Nelson, R. | Search bioRxiv

bioRxiv2019

Spatial and temporal partitioning and tree preference in California woodland ants

Spatial and temporal partitioning of habitat may facilitate diversity and have important impacts on ant communities. To investigate niche overlap in an ant community in a northern California oak woodland, we observed ant foraging on trees in 4 seasonal surveys, each lasting 2 weeks, in a 9.5-hectare plot over the course of a year. Foraging activity in all 5 observed ant species differed by season, time of day, and/or the genera of trees used. Of the 3 ant species most frequently observed, Camponotus semitestaceus was most active during spring and summer nights, Formica moki was most active during spring and summer days, and Prenolepis imparis was most active during both day and night of fall and winter. All ant species preferred native trees to exotic trees and preferred evergreen trees to deciduous trees. Our results suggest that native evergreen oaks such as Quercus agrifolia, currently threatened by sudden oak death (Phytophthora ramorum), may be important for supporting ant biodiversity.

ecology↗

bioRxiv2019

Mutant huntingtin protein alters the response of microglial cells to inflammatory stimuli

Huntingtons disease (HD) is a progressive neurodegenerative disease that affects the striatum and cerebral cortex. It is caused by a dominant CAG trinucleotide expansion in exon 1 of the HTT gene. Mutant huntingtin protein (mHtt) is expressed in neurons and immune cells. HD patients demonstrate altered blood cytokine profiles and altered responses of peripheral immune cells to inflammatory stimuli. However, the effects of mHtt on microglial immune responses are not fully understood. Herein we discuss the current understanding of how mHtt alters microglial inflammatory responses. Using lentivirus, we expressed the N171 N-terminal fragment of wild-type or mhtt containing 18 and 82 glutamine repeats in cultured EOC-20 microglial cells. We then measured responses to lipopolysaccharide or interleukin-6. Mutant huntingtin-expressing microglial cells produced less interleukin-6 and nitric oxide in response to lipopolysaccharide stimulation than wild-type huntingtin-expressing cells. However, mHtt-expressing microglia stimulated with interleukin-6 produced more nitric oxide than wild-type cells. Mutant huntingtin-expressing cells had higher basal NF-{kappa}B and further elevations of NF-{kappa}B after interleukin-6 but not lipopolysaccharide stimulation. Thus we demonstrate the potential of mHtt to dampen responses to lipopolysaccharide but potentiate responses to interleukin-6. This work adds to the emerging understanding that mHtt alters not only baseline status of cells but may also result in altered immune responses dependent on the nature of the inflammatory stimuli. We also present our perspective that in human HD the extent of inflammation may depend, in part, on altered responses to varied inflammatory stimuli including environmental factors such as infection.

neuroscience↗