Abstract

Substrate derived biomarkers are necessary in slowly progressing monogenetic diseases caused by single enzyme deficiencies to identify affected patients and serve as surrogate markers for therapy response. N-glycanase 1 (NGLY1) deficiency is an ultra-rare autosomal recessive disorder characterized by developmental delay, peripheral neuropathy, elevated liver transaminases, hyperkinetic movement disorder, and (hypo)-alacrima. We demonstrate that N-acetylglucosamine-asparagine (GlcNAc-Asn; GNA), is the analyte most closely associated with NGLY1 deficiency, showing consistent separation in levels between patients and controls. GNA accumulation is directly linked to the absence of functional NGLY1, presenting strong potential for its use as a biomarker. In agreement, a quantitative LC-MS/MS assay, developed to assess GNA from 3 to 3000 ng/mL, showed it is conserved as a marker for loss of NGLY1 function in NGLY1 deficient cell lines, rodents (urine, cerebrospinal fluid, plasma, and tissues), and patients (plasma and urine). Elevated GNA levels differentiate patients from controls, are stable over time, and correlate with changes in NGLY1 activity. GNA as a biomarker has the potential to identify and validate patients with NGLY1 deficiency, act as a direct pharmacodynamic marker, and serve as a potential surrogate endpoint in clinical trials.

View details for DOI 10.1093/jb/mvab111

View details for PubMedID 34697629