Hairy and Emc negatively regulate morphogenetic furrow progression in the drosophila eye

Abstract

The initial steps of pattern formation in the developing Drosophila eye involve the coordination of cell cycles, changes in cell shape, and the specification of the R8 photoreceptor cell. These events begin several cell rows ahead of the morphogenetic furrow and are positively regulated by secreted signaling proteins and the proneural HLH transcription factor atonal (ato). Two HLH regulatory proteins that function to suppress neuronal development in other tissues, extra macrochaetae (emc) and hairy (h), are expressed ahead of the morphogenetic furrow. While neither h nor emc is required for photoreceptor cell determination, in emc-h-clones the morphogenetic furrow and differentiated eye field advance up to eight ommatidial rows ahead of adjacent wild-type tissue. This indicates that morphogenetic furrow progression and neuronal differentiation are negatively regulated by a combination of anteriorly expressed HLH regulatory proteins.

Extramacrochaetae imposes order on the Drosophila eye by refining the activity of the Hedgehog signaling gradient

“…Consistent with prior reports, we find that the furrow does not accelerate through h-null mutant clones (supplementary material Fig. S4A-G) (Brown et al, 1995). By contrast, the distance traveled…”

“…6Q,R). This synergism, which was first reported by Brown et al (Brown et al, 1995), supports a model in which emc and h are functioning separately rather than being bound together as a biochemical complex.…”

“…In older third instar eye discs, emc is transcribed throughout the entire retinal field with low expression levels within the furrow and significant enrichment ahead of the advancing furrow and at the equator ( Fig. 1F) (Brown et al, 1995). Eye discs were dissected from larvae of various ages from these enhancer trap lines and the expression pattern of emc was compared with the number of ommatidial rows.…”

Direct control of neurogenesis by selector factors in the fly eye:regulation ofatonalby Ey and So

“…Eye progenitors from this region are at a developmental stage referred to as pre-proneural and are characterized by the expression of the transcription factor Hairy (H) in addition to RD proteins (Greenwood and Struhl, 1999). In the absence of Hairy and its partner Extra Macrochaetae, neurogenesis begins precociously within the eye disc (Brown et al, 1995). Thus, Hairy contributes to the downregulation of ato expression and prevents precocious neurogenesis.…”

eyelidantagonizes wingless signaling during Drosophiladevelopment and has homology to the Bright family of DNA-binding proteins

“…Loss of eld leads to a similar disorganization that is considerably less extreme than the overproduction of neuroblasts seen in N mutants (data not shown). Additional precedents exist for effects on early stages of patterning caused by mutations that also affect neurogenesis; strawberry notch (sno) has defects at the blastoderm stage (Coyle-Thompson and Banerjee 1993), whereas hairy (h), which has neurogenic effects in the notum, wing and eye, acts as a pair-rule gene in the embryo (Rushlow et al 1989;Brown et al 1995). The groucho gene appears to function with h in segmentation, with the E(spl) genes in neurogenesis, and with deadpan in sex determination (Paroush et al 1994), in addition to repressing en expression in the wing disc and embryo (de Celis and Ruiz-Gomez 1995).…”