Biology subjects

Campbell, L. A.

Publications and source records attributed to Campbell, L. A..

5 recordsLinked to original sources

bioRxiv2026

Behavior evolves as a correlated response to selection on cuticle color in Drosophila melanogaster and D. simulans

To predict adaptive evolution, we need to understand the degree to which selection on one trait can constrain or redirect evolutionary responses in other traits. We used artificial selection on cuticle color in Drosophila melanogaster and D. simulans to investigate whether color and behavior evolve in tandem. We selected for light and dark thoracic colors for 16 generations in two populations per species and measured correlated responses in aggression, basal activity, total activity, sleep, and geotaxis. Dark selected individuals consistently showed higher aggression and basal activity than light selected or control flies across both species and sexes, pointing to a modest but repeatable correlated response. In contrast, patterns for geotaxis, sleep, and total activity evolved unpredictably, often varying across species and populations, and showed no clear association with color. Within-population phenotypic correlations between color and aggression were significant but weak (rho = -0.035, rho{superscript 2} = 0.001), suggesting that color is a poor predictor of individual aggressive behavior. Populations evolving higher aggression also tended to evolve higher basal activity (rho = 0.52, p = 0.004), suggesting activity may have evolved as a correlated response rather than through a direct color-activity link. The persistence of correlated responses in aggression and basal activity in response to selection on color is consistent with a conserved genetic basis, such as pleiotropy or linkage disequilibrium, although our data do not distinguish between these mechanisms. Identifying the loci underlying variation in both color and behavior, and testing their effects experimentally, will clarify how multivariate genetic covariance shapes the direction and pace of adaptive evolution.

evolutionary biology↗

bioRxiv2025

Phosphoproteome-derived peptide libraries for deep specificity profiling of phosphatases and phospholyases

Protein phosphorylation is dynamically regulated by the opposing activities of phosphowriter enzymes (kinases) and phosphoeraser enzymes (phosphatases and phospholyases). While significant progress has been made toward defining the sequences preferences of kinases, the selectivity of phosphoerasers has not been explored at scale. Here, we develop an experimental platform based on tandem mass spectrometry analysis of phosphoproteome-derived peptide libraries (PhosPropels) to map phosphoeraser activity across thousands of biologically relevant phosphosites. We extract positional residue preferences to rapidly define sequence motifs recognized by eight phosphoerasers spanning diverse species of origin, protein folds, and enzymatic mechanisms. Taking advantage of the throughput of our approach, we profiled 34 variants of the phosphothreonine lyase OspF from Shigella flexneri, uncovering an intrinsic preference for p38 and Erk MAP kinase activation loops and revealing the enzyme residues that influence its selectivity for phosphothreonine. Our results establish a general method for linking phosphorylation sites to the enzymes that remove them, providing a means to dissect a key component of cellular regulatory networks.

biochemistry↗

bioRxiv2023

The mitochondrial calcium uniporter is necessary for synaptic plasticity and proper mitochondrial morphology and distribution in the distal dendrites of CA2 neurons

Mitochondria are dynamic organelles that are morphologically and functionally diverse across cell types and subcellular compartments in order to meet unique energy demands. Mitochondrial dysfunction has been implicated in a wide variety of neurological disorders, including psychiatric disorders like schizophrenia and bipolar disorder. Despite it being well known that mitochondria are essential for synaptic transmission and synaptic plasticity, the mechanisms regulating mitochondria in support of normal synapse function are incompletely understood. The mitochondrial calcium uniporter (MCU) regulates calcium entry into the mitochondria, which in turn regulates the bioenergetics and distribution of mitochondria to active synapses. Evidence suggests that calcium influx via MCU couples neuronal activity to mitochondrial metabolism and ATP production, which would allow neurons to rapidly adapt to changing energy demands. Intriguingly, MCU is uniquely enriched in hippocampal CA2 distal dendrites relative to neighboring hippocampal CA1 or CA3 distal dendrites, however, the functional significance of this enrichment is not clear. Synapses from the entorhinal cortex layer II (ECII) onto CA2 distal dendrites readily express long term potentiation (LTP), unlike the LTP- resistant synapses from CA3 onto CA2 proximal dendrites, but the mechanisms underlying these different plasticity profiles are unknown. We hypothesized that enrichment of MCU near ECII-CA2 synapses promotes LTP in an otherwise plasticity-restricted cell type. Using a CA2-specific MCU knockout (cKO) mouse, we found that MCU is required for LTP at distal dendrite synapses but does not affect the lack of LTP at proximal dendrite synapses. Loss of LTP at ECII-CA2 synapses correlated with a trend for decreased spine density in CA2 distal dendrites of cKO mice compared to control (CTL) mice, which was predominantly seen in immature spines. Moreover, mitochondria were significantly smaller and more numerous across all dendritic layers of CA2 in cKO mice compared to CTL mice, suggesting an overall increase in mitochondrial fragmentation. Fragmented mitochondria might have functional changes, such as altered ATP production, that might explain a deficit in synaptic plasticity. Collectively, our data reveal that MCU regulates layer-specific forms of plasticity in CA2 dendrites, potentially by maintaining proper mitochondria morphology and distribution within dendrites. Differences in MCU expression across different cell types and circuits might be a general mechanism to tune the sensitivity of mitochondria to cytoplasmic calcium levels to power synaptic plasticity. MAIN TAKE HOME POINTSO_LIThe mitochondrial calcium uniporter (MCU) regulates plasticity selectively at synapses in CA2 distal dendrites. C_LIO_LIThe MCU-cKO induced LTP deficit correlates with a trending reduction in spine density in CA2 distal dendrites. C_LIO_LILoss of MCU in CA2 results in ultrastructural changes in dendritic mitochondria that suggest an increase in mitochondrial fragmentation. These ultrastructural changes could result in functional consequences, such as decreased ATP production, that could underlie the plasticity deficit. C_LIO_LIDendritic mitochondrial fragmentation in MCU cKO occurred throughout the dendritic laminae, suggesting that MCU is dispensable for establishing layer-specific mitochondrial structural diversity. C_LI

neuroscience↗

bioRxiv2022

Functionally competent CD4+ T cells express high levels of T-bet in Plasmodium chabaudi infected young mice

The immune system plays an important role in the elimination of Plasmodium parasites that cause malaria, which affect children the most worldwide. Immunity to malaria, especially in young children is poorly understood due to the absence of a developmentally-equivalent rodent model to study the pathogenesis of disease. We have developed a mouse model using 15-day old mice (pups) of malaria infection in neonatal mice. Using C57BL/6 pups, we determined that P. chabaudi infection decreases the growth rate of young mice compared to controls, and results in 60% mortality, and neurological damage not present in adults, as indicated by a battery of behavioral assays. When all splenic cells were stimulated in vitro stimulation, cells from pups proliferated faster than adult cells, but purified CD4 T cells were slower. Upon infection with Plasmodium parasites, both adult and pup CD4+ T cells were activated and differentiated to an effector T cell (Teff) phenotype; however, pup CD4+ Teff were less differentiated than adult Teff. Pup CD4+ T cells also produced more IL-2 than cells from adult B6 mice, and TNF- was increased in parasite-specific BALB/c pup T cells. Interestingly, there were more pup CD4+T-bethi Teff after infection suggestive of increased Th1 commitment, potentially contributing to cerebral symptoms.

immunology↗

bioRxiv2020

Visualizing subcellular structures in neurons with expansion microscopy

Protein expansion microscopy (proExM) is a powerful technique that crosslinks proteins to a swellable hydrogel to physically expand and optically clear biological samples. The resulting increased resolution (~70 nm) and physical separation of labeled proteins make it an attractive tool for studying the localization of subcellular organelles in densely packed tissues, such as the brain. However, the digestion and expansion process greatly reduces fluorescence signals making it necessary to optimize ExM conditions per sample for specific end goals. Here we describe a proExM workflow optimized for resolving subcellular organelles (mitochondria and the Golgi apparatus) and reporter-labeled spines in fixed mouse brain tissue. By directly comparing proExM staining and digestion protocols, we found that immunostaining before proExM and using a proteinase K based digestion for 8 hours consistently resulted in the best fluorescence signal to resolve subcellular organelles while maintaining sufficient reporter labeling to visualize spines and trace individual neurons. With these methods, we more accurately quantified mitochondria size and number and better visualized Golgi ultrastructure in reconstructed CA2 neurons of the hippocampus.

neuroscience↗