A Fresh Look at Huntingtin mRNA Processing in Huntington\u27s Disease

Huntington\u27s disease (HD) is an inherited neurodegenerative disorder caused by a mutation that expands the polyglutamine (CAG) repeat in exon 1 of the huntingtin (HTT) gene. Wild-type HTT protein interacts with other proteins to protect cells against toxic stimuli, mediate vesicle transport and endocytosis, and modulate synaptic activity. Mutant HTT protein disrupts autophagy, vesicle transport, neurotransmitter signaling, and mitochondrial function. Although many of the activities of wild-type HTT protein and the toxicities of mutant HTT protein are characterized, less is known about the activities of HTT mRNA. Most putative HD therapies aim to target mutant HTT mRNA before it is translated into the protein. Therefore, it is imperative to learn as much as we can about how cells handle both wild-type and mutant HTT mRNA so that effective therapies can be designed. Here, we review the structure of wild-type and mutant HTT mRNA, with emphasis on their alternatively polyadenylated or spliced isoforms. We then consider the abundance of HTT mRNA isoforms in HD and discuss the potential implications of these findings. Evidence in the review should be used to guide future research aimed at developing mRNA-lowering therapies for HD

Switching the stereochemical outcome of 6-endo-trig cyclizations; Synthesis of 2,6-Cis-6-substituted 4-oxopipecolic acids

A base-mediated 6-endo-trig cyclization of readily accessible enone-derived α-amino acids has been developed for the direct synthesis of novel 2,6-cis-6- substituted-4-oxo-L-pipecolic acids. A range of aliphatic and aryl side chains were tolerated by this mild procedure to give the target compounds in good overall yields. Molecular modeling of the 6-endo-trig cyclization allowed some insight as to how these compounds were formed, with the enolate intermediate generated via an equilibrium process, followed by irreversible tautomerization/neutralization providing the driving force for product formation. Stereoselective reduction and deprotection of the resulting 2,6-cis-6-substituted 4-oxo-L-pipecolic acids to the corresponding 4-hydroxy-L-pipecolic acids was also performed

Alterations in mRNA 3′UTR Isoform Abundance Accompany Gene Expression Changes in Huntington\u27s Disease

Huntington’s disease is a neurodegenerative disorder caused by expansion of the CAG repeat in huntingtin exon 1. Early studies demonstrated the huntingtin gene is transcribed into two 3′UTR isoforms in normal human tissue. Decades later, researchers identified a truncated huntingtin mRNA isoform in disease but not control human brain. We speculated the amount of huntingtin 3′UTR isoforms might also vary between control and Huntington’s disease brains. We provide evidence that the abundance of huntingtin 3′UTR isoforms, including a novel mid-3′UTR isoform, differs between patient and control neural stem cells, fibroblasts, motor cortex, and cerebellum. Both alleles of huntingtin contribute to isoform changes. We show huntingtin 3′UTR isoforms are metabolized differently. The long and mid isoforms have shorter half-lives, shorter polyA tails, and more microRNA and RNA binding protein sites than the short isoform. 3′UTR Isoform changes are not limited to huntingtin. Isoforms from 11% of genes change abundance in Huntington’s motor cortex. Only 17% of genes with isoform alterations are differentially expressed in disease tissue. However, gene ontology analysis suggests they share common pathways with differentially expressed genes. We demonstrate knockdown of the RNA binding protein CNOT6 in control fibroblasts results in huntingtin isoform changes similar to those in disease fibroblasts. This study further characterizes Huntington’s disease molecular pathology and suggests RNA binding protein expression may influence mRNA isoform expression in the Huntington’s disease brain

RegVar annotation files

Required annotation files for RegVar; must be in correct directory according to github, https://github.com/RomoL2/RegVar (for example, located in: /Library/Frameworks/R.framework/Versions/4.0/Resources/library//RegVar/inst/extdata)

RegVar annotation files

Required annotation files for RegVar; must be in correct directory according to github, https://github.com/RomoL2/RegVar (for example, located in: /Library/Frameworks/R.framework/Versions/4.0/Resources/library//RegVar/inst/extdata)

RegVar annotation files

Required annotation files for RegVar; must be in correct directory according to github, https://github.com/RomoL2/RegVar (for example, located in: /Library/Frameworks/R.framework/Versions/4.0/Resources/library//RegVar/inst/extdata)

Alterations in mRNA 3′ UTR Isoform Abundance Accompany Gene Expression Changes in Human Huntington’s Disease Brains

The huntingtin gene has two mRNA isoforms that differ in their 3′ UTR length. The relationship of these isoforms with Huntington’s disease is not established. We provide evidence that the abundance of huntingtin 3′ UTR isoforms differs between patient and control neural stem cells, fibroblasts, motor cortex, and cerebellum. Huntingtin 3′ UTR isoforms, including a mid-3′ UTR isoform, have different localizations, half-lives, polyA tail lengths, microRNA sites, and RNA-binding protein sites. Isoform shifts in Huntington’s disease motor cortex are not limited to huntingtin; 11% of alternatively polyadenylated genes change the abundance of their 3′ UTR isoforms. Altered expression of RNA-binding proteins may be associated with aberrant isoform abundance; knockdown of the RNA-binding protein CNOT6 in control fibroblasts leads to huntingtin isoform differences similar to those in disease fibroblasts. These findings demonstrate that mRNA 3′ UTR isoform changes are a feature of molecular pathology in the Huntington’s disease brain