Encephalomyopathy with renal tubulopathy
MTDPS8AB

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Description from OMIM

Mitochondrial DNA depletion syndrome-8A is a severe autosomal recessive disorder characterized by neonatal hypotonia, lactic acidosis, and neurologic deterioration. Renal tubular involvement may also occur (Bourdon et al., 2007). Mitochondrial DNA depletion syndrome-8B is characterized by ophthalmoplegia, ptosis, gastrointestinal dysmotility, cachexia, peripheral neuropathy, and brain MRI changes, known as the MNGIE phenotype (Shaibani et al., 2009). For a discussion of genetic heterogeneity of mtDNA depletion syndromes, see MTDPS1 (603041).



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List of symptoms



Symptom/sign Organ system Percent affected Pubmed id Added on(yyyy-mm-dd) Edit/add reference
Failure to thrive multi 100 % 19138848 2011-10-19
Lactate accumulation circulatory 100 % 17486094 2011-10-06
Feeding difficulties multi 100 % 19138848 2011-10-06
Hypotonia nervous 100 % 19138848 2011-10-10
Death in the first months of life multi 100 % 17486094 2011-10-06
Lactate accumulation circulatory 100 % 19138848 2011-10-06
Hypotonia nervous 100 % 17486094 2011-10-10
Tubulopathy urinary 50 % 19138848 2011-10-13



List of references:


A novel homozygous RRM2B missense mutation in association with severe mtDNA depletion.
Gittan Kollberg, Niklas Darin, Karin Benan, Ali-Reza Moslemi, Sigurd Lindal, Már Tulinius, Anders Oldfors, Elisabeth Holme,

This report describes two brothers, both deceased in infancy, with severe depletion of mitochondrial DNA (mtDNA) in muscle tissue. Both had feeding difficulties, failure to thrive, severe muscular hypotonia and lactic acidosis. One of the boys developed a renal proximal tubulopathy. A novel homozygous c.686 G-->T missense mutation in the RRM2B gene, encoding the p53-inducible ribonucleotide reductase subunit (p53R2), was identified. This is the third report on mutations in RRM2B associated with severe mtDNA depletion, which further highlights the importance of de novo synthesis of deoxyribonucleotides (dNTPs) for mtDNA maintenance.

Neuromuscular disorders : NMD - Feb 2009



Mutation of RRM2B, encoding p53-controlled ribonucleotide reductase (p53R2), causes severe mitochondrial DNA depletion.
Alice Bourdon, Limor Minai, Valérie Serre, Jean-Philippe Jais, Emmanuelle Sarzi, Sophie Aubert, Dominique Chrétien, Pascale de Lonlay, Véronique Paquis-Flucklinger, Hirofumi Arakawa, Yusuke Nakamura, Arnold Munnich, Agnès Rötig,

Mitochondrial DNA (mtDNA) depletion syndrome (MDS; MIM 251880) is a prevalent cause of oxidative phosphorylation disorders characterized by a reduction in mtDNA copy number. The hitherto recognized disease mechanisms alter either mtDNA replication (POLG (ref. 1)) or the salvage pathway of mitochondrial deoxyribonucleosides 5'-triphosphates (dNTPs) for mtDNA synthesis (DGUOK (ref. 2), TK2 (ref. 3) and SUCLA2 (ref. 4)). A last gene, MPV17 (ref. 5), has no known function. Yet the majority of cases remain unexplained. Studying seven cases of profound mtDNA depletion (1-2% residual mtDNA in muscle) in four unrelated families, we have found nonsense, missense and splice-site mutations and in-frame deletions of the RRM2B gene, encoding the cytosolic p53-inducible ribonucleotide reductase small subunit. Accordingly, severe mtDNA depletion was found in various tissues of the Rrm2b-/- mouse. The mtDNA depletion triggered by p53R2 alterations in both human and mouse implies that p53R2 has a crucial role in dNTP supply for mtDNA synthesis.

Nature genetics - Jun 2007