Broadly expressed repressors integrate patterning across orthogonal axes in embryos

Abstract

The role of spatially localized repressors in supporting embryonic patterning is well appreciated, but, alternatively, the role ubiquitously expressed repressors play in this process is not well understood. We investigated the function of two broadly expressed repressors, Runt (Run) and Suppressor of Hairless [Su(H)], in patterning the Drosophila embryo. Previous studies have shown that Run and Su(H) regulate gene expression along anterior-posterior (AP) or dorsal-ventral (DV) axes, respectively, by spatially limiting activator action, but here we characterize a different role. Our data show that broadly expressed repressors silence particular enhancers within cisregulatory systems, blocking their expression throughout the embryo fully but transiently, and, in this manner, regulate spatiotemporal outputs along both axes. Our results suggest that Run and Su(H) regulate the temporal action of enhancers and are not dedicated regulators of one axis but, instead, act coordinately to pattern both axes, AP and DV.embryonic patterning | transcriptional repressor | enhancers | Su(H) | Runt

Decoding the Notch signal

“…Although CSL binds as a monomer, recognizing a conserved 7-mer motif (Castel et al, 2013;Koromila & Stathopoulos, 2017;Tun et al, 1994), ternary complexes (NTC) containing murine NICD1 can form dimers through contacts between the convex face of the Notch1 ANK domains Nam, Sliz, Pear, Aster, & Blacklow, 2007).…”

Odd-paired is a late-acting pioneer factor coordinating with Zelda to broadly regulate gene expression in early embryos

“…Later, at nc14b, the opa mutants do exhibit expression defects. sog is diminished in opa mutant relative to wildtype ( Figure 5G); and the hb pattern found in opa mutants at nc14b is associated with an earlier pattern encompassing the full anterior cap (Koromila and Stathopoulos, 2017) . It appears that the hb_stripe enhancer's anterior stripe is expressed at lower levels in the opa mutant ( Figure 5H).…”

“…F1 MTD-Gal4/UAS-shRNA-opa females were crossed back to shRNA-opa males (#34706), and F2 embryos collected and assayed by in situ for opa mutant phenotypes. Both sh opa and classical opa1 mutant embryos exhibit loss of opa gene expression, as detected by in situ hybridization using an opa riboprobe, as described (Koromila and Stathopoulos, 2017) . In addition, other phenotypes of mutant embryos (i.e.…”

“…In a previous study, we created a reporter in which the 650 bp sog_Distal enhancer sequence was placed upstream of a heterologous promoter from the even-skipped gene ( eve.p ), driving expression of a compound reporter gene containing both tandem array of MS2 sites and the gene yellow including its introns (Koromila and Stathopoulos, 2017) . The MS2 cassette contains 24 repeats of a DNA sequence encoding an RNA stem-loop when transcribed.…”

“…-G). Opa binding (3h) is associated with enhancers that are initiated in nc14: hb_stripe (Figure 3A;Koromila and Stathopoulos, 2017;Perry et al, 2012) , slp1_DESE (Figure 3C;Prazak et al, 2010) , oc_Prox (Figure 3D;Chen et al, 2012;Perry et al, 2011) , and ind_moduleA (Figure 3G;Stathopoulos and Levine, 2005a) .…”