MEAT SCIENCE AND MUSCLE BIOLOGY SYMPOSIUM: Stem cell niche and postnatal muscle growth1,2

Abstract

Stem cell niche plays a critical role in regulating the behavior and function of adult stem cells that underlie tissue growth, maintenance, and regeneration. In the skeletal muscle, stem cells, called satellite cells, contribute to postnatal muscle growth and hypertrophy, and thus, meat production in agricultural animals. Satellite cells are located adjacent to mature muscle fibers underneath a sheath of basal lamina. Microenvironmental signals from extracellular matrix mediated by the basal lamina and from the host myofiber both impinge on satellite cells to regulate their activity. Furthermore, several types of muscle interstitial cells, including intramuscular preadipocytes and connective tissue fibroblasts, have recently been shown to interact with satellite cells and actively regulate the growth and regeneration of postnatal skeletal muscles. From this regard, interstitial adipogenic cells are not only important for marbling and meat quality, but also represent an additional cellular component of the satellite cell niche. At the molecular level, these interstitial cells may interact with satellite cells through cell surface ligands, such as delta-like 1 homolog (Dlk1) protein whose overexpression is thought to be responsible for muscle hypertrophy in callipyge sheep. In fact, extracellular Dlk1 protein has been shown to promote the myogenic differentiation of satellite cells. Understanding the cellular and molecular mechanisms within the stem cell niche that regulate satellite cell differentiation and maintain muscle homeostasis may lead to promising approaches to optimizing muscle growth and composition, thus improving meat production and quality.

Association between DLK1 and IGF-I gene expression and meat quality in sheep

“…In transgenic mice, skeletal muscle DLK1 is overexpressed, caused hypertrophy traits and affected muscle growth; similarly, a double muscled trait was caused in sheep (Davis et al, 2004;Magee et al, 2011;Bi and Kuang, 2012). In the present study, DLK1 expression was higher in the longissimus dorsi of males than in females at different growth stages after birth.…”

Regulation of DLK1 by the maternally expressed miR-379/miR-544 cluster may underlie callipyge polar overdominance inheritance

“…If the point mutation occurs in both the paternal and maternal alleles, it causes no change in DLK1 protein expression (4), which is consistent with the mode of inheritance of the CLPG phenotype. It has been demonstrated that DLK1 protein expression is essential for determining muscle mass (20)(21)(22)(23)(24). Thus, a hypothesis predicting that maternal noncoding RNA might act as a negative regulator of DLK1 expression has been put forth; however, this hypothesis lacks evidence (25).…”

Localization and abundance of early markers of fat cell differentiation in the skeletal muscle of cattle during growth — Are DLK1-positive cells the origin of marbling flecks?

“…These cells may not exclusively provide a pool of preadipocytes capable of differentiation to adipocytes upon stimulation. They can differentiate into other cell types in other tissues and under different conditions (Bi & Kuang, 2012;Ferrón et al, 2011; Yanai et al, 2010). Bi and Kuang (2012) assumed that DLK1 mediates the interaction between adipogenic and myogenic progenitor cells and regulates their differentiation.…”