Abstract
Background: Whole exome sequencing (WES) offers a powerful diagnostic tool to rapidly and efficiently sequence all coding genes in individuals presenting for consideration of phenotypically and genetically heterogeneous disorders such as suspected mitochondrial disease. Here, we report results of WES and functional validation in a consanguineous Indian kindred where two siblings presented with profound developmental delay, congenital hypotonia, refractory epilepsy, abnormal myelination, fluctuating basal ganglia changes, cerebral atrophy, and reduced N-acetylaspartate (NAA).
Methods: Whole blood DNA from one affected and one unaffected sibling was captured by Agilent SureSelect Human All Exon kit and sequenced on the Illumina HiSeq2000. Mutations were validated by Sanger sequencing in all family members. Protein from wild-type and mutant fibroblasts was isolated to assess mutation effects on protein expression and enzyme activity.
Results: A novel SLC25A12 homozygous missense mutation, c.1058G>A; p.Arg353Gln, segregated with disease in this kindred. SLC25A12 encodes the neuronal aspartate-glutamate carrier 1 (AGC1) protein, an essential component of the neuronal malate/aspartate shuttle that transfers NADH and H+ reducing equivalents from the cytosol to mitochondria. AGC1 activity enables neuronal export of aspartate, the glial substrate necessary for proper neuronal myelination. Recombinant mutant p.Arg353Gln AGC1 activity was reduced to 15% of wild type. One prior reported SLC25A12 mutation caused complete loss of AGC1 activity in a child with epilepsy, hypotonia, hypomyelination, and reduced brain NAA.
Conclusions: These data strongly suggest that SLC25A12 disease impairs neuronal AGC1 activity. SLC25A12 sequencing should be considered in children with infantile epilepsy, congenital hypotonia, global delay, abnormal myelination, and reduced brain NAA.
Competing interests: None declared
Authors Marni J. Falk and Dong Li contributed equally
An erratum to this chapter can be found at http://dx.doi.org/10.1007/8904_2014_314
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
Calvo SE, Compton AG, Hershman SG, et al (2012) Molecular diagnosis of infantile mitochondrial disease with targeted next-generation sequencing. Sci Trans Med 4(118): 118ra110
Falk MJ, Pierce EA, Consugar M et al (2012) Mitochondrial disease genetic diagnostics: optimized whole-exome analysis for all MitoCarta nuclear genes and the mitochondrial genome. Discov Med 14(79):389–399
Fiermonte G, Paradies E, Todisco S, Marobbio CM, Palmieri F (2009) A novel member of solute carrier family 25 (SLC25A42) is a transporter of coenzyme A and adenosine 3',5'-diphosphate in human mitochondria. J Biol Chem 284(27):18152–18159
Haas RH, Parikh S, Falk MJ et al (2007) Mitochondrial disease: a practical approach for primary care physicians. Pediatrics 120(6):1326–1333
Haas RH, Parikh S et al (2008) The in-depth evaluation of suspected mitochondrial disease: Mitochondrial Medicine Society's Committee on diagnosis. Mol Genet Metab 94(1):16–37
Iijima M, Jalil A, Begum L et al (2001) Pathogenesis of adult-onset type II citrullinemia caused by deficiency of citrin, a mitochondrial solute carrier protein: tissue and subcellular localization of citrin. Adv Enzyme Regul 41:325–342
Lasorsa FM, Pinton P, Palmieri L, Fiermonte G, Rizzuto R, Palmieri F (2003) Recombinant expression of the Ca(2+)-sensitive aspartate/glutamate carrier increases mitochondrial ATP production in agonist-stimulated Chinese hamster ovary cells. J Biol Chem 278(40):38686–38692
McCormick E, Place E, Falk MJ (2013) Molecular genetic testing for mitochondrial disease: from one generation to the next. Neurotherapeutics: J Am Soc Exper NeuroTherap 10(2):251–261
Molinari F, Raas-Rothschild A, Rio M et al (2005) Impaired mitochondrial glutamate transport in autosomal recessive neonatal myoclonic epilepsy. Am J Hum Genet 76(2):334–339
Molinari F, Kaminska A, Fiermonte G et al (2009) Mutations in the mitochondrial glutamate carrier SLC25A22 in neonatal epileptic encephalopathy with suppression bursts. Clin Genet 76(2):188–194
Palmieri F (2004) The mitochondrial transporter family (SLC25): physiological and pathological implications. Pflugers Archiv: Eur J Physiol 447(5):689–709
Palmieri F (2013) The mitochondrial transporter family SLC25: identification, properties and physiopathology. Mol Aspects Med 34(2–3):465–484
Palmieri F, Indiveri C, Bisaccia F, Iacobazzi V (1995) Mitochondrial metabolite carrier proteins: purification, reconstitution, and transport studies. Methods Enzymol 260:349–369
Palmieri L, Pardo B, Lasorsa FM et al (2001) Citrin and aralar1 are Ca(2+)-stimulated aspartate/glutamate transporters in mitochondria. EMBO J 20(18):5060–5069
Pierri CL, Palmieri F, De Grassi A (2014) Single-nucleotide evolution quantifies the importance of each site along the structure of mitochondrial carriers. Cell Mol Life Sci 71(2):349–364. doi:10.1007/s00018-013-1389-y
Poduri A, Heinzen EL, Chitsazzadeh V et al (2013) SLC25A22 is a novel gene for migrating partial seizures in infancy. Ann Neurol. doi:10.1002/ana.23998(17 Oct 2013)
Ramos M, Pardo B, Llorente-Folch I, Saheki T, Del Arco A, Satrustegui J (2011) Deficiency of the mitochondrial transporter of aspartate/glutamate aralar/AGC1 causes hypomyelination and neuronal defects unrelated to myelin deficits in mouse brain. J Neurosci Res 89(12):2008–2017
Saheki T, Kobayashi K (2002) Mitochondrial aspartate glutamate carrier (citrin) deficiency as the cause of adult-onset type II citrullinemia (CTLN2) and idiopathic neonatal hepatitis (NICCD). J Hum Genet 47(7):333–341
Wibom R, Lasorsa FM, Tohonen V et al (2009) AGC1 deficiency associated with global cerebral hypomyelination. N Engl J Med 361(5):489–495
Wolf NI, van der Knaap MS (2009) AGC1 deficiency and cerebral hypomyelination. The New England journal of medicine 361(20): 1997–1998; author reply 1998
Wong LJ (2010) Molecular genetics of mitochondrial disorders. Dev Disabil Res Rev 16(2):154–162
Acknowledgments
We thank the family for their participation in this study. We also thank Dr. Marc Yudkoff for helpful discussions on the ketogenic diet, and The Children’s Hospital of Philadelphia CytoGenomics Laboratory for assistance with establishment of fibroblast cell lines and tissue culture.
Funding. The study was funded by grants from the National Institutes of Health, including R03-DK082446 (MJF), and the Clinical and Translational Research Center at The Children’s Hospital of Philadelphia (UL1-RR-024134) (MJF). Additional funding for this study was provided by the Comitato Telethon Fondazione Onlus No. GGP11139 and the Center of Excellence in Comparative Genomics, University of Bari (FP); Angelina Foundation Fund from the Division of Metabolic Disease at The Children’s Hospital of Philadelphia (MJF); the Tristan Mullen Fund (MJF); an Institutional Development Fund to the Center for Applied Genomics from The Children’s Hospital of Philadelphia (HH); Adele and Daniel Kubert donation (HH); and donation from the Cotswold Foundation (HH).
Author information
Authors and Affiliations
Corresponding authors
Editor information
Editors and Affiliations
Additional information
Communicated by: Nicole Wolf, MD PhD
Electronic Supplementary Material
Below is the link to the electronic supplementary material.
Appendices
One Sentence Synopsis
SLC25A12 mutations impair neuronal AGC1 activity and should be considered in children with infantile epilepsy, congenital hypotonia, global delay, abnormal myelination, and reduced brain N-acetylaspartate.
Compliance with Ethics Guidelines
Author disclosure statement. Marni J. Falk, Dong Li, Xiaowu Gai, Elizabeth McCormick, Emily Place, Francesco M. Lasorsa, Frederick G. Otieno, Cuiping Hou, Cecilia E. Kim, Nada Abdel-Magid, Lyam Vazquez, Frank D. Mentch, Rosetta Chiavacci, Jinlong Liang, Xuanzhu Liu, Hui Jiang, Giulia Giannuzzi, Eric D. Marsh, Yiran Guo, Lifeng Tian, Ferdinando Palmieri, and Hakon Hakonarson have no conflicts of interest to disclose.
Informed consent. All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000 (5). Informed consent was obtained from all patients for being included in the study.
Animal studies. This article does not contain any studies with animal subjects performed by any of the authors.
Author contributions. MJF and HH designed and supervised all aspects of the study. MJF, EM, EP, and EDM clinically evaluated the subjects. MJF performed the skin biopsy to facilitate fibroblast analyses. FML, GG, and FP performed AGC1 activity studies and AGC1 expression analysis in fibroblasts. RC, FDM, YG, and EP coordinated research study subject enrollment. EM coordinated clinical results validation. FGO, CH, CEK, NA, LV, JL, HL, and XJ performed DNA sample extraction and handling, library preparation, whole exome sequencing, and data transfer. DL, LT, and XG performed bioinformatic analyses. MJF, DL, FP, EDM, and HH wrote the manuscript.
Rights and permissions
Copyright information
© 2014 SSIEM and Springer-Verlag Berlin Heidelberg
About this chapter
Cite this chapter
Falk, M.J. et al. (2014). AGC1 Deficiency Causes Infantile Epilepsy, Abnormal Myelination, and Reduced N-Acetylaspartate. In: Zschocke, J., Gibson, K., Brown, G., Morava, E., Peters, V. (eds) JIMD Reports, Volume 14. JIMD Reports, vol 14. Springer, Berlin, Heidelberg. https://doi.org/10.1007/8904_2013_287
Download citation
DOI: https://doi.org/10.1007/8904_2013_287
Received:
Revised:
Accepted:
Published:
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-662-43747-6
Online ISBN: 978-3-662-43748-3
eBook Packages: MedicineMedicine (R0)