中文 |

Research Progress

Gamete Maturation in Zebrafish Requires m6A Modification Catalyzed by Mettl3 Methyltransferase

Jan 04, 2018

N6-methyladenosine (m6A), catalyzed by methyltransferase-like 3 (Mettl3), is the most abundant RNA modification and has implicated in a variety of biological processes. However, much less is known about its function in vivo because the mutation of mettl3 are embryonic lethal in both mammals and plants.

The Research Group of Fish Gene Engineering at Institute of Hydrobiology (IHB) of Chinese Academy of Sciences has obtained the viable zygotic mettl3 knockout zebrafish line Zmettl3m/m and found that mutant adults disrupt gamete maturation. This study, published in GENETICS, provides the first in vivo evidence that gamete maturation in zebrafish requires m6A modification catalyzed by Mettl3 methyltransferase.

By transcription activator-like effector nucleases (TALENs) and generated Mettl3 overexpressing transgenic zebrafish lines to rescue the homozygotes, viable zygotic mettl3 knockout zebrafish line Zmettl3m/m was obtained by researchers. They analyzed the various process during gametogenesis and gamete maturation in Zmettl3m/m, such as histological analysis and fertility assessment, ovarian follicles isolation and incubation, sperm motility assessments and sex steroid measurements.

Besides, they found that the oocytes in Zmettl3m/m adult females are stalled in early development and the ratio of full grown stage (FG) follicles is significantly lower than that of wild type (WT). The percentage of germinal vesicle breakdown (GVBD) and numbers of eggs ovulated in mutant are also significantly lower than WT follicles. The disruption of gamete maturation was successfully rescued by overexpression of Mettl3 in Zmettl3m/m. 

Synaptonemal complex can be assembled and synapsis is normal in Zmettl3m/m adult males. However, the proportion of spermatogonia (SG) and spermatocytes (SC) stages are significantly higher, yet the proportion of spermatozoa (SZ) stage decrease. In addition, sperm motility is significantly reduced in mutant males.

Sex steroid measurements showed that 11-ketotestosterone (11-KT) and 17β-estradiol (E2) levels are significantly decreased in Zmettl3m/m. Further study showed that the defective gamete maturation is accompanied by decreased overall m6A modification levels and disrupted expression of genes critical for sex hormone synthesis and gonadotropin signaling in Zmettl3m/m.

This study provides the first in vivo evidence that loss of Mettl3 leads to failed gamete maturation and significantly reduced fertility in zebrafish, and Mettl3 and m6A modifications play important roles in regulating fertility in vertebrates.

Contact Us
  • 86-10-68597521 (day)

    86-10-68597289 (night)

  • 86-10-68511095 (day)

    86-10-68512458 (night)

  • cas_en@cas.cn

  • 52 Sanlihe Rd., Xicheng District,

    Beijing, China (100864)

Copyright © 2002 - Chinese Academy of Sciences