ABSTRACT
Extended CAG trinucleotide repeats (TNR) in the genes huntingtin (HTT) and androgen receptor (AR) are the cause of two progressive neurodegenerative disorders: Huntington's disease (HD) and Spinal and Bulbar Muscular Atrophy (SBMA), respectively. Anyone who inherits the mutant gene in the complete penetrance range (>39 repeats for HD and 44 for SBMA) will develop the disease. An inverse correlation exists between the length of the CAG repeat and the severity and age of onset of the diseases. Growing evidence suggests that it is the length of uninterrupted CAG repeats in the mRNA rather than the length of poly glutamine (polyQ) in mutant (m)HTT protein that determines disease progression. One variant of mHTT (loss of inhibition; LOI) causes a 25 year earlier onset of HD when compared to a reference sequence, despite both coding for a protein that contains an identical number of glutamines. Short 21-22 nt CAG repeat (sCAGs)-containing RNAs can cause disease through RNA interference (RNAi). RNA hairpins (HPs) forming at the CAG TNRs are stabilized by adjacent CCG (in HD) or CUG repeats (in SBMA) making them better substrates for Dicer, the enzyme that processes CAG HPs into sCAGs. We now show that cells deficient in Dicer or unable to mediate RNAi are resistant to the toxicity of the HTT and AR derived HPs. Expression of a small HP that mimics the HD LOI variant is more stable and more toxic than a reference HP. We report that the LOI HP is processed by Dicer, loaded into the RISC more efficiently, and gives rise to a higher quantity of RISC-bound 22 nt sCAGs. Our data support the notion that RNAi contributes to the cell death seen in HD and SBMA and provide an explanation for the dramatically reduced onset of disease in HD patients that carry the LOI variant.
Subject(s)
Huntington Disease , Trinucleotide Repeat Expansion , Humans , RNA Interference , Trinucleotide Repeat Expansion/genetics , Trinucleotide Repeats/genetics , Huntington Disease/genetics , Huntington Disease/metabolism , RNA, Messenger/metabolism , Huntingtin Protein/genetics , Huntingtin Protein/metabolismABSTRACT
To evaluate SARS-CoV-2 variants we isolated SARS-CoV-2 temporally during the pandemic starting with first appearance of virus in the Western hemisphere near Seattle, WA, USA, and isolated each known major variant class, revealing the dynamics of emergence and complete take-over of all new cases by current Omicron variants. We assessed virus neutralization in a first-ever full comparison across variants and evaluated a novel monoclonal antibody (Mab). We found that convalescence greater than 5-months provides little-to-no protection against SARS-CoV-2 variants, vaccination enhances immunity against variants with the exception of Omicron BA.1, and paired testing of vaccine sera against ancestral virus compared to Omicron BA.1 shows that 3-dose vaccine regimen provides over 50-fold enhanced protection against Omicron BA.1 compared to a 2-dose regimen. We also reveal a novel Mab that effectively neutralizes Omicron BA.1 and BA.2 variants over clinically-approved Mabs. Our observations underscore the need for continued vaccination efforts, with innovation for vaccine and Mab improvement, for protection against variants of SARS-CoV-2. SummaryWe isolated SARS-CoV-2 temporally starting with emergence of virus in the Western hemisphere. Neutralization analyses across all variant lineages show that vaccine-boost regimen provides protection against Omicron BA.1. We reveal a Mab that protects against Omicron BA.1 and BA.2 variants.
