Histone Arginine Methylation as a Regulator of Gene Expression in the Dehydrating African Clawed Frog (Xenopus laevis)

Abstract

The African clawed frog (Xenopus laevis) endures prolonged periods of dehydration while estivating underground during the dry season. Epigenetic modifications play crucial roles in regulating gene expression in response to environmental changes. The elucidation of epigenetic changes relevant to survival could serve as a basis for further studies on organ preservation under extreme stress. The current study examined the relative protein levels of key enzymes involved in the arginine methylation of histones in the liver and kidney tissues of control versus dehydrated (35 ± 1%) X. laevis through immunoblotting. Protein arginine methyltransferases (PRMT) 4, 5, and 6 showed significant protein level decreases of 35 ± 3%, 71 ± 7%, and 25 ± 5%, respectively, in the liver tissues of the dehydrated frogs relative to controls. In contrast, PRMT7 exhibited an increase of 36 ± 4%. Similarly, the methylated histone markers H3R2m2a, H3R8m2a, and H3R8m2s were downregulated by 34 ± 11%, 15 ± 4%, and 42 ± 12%, respectively, in the livers of dehydrated frogs compared to controls. By contrast, the kidneys of dehydrated frogs showed an upregulation of histone markers. H3R2m2a, H3R8m2a, H3R8m2s, and H4R3m2a were significantly increased by 126 ± 12%, 112 ± 7%, 47 ± 13%, and 13 ± 3%, respectively. These changes can play vital roles in the metabolic reorganization of X. laevis during dehydration, and are likely to increase the chances of survival. In turn, the tissue-specific regulation of the histone arginine methylation mechanism suggests the importance of epigenetic regulation in the adaptation of X. laevis for whole-body dehydration.