Changes in the proportion and number of Pax(7+ve) and MF20(+ve) myoblasts during chick myogenesis in the head and limb.

Abstract

Previous studies suggested that all myoblasts are present in the head and limb prior to the commencement of primary myotube formation. As a consequence, these myoblasts must be in various developmental states during myogenesis, i.e. proliferating, differentiating or terminally differentiated. There are few in vivo studies investigating dynamic quantitative changes of subgroups of these myoblasts during myogenesis. In this report, using anti-Pax7 and anti-myosin heavy chain antibodies, we examined the quantitative change of proliferating (Pax7 +ve ) and terminally differentiated (MF20 +ve ) myoblasts during primary and secondary myogenesis in the chick head and limb. Our results show that during primary myogenesis, less than 30% of myoblasts are in the proliferating phase, but as soon as secondary myogenesis begins, over 95% of myoblasts start to proliferate. Moreover, we have found that the proportion of terminally differentiated myoblasts is maintained at a low level (less than 3%) during primary and secondary myogenesis.

In ovotemperature manipulation influences embryonic motility and growth of limb tissues in the chick (Gallus gallus)

“…In turkeys, increasing the incubation temperature by 1°C throughout the duration of incubation causes a significant reduction in hatchability, whereas shorter periods of around 4·days spent at the higher temperature do not cause decreases in viability (French, 2000). In chick embryos, the period between embryonic day 4 (ED4), roughly HH23 on the Hamburger and Hamilton staging series (Hamburger and Hamilton, 1951), and ED7 (roughly HH30) corresponds to the time when the primary muscle fibres have been laid down in the trunk and is just prior to the formation of the secondary muscle fibres, which begins at ED8 (Crow and Stockdale, 1986;Lee et al, 2004). It is a time when there is a great deal of proliferation among myoblasts, followed by differentiation.…”

Spatial and temporal changes in myogenic protein expression by the microenvironment after freeze injury

“…The primary antibodies used are well characterized within our laboratory (Koishi et al 1995;Lee et al 2004Lee et al , 2018Zhang & Gould, 2017). In addition, there are mouse monoclonal antibodies against Pax7, myogenin F5D or neonatal F59 (Developmental Studies Hybridoma Bank), MyoD 5.8A (BD Biosciences) or embryonic fast MY32 (Sigma); rabbit polyclonal antibodies against Myf5, MyoD M-318 and myogenin M-225 (Santa Cruz); goat polyclonal antibody against Pax3 (Abcam); p38MAPK and phosphorylated p38MAPK (Cell Signalling).…”

In ovotemperature manipulation differentially influences limb musculoskeletal development in two lines of chick embryos selected for divergent growth rates

“…In chicken, muscle fibre formation occurs in two waves. Primary fibres form between embryonic days (ED) 4 and 7 followed by a second wave of myoblast proliferation and differentiation to form secondary fibres between ED8 and 16 (Crow and Stockdale, 1986;Lee et al, 2004). Muscle fibre formation ends by hatch (ED21) (Smith, 1963), after which muscle growth and regeneration occurs through the activation of undifferentiated muscle precursor cells known as satellite cells (Moss, 1968).…”

“…Although not entirely specific to myogenesis, BMP-4 and IGF-I have both been shown to regulate myogenic factor expression and thereby myogenic proliferation and differentiation (Adi et al, 2002;Amthor et al, 1999). Primary fibres are believed to play a scaffolding role for the formation of secondary fibres (ED8-16) (Crow and Stockdale, 1986;Lee et al, 2004); therefore, increased proliferation and myogenic commitment during primary fibre formation (Myf5) followed by a rise in growth factor expression (BMP-4 and IGF-I) help explain the subsequent myofibre hyperplasia observed on ED18 in LT embryos. In broiler embryos, the same temperature treatment led to impaired myogenesis on ED18.…”