We are the fathers of two patients with a newly diagnosed syndrome that is highlighted in the study by Enns et al. 1 Our children are two among a handful of others in the world with this disease caused by mutations in the NGLY1 gene. It is the first recognized disorder of deglycosylation. We fully anticipate that NGLY1 will generate many interesting studies for years to come, but promoting NGLY1 is not our aim here. Instead, we would like to provide you with our perspective on a shift that is occurring in clinical diagnostics. Families of children with serious genetic diseases often enter a diagnostic odyssey, moving from gene to gene in the hope of finding an explanation for the condition. Two new developments in genetics promise to dramatically shorten the time to reach a successful diagnosis: next-generation sequencing (NGS) and family engagement through social media. The very speed with which Need et al. 2 and Enns et al. 1 were published suggests a new model for clinicians and researchers. In this model, families, patients, and scientists work jointly to find new patients, confirm or refute hypotheses, exchange clinical information, enhance collaboration methods, and support research toward understanding and treatment.Our diagnostic quest started in the Fall of 2010, when a team at Duke University sequenced one of our children in an effort to measure the efficacy of exome sequencing in patients whose diagnostic journeys had become intractable. The team concluded that NGLY1 could be causal. This was game changing because the gene had not been implicated in any prior condition. It was difficult to know for sure whether the mutations Duke found were causal or not because there was only one affected patient. Beyond this limitation, many geneticists have raised concern that weak standards in declaring genetic diagnoses using NGS data could do real clinical harm. So why did the Duke team communicate with the family in the absence of a definitive diagnosis? They felt the family could understand this uncertainty (as many families can) and that sharing the NGLY1 suspicion would make the family partners in the discovery efforts. Following a demonstration in a molecular biology laboratory that the mutations found in the child eliminated the protein associated with the NGLY1 gene (this does not happen in the general population), Need et al. 2 shared their nomination of NGLY1 as a likely (but by no means certain) cause of the condition.Until very recently, the fragmented distribution of patients across institutions hindered the discovery of new rare diseases. Clinicians working with a single, isolated patient could steadily eliminate known disorders but do little more. Families would seek clinicians with the longest history and largest clinic volume to increase their chances of finding a second case, but what does a physician do when N = 1 or if the phenotype is inconsistent across patients? These challenges are driving an increase in the use of NGS. Yet this technological advance presents new challenges of its own. Per...
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.
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