Emily Petruccelli and Pavitra Ramachandran will present their research on 13 December 2012

Emily’s research abstract:

Drunk DopEcR Drosophila Mutants

Steroid hormones exhibit profound effects on behavior by regulating transcription through the action of nuclear hormone receptors. However, many steroids also elicit rapid responses independent of new mRNA synthesis via “non-genomic” steroid actions, the mechanisms of which remain poorly understood. Recently, Drosophila DopEcR, a G-protein coupled receptor with homology to vertebrate β-adrenergic receptors, was identified as a potential non-genomic steroid receptor. DopEcR is primarily expressed in the nervous system and activates intracellular signaling cascades in response to both the catecholamine dopamine and the major insect steroid hormone ecdysone. Since both dopamine and steroid hormones are known to affect evolutionarily conserved alcohol-induced behaviors, we examined the responses of DopEcR mutants to alcohol. Interestingly, we found that DopEcR mutants are more resistant to ethanol-induced sedation and more hyperactive during intoxication. Since knockdown of the EGF receptor (EGFR) or increase of cAMP levels restores sensitivity of DopEcR mutants to sedation, DopEcR may normally activate cAMP signaling and inhibit MAPK/Erk signaling in response to alcohol. Further observation of ethanol-induced behaviors following genetic and pharmacologic manipulations will continue to help elucidate the function and mechanism of DopEcR. Additionally, our findings offer important insight into how behavioral response to alcohol is controlled by dopamine and non-canonical steroid signaling.

Pavi’s research abstract:

RNAi therapy for polyglutamine expansion disorders

RNA interference (RNAi) therapy for autosomal dominant polyglutamine (polyQ) expansion disorders such as Huntingtons disease (HD) and spinocerebellar ataxia (SCA) 1, SCA2 and SCA7 are currently being explored in our lab. The goal of RNAi therapy in CNS disorders is to treat the disease directly by targeting silencing of the mutant gene using RNA interference (RNAi). This strategy has shown therapeutic benefit in SCA1 and HD mouse models. We have designed RNAi vectors to target ATXN7 in SCA7 and ATXN2 in SCA2.

SCA7 is unique among the polyQ diseases as it is characterized by retinal cone-rod dystrophy in addition to purkinje cell neurodegeneration. We designed RNAi vectors to test non-allele specific silencing in a mouse model of SCA7. RNAi triggers were designed to target coding sequences found in both human and mouse ATXN7 to facilitate non-allele specific silencing in the SCA7 mouse.  The RNAi triggers and a scrambled control were tested for knockdown of human mutant ATXN7-92Q in vitro in HEK293 cells. Significant knockdown of ATXN7 protein was seen with two sequences by western blot.  We are currently testing these sequences in vivo in the retina and the cerebellum using the SCA7 mouse model.

Similar to HD and SCA7, SCA2 is a neurodegenerative disorder caused by a polyQ expansion in ATXN2. RNAi sequences were designed to target coding sequences found in both human and mouse ATXN2 to facilitate non-allele specific silencing. These RNAi triggers including  a scrambled control were tested for knockdown of ATXN2 in vitro in HeLA cells, which endogenously express human ATXN2. In HeLa cells, two RNAi triggers transfected showed a significant (P<0.05) knockdown efficiency of ~25%. We are currently testing many more RNAi sequences to identify more potent sequences to target ATXN2 for SCA2 therapy.

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Posted on December 7, 2012, in Student Seminar. Bookmark the permalink. Leave a comment.

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