Double-layered two-directional somatopleural cell migration during chicken body wall development revealed with local fluorescent tissue labeling

The ventral body wall is derived from the somatic layer of the lateral plate mesoderm, somatopleure, and somite. The primary ventral body wall is formed as a result of the lateral growth of the somatopleure. The secondary body wall is generated through the migration of somitic cells into the somatopleure. While it is reported that the cervical somatopleural cells migrate caudally to the thoracic region during body wall development, the migration of the thoracic somatopleural cells has not been elucidated. To investigate the migration behavior of the somatopleural cells in the thorax during chicken ventral body wall development, we labeled the thoracic somatopleural cells of one somite wide by DiI labeling or gene transfection of enhanced green fluorescent protein and observed the three-dimensional distribution of the labeled cells with the tissue-clearing technique FRUIT. Our labeling experiments revealed the rostral migration of the somatopleural cells into a deep part of the thoracic body wall in embryonic day 6.5 chickens. For embryonic day 8.5 chickens, these deep migrating somatopleural cells were found around the sternal ribs. Thus, we identified the double-layered two-directional migrating pathways of the somatopleural cells: the rostral migration of the deep somatopleural cells and the lateral migration of the superficial somatopleural cells. Our findings imply that the rostral migration of deep somatopleural cells and the lateral migration of superficial ones might be associated with the developing sternal ribs and the innervation of the thoracic cutaneous nerves, respectively. Mini-abstractDouble-layered two-directional migrations of the somatopleural cells in the thoracic body wall during chicken development were revealed by one-somite-wide labeling of the somatopleure.