Quantitative multiplex PCR of short fluorescent fragments for the detection of large intragenic POLG rearrangements in a large French cohort.
Polymerase gamma (POLG) is the gene most commonly involved in mitochondrial disorders with mitochondrial DNA instability and causes a wide range of diseases with recessive or dominant transmission. More than 170 mutations have been reported. Most of them are missense mutations, although nonsense mutations, splice-site mutations, small deletions and insertions have also been identified. However, to date, only one large-scale rearrangement has been described in a child with Alpers syndrome. Below, we report a large cohort of 160 patients with clinical, molecular and/or biochemical presentation suggestive of POLG deficiency. Using sequencing, we identified POLG variants in 22 patients (18 kindreds) including five novel pathogenic mutations. Two patients with novel mutations had unusual clinical presentation: the first exhibited an isolated ataxic neuropathy and the second was a child who presented with endocrine signs. We completed the sequencing step by quantitative multiplex PCR of short fluorescent fragments (QMPSF) analysis in 37 patients with either only one POLG heterozygous variant or a family history suggesting a dominant transmission. We identified a large intragenic deletion encompassing part of intron 21 and exon 22 of POLG in a child with refractory epilepsia partialis continua. In conclusion, we describe the first large French cohort of patients with POLG mutations, expanding the wide clinical and molecular spectrum observed in POLG disease. We confirm that large deletions in the POLG gene are rare events and we highlight the importance of QMPSF in patients with a single heterozygous POLG mutation, particularly in severe infantile phenotypes.
1] Department of Medical Genetics, National Centre for Mitochondrial diseases, Nice Teaching Hospital, Nice, France [2] IRCAN, CNRS UMR 7284/INSERM U1081/UNS, School of Medicine, Nice Sophia-Antipolis University, Nice, France.
Cécile
C
Rouzier
Department of Medical Genetics, National Centre for Mitochondrial diseases, Nice Teaching Hospital, Nice, France.
Annabelle
A
Chaussenot
Jacques Monod Institute, CNRS-University Paris Diderot, Sorbonne, Paris, France.
Valérie
V
Serre
1] Department of Medical Genetics, National Centre for Mitochondrial diseases, Nice Teaching Hospital, Nice, France [2] IRCAN, CNRS UMR 7284/INSERM U1081/UNS, School of Medicine, Nice Sophia-Antipolis University, Nice, France.
Konstantina
K
Fragaki
1] Department of Medical Genetics, National Centre for Mitochondrial diseases, Nice Teaching Hospital, Nice, France [2] IRCAN, CNRS UMR 7284/INSERM U1081/UNS, School of Medicine, Nice Sophia-Antipolis University, Nice, France.
Sylvie
S
Bannwarth
1] Department of Medical Genetics, National Centre for Mitochondrial diseases, Nice Teaching Hospital, Nice, France [2] IRCAN, CNRS UMR 7284/INSERM U1081/UNS, School of Medicine, Nice Sophia-Antipolis University, Nice, France.
Samira
S
Ait-El-Mkadem
Department of Neurology, Timone Hospital, Marseille Teaching Hospital, Marseille, France.
Shahram
S
Attarian
Department of Neurology, Timone Hospital, Marseille Teaching Hospital, Marseille, France.
Elsa
E
Kaphan
Department of Neuropediatrics, Timone Hospital, Marseille Teaching Hospital, Marseille, France.
Aline
A
Cano
Department of Neurology, Nice Teaching Hospital, Nice, France.
Emilien
E
Delmont
Department of Neurology, Nice Teaching Hospital, Nice, France.
Sabrina
S
Sacconi
Department of Metabolic Diseases, Biology and Pathology Centre Est, Lyon Teaching Hospital, Lyon, France.
Bénédicte
B
Mousson de Camaret
Department of Medical Genetics, Necker Hospital, Paris Teaching Hospital, Paris, France.
Marlène
M
Rio
Department of Medical Genetics, Necker Hospital, Paris Teaching Hospital, Paris, France.
Anne-Sophie
AS
Lebre
Department of Molecular and Chromosomal Genetics, Pitié-Salpétrière Hospital, Paris Teaching Hospital, Paris, France.
Claude
C
Jardel
Department of Neuromuscular disorders, Fort-de-France Teaching Hospital, Martinique, France.
Romain
R
Deschamps
Department of Pediatrics, Lenval Hospital, Nice Teaching Hospital, Nice, France.
Christian
C
Richelme
Department of Neurology, Timone Hospital, Marseille Teaching Hospital, Marseille, France.
Jean
J
Pouget
Department of Neuropediatrics, Timone Hospital, Marseille Teaching Hospital, Marseille, France.
Brigitte
B
Chabrol
1] Department of Medical Genetics, National Centre for Mitochondrial diseases, Nice Teaching Hospital, Nice, France [2] IRCAN, CNRS UMR 7284/INSERM U1081/UNS, School of Medicine, Nice Sophia-Antipolis University, Nice, France.
Véronique
V
Paquis-Flucklinger
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D000074002:DNA Polymerase gamma; D004272:DNA, Mitochondrial / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000172:deficiency* / Q000235:genetics*; D017036:Epilepsia Partialis Continua / Q000235:genetics; D005091:Exons; D005260:Female; D005602:France; D015321:Gene Rearrangement; D006579:Heterozygote; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D028361:Mitochondrial Diseases / Q000235:genetics; D060885:Multiplex Polymerase Chain Reaction; D010641:Phenotype; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D044465:White People; D055815:Young Adult
D004272:DNA, Mitochondrial; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; C413027:POLG protein, human