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A new water-soluble zinc(II) porphyrin has been synthesized and characterized by high resolution mass spectroscopy, elemental analysis, and electronic absorption spectroscopy. The zinc(II) porphyrin (ZnPor) is designed with three Nmethylated pyridyl groups at the meso-positions to make the compound water soluble. In addition, a meso-pentafluorophenyl substituent has been incorporated to enhance the excited state lifetime of the porphyrin. The addition of zinc(II) into the porphyrin core lends itself to longer excited lifetimes as well as the ability to coordinate to DNA bases exposed in the major groove. The ZnPor and its free-base analog (FBPor) demonstrate high binding affinity to calf thymus DNA (ctDNA) with binding constants greater than 100000 M-1. Both porphyrins show the ability to photonick DNA when irradiated within the photodynamic therapy window (600-850 nm); however, ZnPor shows enhanced photoreactions and the ability to cause double strand breaks. Under hypoxic conditions only ZnPor is capable of causing single strand breaks when irradiated with visible light. Both ZnPor and FBPor are nontoxic to the lung cancer cell line A549 in the dark at concentrations as high as 100 μM but show cytotoxicity to A549 cells at concentrations as low as 75 nM when irradiated with visible light. Studies of the ZnPor in Drosophila melanogaster indicate statistically insignificant toxicity when compared to control at concentrations well above the light-induced toxicity levels. Evidence for localization of ZnPor in the nuclei of the Drosophila salivary gland cells suggests a mechanism for cellular transport, which may prove beneficial in PDT treatment. [ABSTRACT FROM AUTHOR]

Background: One of the hallmarks of Alzheimer's disease (AD), an age‐related progressive form of dementia, is accumulation of the amyloid beta (Aβ42) plaque, which manifests in decline in cognitive function. The accumulation of these Aβ42 plaques trigger the hyperphosphorylation of tau, a microtubule associated protein, which results in the intracellular accumulation of neurofibrillary tangles (NFTs) due to destabilization of microtubules. Method: We employed the Gal4/UAS system in Drosophila melanogaster to misexpress human Aβ42 within the developing fly retina, exhibiting AD‐like neuropathology. Accumulation of Aβ42 plaque(s) triggers the aberrant activation of signaling pathways like the JNK pathway resulting in neuronal cell death by unknown mechanism(s). Using candidate based forward genetic screening, we identified N‐acetyltransferase 9 (NAT9) as one of the genetic modifiers of GMR>Aβ42 reduced eye phenotype. Previously NAT9 has been shown to stabilize microtubules by acetylation of tubulins, thereby inhibiting JNK signaling. This study aims to understand the role of NAT9 in Aβ42‐mediated neurodegeneration. Result: The gain‐of‐function of NAT9 rescues Aβ42‐mediated neurodegeneration whereas loss‐of‐function of NAT9 enhances Aβ42‐mediated neurodegeneration. We have also found that the gain‐of‐function of human NAT9 also suppresses Aβ42‐mediated neurodegeneration suggesting the functional conservation. Interestingly, mutated NAT9 in the acetyl‐ CoA binding site shows similar phenotype as gain‐of‐function of NAT9 suggesting its function is independent of acetylation activity. Moreover, the eye antennal imaginal discs of loss‐of‐function of NAT9 in GMR>Aβ42 background shows the activation of JNK pathway by increased pJNK levels. Conclusion: Our data suggests that NAT9 downregulates JNK signaling pathway which can ameliorate Aβ42‐mediated neurodegeneration. [ABSTRACT FROM AUTHOR]

The evolutionarily conserved Hippo signaling pathway is known to regulate cell proliferation and maintain tissue homeostasis during development. We found that activation of Yorkie (Yki), the effector of the Hippo signaling pathway, causes separable effects on growth and differentiation of the Drosophila eye. We present evidence supporting a role for Yki in suppressing eye fate by downregulation of the core retinal determination genes. Other upstream regulators of the Hippo pathway mediate this effect of Yki on retinal differentiation. Here, we show that, in the developing eye, Yki can prevent retinal differentiation by blocking morphogenetic furrow (MF) progression and R8 specification. The inhibition of MF progression is due to ectopic induction of Wingless (Wg) signaling and Homothorax (Hth), the negative regulators of eye development. Modulating Wgsignaling can modify Yki-mediated suppression of eye fate. Furthermore, ectopic Hth induction due to Yki activation in the eye is dependent on Wg. Last, using Cut (Ct), a marker for the antennal fate, we show that suppression of eye fate by hyperactivation of yki does not change the cell fate (from eye to antenna-specific fate). In summary, we provide the genetic mechanism by which yki plays a role in cell fate specification and differentiation - a novel aspect of Yki function that is emerging from multiple model organisms. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD, OMIM: 104300), a progressive neurodegenerative disorder with no cure to date, is caused by the generation of amyloid-beta-42 (Aβ42) aggregates that trigger neuronal cell death by unknown mechanism(s). We have developed a transgenic Drosophila eye model where misexpression of human Aβ42 results in AD-like neuropathology in the neural retina. We have identified an apical-basal polarity gene crumbs (crb) as a genetic modifier of Aβ42-mediated-neuropathology. Misexpression of Aβ42 caused upregulation of Crb expression, whereas downregulation of Crb either by RNAi or null allele approach rescued the Aβ42-mediated-neurodegeneration. Co-expression of full length Crb with Aβ42 increased severity of Aβ42-mediated-neurodegeneration, due to three fold induction of cell death in comparison to the wild type. Higher Crb levels affect axonal targeting from the retina to the brain. The structure function analysis identified intracellular domain of Crb to be required for Aβ42-mediated-neurodegeneration. We demonstrate a novel neuroprotective role of Crb in Aβ42-mediated-neurodegeneration. [ABSTRACT FROM AUTHOR]

During organogenesis in all multi-cellular organisms, axial patterning is required to transform a single layer organ primordium into a three-dimensional organ. The Drosophila eye model serves as an excellent model to study axial patterning. Dorso-ventral (DV) axis determination is the first lineage restriction event during axial patterning of the Drosophila eye. The early Drosophila eye primordium has a default ventral fate, and the dorsal eye fate is established by onset of dorsal selector gene pannier ( pnr) expression in a group of cells on the dorsal eye margin. The boundary between dorsal and ventral compartments called the equator is the site for Notch (N) activation, which triggers cell proliferation and differentiation. This review will focus on (1) chronology of events during DV axis determination; (2) how early division of eye into dorsal and ventral compartments contributes towards the growth and patterning of the fly retina, and (3) functions of DV patterning genes. Developmental Dynamics 241:69-84, 2012. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Organ size control is a fundamental and core process of development of all multicellular organisms. One important facet of organ size control is the regulation of cell proliferation and cell death. Here we address the question, What are the developmental mechanisms that control intrinsic organ size? In several multicellular animals including humans and flies, organs develop according to an instructive model where proliferation is regulated by extracellular signals. However, the signals that regulate proliferation (and organ size) remain poorly understood. Recent data from flies have shed some light on the molecular mechanisms that regulate growth and size of organs. In this review, we will briefly discuss classic studies that revealed the mysteries of growth regulation. We will then focus on the recent findings from the Drosophila Hippo signaling pathway and its role in the regulation of organ size. Finally, we will discuss the mammalian Hippo pathway, and its implications in regulation of growth/proliferation during development and disease. Developmental Dynamics 238:1627-1637, 2009. © 2009 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Merlin, the protein product of the Neurofibromatosis type-2 gene, acts as a tumour suppressor in mice and humans. Merlin is an adaptor protein with a FERM domain and it is thought to transduce a growth-regulatory signal. However, the pathway through which Merlin acts as a tumour suppressor is poorly understood. Merlin, and its function as a negative regulator of growth, is conserved in Drosophila, where it functions with Expanded, a related FERM domain protein. Here, we show that Drosophila Merlin and Expanded are components of the Hippo signalling pathway, an emerging tumour-suppressor pathway. We find that Merlin and Expanded, similar to other components of the Hippo pathway, are required for proliferation arrest and apoptosis in developing imaginal discs. Our genetic and biochemical data place Merlin and Expanded upstream of Hippo and identify a pathway through which they act as tumour-suppressor genes. [ABSTRACT FROM AUTHOR]

Background:Alzheimer's disease (AD) is a debilitating age related progressive neurodegenerative disorder characterized by the loss of cognition, and eventual death of the affected individual. One of the major causes of AD is the accumulation of Amyloid-beta 42 (Aβ42) polypeptides formed by the improper cleavage of amyloid precursor protein (APP) in the brain. These plaques disrupt normal cellular processes through oxidative stress and aberrant signaling resulting in the loss of synaptic activity and death of the neurons. However, the detailed genetic mechanism(s) responsible for this neurodegeneration still remain elusive. Methodology/ Principle Findings:We have generated a transgenic Drosophila eye model where high levels of human Aβ42 is misexpressed in the differentiating photoreceptor neurons of the developing eye, which phenocopy Alzheimer's like neuropathology in the neural retina. We have utilized this model for a gain of function screen using members of various signaling pathways involved in the development of the fly eye to identify downstream targets or modifiers of Aβ42 mediated neurodegeneration. We have identified the homeotic gene teashirt (tsh) as a suppressor of the Aβ42 mediated neurodegenerative phenotype. Targeted misexpression of tsh with Aβ42 in the differentiating retina can significantly rescue neurodegeneration by blocking cell death. We found that Tsh protein is absent/ downregulated in the neural retina at this stage. The structure function analysis revealed that the PLDLS domain of Tsh acts as an inhibitor of the neuroprotective function of tsh in the Drosophila eye model. Lastly, we found that the tsh paralog, tiptop (tio) can also rescue Aβ42 mediated neurodegeneration. Conclusions/Significance:We have identified tsh and tio as new genetic modifiers of Aβ42 mediated neurodegeneration. Our studies demonstrate a novel neuroprotective function of tsh and its paralog tio in Aβ42 mediated neurodegeneration. The neuroprotective function of tsh is independent of its role in retinal determination. [ABSTRACT FROM AUTHOR]