Cullin-4 regulates Wingless and JNK signaling-mediated cell death in the Drosophila eye

Abstract

In all multicellular organisms, the fundamental processes of cell proliferation and cell death are crucial for growth regulation during organogenesis. Strict regulation of cell death is important to maintain tissue homeostasis by affecting processes like regulation of cell number, and elimination of unwanted/unfit cells. The developing Drosophila eye is a versatile model to study patterning and growth, where complex signaling pathways regulate growth and cell survival. However, the molecular mechanisms underlying regulation of these processes is not fully understood. In a gain-of-function screen, we found that misexpression of cullin-4 (cul-4), an ubiquitin ligase, can rescue reduced eye mutant phenotypes. Previously, cul-4 has been shown to regulate chromatin remodeling, cell cycle and cell division. Genetic characterization of cul-4 in the developing eye revealed that loss-of-function of cul-4 exhibits a reduced eye phenotype. Analysis of twin-spots showed that in comparison with their wild-type counterparts, the cul-4 loss-of-function clones fail to survive. Here we show that cul-4 clones are eliminated by induction of cell death due to activation of caspases. Aberrant activation of signaling pathways is known to trigger cell death in the developing eye. We found that Wingless (Wg) and c-Jun-amino-terminal-(NH2)-Kinase (JNK) signaling are ectopically induced in cul-4 mutant clones, and these signals co-localize with the dying cells. Modulating levels of Wg and JNK signaling by using agonists and antagonists of these pathways demonstrated that activation of Wg and JNK signaling enhances cul-4 mutant phenotype, whereas downregulation of Wg and JNK signaling rescues the cul-4 mutant phenotypes of reduced eye. Here we present evidences to demonstrate that cul-4 is involved in restricting Wg signaling and downregulation of JNK signaling-mediated cell death during early eye development. Overall, our studies provide insights into a novel role of cul-4 in promoting cell survival in the developing Drosophila eye.

A soy protein Lunasin can ameliorate amyloid-beta 42 mediated neurodegeneration in Drosophila eye

“…Cell death was detected using TUNEL assays 27 , 53 , 54 , 90 , 91 . TUNEL assays were used to identify the cells undergoing cell death where the cleavage of double and single stranded DNA is labeled by a Fluorescent tag (TMR Red).…”

“…Adult flies were prepared for imaging by freezing at −20 °C for approximately 2 hours followed by mounting the fly on a dissection needle 54 , 86 . The needle with the fly was aligned horizontally over a glass slide using molding putty.…”

“…Previous work from our lab showed that evolutionarily conserved Wingless (Wg) and Jun-N terminal kinase (JNK) signaling pathway are tightly regulated to allow differentiation to occur and to prevent premature cell death in the developing fields 54 . Wg, a member of highly conserved Wnt/Wg, is responsible for regulating early growth, restricting eye fate and later Wg plays a role in triggering programmed cell death (PCD) 55 , 56 in the pupal retina.…”

Proximal fate marker homothorax marks the lateral extension of stalk‐eyed fly Cyrtodopsis whitei

“…The stalk‐eyed imaginal disc were photo‐documented on a Zeiss LSM510 confocal microscope. While the Drosophila eye‐antennal imaginal discs were mounted in Vectashield (Vector labs), and images were taken on Olympus Fluoview Laser scanning Confocal Microscope (Tare, Sarkar, Bedi, Kango‐Singh, & Singh, ). The final images and figures were prepared using Adobe Photoshop CS6 software.…”

A Positive Feedback Loop of Hippo- and c-Jun-Amino-Terminal Kinase Signaling Pathways Regulates Amyloid-Beta-Mediated Neurodegeneration

“…After retinal differentiation, few undifferentiated cells undergo programmed cell death (PCD) during pupal development (Brachmann and Cagan, 2003). It is notable that PCD does not normally occur during early eye development; however, cell death may occur due to abnormal signaling (Mehlen et al, 2005;Singh et al, 2006;Tare et al, 2016). We have developed a Drosophila AD model by misexpressing high levels of human Aβ42 polypeptide in the differentiating photoreceptor neurons of the developing Drosophila eye.…”