Enzymatic diagnosis of neuronal lipofuscinoses in dried blood spots using substrates for concomitant tandem mass spectrometry and fluorimetry

Michael Przybylski (1948-2023) Devoted Half a Century to Mass Spectrometry

Michael Przybylski (1948-2023) was a Polymer Chemist by training and devoted nearly his entire scientific life, almost 50 years, to mass spectrometry and its biomedical applications. After earning his PhD in Chemistry, there followed a Postdoc stay at the National Cancer Institute, Bethesda, MD, USA, and his habilitation at the University of Mainz, Germany. Soon thereafter, Michael Przybylski took the Chair for Analytical Chemistry at the University of Konstanz, Germany, where he served as Director of the Analytical Chemistry and Biopolymer Structure Analysis Laboratory. As Emeritus Michael Przybylski moved the Steinbeis Centre for Biopolymer Analytics and Biomedical Mass Spectrometry to Rüsselsheim, Germany. Michael Przybylski's research was from the beginning interdisciplinary-oriented and in many ways groundbreaking: leading to over 400 scientific papers published in internationally renowned journals and to about 25 patents. Michael Przybylski gave approximately 150 invited lectures and was awarded several scientific prizes. In recognition of his outstanding achievements and fruitful collaboration, he received the Doctorate of honor from the "Alexandru Ioan Cuza" University of Iaşi, Romania. Michael Przybylski was the Director of the by him founded "Biopolymer Analytics and Biomedical Mass Spectrometry" research center until his sudden and unexpected death.

Neuronal Ceroid Lipofuscinosis: The Multifaceted Approach to the Clinical Issues, an Overview

The main aim of this review is to summarize the current state-of-art in the field of childhood Neuronal Ceroid Lipofuscinosis (NCL), a group of rare neurodegenerative disorders. These are genetic diseases associated with the formation of toxic endo-lysosomal storage. Following a brief historical review of the evolution of NCL definition, a clinically-oriented approach is used describing how the early symptoms and signs affecting motor, visual, cognitive domains, and including seizures, may lead clinicians to a rapid molecular diagnosis, avoiding the long diagnostic odyssey commonly observed. We go on to focus on recent advances in NCL research and summarize contributions to knowledge of the pathogenic mechanisms underlying NCL. We describe the large variety of experimental models which have aided this research, as well as the most recent technological developments which have shed light on the main mechanisms involved in the cellular pathology, such as apoptosis and autophagy. The search for innovative therapies is described. Translation of experimental data into therapeutic approaches is being established for several of the NCLs, and one drug is now commercially available. Lastly, we show the importance of palliative care and symptomatic treatments which are still the main therapeutic interventions.

The LINCE Project: A Pathway for Diagnosing NCL2 Disease

INTRODUCTION

Neuronal Ceroid Lipofuscinosis (NCL) comprises a clinically and genetically heterogeneous group of 13 neurodegenerative lysosomal storage disorders. Neuronal Ceroid lipofuscinosis type 2 disease (NCL2), caused by the deficient lysosomal enzyme tripeptidyl peptidase 1 (TPP1), is the only one with an approved enzyme replacement treatment (ERT). Early initiation of ERT appears to modify significantly the natural history of the disease. We aimed to shorten the time to diagnosis of NCL2.

METHODS

In March 2017, we started per first time in Spain a selective screening program, the LINCE project, in pediatric patients with clinical symptoms compatible with NCL2 disease. The program covered the whole country. We distributed kits to pediatricians with the necessary material to assess patients. All samples in this study were received within one week of collection. Enzymatic activity determined on dried blood spots was the main method used to screen for TPP1 and palmitoyl protein thioesterase 1 (PPT1) for the differential diagnosis with neuronal ceroid lipofuscinosis type 1 (NCL1).

RESULTS

Over a period of three years, we received 71 samples. The analysis was minimally invasive, relatively cheap and fast-executing. Three cases identified as a direct result of the selective screening strategy were confirmed by genetic study of NCL2 disease with a median age of 4.5 years. Our screening method has a specificity of 100%, and, with the absence to date of false negatives. We did not detect any NCL1-positive cases.

CONCLUSIONS

LINCE proved to be a simple, useful, and reliable tool for the diagnosis of NCL2, enabling clinicians to diagnose NCL2 faster. The presence of NCL2-positive cases in our population and availability of treatment may facilitate the inclusion of NCL2 in neonatal screening programs for early diagnosis.