool of the Evens. The Udegey, in contrast, appear quite divergent from their linguistic relatives in the maternal line, with a mtDNA haplogroup composition characteristic of populations of the Amur-Ussuri region. Nevertheless, they show affinities with the Evenks, indicating that they might be the result of admixture between local Amur-Ussuri populations and Tungusic populations from the north

The olfactory bulb does not react immunologically.

<p>After both one week and two weeks there were significantly regulated genes in the olfactory bulb when comparing SPF to non-SPF conditions. To compare the regulated genes at each point of time, an overlap analysis was performed. 70 genes were regulated at both points of time (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0187192#pone.0187192.s001" target="_blank">S1 Table</a>). 438 genes were regulated only after one week, 454 only after two weeks.</p

Statistics of SPF and non-SPF mouse transcriptome of the olfactory bulb and the nasal mucosa after one and two weeks mapping to July 2007 NCBI37/mm9 reference mouse genome.

<p>Statistics of SPF and non-SPF mouse transcriptome of the olfactory bulb and the nasal mucosa after one and two weeks mapping to July 2007 NCBI37/mm9 reference mouse genome.</p

Heatmap illustrating separation of olfactory bulb and nasal mucosa.

<p>The X axis exhibits the particular probes of mucosa (e.g. mucosa after 2 weeks of SPF husbandry, probe 1 = "muc_2_spf_1") and olfactory bulb. On the Y axis expression of all mapped genes is displayed. The hierarchical clustering on top shows the actual splitting of the two tissues.</p

Experimental setup.

<p>30 mice were obtained for this experiment and kept together for one week in a SPF facility for adaptation. Afterwards 15 mice were transferred to a non-SPF environment. After one week of different husbandry conditions (SPF vs. non-SPF) 7 animals of each group were euthanized followed by the removal of the olfactory bulb and the nasal mucosa. The same procedure was performed with the remaining mice after two weeks.</p

Non-SPF environment evokes a strong immune response in nasal mucosa.

<p>Comparison of nasal mucosa of both SPF and non-SPF conditions after one and two weeks showed a significant change of numerous transcripts. Overlap analysis revealed 421 DEGs after 7 days and 1,588 DEGs after 14 days.) The overlapping subset contained 79 DEGs.</p

Gene ontology analysis of differentially expressed genes of nasal mucosa after one and two weeks when compared between SPF and non-SPF conditions revealed numerous immune-related GOs.

<p>Gene ontology analysis of differentially expressed genes of nasal mucosa after one and two weeks when compared between SPF and non-SPF conditions revealed numerous immune-related GOs.</p

Gram staining of a mouse whole head section.

<p>A horizontal section of a mouse head was stained by Gram´s method to show the occurrence of gram positive bacteria at the nasal mucosa (*).</p

Quantification of activated and ramified microglia in the olfactory bulb under SPF and non-SPF conditions shows no difference in morphological microglial activation.

<p>The olfactory bulbs of mice kept under non-SPF conditions for 5 days and the olfactory bulbs of mice kept under SPF conditions were stained with IBA-1. Five pictures of each group were analyzed and the number of activated and ramified microglia was counted. No difference in microglial activation between SPF and non-SPF conditions was found.</p