In stage 14 embryos, embryonic heart anchoring cells (HANCs) expressing lbe
reach the tin
-positive cardioblasts at the level of thoracic segment T2.
is dynamically expressed in myoblasts associated with the leg imaginal disc proper. All leg myoblasts express twi
is expressed initially in early third instar larvae in a small subset of twi
-expressing cells located in the dorsal femur and giving rise to the levator muscle. Most ventrally, lbe
marks individual myoblasts that give rise to the tibial depressor muscle. The number of leg myoblasts expressing lbe
gradually increases, and at the beginning of pupation, all of them express lbe
at least at a low level. Myoblasts associated with the proximal portion of the leg disc are lbe
-negative. 3D analysis reveals that lbe
myoblasts form spatially restricted groups of cells lying at highly stereotyped positions that can be correlated with defined muscles in the adult leg. In the tibia and femur at 0hr APF, the groups of lbe
-expressing myblasts are located dorsally and ventrally at positions representing the levator and the depressor muscles. They are also seen at muscle-forming sites for the trochanter and coxa. lbe
is also expressed in leg disc epithelium in the ventral region and in the long tendon.
is expressed in the two central cardioblasts of every hemisegment.
Expression in procephalic neuroblasts stage 9-11: tritocerebrum - d4; deuterocerebrum - d7; protocerebrum - cv8, pv3
gene product appears earlier, and is more abundant, than the lbl
gene product. lbe
protein first appears at stage 8 of embryogenesis, in the anal plate primordium, and subsequently in stage 10-11, in some neuroblasts and in the ectoderm of gnathal segments. At stage 10-11, expression is also detected in a cluster of cells corresponding to the heart primordium. During stage 10-13, lbe
are both expressed in the dorsal ectoderm of abdominal segments 1-7, and to a lesser extent, in the ventral ectoderm. At stage 15, lb
gene products persist in the dorsal, but not in the ventral epidermis. Later in embryogenesis, lbl
gene products are restricted to clusters of cells in the central and peripheral nervous systems, and to the segment border muscles.