<i>tin</i> regulates <i>Unc-5</i> expression in vivo.

<p>(A) Organization and cellular composition and development of the Drosophila dorsal vessel. Schematic represents Drosophila DV at embryonic stages 15 (migrating cells, top) and 17 (tubular heart already formed, bottom) with different cell types color-coded based on the marker TF expressed. Aortic portion is oriented anteriorly and the beating portion (heart) posteriorly. CBs are divided into Tin- (light green) or Svp-expressing SMCs (dark green) subtypes. The three most posterior pairs of Svp-expressing CBs will make the future ostial (inflow valve) cells. Pericardial cells (gray) surround the CBs on their ventrolateral side and fall into two major types; Tin-positive or Tin-negative PCs (not colored). Bottom is a schematic cross section of the heart lumen at stage 17 where CBs on opposite sides take a crescent-like shape after contact, leaving in between them a hollow luminal space. (B) <i>Unc-5</i> mRNA (magenta) is present in the DV in embryos heterozygous for <i>tin</i>^<i>346</i> (B). In <i>tinABD;tin</i>^<i>346</i><i>/tin</i>^<i>346</i> homozygous mutant embryos, however, <i>Unc-5</i> mRNA expression is significantly reduced (C). Anterior side of the embryo is to the left in panels B and C.