Proteomic Profiling of Angelman Syndrome for Disease-associated Biomarker Discovery
Rachael Hawtin1, Julien Couthouis1, Showkhin Khan1, Grace Wang1, Jennifer Panagoulias2, Larry Gold3, Sean Daugherty1, Dariusz Kunecki4, Elizabeth Berry-Kravis4, Allyson Berent2
1Ultragenyx Pharmaceutical Inc., 2Foundation for Angelman Syndrome Therapeutics, 3SomaLogic Operating Co., Inc., 4Rush University Medical Center
Objective:
To explore the feasibility of identifying Angelman syndrome (AS)-associated biomarkers in the cerebrospinal fluid (CSF) of patients with AS as part of a pre-competitive consortium funded by the Foundation for Angelman Syndrome Therapeutics.
Background:
AS is a rare neurodevelopmental disorder characterized by severe impairment of speech, cognition, and motor function, as well as epilepsy and sleep disorders. Biomarkers could reduce the complexity of therapeutic development for AS by: 1) providing a measurement of target coverage, 2) connecting clinical effects with changes in underlying disease biology, and 3) allowing the development of quantifiable molecular efficacy measures that complement novel AS-specific clinical outcome measures.
Design/Methods:
CSF samples were collected from patients with AS (N=29), neurotypical controls (NTC; N=22), and genetic disease controls (GDC; N=14) comprising Niemann Pick Type C (NPC; n=10) and Batten Disease (CLN2; n=4). Mean age (years) was 6.8 for patients with AS, 13.0 for NTC, 11.3 for NPC, and 8.0 for CLN2. Proteomic profiling was performed using the aptamer-based Somalogic SomaScan® assay covering 7,000 proteins. Following quality control, a paired t-test statistical comparison was run between NTC/GDC and AS datasets. Intra-patient comparisons were also performed.
Results:
The criticality of controlling pre-analytical variables in the analysis of CSF was established following iterative QC. Three neuroligins (NLGN1, NLGN2, and NLGN3), highly expressed cell-surface molecules in central nervous system tissues that are involved in the regulation of synaptic function, were found to be increased ~2.5x in AS samples vs controls. Additional potential differentially detected molecules were identified by examination of both fold‑change and statistical significance.
Conclusions:
NLGN1, NLGN2, and NLGN3 are potential AS-associated biomarkers, a finding that should be validated using an independent sample set and with quantifiable assays specific to NLGN1, NLGN2, and NLGN3. Further analyses are ongoing.