Fig. 1: A subpopulation of muscle cells does not originate from somites but from the lateral plate in the chicken limb.
From: Unexpected contribution of fibroblasts to muscle lineage as a mechanism for limb muscle patterning
a–c Limb muscle organisation after quail-into-chicken presomitic mesoderm grafts. a Schematic of limb presomitic mesoderm grafts. b, c Transverse and adjacent forelimb sections of E9 presomitic mesoderm grafted embryos immunostained with QCPN (quail nuclei, red) and MF20 (myosins, green) (b), and with QCPN (quail nuclei, red) and ColXII (tendons, green) antibodies (c). d High magnification of FCU, a ventral and posterior muscle immunostained with QCPN (quail nuclei, red), MF20 (myosins, green) and COLXII (tendons, green) antibodies combined with DAPI (nuclei, blue). e High magnification of muscle tips (close to tendons), squared in d, showing non-quail nuclei within myosin+ cells (arrows). f High magnification of FCU immunostained with QCPN (quail nuclei, red) and MYOG (green) antibodies. g Focus on muscle tip regions showing MYOG+ nuclei (green) that are not quail+ (red) (white arrows) close to myosin+ cells (grey). Yellow arrowheads point to MYOG+ (green) that are quail+ (red). h Percentage of MYOG+/QCPN− cells versus total MYOG+ cells. Data are presented as mean values ± SD from 3 grafted limbs. i–l Limb muscle organisation after quail-into-chicken lateral plate mesoderm grafts. i Schematic of limb lateral plate mesoderm grafts. j, k Transverse and adjacent limb sections were hybridised with SCX probe (blue) to label tendons (j) and immunostained with QCPN (quail nuclei, red), MF20 (myosins, green) antibodies combined with DAPI (blue) (k), focused on the FCU muscle. l High magnification of muscle tip regions (close to tendons) showing the high density of quail nuclei of lateral plate mesoderm origin. Arrows point to quail myonuclei (red) in myosin+ fibres (green).
