Early white matter pathology in the fornix of the limbic system in Huntington disease

Sanaz Gabery, Jing Eugene Kwa, Rachel Y. Cheong, Barbara Baldo, Costanza Ferrari Bardile, Brendan Tan, Catriona McLean, Nellie Georgiou-Karistianis, Govinda R. Poudel, Glenda Halliday, Mahmoud A. Pouladi, Åsa Petersén

Research output: Contribution to journalArticlepeer-review

Abstract

Huntington disease (HD) is a fatal neurodegenerative disorder caused by an expanded CAG repeat in the huntingtin (HTT) gene. The typical motor symptoms have been associated with basal ganglia pathology. However, psychiatric and cognitive symptoms often precede the motor component and may be due to changes in the limbic system. Recent work has indicated pathology in the hypothalamus in HD but other parts of the limbic system have not been extensively studied. Emerging evidence suggests that changes in HD also include white matter pathology. Here we investigated if the main white matter tract of the limbic system, the fornix, is affected in HD. We demonstrate that the fornix is 34% smaller already in prodromal HD and 41% smaller in manifest HD compared to controls using volumetric analyses of MRI of the IMAGE-HD study. In post-mortem fornix tissue from HD cases, we confirm the smaller fornix volume in HD which is accompanied by signs of myelin breakdown and reduced levels of the transcription factor myelin regulating factor but detect no loss of oligodendrocytes. Further analyses using RNA-sequencing demonstrate downregulation of oligodendrocyte identity markers in the fornix of HD cases. Analysis of differentially expressed genes based on transcription-factor/target-gene interactions also revealed enrichment for binding sites of SUZ12 and EZH2, components of the Polycomb Repressive Complex 2, as well as RE1 Regulation Transcription Factor. Taken together, our data show that there is early white matter pathology of the fornix in the limbic system in HD likely due to a combination of reduction in oligodendrocyte genes and myelin break down.

Original languageEnglish
Pages (from-to)791-806
JournalActa Neuropathologica
Volume142
Issue number5
DOIs
Publication statusPublished - 2021

Subject classification (UKÄ)

  • Neurosciences

Free keywords

  • Fornix
  • Huntingtin
  • MRI
  • Oligodendrocyte
  • RNA sequencing

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