Slc25a19 is a mouse mitochondrial transporter necessary for viability, neural tube closure, erythropoiesis, and maintenance of mitochondrial thiamine pyrophosphate pools. M.J. Lindhurst¹, G. Fiermonte², S. Song³, E. Struys⁴, F. De Leonardis², A. Chen¹, A. Castegna², N. Verhoeven⁴, C.K. Mathews³, F. Palmieri², L.G. Biesecker¹. 1) National Human Genome Research Institute, National Institutes of Health, Bethesda, MD; 2) Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, Bari, Italy; 3) Department of Biochemistry and Biophysics Oregon State University, Corvallis, OR; 4) Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands.
   A missense mutation in SLC25A19 causes Amish lethal microcephaly (MCPHA), which is characterized by severe microcephaly, brain malformations, -ketoglutaric aciduria and premature death. Previous data suggested that SLC25A19, also called DNC, was a mitochondrial deoxyribonucleotide transporter. We generated a knockout mouse model of Slc25a19. These animals had 100% prenatal lethality by E12. Affected embryos at E10.5 have a neural tube closure defect with ruffling of the neural fold ridges, a yolk sac erythropoietic failure and elevated -ketoglutarate in the amniotic fluid. We found that these animals have normal mitochondrial ribo- and deoxyribonucleoside triphosphate levels, suggesting that transport of these molecules is not the primary role of SLC25A19. We identified thiamine pyrophosphate (ThPP) transport as a candidate function of SLC25A19 through homology searching and confirmed it using transport assays of the recombinant reconstituted protein. The mitochondria of Slc25a19^-/- and MCPHA cells have undetectable and markedly reduced ThPP content, respectively. The reduction of ThPP levels causes dysfunction of the -ketoglutarate dehydrogenase complex, which explains the high levels of this organic acid in MCPHA. In addition, pyruvate dehydrogenase activity is also decreased suggesting that transport of this cofactor into the mitochondria is important for central nervous system development and supports the hypothesis that the developing brain has a higher need for oxidative metabolism than other organs.