Integrins in the mouse myotome: Developmental changes and differences between the epaxial and hypaxial lineage

Abstract

Integrins are cellular adhesion receptors that mediate signaling and play key roles in the development of multicellular organisms. However, their role in the cellular events leading to myotome formation is completely unknown. Here, we describe the expression patterns of the ␣1, ␣4, ␣5, ␣6, and ␣7 integrin subunits in the mouse myotome and correlate them with the expression of several differentiation markers. Our results indicate that these integrin subunits may be differentially involved in the various phases of myogenic determination and differentiation. A detailed characterization of the myogenic cell types expressing the ␣4 and ␣6 subunits showed a regionalization of the myotome and dermomyotome based on cell-adhesion properties. We conclude that ␣6␤1 may be an early marker of epaxial myogenic progenitor cells. In contrast, ␣4␤1 is up-regulated in the intercalated myotome after myocyte differentiation. Furthermore, ␣4␤1 is expressed in the hypaxial dermomyotome and is maintained by early hypaxial myogenic progenitor cells colonizing the myotome. Developmental Dynamics 231:402-415, 2004.

Extracellular matrix remodeling accompanies axial muscle development and morphogenesis in the mouse

“…Furthermore, mRNA for Itga5, the a chain of the a5b1 fibronectin receptor, is present in the myotome (Bajanca et al, 2004;Cachaço et al, 2005). We have extended those observations to other fibronectin receptors as well as tenascin receptors on the myocytes.…”

“…Myocytes have been reported to engage the myotomal laminin matrix through a6b1 integrin (Bajanca et al, 2006) and probably also, later on, a7b1 integrin (Bajanca et al, 2004). Because myotomal myocytes are not contained by the laminin matrix at the epaxial lip (Fig.…”

“…In the mouse, the formation of the epaxial myotome starts at embryonic day (E) 8.5 in the rostral somites (Venters et al, 1999;Bajanca et al, 2004) and by E12.5, the myotomes have completely disappeared as segmented structures (Deries et al, 2010). During these few days, the myotome develops gradually, and different stages of development can be identified in different embryo ages and in different rostro-caudal levels of the same embryo.…”

“…The a4b1 integrin, a fibronectin and VCAM1 receptor, is enriched at the tips of elongated myocytes (Bajanca et al, 2004), thus being in a position to mediate their attachment to the intersegmental fibronectin matrix. Furthermore, mRNA for Itga5, the a chain of the a5b1 fibronectin receptor, is present in the myotome (Bajanca et al, 2004;Cachaço et al, 2005).…”

“…Earlier analyses of laminin distribution in mouse embryo sections, using an antibody that recognizes all laminins present (except the epidermal laminin 332), reveals a continuous line of immunoreactivity on the dermomyotome and a line of matrix separating the myotome from the sclerotome (Bajanca et al, 2004;Cachaço et al, 2005;Anderson et al, 2009). The other basement membrane molecules (collagen type IV, nidogen, and perlecan) have an identical pattern (Bajanca et al, 2006;Anderson et al, 2009).…”