title: Identification of novel alternative splicing events in the huntingtin gene and assessment of the functional consequences using structural protein homology modelling.
abstract: Huntington's disease (HD) is an inherited progressive neurodegenerative disorder caused by a pathological CAG trinucleotide repeat expansion in the large multi-exon gene, huntingtin (HTT). Although multiple pathogenic mechanisms have been proposed for HD, there is increasing interest in the RNA processing of the HTT gene. In mammals, most multi-exon genes are alternatively spliced; however, few alternative transcripts have been described for HTT. Given the numerous protein bands detected in mouse and human brain tissue by Western blotting using anti-huntingtin antibodies, we examined whether alternative splicing of HTT may account for some of these fragments. Using RT-PCR in mouse brain, we detected two novel splice variants of Htt that lacked the 111-bp exon 29 (Htt∆ex29) or retained a 57-bp portion of intron 28 (Htt(+57)in28) via use of a cryptic splice site. The alternative transcripts were present in wild-type and homozygous Hdh(Q150/Q150) mouse brain at all ages and in all brain regions and peripheral tissues studied. Differential splicing of Htt∆ex29 was found in the cerebellum of Hdh(Q150/Q150) mice with a significant reduction in transcript levels in mutant animals. In human brain, we detected similar splice variants lacking exons 28 and 29. The ability of alternatively spliced transcripts to encode different protein isoforms with individual functions in the cell, combined with the known role of splicing in disease, renders these novel transcripts of interest in the context of HD pathogenesis.
authors.affiliation: Institute of Psychological Medicine and Clinical Neuroscience, MRC Centre for Neuropsychiatric Genetics and Genomics, Hadyn Ellis Building, Cardiff University, Cardiff CF24 4HQ, UK. Electronic address: HughesAC@cardiff.ac.uk.
authors.forename: Alis C
authors.initials: AC
authors.lastname: Hughes
authors.affiliation: Institute of Medical Genetics, Cardiff University, Heath Park, Cardiff CF14 4XN, UK. Electronic address: MortM@cardiff.ac.uk.
authors.forename: Matthew
authors.initials: M
authors.lastname: Mort
authors.affiliation: Institute of Psychological Medicine and Clinical Neuroscience, MRC Centre for Neuropsychiatric Genetics and Genomics, Hadyn Ellis Building, Cardiff University, Cardiff CF24 4HQ, UK. Electronic address: EllistonLA@cardiff.ac.uk.
authors.forename: Lyn
authors.initials: L
authors.lastname: Elliston
authors.affiliation: Institute of Psychological Medicine and Clinical Neuroscience, MRC Centre for Neuropsychiatric Genetics and Genomics, Hadyn Ellis Building, Cardiff University, Cardiff CF24 4HQ, UK. Electronic address: ThomasRM5@cardiff.ac.uk.
authors.forename: Rhian M
authors.initials: RM
authors.lastname: Thomas
authors.affiliation: Brain Repair Group, School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3AX, UK. Electronic address: BrooksSP@cardiff.ac.uk.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Brooks
authors.affiliation: Brain Repair Group, School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3AX, UK. Electronic address: DunnettSB@cardiff.ac.uk.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Dunnett
authors.affiliation: Institute of Psychological Medicine and Clinical Neuroscience, MRC Centre for Neuropsychiatric Genetics and Genomics, Hadyn Ellis Building, Cardiff University, Cardiff CF24 4HQ, UK. Electronic address: JonesL1@cardiff.ac.uk.
authors.forename: Lesley
authors.initials: L
authors.lastname: Jones
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D000818:Animals; D005260:Female; D006801:Humans; D000071058:Huntingtin Protein; D008297:Male; D051379:Mice; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics*; D016133:Polymerase Chain Reaction; D050486:Serotonin Plasma Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics*; D040681:Structural Homology, Protein
chemical_list: C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D050486:Serotonin Plasma Membrane Transport Proteins; C493231:Slc6a4 protein, mouse
keywords: Huntington's disease; RNA processing; alternative transcripts; pathogenesis; protein modelling