Biology subjects

Cobb, M.

Publications and source records attributed to Cobb, M..

6 recordsLinked to original sources

bioRxiv2026

A fast neutron mutant resource for Ipomoea purpurea reveals dose-dependent genomic and phenotypic variation

A central goal in evolutionary biology is to understand the genomic basis of phenotypic traits, yet this pursuit is often constrained by a lack of accessible phenotypic and genetic variation, particularly in non-model organisms. Fast neutron irradiation offers a powerful approach for generating such variation, as it does not require prior genomic resources, established transformation systems, or reference mutant collections. Here, we describe the development and characterization of the first fast neutron mutant library in Ipomoea purpurea (common morning glory), a noxious agricultural weed and established model system in evolutionary ecology. We exposed an I. purpurea reference genotype to three levels of irradiation and developed 1,043 lines third generation lines and characterized the phenotypic and genetic variation in a subset of 200. Phenotypic screens identified seven mutant lines exhibiting eleven distinct phenotypes, and revealed higher phenotypic variance for anther-stigma distance, flower number, and pollen count relative to a non-irradiated control line. We further identified genetic variation across eight phenotypic traits among the mutant lines. Together, these results show that fast neutron mutagenesis generates novel phenotypic and genetic variation in ecologically relevant traits, offering the research community a new genomic resource for an established model in evolutionary ecology.

plant biology↗

bioRxiv2026

Characterization of a cofilin mutant with high actin bundling activity in living cells

Cofilin is a key regulator of actin dynamics that, along with a myriad of other actin-binding proteins, controls the balance of F- and G-actin in numerous cell types. While prior structural studies of the cofilin-actin binding interface have delineated many critical interactions between cofilin and actin, the roles of some residues within the cofilin-actin binding interface remain poorly defined. In this study, we investigate the role of cofilin S119 in the cofilin-actin interaction. Despite its unique position within the cofilin-actin interface and its putative role as a phosphorylation site, relatively little direct evidence exists to define whether it plays an important role in cofilin-actin dynamics. Using site-directed mutagenesis, we demonstrate that mutation of S119 to aromatic amino acids (W, F, Y) results in cofilins with strong actin bundling activity in living cells. This activity can be countered by the incorporation of mutants that disfavor actin rod forming activity (R21Q). Mutation of S119 to phospho-mimic (E) and non-phosphorylated (A) residues either strongly inhibits (E) or modestly increases (A) actin bundling activity. Expression of the S119W mutant in neurons reveals its impacts on spine length and size, while FRAP studies show that its mobile fraction is intermediate between that of LifeAct and WT cofilin. Finally, it is shown that the strong actin bundling phenotype associated with S119W inhibits the progression of optogenetically induced apoptosis.

cell biology↗

bioRxiv2022

Age and experience affect the biosynthesis and emission of a Drosophila pheromone

The most studied pheromone in Drosophila melanogaster, cis-Vaccenyl Acetate (cVA), is synthesized in the male ejaculatory bulb and transferred to the female during copulation. Combined with other chemicals cVA can modulate fly aggregation, courtship, mating and fighting. It is not detected on the cuticle of isolated males and is only released by males involved in social or sexual interaction. We explored the mechanisms underlying both cVA biosynthesis and emission in males of two wild types and a pheromonal mutant line. The effects of ageing, adult social interaction, and maternally-transmitted cVa and microbes -- both associated with the egg chorion-- on cVA biosynthesis and emission were measured. While ageing and genotype changed both biosynthesis and emission in similar ways, early developmental exposure to maternally-transmitted cVA and microbes strongly decreased cVA emission but not the biosynthesis of this molecule. This indicates that the release -- but not the biosynthesis -- of this sex pheromone strongly depends on early developmental context. The mechanism by which the preimaginal effects occur is unknown, but reinforces the significance of development in determining adult physiology and behaviour. Summary statementWe show how the biosynthesis and release of a key Drosophila pheromone is affected by ageing, by early exposure to this pheromone and to microbes, and by social context.

animal behavior and cognition↗

bioRxiv2021

Genetic and functional odorant receptor variation in the Homo lineage

Using ancient DNA sequences, we explored the function of olfactory receptor genes in the genus Homo. Humans, Neandertals, and Denisovans independently adapted to a wide range of geographic environments and the odours produced by their food. Variations in their odorant receptor protein sequence and structure resulted in variation in detection and perception. Studying thirty olfactory receptor genes, we found our relatives showed highly conserved receptor structures, but Homo sapiens did not. Variants led to changes in sensitivity to some odors, but no change in specificity, indicating a common olfactory repertoire in our genus. Diversity of geographic adaptations in H. sapiens may have produced greater functional variation in our lineage, increasing our olfactory repertoire and expanding our adaptive capacity. One-Sentence SummaryUsing ancient DNA we studied the sense of smell in our extinct ancestors and in our relatives, Denisovans and Neanderthals

evolutionary biology↗

bioRxiv2021

Quantitative Tyr Phosphoproteomic Analyses Identify Cholesterol as a Master Regulator of Tumor Adaptive Resistance to MAPK Inhibition

Although targeted inhibition of the MAPK pathway has achieved remarkable patient responses in many cancers with MAPK hyperactivation, the development of resistance has remained a critical challenge. Besides genomic resistance mechanisms, adaptive tumor response also underlies the resistance to targeted MAPK inhibitors. It is being increasingly appreciated that such bypass mechanisms often lead to the activation of many pro-survival kinases, which complicates the rational design of combination therapies. Here we performed global tyrosine phosphoproteomic (pTyr) analyses and demonstrated that targeted inhibition of MAPK signaling in melanoma cells leads to a profound remodeling of the pTyr proteome. Intriguingly, many of these kinases contain a cholesterol binding motif, suggesting that altered cholesterol metabolism might drive, in a coordinated fashion, the activation of these kinases. Indeed, we found a dramatic accumulation of intracellular cholesterol in melanoma cells (with BRAFV600E mutations) and non-small cell lung cancer cells (with KRASG12C mutations) treated with MAPK and KRASG12C inhibitors, respectively. Importantly, depletion of cholesterol not only prevented the MAPK inhibition-induced feedback activation of pTyr singling but also enhanced the cytotoxic effects of MAPK inhibitors, both in vitro and in vivo. Taken together, our findings provide the evidence suggesting that cholesterol functions as a master regulator of the tumor adaptive response to targeted MAPK inhibitors. These results also suggest that MAPK inhibitors could be combined with cholesterol-lowering agents to achieve a more complete and durable response in tumors with hyperactive MAPK signaling.

cell biology↗

bioRxiv2018

BDNF/TrkB signaling in pancreatic islet beta cells

Adrenergic signaling is a well-known input into pancreatic islet function. Specifically, the insulin-secreting islet {beta} cell expresses the Gi/o-linked 2-adrenergic receptor, which upon activation suppresses insulin secretion. The use of adrenergic agonist epinephrine at micromolar doses may have supraphysiological effects. We found that pretreating {beta} cells with micromolar concentrations of epinephrine differentially inhibited activation of receptor tyrosine kinases. We chose TrkB as an example because of its relative sensitivity to the effects of epinephrine and due to its potential regulatory role in the {beta} cell. Our characterization of brain-derived neurotrophic factor (BDNF)-TrkB signaling in MIN6 {beta} cells showed that TrkB is activated by BDNF as expected, leading to canonical TrkB autophosphorylation and subsequent downstream signaling, as well as chronic effects on {beta} cell growth. Micromolar, but not nanomolar, concentrations of epinephrine blocked BDNF-induced TrkB autophosphorylation and downstream mitogen-activated protein kinase pathway activation, suggesting an inhibitory phenomenon at the receptor level. We determined epinephrine-mediated inhibition of TrkB activation to be Gi/o-dependent using pertussis toxin, arguing against an off-target effect of high dose epinephrine. Published data suggested that inhibition of potassium channels or phosphoinositide-3-kinase signaling may abrogate the negative effects of epinephrine, however these did not rescue TrkB signaling in our experiments. Taken together, these results show that 1) TrkB kinase signaling occurs in {beta} cells and 2) use of epinephrine in studies of insulin secretion requires careful consideration of concentration-dependent effects. BDNF-TrkB signaling in {beta} cells may underlie pro-survival or growth signaling and warrants further study.

cell biology↗