are coexpressed in the entire mesoderm at embryonic stage 8 and 9. By stage 10, tin
expression is restricted to the dorsal mesoderm while eya
expression is restricted to the dorsal mesoderm.
is first expressed between 2 and 4 hours of embryogenesis, peaks between 4 and 8 hours and decreases dramatically in late embryogenesis. It is not expressed postembryonically. tin
is first expressed in the cellular blastoderm embryo in the ventral-most region of the embryo. After invagination of the ventral-most cells, tin
mRNA is found exclusively in the mesoderm. During stage 9, tin
expression is reduced in some mesodermal cells and by stage 10, tin
expression is restricted to 6-8 cells on either side in the dorsal-most reigons of the mesoderm. During stage 11, each tin
-expressing region splits into two separate domains. One corresponds to part of the visceral mesoderm and the other to cells at the dorsal tip of the mesoderm that include the precursors to the heart. tin
expression continues in heart progenitors until late stages of embryogenesis when they differentiate into the dorsal blood vessel.
transcripts are expressed predominantly between 3 and 9 hours of embryogenesis and are present at low levels between 9 and 12 hours. They are first expressed along the ventral longitudinal axis in the late blastoderm just prior to the ventral invagination of the mesoderm. The strip of tin
-expressing cells is about 14-16 cells wide. After gastrulation, tin
is expressed in the mesoderm. At about 4.5 hours, the mesodermal mass starts to spread dorsally. As the cell layer reaches the dorsal margin, ventrally located mesodermal cells cease tin
expression. The dorsally located cells which are the primordia for the visceral musculature express tin
for another 1-2 hours. In stage 11, tin
expression in the dorsal mesoderm is reduced to patches of cells. tin
expression is also seen in the cephalic region at ~stage 10-11 surrounding the stomodeum. In stage 11, a row of cells at the dorsal margin begins expressing tin
. These cells which correspond to heart primordia, are the only ones that continue to express tin
after the germ band extended stage.