Development of cell free messenger RNA-based non-invasive diagnostic biomarker for Alzheimer's Disease

Alzheimer’s disease (AD) is the most common cause of dementia, affecting over 40 million people and is projected to triple by 2050. Although post-mortem examination is the gold standard for establishing AD pathology, assessment of amyloid β (Aβ) and tau levels in cerebrospinal fluid (CSF) and/or positron-emission tomography (PET) are currently used widely as surrogates. However, imaging modalities are costly and CSF procedure is invasive. Therefore, there is a need for highly accessible and cost-effective non-invasive diagnostic tests for AD and patients with mild cognitive impairment (MCI) who will eventually develop AD. Over the last two decades, circulating nucleic acids have emerged as a viable source of liquid biopsy in multiple diseases. Recent whole-transcriptome characterization studies using post-mortem human brain tissue samples have demonstrated that the transcriptional profile of AD patients differ significantly from healthy individuals. Therefore, circulating messenger RNA (mRNA) appear to be a promising non-invasive diagnostic biomarker source for AD. Although quantification of cell-free mRNAs (cf-mRNAs) was once considered challenging due to their low abundance in the circulation, we and others have developed a robust next generation sequencing (NGS) based platform for accurate quantification of cf-mRNA. Subsequently, we have conducted preliminary cf-mRNA profiling studies in multiple diseases including neurodegenerative diseases, liver diseases and cancers and demonstrated its utility as a platform to develop non-invasive biomarkers for diagnosis and monitoring of diseases. In particular, we have recently profiled plasma cf-mRNA transcriptomes of 126 AD subjects and compared to those of 115 age matched controls. We discovered that a substantial number of genes were dysregulated in plasma of AD subjects and some of these genes correlated with severity of cognitive impairment in AD subjects. These AD associated dysregulated cf-mRNA transcripts were able to robustly identify AD subjects and demonstrated the potential of cf-mRNA as a source for non-invasive biomarker development. In this proposal, we will first optimize and establish clinical-grade protocols to minimize potential variabilities for the downstream cf-mRNA Seq profiling. We will then profile the cf-mRNA transcriptome of well-characterized AD and MCI subject samples as well as other neurological diseases and build diagnostic and prognostic classifiers for AD and MCI using comprehensive bioinformatic approaches. We will subsequently validate the performance of these classifiers in intended-use clinical validation cohorts.