Advances in polyglutamine disease research & therapy Albert La Spada, M.D., Ph.D. Professor of Pediatrics and Cellular & Molecular Medicine Division Chief of Genetics, Dept. of Pediatrics Associate Director, Institute for Genomic Medicine NAF meeting March 18, 2011

Advances in molecular genetics fueled a decade (or so) of discovery (1988-2000)

CAG = glutamine (Q)

CAG / polyglutamine repeat diseases Spinal & bulbar muscular atrophy Huntington’s disease Dentatorubral pallidoluysian atrophy Spinocerebellar ataxia 1, 2, 3, 6, 7 & 17 all affect the nervous system all are dominant (except SBMA which is X-linked) all comparable median ages of onset all are slowly progressive all show a correlation between increasing expansion size and disease severity - this correlation + tendency of the repeats to expand when transmitted from parent to child explains: ANTICIPATION all are caused exclusively by CAG repeat expansions that are translated into polyglutamine tracts (except SCA6)

successive generations SCA7 pedigree (UWMC Neurogenetics Clinic) - presented with coordination problem in her late 60s d. 80 yo Example of ANTICIPATION = worsening of disease phenotype in successive generations ? - presented at age 50 with visual problems; ataxia / spasticity d. 63 yo - blind, walks with cane; 50 CAGs - presented with visual problems at age 6; developed ataxia, went blind, cognitive decline 38 yo 36 yo d. 16 yo - dysarthria, ataxia, and central scotoma 48 CAGs

...CAGCAGCAGCAGCAGCAGCAGCAGCAGCAGCAG...  DNA sequence = trinucleotide repeat expansion …QQQQQQQQQQQQQQQQQQQQQQQ... Amino acid sequence = glutamine tract expansion Protein product = misfolded conformation

Formation of protein aggregates in neurodegeneration: a common link Disease Implicated protein Histopathology CAG / polyQ Various Nuclear inclusions diseases (e.g. HD) Alzheimer’s dz APP, apoE, others Neurofibrillary tangles & beta-amyloid plaques Parkinson’s dz synuclein, others Lewy bodies ALS (Lou Gehrig’s) TDP-43 Bunina bodies Jacob-Creutzfeldt prion Prions (mad cow disease)

Towards Therapy

Normal cell in the body DNA (genes) Protein Messenger RNA The central dogma of biology DNA – RNA- protein Protein is essential for basic biological function and participate in every process that happens inside the cell

Cell affected By SCA7 Abnormal DNA Protein Toxic Incorrect message

Andrew Fire and Craig Mello won the Nobel Prize in 2006 for their discovery of RNA interference Andrew Fire Stanford University Craig Mello University of Massachussets

RNA interference was first discovered in plants and worms Petunias Round worms

RNA interference targets the messenger DNA (genes) protein

RNA interference is a promising therapy for many different diseases: Huntington’s disease 2. Other degenerative brain disorders Cancer 4. HIV

RNAi as a therapy for SCA7 X Trafficking defects Therapy targets in SCA7 X mutant atx7