Investigating the function of the histone methyltransferase PRMT1 during post‐embryonic development in Xenopus tropicalis.

Abstract

Anuran amphibians such as Xenopus tropicalis offer a unique opportunity to study how the adult organs and their organ‐specific stem cells are formed in vertebrates during the so‐called postembryonic development. The postembryonic events such as the maturation/remodeling of many organs are totally regulated by thyroid hormone (TH). Of particularly interest among TH target genes is protein arginine methyltransferase1 (PRMT1), which can function as a TR co‐activator. We have shown that PRMT1 mRNA and protein expression peaks at the climax of metamorphosis in the intestine when adult stem cells are forming de novo and proliferating, and PRMT1 overexpression enhanced the expression of TH target genes and increased the number of adult intestinal stem cells during metamorphosis, suggesting a critical role during the formation of adult stem cells in the intestine. To determine the function of the endogenous PRMT1 gene during post‐embryonic development and intestinal stem cell development, we adapted the gene editing technology to knockout PRMT1 gene in X. tropicalis.We used Transcriptional activator–like effector nuclease (TALEN) technology to generate PRMT1 knockdown frogs (F0). After generating PRMT1 heterozygous frogs (F1) with out of frame mutations from the F0 animals, we tried to produce PRMT1 homozygous knockout frogs by intercross the F1 frogs. We measured the survival rate, animal size, and the developmental stage of the resulting tadpoles, including wild type, heterozygous and homozygous animals.As the result, we successfully generated PRMT1 heterozygous (F1) frogs including out frame mutation (8 base deletion), and PRMT1 homozygous knockout (F2) animals by intercross with F1 frogs. Surprisingly, all PRMT1 homozygous tadpoles died within 14 days after fertilization although they completed embryogenesis to form apparently normal tadpoles. In addition, morphological analysis showed that PRMT1 knockout tadpoles delayed animal development and growth.PRMT1 knockout tadpoles completed embryogenesis normally but had delayed development and tadpole lethality. The availability of knockout tadpoles will allow us to study the role of PRMT1 during T3 ‐induced metamorphosis, thus overcoming the difficulty to study PRMT1 during postembryonic development in mammals due to the lethal phenotype in PRMT1 knockout mice.Support or Funding InformationJSPS Research Fellowship for Japanese Biomedical and Behavioral Researchers at NIHThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.