Fluorescence microscopy data on expression of Paired Box Transcription Factor 7 in skeletal muscle of APOBEC2 knockout mice

The data presented in this article are related to the research articles entitled “APOBEC2 negatively regulates myoblast differentiation in muscle regeneration” and “Data supporting possible implication of APOBEC2 in self-renewal functions of myogenic stem satellite cells: toward understanding the negative regulation of myoblast differentiation” (Ohtsubo et al., 2017a, 2017b) [1,2]. This article provides in vivo phenotypical data to show that Paired Box Transcription Factor 7 (Pax7)-positive cell number (per myofiber) is significantly lower in APOBEC2 (a member of apoB mRNA editing enzyme, catalytic polypeptide-like family)-knockout muscle than the control wild-type tissue at the same age of 8-wk-old in mice. The emerging results support an essential role for APOBEC2 in the self-renewal functions of myogenic stem satellite cells, namely the re-establishment of quiescent status after activation and proliferation of myoblasts.


a b s t r a c t
The data presented in this article are related to the research articles entitled "APOBEC2 negatively regulates myoblast differentiation in muscle regeneration" and "Data supporting possible implication of APOBEC2 in self-renewal functions of myogenic stem satellite cells: toward understanding the negative regulation of myoblast differentiation" (Ohtsubo et al., 2017a(Ohtsubo et al., , 2017b [1,2]. This article provides in vivo phenotypical data to show that Paired Box Transcription Factor 7 (Pax7)-positive cell number (per myofiber) is significantly lower in APOBEC2 (a member of apoB mRNA editing enzyme, catalytic polypeptide-like family)-knockout muscle than the control wild-type tissue at the same age of 8-wk-old in mice. The emerging results support an essential role for APOBEC2 in the self-renewal functions of myogenic stem satellite cells,

Subject area
Biology More specific subject area Skeletal muscle biology, tissue-specific stem cell physiology Type of data Image (microscopy), graph How data was acquired APOBEC2 expression is predominant in skeletal and cardiac muscles and elevated exclusively at the early-differentiation phase of myoblasts in muscle regeneration; however the biological and physiological significance is still unclear (see Refs. [3,4]).
The particular idea of an essential role for APOBEC2 in the self-renewal functions was raised by the previous study in single myofiber culture (see Ref. [2]) and further supported by the present in vivo study to show that Pax7-positive satellite cell population was significantly lower in APOBEC2-KO muscle than the control at the same adult phase in mice.
The idea extends our understanding of the previous finding that APOBEC2 negatively drives regulation of myoblast differentiation and fusion (see Ref. [1]).

Data
We tested a hypothesis that cytidine deaminase APOBEC2 may be an important mediator in the self-renewal functions of satellite cells, namely in the re-establishment of quiescent status after activation and proliferation of myoblasts. De Luca et al. [5] reported that defect of the ability of satellite cell self-renewal led to diminished number of satellite cells in skeletal muscle tissues. Accordingly, we compared satellite cell number in TA muscle between wild-type (WT) and APOBEC2-KO mice by immunofluorescence using antibody against Pax7, a well-known reliable marker for quiescent satellite cells. In APOBEC2-KO muscle cross-sections, Pax7-positive cell number (per myofiber) was significantly lower than the control WT tissue at the same age (p o 0.01), supporting the hypothesis that APOBEC2 deficiency leads to defect of the self-renewal of satellite cells (Fig. 1).

Experimental design
To further evaluate the above particular idea of a role for APOBEC2 in the self-renewal functions, TA muscles were collected from adult male WT and APOBEC2-KO mice (8-wk-old) and assayed for the number of quiescent myogenic stem satellite cells (Pax7-positive cells) on cryo-sections by Pax7immunofluorescence microscopy.

Animal care and use
APOBEC2-KO mice (C57BL/6 as the background strain) were generated by Dr. Neuberger (Medical Research Council Laboratory of Molecular Biology, United Kingdom) [6] and bred in our laboratory. Inbred C57BL/6 mice were used as WT controls. All animal experiments were conducted in strict accordance with the Guidelines for Proper Conduct of Animal Experiments published by the Science Council of Japan and ethics approvals from the Kyushu University Institutional Review Board (approval nos. 20-12, 23-62, A22-218, A24-75, A26-078, and A28-090).

Statistical analysis
Student's t-test was employed for statistical analysis of experimental results using Microsoft Excel X for Macintosh. Data are represented as mean 7 S.E.M. for three mice per group and the level of significance was set to p o 0.05.