Morphological, biochemical, transcriptional and epigenetic responses to fasting and refeeding in intestine of Xenopus laevis

Abstract

BackgroundAmphibians are able to survive for several months without food. However, it is unclear what molecular mechanisms underlie their survival. To characterize the intestinal responses to fasting and refeeding, we investigated morphological, biochemical, transcriptional and epigenetic changes in the intestine from adult male Xenopus laevis.ResultsFrogs were fed for 22 days, fasted for 22 days, or fasted for 21 days and refed for 1 day. Fasting reduced, and refeeding recovered partially or fully, morphological parameters (wet weight of the intestine, circumference of the epithelial layer and number of troughs in a villus-trough unit), activities of digestive enzymes and plasma biochemical parameters (glucose, triglycerides, cholesterol and free fatty acids). Reverse transcription-quantitative polymerase chain reaction analysis revealed overall suppression of the transcript levels by fasting, with various recovery rates on refeeding. Chromatin immunoprecipitation assays on the selected genes whose transcript levels declined with fasting and recovered quickly with refeeding, showed several euchromatin marks in histone (acetylation and methylation) and RNA polymerase II modifications (phosphorylation) with fasting, and returned to the feeding levels by refeeding. The mRNA levels of these genes responded to fasting and refeeding to greater extents than did the pre-mRNA levels, suggesting the involvement of post-transcriptional regulation.ConclusionsOur results demonstrate that the X. laevis intestine may undergo overall metabolic suppression at least at the transcriptional level to save energy during fasting and quickly recovered to moderate nutritional deficiency by refeeding, and suggest that these dietary responses of the intestine are epigenetically and post-transcriptionally regulated.Electronic supplementary materialThe online version of this article (doi:10.1186/s13578-016-0067-9) contains supplementary material, which is available to authorized users.

Using Xenopus to understand human disease and developmental disorders

“…For example, investigations of the molecular regulation of the cell cycle continue to use Xenopus oocytes, eggs and embryos as a major model (Malhotra, Vinod, Mansfeld, Stemmann, & Mayer, ; Sabherwal, Thuret, Lea, Stanley, & Papalopulu, ; Sanuki et al, ). Xenopus also has greatly enhanced our understanding of DNA replication and repair (Kalb, Mallery, Larkin, Huang, & Hiom, ; Long, Joukov, Budzowska, & Walter, ; Räschle et al, ; Shintomi, Takahashi, & Hirano, ; Zhang et al, ), and the mechanisms of genome organization, transcriptional regulation, and epigenetics (Belikov, Berg, & Wrange, ; Bogdanović et al, ; Buisine et al, ; Gazdag, Jacobi, van Kruijsbergen, Weeks, & Veenstra, ; Gao et al, ; Hontelez et al, ; Owens et al, ; Tamaoki et al, ; Wang et al, ; Wen, Fu, Guo, Chen, & Shi, ). Numerous studies in Xenopus elucidate mechanisms of morphogenesis and organogenesis ( Agricola et al, ; Bestman, Huang, Lee‐Osbourne, Cheung, & Cline, ; Metikala, Neuhaus, & Hollemann, ; Mimoto, Kwon, Green, Goldman, & Christian, ; Nie & Bronner, ; Okada, Wen, Miller, Su, & Shi, ; Ossipova et al, ; Tanizaki, Ishida‐Iwata, Obuchi‐Shimoji, & Kato, ).…”

“…, and the mechanisms of genome organization, transcriptional regulation, and epigenetics (Belikov, Berg, & Wrange, 2016;Bogdanović et al, 2016;Buisine et al, 2015;Gazdag, Jacobi, van Kruijsbergen, Weeks, & Veenstra, 2016;Gao et al, 2016;Hontelez et al, 2015;Owens et al, 2016;Tamaoki et al, 2016;Wang et al, 2014;Wen, Fu, Guo, Chen, & Shi, 2015). Numerous studies in Xenopus elucidate mechanisms of morphogenesis and organogenesis (Agricola et al, 2016;Bestman, Huang, Lee-Osbourne, Cheung, & Cline, 2015;Metikala, Neuhaus, & Hollemann, 2016;Mimoto, Kwon, Green, Goldman, & Christian, 2015;Nie & Bronner, 2015;Okada, Wen, Miller, Su, & Shi, 2015;Ossipova et al, 2015;Tanizaki, Ishida-Iwata, Obuchi-Shimoji, & Kato, 2015).…”

Preimplantation Genetic Screening

“…Indeed, heterozygous Brd4-knockout mice showed growth abnormalities, such as reduced adiposity and abnormal bone metabolism, similar to those of mice exposed to fetal malnutrition [17]. Although there is little evidence supporting a role for the histone H3K36 in this process, our recent study demonstrated that a starvation signal induced H3K36 tri/dimethylation in genes expressed in the small intestine of Xenopus laevis [18].…”

“…On the other hand, transcriptional elongation is terminated by methylation of DNA in the gene body region [16]. Histone H3K36 methylation induced by a histone methyltransferase, SET2, represses the transcriptional elongation reaction by reducing histone acetylation via recruiting HDACs on the gene body [17][18][19]. The methylated histone H3K36 recruits another DNMT, DNMT3b, to induce DNA methylation in the gene body region ( Figure 6B).…”

Modern approaches for the screening of epigenetically active xenobiotics

“…Особенностью данной модели является возможность проведения экспериментов как на целом организме, так и на культуре ооцитов, что позволяет сравнивать эффекты in vivo и in vitro. В связи с этим X. laevis является одной из наиболее удобных моделей для изучения механизмов эпигенетической регуляции экспрессии генов [43,44]. В ооциты X. laevis с помощью инъекций можно вводить ДНК, РНК и плазмидную ДНК, что позволяет варьировать уровень того или иного гена (в том числе гена компонента системы эпигенетической регуляции транскрипции) при изучении влияния факторов окружающей среды на функции генов и процесс сборки хроматина [52].…”