Biology subjects

Segev, A.

Publications and source records attributed to Segev, A..

3 recordsLinked to original sources

bioRxiv2025

Programmed DNA breaks drive chromatin reconfiguration and facilitate transcriptional potentiation at neuronal early response genes

Neuronal activity causes topoisomerase II{beta} (TOP2B) to form DNA double strand breaks (DSBs) within the promoters of key early response genes (ERGs), such as Fos and Npas4. TOP2B-mediated DSBs facilitate rapid ERG transcription, yet how this occurs remains unclear. Here, using chromosome conformation capture methods (3C and 4C-seq), we report that DSB formation within the promoters of Fos and Npas4 is sufficient to emulate contact profiles observed at these regions following neuronal stimulation, including their elevated interactions with cognate enhancers. Furthermore, despite their purported risk, repeated DSB cycles within ERG promoters progressively potentiated ERG induction in both mouse cortical neurons and HEK293T cells, evoking the effects of transcriptional memory. Potentiated ERG inducibility following recurrent DSBs persisted through intervening cell cycles, occurred even when DNA repair was likely mutagenic, and was associated with a substantial loss of cis chromosome interactions and an increase in trans interactions with ERG promoters. Together, these results reveal how single and recurrent TOP2B-mediated DSBs could affect stimulus-dependent transcription patterns by affecting chromatin dynamics at ERG promoters.

molecular biology↗

bioRxiv2021

Oxytocin Signaling Regulates the Homeostatic Response to Cold Stress in Poikilothermic Vertebrates

When exposed to low temperature, homeothermic vertebrates maintain internal body temperature by activating thermogenesis and by altered metabolism, synchronized by neuroendocrine responses. Although such physiological responses also occur in poikilothermic vertebrates, the prevailing notion is that their reactions are passive. Here, we explored molecular hypothalamic and physiological responses to cold stress in the tropical poikilotherm Nile tilapia (Oreochromis niloticus). We show that cold exposed tilapia exhibit complex homeostatic responses, including increased hypothalamic oxytocin, plasma glucose and cortisol concomitant with reduced plasma lactate and metabolic rate. Pharmacological or genetic blockage of oxytocin signaling further affected metabolic rate in two cold-exposed poikilothermic models. This indicates that oxytocin, a known thermoregulator in homeotherms, actively regulates temperature-related homeostasis in poikilotherms. Overall, our findings show that the brain of poikilotherms actively responds to cold temperature by regulating metabolic physiology. Moreover, we identify oxytocin signaling as an adaptive and evolutionarily conserved metabolic regulator of temperature-related homeostasis.

physiology↗

bioRxiv2021

Re-evaluation of ethylene role in Arabidopsis cauline leaf abscission induced by water stress and rewatering

Patharkar and Walker (2016) reported that cauline leaf abscission in Arabidopsis is induced by a cycle of water stress and rewatering, which is regulated by the complex of INFLORESCENCE DEFICIENT IN ABSCISSION (IDA), HAESA (HAE), and HAESA-LIKE2 (HSL2) kinases. However, they stated without presenting experimental results that ethylene is not involved in this process. Since this statement contradicts the well-established role of ethylene in organ abscission induced by a cycle of water stress and rewatering, our present study was aimed to re-evaluate the possible involvement of ethylene in this process. For this purpose, we examined the endogenous ethylene production during water stress and following rewatering, as well as the effects of exogenous ethylene and 1-methylcyclopropene (1-MCP), on cauline leaf abscission of Arabidopsis wild type. Additionally, we examined whether this stress induces cauline leaf abscission in ethylene-insensitive Arabidopsis mutants. The results of the present study demonstrated that ethylene production rates increased significantly in cauline leaves at 4 h after rewatering of stressed plants, and remained high for at least 24 h in plants water-stressed to 40 and 30% of system weight. Ethylene treatment applied to well-watered plants induced cauline leaf abscission, which was inhibited by 1-MCP. Cauline leaf abscission was also inhibited by 1-MCP applied during a cycle of water stress and rewatering. Finally, no abscission occurred in two ethylene-insensitive mutants, ein2-1 and ein2-5, following a cycle of water stress and rewatering. Taken together, these results clearly indicate that ethylene is involved in Arabidopsis cauline leaf abscission induced by water stress. One sentence summaryUnlike Patharker and Walker (2016), our results show that ethylene is involved in Arabidopsis cauline leaf abscission induced by water stress and rewatering, similar to leaf abscission in other plants.

physiology↗