Novel cases of D-2-hydroxyglutaric aciduria with IDH1 or IDH2 mosaic mutations identified by amplicon deep sequencing.
BACKGROUND
Mosaic IDH1 mutations are described as the cause of metaphyseal chondromatosis with increased urinary excretion of D-2-hydroxyglutarate (MC-HGA), and mutations in IDH2 as the cause of D-2-hydroxyglutaric aciduria (D-2HGA) type II. Mosaicism for IDH2 mutations has not previously been reported as a cause of D-2HGA. Here we describe three cases: one MC-HGA case with IDH1 mosaic mutations, and two D-2HGA type II cases. In one D-2HGA case we identified mosaicism for an IDH2 mutation as the genetic cause of this disorder; the other D-2HGA case was caused by a heterozygous IDH2 mutation, while the unaffected mother was a mosaic carrier.


METHODS
We performed amplicon deep sequencing using the 454 GS Junior platform, next to Sanger sequencing, to identify and confirm mosaicism of IDH1 or IDH2 mutations in MC-HGA or D-2HGA, respectively.


CONCLUSIONS
We identified different mutant allele percentages in DNA samples derived from different tissues (blood vs fibroblasts). Furthermore, we found that mutant allele percentages of IDH1 decreased after more passages had occurred in fibroblast cell cultures. We describe a method for the detection and validation of mosaic mutations in IDH1 and IDH2, making quantification with laborious cloning techniques obsolete.
Metabolic Unit, Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands.
Benjamin
B
Nota
Eline M
EM
Hamilton
Daoud
D
Sie
Senay
S
Ozturk
Silvy J M
SJ
van Dooren
Matilde R Fernandez
MR
Ojeda
Cornelis
C
Jakobs
Ernst
E
Christensen
Edwin P
EP
Kirk
Jolanta
J
Sykut-Cegielska
Allan M
AM
Lund
Marjo S
MS
van der Knaap
Gajja S
GS
Salomons
D020739:Brain Diseases, Metabolic, Inborn / Q000175:diagnosis / Q000235:genetics*; D002478:Cells, Cultured; D002648:Child; D005260:Female; D005787:Gene Frequency; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007521:Isocitrate Dehydrogenase / Q000235:genetics*; D008297:Male; D009030:Mosaicism; D009154:Mutation; D010290:Parents
C538784:IDH2 protein, human; D007521:Isocitrate Dehydrogenase; C543588:IDH1 protein, human
2-hydroxyglutarate; Cancer; Inborn Error of Metabolism; Mosaicism; Neurometabolic Disorder