Biology subjects

Arai, E.

Publications and source records attributed to Arai, E..

6 recordsLinked to original sources

bioRxiv2023

Reduced ornamentation became elaborated in benign environments in a bird species

Many empirical studies have focused on highly-ornamented species to identify ecological factors that maintain the ornamentation or favour its exaggeration. By contrast, although reduction or loss of ornamentation appears to be widespread, species with reduced/lost ornamentation and its relationship with ecological factors are rarely focused on. Here, based on data collected over four years, we studied outermost tail feather length, i.e. a well-known sexual ornamentation in this clade, in relation to roosting location in the Pacific swallow Hirundo tahitica during winter. In contrast to congeners, this species has inconspicuous tail ornamentation, i.e. very shallowly forked tails with vestigial streamers, providing a rare opportunity to study the ecological factors driving reduced ornamentation. We found that Pacific swallows mainly roost in old nests under bridges over rivers, which resemble their original roosting sites, but some roost in old nests under the eaves of houses above the ground. Individuals roosting under the eaves of houses had significantly longer outermost (but not central) tail feathers than those roosting under bridges. Individuals roosting under the eaves of houses were heavier and showed lower physiological stress, and thus might better endure the maintenance cost, favouring ornament elaboration. Because we controlled for the effects of sex and age, these factors would not confound the observed pattern. Reduced ornamentation, as found in Pacific swallows roosting under their original roosting sites, could become elaborated in benign environments (i.e., under eaves, here), stressing the importance of balance between the costs and benefits of ornamentation.

ecology↗

bioRxiv2023

UV-induced feather color change reflects its porphyrin content

Pigmentary coloration is widespread in animals. Its evolutionary and ecological features are often attributed to the property of predominant pigments; therefore, most research has focused on predominant pigments such as carotenoids in carotenoid-based coloration. However, coloration results from predominant pigments and many other minority pigments, and the importance of the latter is overlooked. Here, we focused on porphyrin, an "uncommon" pigment found in bird feathers, and investigate its importance in the context of feather color changes in the barn swallow Hirundo rustica. We found that the "pheomelanin-based coloration" of the barn swallow faded after the irradiation of UV light, and this effect was particularly strong in the feathers of young swallows (nestlings and fledglings, here). We also found that it is not the predominant pigment, pheomelanin, but protoporphyrin IX pigment that showed the same pattern of depigmentation after the irradiation of UV light, particularly in the feathers of young swallows. In fact, the abovementioned age-dependent feather color change was statistically explained by the amount of porphyrin in the feathers. The current study demonstrates that a minority pigment, porphyrin, explains within-season dynamic color change, an ecological feature of feather coloration. The porphyrin-mediated rapid color change would benefit young birds, in which feather coloration affects the parental food allocation during a few weeks before independence, but not later. Future studies should not ignore these minor but essential pigments and their evolutionary and ecological functions. Significance statementPredominant pigments are assumed to determine animal coloration and its ecological features. It is then not surprising that the evolutionary and ecological features of animal coloration are often attributed to the chemical properties of predominant pigments. However, coloration results from predominant pigments and several other minority pigments. By irradiating UV light on reddish throat feathers of the barn swallow Hirundo rustica, we examined within-season dynamic color change in relation to a minority pigment, porphyrin, which has not previously been examined but is a candidate pigment for feather color change, because porphyrin can be easily photodegraded. We found that not the predominant pigment, pheomelanin, but porphyrin pigments explained the feather color change. Minor pigments and their chemical properties should not be dismissed to understand the ecological and evolutionary functions of animal coloration.

zoology↗

bioRxiv2022

Male mate preference against tail-elongated females in the barn swallow

The function of female ornamentation in the context of (inter)sexual selection attracts keen attention these days, but empirical field studies are mostly based on indirect measures such as mating patterns; direct evidence of male mate preference on female ornamentation while controlling for confounding factors is needed. Here we performed model presentation experiments to study male mate preference in the barn swallow Hirundo rustica, a model species of sexual selection. Female barn swallows have somewhat shorter tails than males, but their tails are still long and costly. Although many correlational and experimental studies of live females have focused on long tails in female barn swallows over the last three decades, direct behavioral tests of male mate preference are lacking. By using a sequential model presentation experiment, in which we repeated the trials with the same males, we found that males significantly reduced the number of pairing displays when they were presented with tail-elongated female models compared to control female models. Interaction between treatment and male tail length was far from significant. The observed pattern is inconsistent with the prevailing view that costly female ornamentation is maintained via male preference for more ornamented females. Rather, the observed pattern is consistent with the sexual mimicry hypothesis, in which females can avoid sexual (and social) harassment by mimicking males.

animal behavior and cognition↗

bioRxiv2020

ALC1 links chromatin accessibility to PARP inhibitor response in homologous recombination deficient cells

The response to Poly (ADP-ribose) polymerase inhibitors (PARPi) is dictated by homologous recombination (HR) DNA repair mechanisms and the abundance of lesions that trap PARP enzymes on chromatin. It remains unclear, however, if the established role of PARP in promoting chromatin accessibility impacts viability in these settings. Using a CRISPR based screen, we identify the PAR-binding Snf2-like ATPase, ALC1/CHD1L, as a key determinant of PARPi toxicity in HR-deficient cells. ALC1 loss reduced viability of BRCA mutant cells and enhanced their sensitivity to PARPi by up to 250-fold, while overcoming several known resistance mechanisms. ALC1 loss was not epistatic to other repair pathways that execute the PARPi response. Instead, ALC1 deficiency reduced chromatin accessibility concomitant with a decrease in the association of repair factors. This resulted in an accumulation of replication associated DNA damage and a reliance on HR. These findings establish PAR-dependent chromatin remodeling as a mechanistically distinct aspect of PARPi responses, implicating ALC1 inhibition as a new approach to overcome therapeutic resistance in HR-deficient cancers.

cancer biology↗

bioRxiv2020

In vivo CRISPR screening identifies Fli1 as a transcriptional safeguard that restrains effector CD8 T cell differentiation during infection and cancer

Improving effector activity of antigen specific T cells is a major goal in cancer immunotherapy. Despite the identification of several effector T cell (TEFF)-driving transcription factors (TF), the transcriptional coordination of TEFF biology remains poorly understood. We developed an in vivo T cell CRISPR screening platform and identified a novel mechanism restraining TEFF biology through the ETS family TF, Fli1. Genetic deletion of Fli1 enhanced TEFF responses without compromising memory or exhaustion precursors. Fli1 restrained TEFF lineage differentiation by binding to cis-regulatory elements of effector-associated genes. Loss of Fli1 increased chromatin accessibility at ETS:RUNX motifs allowing more efficient Runx3-driven TEFF biology. CD8 T cells lacking Fli1 provided substantially better protection against multiple infections and tumors. These data indicate that Fli1 safeguards the developing CD8 T cell transcriptional landscape from excessive ETS:RUNX-driven TEFF cell differentiation. Moreover, genetic deletion of Fli1 improves TEFF differentiation and protective immunity in infections and cancer.

immunology↗

bioRxiv2019

Genetic screening for single-cell variability modulators driving therapy resistance

Cellular plasticity describes the ability of cells to transition from one set of phenotypes to another. In the context of cancer therapeutics, plasticity refers to transient fluctuations in the molecular state of tumor cells, driving the formation of rare cells primed to survive drug treatment and ultimately reprogram into a stably resistant fate. However, the biological processes governing this cellular plasticity remain unknown. We used CRISPR/Cas9 genetic screens to reveal genes that affect cell fate decisions by altering cellular plasticity across a range of functional categories. We found that cellular plasticity and cell fate decision making can be decoupled in that factors can affect cell fate decisions in both plasticity-dependent and independent manners. We discovered a novel mode of altering resistance based on cellular plasticity that, contrary to known mechanisms, pushes cells towards a more differentiated state. We further confirmed our prediction that manipulating cellular plasticity before the addition of the main therapy would result in changes in therapy resistance more than concurrent administration. Together, our results indicate that identifying pathways modulating cellular plasticity has the potential to alter cell fate decisions and may provide a new avenue for treating drug resistance.

cell biology↗