Dorsal eye selector pannier (pnr) suppresses the eye fate to define dorsal margin of the Drosophila eye

Abstract

Axial patterning is crucial for organogenesis. During Drosophila eye development, dorso-ventral (DV) axis determination is the first lineage restriction event. The eye primordium begins with a default ventral fate, on which the dorsal eye fate is established by expression of the GATA-1 transcription factor pannier (pnr). Earlier, it was suggested that loss of pnr function induces enlargement in the dorsal eye due to ectopic equator formation. Interestingly, we found that in addition to regulating DV patterning, pnr suppresses the eye fate by downregulating the core retinal determination genes eyes absent (eya), sine oculis (so) and dacshund (dac) to define the dorsal eye margin. We found that pnr acts downstream of Ey and affect the retinal determination pathway by suppressing eya. Further analysis of the “eye suppression” function of pnr revealed that this function is likely mediated through suppression of the homeotic gene teashirt (tsh) and is independent of homothorax (hth), a negative regulator of eye. Pnr expression is restricted to the peripodial membrane on the dorsal eye margin, which gives rise to head structures around the eye, and pnr is not expressed in the eye disc proper that forms the retina. Thus, pnr has dual function, during early developmental stages pnr is involved in axial patterning whereas later it promotes the head specific fate. These studies will help in understanding the developmental regulation of boundary formation of the eye field on the dorsal eye margin.

Genetic architecture of natural variation in visual senescence in Drosophila

“…For example, the highly interconnected hub gene, pnr, which participates in 23 interactions in the phototaxis network (Fig. 4), encodes a GATA-1 transcription factor that regulates dorsal-ventral axis determination during Drosophila eye development and plays a role in defining the dorsal eye margin by downregulating the core retinal determination genes eya, so, and dac (64). frizzled (fz), hth, and pros function in the differentiation of cellular components of the compound eye such as ommatidia, photoreceptor, and rhabdomere cells, respectively, whereas cacophony (cac), ktub, Mob2, and rdgA play major roles in phototransduction (65)(66)(67).…”

Inhibition of Daughterless by Extramacrochaetae mediates Notch-induced cell proliferation

“…These cells express fringe ( fng), which encodes a glycosyltransferase (Irvine and Wieschaus, 1994). In the latter half of the first instar, pannier ( pnr) expression is activated along the dorsal margin of the eye and in turn Pnr protein initiates a cascade of events that leads to the repression of fng with the dorsal half of the retina (Heitzler et al, 1996;Cho and Choi, 1998;Heberlein et al, 1998;Cavodeassi et al, 1999;Yang et al, 1999;Maurel-Zaffran and Treisman, 2000;Sato and Tomlinson, 2007;Oros et al, 2010). The juxtaposition of fng-positive and fng-negative cells leads to the activation of Notch signaling at the midline, which plays an essential role in promoting localized growth in the eye (Panin et al, 1997;Cho and Choi, 1998;Domínguez and de Celis, 1998;Papayannopoulos et al, 1998).…”

Extramacrochaetae functions in dorsal-ventral patterning ofDrosophilaimaginal discs

“…Prior to the imposition of dorsal identity, the entire eye disc expresses the ventral selector gene fringe ( fng). During the late first/early second instar, expression of pannier ( pnr), which encodes a GATA transcription factor, is activated via an unknown mechanism in a small group of cells within the peripodial membrane along the dorsal margin (Heitzler et al, 1996;Maurel-Zaffran and Treisman, 2000;Oros et al, 2010). Pnr is then responsible for inducing the expression of wingless (wg) (Maurel-Zaffran and Treisman, 2000), which in turn activates expression of the Iroquois complex (Iro-C) genes within the dorsal half of the eye (McNeill et al, 1997;Heberlein et al, 1998).…”