Combined malonic and methylmalonic aciduria: exome sequencing reveals mutations in the ACSF3 gene in patients with a non-classic phenotype.

Abstract

BACKGROUND:

Combined Malonic and Methylmalonic Aciduria (CMAMMA) is a rare recessive inborn error of metabolism characterised by elevations of urine malonic acid (MA) and methylmalonic acid (MMA). Nearly all reported cases are caused by malonyl-CoA decarboxylase (MCD) deficiency. Most patients have metabolic acidosis, developmental delay, seizures and cardiomyopathy. CMAMMA was also described in symptomatic patients with normal MCD activity, suggesting heterogeneity in this disorder.

METHODS AND RESULTS:

We identified two probands with a non-classical CMAMMA variant through the Quebec newborn urine screening program. While they share the biochemical phenotype of elevated MA and MMA, the MMA excretion was higher than MA, the clinical courses were benign, MYLCD gene sequencing was normal and MCD activity, measured in one proband, was normal. Using exome sequencing in the single consanguineous proband, we identified a homozygous missense allele in the ACSF3 gene, encoding an Acyl-CoA Synthetase (ACS) with unknown substrate and function. The second proband was homozygous for a different ACSF3 missense allele. Both substitutions were in conserved residues and were identified in less than 0.5% of their respective ethnic control populations.

CONCLUSION:

These results suggest that ACSF3 is a candidate gene for non-classical CMAMMA observed in our patients and document the value of exome sequencing of a limited number of patients for the identification of novel disease genes.

• Authors: Ahmed Alfares, Laura Dempsey Nunez, Khalid Al-Thihli, John Mitchell, Serge Melançon, Natascia Anastasio, Kevin C H Ha, Jacek Majewski, David S Rosenblatt, Nancy Braverman
• Journal: Journal of medical genetics (J Med Genet) Vol. 48 Issue 9 Pg. 602-5 (Sep 2011) ISSN: 1468-6244 [Electronic] England
• PMID: 21785126 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Malonates
• Malonyl Coenzyme A
• Methylmalonic Acid
• malonic acid
• Carboxy-Lyases
• ACSF3 protein, human
• Coenzyme A Ligases

Topics

• Alleles
• Amino Acid Metabolism, Inborn Errors (genetics)
• Base Sequence
• Carboxy-Lyases (deficiency, genetics)
• Coenzyme A Ligases (genetics)
• Exome
• Genetic Association Studies
• Humans
• Infant
• Malonates (urine)
• Malonyl Coenzyme A
• Metabolism, Inborn Errors (genetics)
• Methylmalonic Acid (urine)
• Molecular Sequence Data
• Mutation
• Pedigree
• Phenotype
• Sequence Analysis, DNA