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J Inherit Metab Dis. 2018 May;41(3):447-456. doi: 10.1007/s10545-017-0134-3. Epub 2018 Feb 8.

Targeted versus untargeted omics - the CAFSA story.

Author information

1
Assistance Publique-Hôpitaux de Paris, Département de Neurologie, La Pitié-Salpêtrière University Hospital, Paris, France.
2
Service de Pharmacologie et Immuno-Analyse (SPI), Laboratoire d'Etude du Métabolisme des Médicaments, CEA, INRA, Université Paris Saclay, MetaboHUB, F-91191, Gif-sur-Yvette, France.
3
Assistance Publique-Hôpitaux de Paris, Laboratoire de Biochimie Métabolique, La Pitié-Salpêtrière University Hospital, Paris, France.
4
Université Pierre et Marie Curie, Groupe de Recherche Clinique Neurométabolique et Centre de Référence Neurométabolique Adulte, Paris, France.
5
Institute of Cardiometabolism And Nutrition, ICAN, Metabolomics Core Facility, Paris, France.
6
Sorbonne Universités, UPMC-Paris 6, UMR S 1127, and Inserm U 1127, and CNRS UMR 7225, and ICM, F-75013, Paris, France.
7
MedDay Pharmaceuticals, Paris, France.
8
Université de Toulouse, INRA, Université de Toulouse 3 Paul Sabatier, Toulouse, France.
9
Radboud University Medical Centre, Translational Metabolic Laboratory, Department Laboratory Medicine, Nijmegen, the Netherlands.
10
Hôpitaux Universitaires de Strasbourg, Unité de cytogénétique chromosomique et moléculaire, Strasbourg, France.
11
Université Pierre et Marie Curie, Groupe de Recherche Clinique Neurométabolique et Centre de Référence Neurométabolique Adulte, Paris, France. fanny.mochel@upmc.fr.
12
Sorbonne Universités, UPMC-Paris 6, UMR S 1127, and Inserm U 1127, and CNRS UMR 7225, and ICM, F-75013, Paris, France. fanny.mochel@upmc.fr.
13
Assistance Publique-Hôpitaux de Paris, Département de Génétique, La Pitié-Salpêtrière University Hospital, Paris, France. fanny.mochel@upmc.fr.
14
Reference Center for Neurometabolic Diseases, Department of Genetics, La Pitié-Salpêtrière University Hospital, 47 Boulevard de l'Hôpital, 75013, Paris, France. fanny.mochel@upmc.fr.

Abstract

BACKGROUND:

In 2009, untargeted metabolomics led to the delineation of a new clinico-biological entity called cerebellar ataxia with elevated cerebrospinal free sialic acid, or CAFSA. In order to elucidate CAFSA, we applied sequentially targeted and untargeted omic approaches.

METHODS AND RESULTS:

First, we studied five of the six CAFSA patients initially described. Besides increased CSF free sialic acid concentrations, three patients presented with markedly decreased 5-methyltetrahydrofolate (5-MTHF) CSF concentrations. Exome sequencing identified a homozygous POLG mutation in two affected sisters, but failed to identify a causative gene in the three sporadic patients with high sialic acid but low 5-MTHF. Using targeted mass spectrometry, we confirmed that free sialic acid was increased in the CSF of a third known POLG-mutated patient. We then pursued pathophysiological analyses of CAFSA using mass spectrometry-based metabolomics on CSF from two sporadic CAFSA patients as well as 95 patients with an unexplained encephalopathy and 39 controls. This led to the identification of a common metabotype between the two initial CAFSA patients and three additional patients, including one patient with Kearns-Sayre syndrome. Metabolites of the CSF metabotype were positioned in a reconstruction of the human metabolic network, which highlighted the proximity of the metabotype with acetyl-CoA and carnitine, two key metabolites regulating mitochondrial energy homeostasis.

CONCLUSION:

Our genetic and metabolomics analyses suggest that CAFSA is a heterogeneous entity related to mitochondrial DNA alterations either through POLG mutations or a mechanism similar to what is observed in Kearns-Sayre syndrome.

KEYWORDS:

Cerebellar ataxia; Exome; Folate; Metabolomics. Cerebrospinal fluid; Mitochondrial disease; Sialic acid

PMID:
29423831
DOI:
10.1007/s10545-017-0134-3

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