Expression of Lbx1 involved in the hypaxial musculature formation of the mouse embryo

Abstract

Somites are the source of hypaxial musculature including skeletal muscles of the limb, tongue, and trunk. To get insight into the function of mouse Lbx1 homeobox gene in early somitic mesoderm differentiation, in situ hybridization analyses were performed. At the 4-6 somite stage (8 dpc), Lbx1 was first expressed in the lateral portion of the epithelial somite and dermomyotomal epithelium. This was in contrast to the expression of myf-5 in the medial region of the somite. The lateral expression of Lbx1 in somitic mesoderm then occurred regionally along the anterior-posterior body axis. Later, at 10 dpc (stage 1 of limb bud development), Lbx1-positive migrating cells originated in the lateral dermomyotomal lips at occipital, forelimb, and hindlimb levels. They also expressed Pax-3 and c-met, known as markers of the migrating limb muscle precursor cells. In stage 4 hindlimb bud (11.5 dpc), the dorsal and ventral muscle precursor populations expressed Lbx1. In stage 8 forelimb buds (12.5 dpc), Lbx1 expression was reduced in the proximal muscle masses, where the high expression of myogenin accompanying muscle differentiation was detected. These results suggest that mouse Lbx1 might be involved in the commitment or determination of a muscle cell subpopulation during hypaxial musculature development. J. Exp. Zool. 286:270-279, 2000.

The differentiation and morphogenesis of craniofacial muscles

“…Most (all?) of these cells are pax3-dependent (Brown et al, 2005), and express the transcription factors lbx1, paraxis, and six1 (Delfini and Duprez, 2000;Gross et al, 2000;Uchiyama et al, 2000;Williams and Ordahl, 2000). Lbx1 and both the c-Met and CXCR4 receptors are essential for their emigrations.…”

“Soft” tissue patterning: Muscles and tendons of the limb take their form

“…Thus, while Lbx1 is expressed in all migrating myoblasts, mice mutant for Lbx1 display specific limb muscle defects, presumably due to failure of progenitors to migrate (Mankoo et al, 1999;Schafer and Braun, 1999;Brohmann et al, 2000;Gross et al, 2000;Uchiyama et al, 2000). Mox2 mutant mice also show muscle specific defects, yet in this case, this is caused by their inability to proliferate as a result of defective Pax3 expression (Mankoo et al, 1999).…”

Gli2 and Gli3 have redundant and context-dependent function in skeletal muscle formation

“…In contrast, Lbx1 is activated at E9.5 at the level of occipital and limb somites in a subset of hypaxial muscle progenitor cells (Fig. 5F) (Jagla et al, 1995;Uchiyama et al, 2000), which are committed to migrate to the limb bud or to the head (Brohmann et al, 2000;Dietrich et al, 1998;Gross et al, 2000). As expected from our previous analysis of Shh mutant mice (Borycki et al, 1999), none of the mutant combinations studied shows a defect in the onset of hypaxial muscle progenitor cell specification (Fig.…”