Embryonic, fetal, and neonatal tongue myoblasts exhibit molecular heterogeneity in vitro

Abstract

Variable gene expression patterns have been shown to exist between embryonic, fetal, and neonatal lineages of limb skeletal myoblasts in vitro and in vivo. In this study, we examined the molecular phenotype of embryonic, fetal, and neonatal tongue myoblasts in primary culture for comparison with in vivo developmental tongue myoblasts. Myogenic regulatory factor (MRF) and myosin heavy chain (MHC) gene expression were determined in culture during both growth and differentiation conditions by PCR, immunoblotting, and immunohistochemistry. Unlike their in vivo tongue myoblast equivalents, developmental tongue myoblast cultures featured the expression of MyoD when kept in growth conditions. Differentiation conditions in vitro induced myogenic tongue lineages to maintain characteristics of their in vivo morphologic and contractile gene phenotype. Both in vivo and in vitro, embryonic tongue lineages predominantly expressed MHC-embryonic isoforms, while fetal and neonatal tongue lineages predominantly expressed fast and perinatal isoforms of contractile genes. A notable difference from the in vivo condition that was observed in differentiated tongue myotubes in vitro was the presence of the MHC-slow protein. It was previously demonstrated that MHC-slow protein was undetectable during the in vivo development of the tongue musculature despite the abundance of slow isoform transcripts. The present characterization of primary tongue myogenic cultures indicates that murine myoblast heterogeneity exists primarily between developmental lineages at the level of contractile gene expression. Outside their native surroundings, developmental myogenic tongue populations are unable to recapitulate the determination and differentiation molecular profiles that occur in vivo.

Normal and aberrant craniofacial myogenesis by grafted trunk somitic and segmental plate mesoderm

“…In both avian and murine embryos, tongue and laryngeal muscle precursors maintain myf5 expression throughout their ventral movements; appendicular myogenic cells do not (Bladt et al, 1995;Dalrymple et al, 2000;Mackenzie et al, 1998;Noden et al, 1999).…”

In vivo cell tracking of mouse embryonic myoblasts and fast fibers during development

“…Thus, we characterized the expression GFP in several muscle and non‐muscle tissues and organs from adult FastTnI/GFP mice (>2 months old), both in western blots and by fluorescence microscopy. The skeletal muscles studied were the Soleus (a slow‐twitch oxidative muscle enriched in type I slow fibers), the Extensor Digitorum Longus (EDL), the complex Gastrocnemius‐Plantaris (GP) and the Diaphragm (all three being fast‐twitch glycolytic muscles composed mainly of variable amounts of IIA, IIB and IIX fast fibers), as well as the tongue musculature (uniformly composed of fast fibers in mouse (Dalrymple et al ., ; Shuler and Dalrymple, ). The heart was also examined as another type of muscle, while the brain, liver and spleen were assessed as non‐muscle organs (Fig.…”

Myosin heavy chain composition of tongue muscle in microphthalmic (mi/mi) mice before and after weaning

“…Since it was first shown that the muscle fibers of mouse tongue consisted entirely of fast isoforms of MyHC (Dalrymple et al, 1999(Dalrymple et al, , 2000Shuler and Dalrymple, 2001), the composition ratio for each isoform has been studied in detail using gel electrophoresis (Agbulut et al, 2003). These studies have indicated that although MyHC-2b continues to increase after birth, MyHC-2a is expressed only transiently for several weeks postpartum.…”

“…Previous investigations have shown that tongue muscle consists of fast MyHC 4 isoforms (Dalrymple et al, 1999(Dalrymple et al, , 2000Shuler and Dalrymple, 2001). Agbulut et al determined MyHC composition ratios in mouse tongue muscle and reported that while MyHC-2b increases from birth onward, MyHC-2a is expressed transiently, for only a few weeks postpartum (Agbulut et al, 2003).…”