Biology subjects

Karasawa, T.

Publications and source records attributed to Karasawa, T..

3 recordsLinked to original sources

bioRxiv2023

Cis-regulatory evolution that caused change in wingless expression pattern associated with wing pigmentation pattern of Drosophila

Genetic mechanisms underlying the acquisition of new traits are an important topic in evolutionary developmental biology. Especially, the co-option of important regulatory genes potentially plays an important role in the gain of new traits. However, how the co-option occurs at the sequence level is still elusive. Drosophila guttifera has a unique wing pigmentation pattern and this is newly gained via the evolution of the expression pattern of wingless, which induces the pigmentation pattern formation. In this study, to reveal the changes in the cis-regulatory sequence which caused the co-option of wingless that lead to the expression in a new place, we conducted transgenic EGFP reporter assays of altered cis-regulatory sequences. As a result, the sequence was divided into regions needed to activate expression in the entire wing veins and a region required for repressing expression in excess parts. Comparisons with the homologous sequence of Drosophila melanogaster showed that the repressive function of the cis-regulatory region is also possessed by D. melanogaster while the activating function is newly gained in a lineage leading to D. guttifera. Furthermore, a putative binding site of SMAD transcription factors is shown to be essential for activating expression but also existing in the homologous region of D. melanogaster. Our results suggest that the pre-existing regulatory sequences in the cis-regulatory region coordinate with the newly gained sequences to acquire the new expression pattern of wingless. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

developmental biology↗

bioRxiv2022

DHCR7 as a novel regulator of ferroptosis in hepatocytes

Recent evidence indicates that ferroptosis is implicated in the pathophysiology of various liver diseases; however, the mechanism of ferroptosis regulation in the liver is poorly understood. Here, using the whole-genome screening approach, we identified 7-dehydrocholesterol reductase (DHCR7), the terminal enzyme of cholesterol biosynthesis, as a novel regulator of ferroptosis in hepatocytes. Genetic and pharmacological inhibition (with AY9944) of DHCR7 suppressed lipid peroxidation and ferroptosis in human hepatocellular carcinoma Huh-7 cells. DHCR7 inhibition increased its substrate, 7-dehydrocholesterol (7-DHC), and extrinsic 7-DHC supplementation in turn suppressed ferroptosis. On the other hand, cholesterol deprivation had no effect on ferroptosis. A 7-DHC-derived oxysterol metabolite, 3{beta},5-dihydroxycholest-7-en-6-one (DHCEO), was increased by a ferroptosis inducer RSL-3 in DHCR7-deficient cells, suggesting that the ferroptosis-suppressive effect of DHCR7 inhibition was driven by intracellular 7-DHC as a radical scavenger. While extrinsic 7-DHC supplementation suppressed ferroptosis in various cancer cells, pharmacological DHCR7 inhibition by AY9944 showed cell-type specific effects, which could be explained by high DHCR7 expression in Huh-7 cells. We further showed that AY9944 suppressed ferroptosis in murine primary hepatocytes in vitro and systemic administration of AY9944 inhibited hepatic ischemia-reperfusion injury in vivo. These findings provide new insights into the regulatory mechanism of liver ferroptosis and suggest that DHCR7 inhibition is a potential therapeutic option for ferroptosis-related liver diseases.

molecular biology↗

bioRxiv2021

Cryo-sensitive aggregation triggers NLRP3 inflammasome assemblyin cryopyrin-associated periodic syndrome

Cryopyrin-associated periodic syndrome (CAPS) is an autoinflammatory syndrome caused by mutations of NLRP3, which was originally identified as cryopyrin. Familial cold autoinflammatory syndrome (FCAS), the mildest form of CAPS, is characterized by cold-induced inflammation induced by the overproduction of IL-1{beta}. However, the molecular mechanism of how mutated NLRP3 causes inflammasome activation in CAPS remains unclear. Here, we found that CAPS-associated NLRP3 mutants form cryo-sensitive aggregates that function as a scaffold for inflammasome activation. Cold exposure promoted inflammasome assembly and subsequent IL-1{beta} release triggered by mutated NLRP3. While K+ efflux was dispensable, Ca2+ was indispensable for mutated NLRP3-mediated inflammasome assembly. Notably, Ca2+ influx was induced during mutated NLRP3-mediated inflammasome assembly. Furthermore, caspase-1 inhibition prevented Ca2+ influx and inflammasome assembly induced by the mutated NLRP3, suggesting a feed-forward Ca2+ influx loop triggered by mutated NLRP3. Thus, the mutated NLRP3 forms cryo-sensitive aggregates to promote inflammasome assembly distinct from canonical NLRP3 inflammasome activation.

immunology↗