Research Note: Increased myostatin expression and decreased expression of myogenic regulatory factors in embryonic ages in a quail line with muscle hypoplasia

Abstract

Genetic selection of quail for a low body weight for more than 80 generations established a low-weight (LW) Japanese quail line that has been previously characterized to have a muscle hypoplasia phenotype. The aim of this study is to investigate the relationship of temporal expression levels of myostatin (Mstn) and myogenic regulatory factors (MRFs) with hypoplastic muscle growth in the LW line. During embryonic day (E) 13 to 15, gain of embryo weight was 2-fold lower (P < 0.001) in the LW line than that in the random bred control (CON). Gains in body weight and pectoralis muscle weight from hatch to posthatch day (P) 28 were also significantly lower (P < 0.01) in the LW line but increased by 4-fold (P < 0.05) during P42 to P75. PCR analysis showed that expression levels of Mstn were greater in the LW at embryonic stage (E12 to E14, P < 0.05), but there was no difference after hatch. In addition, expression levels of Pax7 and myogenin (MyoG) at E12 were 23-fold (P < 0.05) and 3.4-fold (P < 0.05) lesser in the LW line, respectively. At E14, expression of Pax3, Pax7, and MyoG gene was 3.5-fold (P < 0.05), 6.5-fold (P = 0.065), and 4.4-fold (P < 0.01) less than that in the CON. Taken together, high expression levels of Mstn and low expression of MRFs during embryonic stages can be associated with development of muscle hypoplasia and delayed muscle growth in the LW quail line. These data provide evidence that genetic selection for a low body weight resulting in an avian model with muscle hypoplasia has altered the expression profiles of myogenic factors.

Keywords: muscle development; myofiber number; myogenic regulatory factor; myostatin; quail.

Figure 1

Comparison of embryo weight (EW), body weight (BW), and pectoralis major muscle (PM) weight. (A) EW gain. (B) and (C) BW and PM weight (PMW) muscle gain and gain fold. The value was shown by weight gains of body and PM during development. Multiple t test was used for statistical analysis by the Graphpad PRISM 6.02 program. Values presented as means ± SEM (n = 6). Black square: the CON line. White square: the LW line. ∗P < 0.05, ∗∗P < 0.01, and ∗∗∗P < 0.001. Abbreviations: E, embryonic day; P, postnatal day.

Figure 2

Comparisons of expression levels of myostatin (Mstn) and myogenic regulatory factors (MRFs). (A) Quantitative analysis of gene expression levels, Mstn during development by qPCR; n = 4. (B) Gel electrophoresis of Mstn by RT-PCR at E12, E14, P42, and P75. The expression of Mstn in CON and LW lines during development by RT-PCR; n = 3. (C) Quantitative analysis of MRFs expression levels by qPCR; n = 4. RPS13 was used as an internal control for qPCR and RT-PCR. Multiple t test was used for statistical analysis by the Graphpad PRISM 6.02 program. Values presented as means ± SEM. Black square: the CON line and white square: the LW line. ∗P < 0.05 and ∗∗P < 0.01. Abbreviations: E, embryonic day, P, postnatal day.