Shobi Veleri - Academia.edu (original) (raw)

Papers by Shobi Veleri

Cc2d2a is utilized in assembling subdistal appendages required for ciliogenesis

Investigative Ophthalmology & Visual Science, 2014

In Drosophila, naturally the circadian clock is entrained by environmental light-dark cycles. Pho... more In Drosophila, naturally the circadian clock is entrained by environmental light-dark cycles. Photoreceptors like rhodopsins and cryptochrome perceive light signals for light entrainment of the circadian clock. It is known that there is a light-dependent CRY:TIM interaction, leading to the degradation of TIM coupled with molecular re-setting of the clock-gene cyclings. However, functional double mutants (norpAP41;cryb), blocking simultaneously the known rhodopsin mediated transduction cascade and the largely unknown cryptochrome mediated transduction cascade do not confer the circadian clock absolutely blind to light signals. The double mutants� circadian clock still shows residual light entrainment ability, indicating that a novel photoreceptor entrains the circadian clock. On the other hand, in gl60j cryb double mutants the circadian clock is absolutely blind to light signals. The gl60j mutation removes morphological structures like the compound eyes and the ocelli (signaling from...

Knockdown of Bardet-Biedl Syndrome Gene BBS9 Leads to Primary Cilia Defects and Retinal Degeneration in the Zebrafish

Investigative Ophthalmology & Visual Science, 2011

Cc2d2a is required for cilia axoneme development

Investigative Ophthalmology & Visual Science, 2013

Human molecular genetics, Jun 23, 2017

In retinal photoreceptors, vectorial transport of cargo is critical for transduction of visual si... more In retinal photoreceptors, vectorial transport of cargo is critical for transduction of visual signals, and defects in intracellular trafficking can lead to photoreceptor degeneration and vision impairment. Molecular signatures associated with routing of transport vesicles in photoreceptors are poorly understood. We previously reported the identification of a novel rod photoreceptor specific isoform of Receptor Expression Enhancing Protein (REEP) 6, which belongs to a family of proteins involved in intracellular transport of receptors to the plasma membrane. Here we show that loss of REEP6 in mice (Reep6-/-) results in progressive retinal degeneration. Rod photoreceptor dysfunction is observed in Reep6-/- mice as early as one month of age and associated with aberrant accumulation of vacuole-like structures at the apical inner segment and reduction in selected rod phototransduction proteins. We demonstrate that REEP6 is detected in a subset of Clathrin-coated vesicles and interacts w...

PLoS ONE, 2012

Bardet-Biedl Syndrome (BBS, MIM#209900) is a genetically heterogeneous disorder with pleiotropic ... more Bardet-Biedl Syndrome (BBS, MIM#209900) is a genetically heterogeneous disorder with pleiotropic phenotypes that include retinopathy, mental retardation, obesity and renal abnormalities. Of the 15 genes identified so far, seven encode core proteins that form a stable complex called BBSome, which is implicated in trafficking of proteins to cilia. Though BBS9 (also known as PTHB1) is reportedly a component of BBSome, its direct function has not yet been elucidated. Using zebrafish as a model, we show that knockdown of bbs9 with specific antisense morpholinos leads to developmental abnormalities in retina and brain including hydrocephaly that are consistent with the core phenotypes observed in syndromic ciliopathies. Knockdown of bbs9 also causes reduced number and length of cilia in Kupffer's vesicle. We also demonstrate that an orthologous human BBS9 mRNA, but not one carrying a missense mutation identified in BBS patients, can rescue the bbs9 morphant phenotype. Consistent with these findings, knockdown of Bbs9 in mouse IMCD3 cells results in the absence of cilia. Our studies suggest a key conserved role of BBS9 in biogenesis and/or function of cilia in zebrafish and mammals.

Nature Communications, 2014

The primary cilium originates from the mother centriole and participates in critical functions du... more The primary cilium originates from the mother centriole and participates in critical functions during organogenesis. Defects in cilia biogenesis or function lead to pleiotropic phenotypes. Mutations in centrosome-cilia gene CC2D2A result in Meckel and Joubert syndromes. Here we generate a Cc2d2a À / À mouse that recapitulates features of Meckel syndrome including embryonic lethality and multiorgan defects. Cilia are absent in Cc2d2a À / À embryonic node and other somatic tissues; disruption of cilia-dependent Shh signalling appears to underlie exencephaly in mutant embryos. The Cc2d2a À / À mouse embryonic fibroblasts (MEFs) lack cilia, although mother centrioles and pericentriolar proteins are detected. Odf2, associated with subdistal appendages, is absent and ninein is reduced in mutant MEFs. In Cc2d2a À / À MEFs, subdistal appendages are lacking or abnormal by transmission electron microscopy. Consistent with this, CC2D2A localizes to subdistal appendages by immuno-EM in wild-type cells. We conclude that CC2D2A is essential for the assembly of subdistal appendages, which anchor cytoplasmic microtubules and prime the mother centriole for axoneme biogenesis.

Journal of Neuroscience, 2012

Cone photoreceptors are the primary initiator of visual transduction in the human retina. Dysfunc... more Cone photoreceptors are the primary initiator of visual transduction in the human retina. Dysfunction or death of rod photoreceptors precedes cone loss in many retinal and macular degenerative diseases, suggesting a rod-dependent trophic support for cone survival. Rod differentiation and homeostasis are dependent on the basic motif leucine zipper transcription factor neural retina leucine zipper (NRL). The loss of Nrl (Nrl Ϫ/Ϫ) in mice results in a retina with predominantly S-opsin-containing cones that exhibit molecular and functional characteristics of wild-type cones. Here, we report that Nrl Ϫ/Ϫ retina undergoes a rapid but transient period of degeneration in early adulthood, with cone apoptosis, retinal detachment, alterations in retinal vessel structure, and activation and translocation of retinal microglia. However, cone degeneration stabilizes by 4 months of age, resulting in a thinner but intact outer nuclear layer with residual cones expressing Sand M-opsins and a preserved photopic electroretinogram. At this stage, microglia translocate back to the inner retina and reacquire a quiescent morphology. Gene profiling analysis during the period of transient degeneration reveals misregulation of genes related to stress response and inflammation, implying their involvement in cone death. The Nrl Ϫ/Ϫ mouse illustrates the long-term viability of cones in the absence of rods and retinal pigment epithelium defects in a rodless retina. We propose that Nrl Ϫ/Ϫ retina may serve as a model for elucidating mechanisms of cone homeostasis and degeneration that would be relevant to understanding diseases of the cone-dominant human macula.

Journal of Neurochemistry, 2012

NeuroD1 encodes a basic helix-loop-helix (bHLH) transcription factor involved in the development ... more NeuroD1 encodes a basic helix-loop-helix (bHLH) transcription factor involved in the development of neural and endocrine structures, including the retina and pineal gland. To determine the effect of NeuroD1 knockout in these tissues, a Cre/loxP recombination strategy was used to target a NeuroD1 floxed gene and generate NeuroD1 conditional knockout (cKO) mice. Tissue specificity was conferred using Cre recombinase expressed under the control of the promoter of Crx, which is selectively expressed in the pineal gland and retina. At two months of age NeuroD1 cKO retinas have a dramatic reduction in rod-and cone-driven electroretinograms and contain shortened and disorganized outer segments; by four months NeuroD1 cKO retinas are devoid of photoreceptors. In contrast, the NeuroD1 cKO pineal gland appears histologically

Journal of Clinical Investigation, 2012

Cilia are highly specialized microtubule-based organelles that have pivotal roles in numerous bio... more Cilia are highly specialized microtubule-based organelles that have pivotal roles in numerous biological processes, including transducing sensory signals. Defects in cilia biogenesis and transport cause pleiotropic human ciliopathies. Mutations in over 30 different genes can lead to cilia defects, and complex interactions exist among ciliopathy-associated proteins. Mutations of the centrosomal protein 290 kDa (CEP290) lead to distinct clinical manifestations, including Leber congenital amaurosis (LCA), a hereditary cause of blindness due to photoreceptor degeneration. Mice homozygous for a mutant Cep290 allele (Cep290 rd16 mice) exhibit LCA-like early-onset retinal degeneration that is caused by an in-frame deletion in the CEP290 protein. Here, we show that the domain deleted in the protein encoded by the Cep290 rd16 allele directly interacts with another ciliopathy protein, MKKS. MKKS mutations identified in patients with the ciliopathy Bardet-Biedl syndrome disrupted this interaction. In zebrafish embryos, combined subminimal knockdown of mkks and cep290 produced sensory defects in the eye and inner ear. Intriguingly, combinations of Cep290 rd16 and Mkks ko alleles in mice led to improved ciliogenesis and sensory functions compared with those of either mutant alone. We propose that altered association of CEP290 and MKKS affects the integrity of multiprotein complexes at the cilia transition zone and basal body. Amelioration of the sensory phenotypes caused by specific mutations in one protein by removal of an interacting domain/protein suggests a possible novel approach for treating human ciliopathies.

Chronobiology International, 2004

In Drosophila circadian rhythms persist in constant darkness (DD). The small ventral Lateral Neur... more In Drosophila circadian rhythms persist in constant darkness (DD). The small ventral Lateral Neurons (s-LN v) mainly control the behavioral circadian rhythm in consortium with the large ventral Lateral Neurons (l-LN v) and dorsal Lateral Neurons (LN d). It is believed that the molecular oscillations of clock genes are the source of this persistent behavior. Indeed the s-LN v , LN d , Dorsal Neurons (DN)-DN 2 and DN 3 displayed self-sustained molecular oscillations in DD both at RNA and protein levels, except the DN 2 oscillates in anti-phase. In contrast, the l-LN v and DN 1 displayed self-sustained oscillations at the RNA level, but protein oscillations quickly dampened. Having self-sustained and dampened molecular oscillators together in the DN groups suggested that they play different roles. However, all DN groups seemed to contribute together to the light-dark (LD) behavioral rhythm. The LD entrainment of LN oscillators is achieved through Rhodopsin (RH) and Cryptochrome (CRY). CRY's expression in all DN groups implicates also its role in LD entrainment of DN, like in DN 1. However, mutations in cry and glass that did not inflict LD synchronization of the DN 2 , DN 3 oscillator implicate the existence of a novel photoreceptor at least in DN 3 .

Disease models & mechanisms, 2015

Retinal neurodegeneration associated with the dysfunction or death of photoreceptors is a major c... more Retinal neurodegeneration associated with the dysfunction or death of photoreceptors is a major cause of incurable vision loss. Tremendous progress has been made over the last two decades in discovering genes and genetic defects that lead to retinal diseases. The primary focus has now shifted to uncovering disease mechanisms and designing treatment strategies, especially inspired by the successful application of gene therapy in some forms of congenital blindness in humans. Both spontaneous and laboratory-generated mouse mutants have been valuable for providing fundamental insights into normal retinal development and for deciphering disease pathology. Here, we provide a review of mouse models of human retinal degeneration, with a primary focus on diseases affecting photoreceptor function. We also describe models associated with retinal pigment epithelium dysfunction or synaptic abnormalities. Furthermore, we highlight the crucial role of mouse models in elucidating retinal and photor...

Centriole is the pivot co‐ordinating dynamic signaling for cell proliferation and organization during early development in the vertebrates

Cell Biology International, 2021

Vertebrates have an elaborate and functionally segmented body. It evolves from a single cell by s... more Vertebrates have an elaborate and functionally segmented body. It evolves from a single cell by systematic cell proliferation but attains a complex body structure with exquisite precision. This development requires two cellular events: cell cycle and ciliogenesis. For these events, the dynamic molecular signaling is converged at the centriole. The cell cycle helps in cell proliferation and growth of the body and is a highly regulated and integrated process. Its errors cause malignancies and developmental disorders. The cells newly proliferated are organized during organogenesis. For a cellular organization, dedicated signaling hubs are developed in the cells, and most often cilia are utilized. The cilium is generated from one of the centrioles involved in cell proliferation. The developmental signaling pathways hosted in cilia are essential for the elaboration of the body plan. The cilium's compartmental seclusion is ideal for noise‐free molecular signaling and is essential for the precision of the body layout. The dysfunctional centrioles and primary cilia distort the development of body layout that manifest as serious developmental disorders. Thus, centriole has a dual role in the growth and cellular organization. It organizes dynamically expressed molecules of cell cycle and ciliogenesis and plays a balancing act to generate new cells and organize them during development. A putative master molecule may regulate and co‐ordinate the dynamic gene expression at the centrioles. The convergence of many critical signaling components at the centriole reiterates the idea that centriole is a major molecular workstation involved in elaborating the structural design and complexity in vertebrates.

NeuroMolecular Medicine, 2018

In eukaryotes, the cellular functions are segregated to membrane-bound organelles. This inherentl... more In eukaryotes, the cellular functions are segregated to membrane-bound organelles. This inherently requires sorting of metabolites to membrane-limited locations. Sorting the metabolites from ribosomes to various organelles along the intracellular trafficking pathways involves several integral cellular processes, including an energy-dependent step, in which the sorting of metabolites between organelles is catalyzed by membrane-anchoring protein Rab-GTPases (Rab). They contribute to relaying the switching of the secretory proteins between hydrophobic and hydrophilic environments. The intracellular trafficking routes include exocytic and endocytic pathways. In these pathways, numerous Rab-GTPases are participating in discrete shuttling of cargoes. Long-distance trafficking of cargoes is essential for neuronal functions, and Rabs are critical for these functions, including the transport of membranes and essential proteins for the development of axons and neurites. Rabs are also the key players in exocytosis of neurotransmitters and recycling of neurotransmitter receptors. Thus, Rabs are critical for maintaining neuronal communication, as well as for normal cellular physiology. Therefore, cellular defects of Rab components involved in neural functions, which severely affect normal brain functions, can produce neurological complications, including several neurodegenerative diseases. In this review, we provide a comprehensive overview of the current understanding of the molecular signaling pathways of Rab proteins and the impact of their defects on different neurodegenerative diseases. The insights gathered into the dynamics of Rabs that are described in this review provide new avenues for developing effective treatments for neurodegenerative diseases-associated with Rab defects. Keywords Membrane anchoring • Rab proteins • Molecular switches • Synaptic vesicles • Exocytosis • Neurodegeneration Abbreviations α-Syn Alpha-synuclein AD Alzheimer's disease Aβ Amyloid beta protein AMPA α-Amino-3-hydroxy-5-methyl-4isoxazolepropionic acid APP Amyloid precursor proteins APPL Adaptor protein phosphotyrosine interacting with PH domain and leucine zipper BBSome Bardet-Biedl syndrome BDNF Brain-derived neurotropic factor CAG Triplet nucleotide codes for glutamine CCV Clathrin-coated vesicles CMTB Charcot-Marie-Tooth-type 2B CRD Cone-rod dystrophy CR Carpenter syndrome DA Dopamine DENN Differentially expressed in normal and neoplastic cells EE Early endosomes EEA1 Early endosome adapter1 EAAC1 Glutamate/cysteine transporter ER Endoplasmic reticulum

BioMed Research International, 2014

The intra- and extracellular accumulation of misfolded and aggregated amyloid proteins is a commo... more The intra- and extracellular accumulation of misfolded and aggregated amyloid proteins is a common feature in several neurodegenerative diseases, which is thought to play a major role in disease severity and progression. The principal machineries maintaining proteostasis are the ubiquitin proteasomal and lysosomal autophagy systems, where heat shock proteins play a crucial role. Many protein aggregates are degraded by the lysosomes, depending on aggregate size, peptide sequence, and degree of misfolding, while others are selectively tagged for removal by heat shock proteins and degraded by either the proteasome or phagosomes. These systems are compromised in different neurodegenerative diseases. Therefore, developing novel targets and classes of therapeutic drugs, which can reduce aggregates and maintain proteostasis in the brains of neurodegenerative models, is vital. Natural products that can modulate heat shock proteins/proteosomal pathway are considered promising for treating ne...

Extra-retinal photoreceptors synchronise the circadian clock of Drosophila melanogaster

GBM Annual Spring meeting Mosbach 2003, 2003

Journal of Neuroscience, 2009

The neuropeptide pigment-dispersing factor (PDF) is a key transmitter in the circadian clock of D... more The neuropeptide pigment-dispersing factor (PDF) is a key transmitter in the circadian clock of Drosophila melanogaster. PDF is necessary for robust activity rhythms and is thought to couple the circadian oscillations of the clock neurons. However, little is known about the action of PDF on individual clock neurons. Here, we combined the period-luciferase reporter system with immunolabeling of clock proteins in wild-type and Pdf 01 mutants to dissect the effects of PDF on specific subgroups of clock neurons. Additionally, PDF levels were elevated to higher than normal levels using specific neural mutants, and a correlation analysis of locomotor activity and clock protein staining served to determine the periods of specific clock cells. We found that PDF has multiple effects on the clock neurons: In some groups of clock neurons, PDF was required for maintaining the oscillations of individual cells, and in others, PDF was required for synchronous cycling of the individual members. Other clock neurons cycled with high amplitude in absence of PDF, but PDF affected their intrinsic clock speed. Sometimes PDF shortened and sometimes PDF lengthened period. Our observations indicate that PDF is crucial for adjusting cycling amplitude, period, and phase of the different players in the circadian clock. Under natural conditions PDF may be required for adapting Drosophila's clock to varying photoperiods. Indeed, we show here that Pdf 01 mutants are not able to adapt their activity to long photoperiods in a wild-type manner.

Proceedings of the National Academy of Sciences, 2006

Organisms use the daily cycles of light and darkness to synchronize their internal circadian cloc... more Organisms use the daily cycles of light and darkness to synchronize their internal circadian clocks with the environment. Because they optimize physiological processes and behavior, properly synchronized circadian clocks are thought to be important for the overall fitness. In Drosophila melanogaster , the circadian clock is synchronized with the natural environment by light-dependent degradation of the clock protein Timeless, mediated by the blue-light photoreceptor Cryptochrome (Cry). Here we report identification of a genetic variant, Veela , which severely disrupts this process, because these genetically altered flies maintain behavioral and molecular rhythmicity under constant-light conditions that usually stop the clock. We show that the Veela strain carries a natural timeless allele ( ls-tim ), which encodes a less-light-sensitive form of Timeless in combination with a mutant variant of the F-box protein Jetlag. However, neither the ls-tim nor the jetlag genetic variant alone ...

Current Biology, 2003

negative feedback loop (reviewed in [1]). In flies the most prominent biological rhythm con-Insti... more negative feedback loop (reviewed in [1]). In flies the most prominent biological rhythm con-Institut fü r Zoologie Lehrstuhl fü r Entwicklungsbiologie trolled by the circadian clock is the rest-activity cycle. Under free-running conditions of constant darkness and 93040 Regensburg Germany constant temperature (DD), this rhythm persists for at least five weeks (e.g., [2]). In stark contrast to these 2 Department of Biology Brandeis University robust behavioral rhythms, studies of clock-gene expression under such free-running conditions revealed a Waltham, Massachusetts 02454 rapid dampening of molecular oscillations within 2-4 days [1]. It is therefore not proven if cycling gene products are required for generating behavioral rhythmicity. Summary Several arguments have been put forward in order to explain the observed discrepancies. (1) Molecular rhythms Background: The circadian clock of Drosophila is able are usually measured after extraction of mRNA or protein to drive behavioral rhythms for many weeks in continufrom many individuals (typically 30-50) at a given time of ous darkness (DD). The endogenous rhythm generator day. Since the internal free-running periods vary slightly is thought to be generated by interlocked molecular between the different animals, this will lead to an overall feedback loops involving circadian transcriptional and amplitude dampening the longer the flies are kept in posttranscriptional regulation of several clock genes, DD (e.g., [3, 4]). (2) Many tissues within one fly contain including period. However, all attempts to demonstrate circadian clocks (e.g., [5, 6]). Without entrainment cues sustained rhythms of clock gene expression in DD have they could internally desynchronize, resulting in damped failed, making it difficult to link the molecular clock modmolecular rhythms when all such tissues are monitored els with the circadian behavioral rhythms. Here we resimultaneously; the same could also apply for the clock stricted expression of a novel period-luciferase transcells within a given tissue. (3) There is a qualitative differgene to certain clock neurons in the Drosophila brain, ence between "pacemaker oscillators" (e.g., those drivpermitting us to monitor reporter gene activity in these ing robust behavioral rhythms) and "peripheral oscillacells in real-time. tors" (e.g., the fly's eyes, in which clock gene expression Results: We show that only a subset of the previously has been analyzed for the majority of chronomolecular described pacemaker neurons is able to sustain PERIOD studies); only bona-fide pacemakers are able to maintain protein oscillations after 5 days in constant darkness. molecular oscillations in DD. Establishment of luciferase In addition, we identified a sustained and autonomous as a real-time reporter gene helped to rule out the first molecular oscillator in a group of clock neurons in the possibility; recordings from individual transgenic perdorsal brain with heretofore unknown function. We luc flies also showed rapid dampening in DD [7]. Tofound that these "dorsal neurons" (DNs) can synchrogether with the finding that isolated Drosophila body nize behavioral rhythms and that light input into these parts and organs contain circadian clocks (e.g., [5, 6, 8, cells involves the blue-light photoreceptor cryptochrome. 9]), this made the second possibility seem likely. But the Conclusions: Our results suggest that the DNs play a fact that transcriptional rhythms in individually cultured prominent role in controlling locomotor behavior when body parts and organs also rapidly dampen in DD favors flies are exposed to natural light-dark cycles. Analysis the third argument [5, 6, 9]. Therefore, true circadian of similar "stable mosaic" transgenes should help to molecular oscillations could be a unique feature of a set reveal the function of the other clock neuronal clusters of brain neurons known to control behavioral rhythmicity within the fly brain. (e.g., [10, 11]). Little is known about the features of molecular oscilla

Brain Research, 2007

Hypobaric hypoxia (HH), a predisposing environmental condition at high altitude (HA), encountered... more Hypobaric hypoxia (HH), a predisposing environmental condition at high altitude (HA), encountered by many mountaineers, jeopardizes their normal physiology like motor coordination and cognitive functions. A large body of evidence shows that HH has deleterious effect on cognitive functions. Among them the hippocampal dependent memory deficit is well known. However, our current understanding of the mechanistic details of cognitive deficits at HA remains largely unclear and hence limits a solution for this problem. Therefore, the present study was designed to investigate the temporal component of the hippocampal pyramidal neuron damage in the rat brain subjected to chronic HH exposure. Three groups (sham HH, 3 days HH and 7 days HH) of rats were exposed to simulated HH equivalent to 6100 m in an animal decompression chamber for 3 or 7 days. Later, the hippocampal (CA1 and CA3) neurons were analysed for the cell morphology, neurodegeneration and DNA fragmentation. The CA1 and CA3 neurons showed HH induced neuronal pyknosis, cell shrinkage, and consequent inter-cellular vacuolization in the CA1 and CA3 areas. In addition, the total neuron (intact) numbers and mean surface area were decreased. The number of dead neurons increased significantly following exposure to HH for 3 or 7 days. The neurodegenerative (Fluoro jade B) and apoptotic (TUNEL) markers were more positive in CA1 and CA3 neurons. The magnitude of morphological changes, neurodegeneration and apoptosis was enhanced in 7 days HH group than 3 days HH group. Our studies indicate that CA3 neurons are more vulnerable to HH than CA1 neurons, and that may destabilize the neural circuits in the hippocampus and thus cause memory dysfunction.