Effect of post-mortem delay on N-terminal huntingtin protein fragments in human control and Huntington disease brain lysates

• Published in: PloS one 2017-06, Vol.12 (6), p.e0178556-e0178556
• Main Authors: Schut, Menno H, Patassini, Stefano, Kim, Eric H, Bullock, Jocelyn, Waldvogel, Henry J, Faull, Richard L M, Pepers, Barry A, den Dunnen, Johan T, van Ommen, Gert-Jan B, van Roon-Mom, Willeke M C
• Format: Article
• Language: English
• Subjects: 3' Untranslated Regions; Aged; Aged, 80 and over; Amino Acid Sequence; Artefacts; Biology and Life Sciences; Brain; Brain - metabolism; Brain - pathology; Brain research; Care and treatment; Case-Control Studies; Cell Line; Delay; Diagnosis; Disease control; Elongation; Female; Fragmentation; Fragments; Freeze thaw cycles; Freeze-thawing; HEK293 Cells; Humans; Huntingtin; Huntingtin Protein - metabolism; Huntington Disease - metabolism; Huntington Disease - pathology; Huntington's disease; Huntingtons disease; Lysates; Male; Medicine and Health Sciences; Middle Aged; Neostriatum; Open Reading Frames; Pathogenesis; Pathology; Physical Sciences; Polyglutamine; Postmortem Changes; Proteins; Research and Analysis Methods; Risk factors; Sequence Homology, Amino Acid; Studies; Trinucleotide repeat diseases; Trinucleotide repeats
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0178556

Huntington disease is associated with elongation of a CAG repeat in the HTT gene that results in a mutant huntingtin protein. Several studies have implicated N-terminal huntingtin protein fragments in Huntington disease pathogenesis. Ideally, these fragments are studied in human brain tissue. However, the use of human brain tissue comes with certain unavoidable variables such as post mortem delay, artefacts from freeze-thaw cycles and subject-to-subject variation. Knowledge on how these variables might affect N-terminal huntingtin protein fragments in post mortem human brain is important for a proper interpretation of study results. The effect of post mortem delay on protein in human brain is known to vary depending on the protein of interest. In the present study, we have assessed the effect of post mortem delay on N-terminal huntingtin protein fragments using western blot. We mimicked post mortem delay in one individual control case and one individual Huntington disease case with low initial post mortem delay. The influence of subject-to-subject variation on N-terminal huntingtin fragments was assessed in human cortex and human striatum using two cohorts of control and Huntington disease subjects. Our results show that effects of post mortem delay on N-terminal huntingtin protein fragments are minor in our individual subjects. Additionally, one freeze-thaw cycle decreases the huntingtin western blot signal intensity in the cortex control subject, but does not introduce additional N-terminal huntingtin fragments. Our results suggest that subject-to-subject variation contributes more to variability in N-terminal huntingtin fragments than post mortem delay.