DNA Damage Signatures in Peripheral Blood Cells as Biomarkers in Prodromal Huntington's Disease

Abstract

Background: Blood biomarkers, that may improve the management of the pre−manifest phase of Huntington's disease (PRE−HD), are actively searched. We investigated telomere length (TL) and DNA damage signatures (DDS) as potential predictive biomarkers in peripheral blood mononuclear cells (PBMC) of PRE−HD and HD patients. Methods: We analysed the DNA isolated from fresh PBMC of 58 HD and 23 PRE−HD subjects with similar CAG expansion in the huntingtin (HTT) gene (44·20±2·85, 43·55±2·70; mean±SD) and 44 healthy controls (HC). We measured the TL by qPCR and double−strand DNA breaks by flow cytometric analysis of phosphorylated γ−H2AX (pγ−H2AX). Findings: PBMC from PRE−HD and HD groups showed shorter telomeres (p<0·0001) and significant increase of DDS compared to the controls (p<0·0001). Four individuals with pre−HD were monitored at several time points: the pγ−H2AX signal increased overtime; in three of them pγ−H2AX levels decreased with the appearance of clinical signs, although remained higher compared to HC. In PRE−HD subjects, the baseline levels of pγ−H2AX correlated robustly with the progression of the HD phenotype measured after three years. Interpretation: PBMC from PRE−HD subjects show progressive DDS in the absence of clinical signs. The basal levels of DNA damage are predictive factors of disease progression over time. The availability of an easily accessible and detectable biomarker in PRE−HD, negligible in HC, and potentially reversible, provides a novel tool to identify patient−specific drugs that prevent or slow down the appearance of HD phenotype in carriers. Funding Statement: LIRH Foundation received funding from the Cure Huntington’s Disease Initiative Foundation for collecting patient data and samples in the REGISTRY and ENROLL-HD platforms and from the Italian Government (funds from “5x1000” of taxes). The Italian Ministry of Health supports the research on Huntington’s disease to IRCCS Casa Sollievo della Sofferenza (CSS, funds from Ricerca Corrente [RC1601MD13] and from Ricerca Finalizzata [RF2016-02364123] to FS and SM). GR received funding from the University of Rome La Sapienza (Ricerca di Ateneo RM116154EC242C10). GR and SR received funding from the Cure Huntington’s Disease Initiative Foundation for collecting patient data and samples in the REGISTRY and ENROLLHD platforms. Declaration of Interests: All the authors declare no competing interests. Ethics Approval Statement: All human studies were carried in compliance with the Declaration of Helsinki, approved by local ethics committees and all participants have given written informed consent.