eLife (Oct 2024)

A MSTNDel73C mutation with FGF5 knockout sheep by CRISPR/Cas9 promotes skeletal muscle myofiber hyperplasia

  • Ming-Ming Chen,
  • Yue Zhao,
  • Kun Yu,
  • Xue-Ling Xu,
  • Xiao-Sheng Zhang,
  • Jin-Long Zhang,
  • Su-Jun Wu,
  • Zhi-Mei Liu,
  • Yi-Ming Yuan,
  • Xiao-Fei Guo,
  • Shi-Yu Qi,
  • Guang Yi,
  • Shu-Qi Wang,
  • Huang-Xiang Li,
  • Ao-Wu Wu,
  • Guo-Shi Liu,
  • Shou-Long Deng,
  • Hong-Bing Han,
  • Feng-Hua Lv,
  • Di Lian,
  • Zheng-Xing Lian

DOI
https://doi.org/10.7554/eLife.86827
Journal volume & issue
Vol. 12

Abstract

Read online

Mutations in the well-known Myostatin (MSTN) produce a ‘double-muscle’ phenotype, which makes it commercially invaluable for improving livestock meat production and providing high-quality protein for humans. However, mutations at different loci of the MSTN often produce a variety of different phenotypes. In the current study, we increased the delivery ratio of Cas9 mRNA to sgRNA from the traditional 1:2 to 1:10, which improves the efficiency of the homozygous mutation of biallelic gene. Here, a MSTNDel73C mutation with FGF5 knockout sheep, in which the MSTN and FGF5 dual-gene biallelic homozygous mutations were produced via the deletion of 3-base pairs of AGC in the third exon of MSTN, resulting in cysteine-depleted at amino acid position 73, and the FGF5 double allele mutation led to inactivation of FGF5 gene. The MSTNDel73C mutation with FGF5 knockout sheep highlights a dominant ‘double-muscle’ phenotype, which can be stably inherited. Both F0 and F1 generation mutants highlight the excellent trait of high-yield meat with a smaller cross-sectional area and higher number of muscle fibers per unit area. Mechanistically, the MSTNDel73C mutation with FGF5 knockout mediated the activation of FOSL1 via the MEK-ERK-FOSL1 axis. The activated FOSL1 promotes skeletal muscle satellite cell proliferation and inhibits myogenic differentiation by inhibiting the expression of MyoD1, and resulting in smaller myotubes. In addition, activated ERK1/2 may inhibit the secondary fusion of myotubes by Ca2+-dependent CaMKII activation pathway, leading to myoblasts fusion to form smaller myotubes.

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