Characterization of mice with mutations disrupting binding of a transcriptional repressor of insulin-like growth factor 2 and loss-of-function mutation of myostatin

Chen, Xuenan

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https://hdl.handle.net/2142/117753 Copy

Description

Title

Characterization of mice with mutations disrupting binding of a transcriptional repressor of insulin-like growth factor 2 and loss-of-function mutation of myostatin

Author(s)

Chen, Xuenan

Issue Date

2022-11-17

Director of Research (if dissertation) or Advisor (if thesis)

Dilger, Anna C

Committee Member(s)

• Harsh, Bailey
• Beever, Jon

Department of Study

Animal Sciences

Discipline

Animal Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• IGF2
• Myostatin

Abstract

Insulin-like growth factors 2 (Igf2) is a positive regulator for fetal development. Disrupting binding site of ZBED6, a transcriptional repressor of Igf2, upregulates postnatal Igf2 expression in pigs, leading to increased skeletal muscle growth and decreased fat deposition. Myostatin (Mstn) is a negative regulator for skeletal muscle growth, which loss-of-function (LOF) mutation causes “double muscle” phenotype. The goals of this study were to characterize phenotype of mice with mutations in insulin-like growth factor 2 (Igf2) that disrupt ZBED6 binding and evaluate the effect of introducing myostatin (Mstn) loss-of-function (LOF) mutation to mice with Igf2 overexpression mutations. Mice with mutations around Igf2 intron3 nucleotide 14195 that predicted to disrupt ZBED6 binding were used in the experiment: G>A mutation at 14195 (G>A); G>A mutation at 14195 and A>G mutation at 14180 (A>G/G>A); C insertion at 14193 (+C). Four genotypes were selected: wild-type mice (WT); mice with Igf2 mutations (IGF2); mice with Mstn LOF mutation (MN), and mice with both Mstn and Igf2 mutations (MI). Within each strain of Igf2 mutation, 4 males and 4 females from each genotype were collected. In experiment 1, WT mice were compared with IGF2 mice (N=48). In experiment 2, all four genotypes were compared with each other with strain of Igf2 mutation as a fixed block (N=91). All mice were sacrificed at 63 ± 2d and dissected. Muscle fiber analysis was performed on right tibialis anterior (TA). Gene expression was analyzed on left TA. In experiment 1, disruption of ZBED6 binding increased postnatal Igf2 expression (P < 0.05) in both skeletal muscle and liver with minimal differences between strains. Igf2 mutation increased skeletal muscle and decreased fat pad weights (P < 0.05). However, the increase in skeletal muscle weight was only detectable (P < 0.05) in IGF2 mice from A>G/G>A and +C strains. Heart and kidney weights were also elevated (P < 0.05) in IGF2 mice from A>G/G>A and +C strains. Igf2 mutations increased muscle hypertrophy (P < 0.05) but did not alter muscle hyperplasia or fiber types in all strains (P > 0.25). In experiment 2, Mstn LOF mutation increased skeletal muscle and decreased fat pad weights in MN and MI mice (P < 0.01). The combination of Igf2 overexpression and Mstn LOF mutation had a potentially synergistic effect in promoting skeletal muscle growth, likely due to greater muscle hypertrophy (P < 0.05). Mstn LOF mutation increased muscle fiber number (P < 0.05) and shifted muscle fiber composition toward glycolytic (P < 0.05). Mstn LOF mutation reduced Igf2r expression (P < 0.05) in skeletal muscle of MN and MI mice. These data indicate that Igf2 G>A mutation did not promote skeletal muscle growth as robustly as A>G/G>A or +C strains. Additionally, Mstn LOF could promote skeletal muscle hypertrophy more effectively in the presence of Igf2 overexpression mutation.

Graduation Semester

2022-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Xuenan Chen

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