Progressive External Ophthalmoplegia in Polish Patients-From Clinical Evaluation to Genetic Confirmation

Mitochondrial encephalomyopathies comprise a group of heterogeneous disorders resulting from impaired oxidative phosphorylation (OxPhos). Among a variety of symptoms progressive external ophthalmoplegia (PEO) seems to be the most common. The aim of this study is to present clinical and genetic characteristics of Polish patients with PEO. Clinical, electrophysiological, neuroradiological, and morphological data of 84 patients were analyzed. Genetic studies of mitochondrial DNA (mtDNA) were performed in all patients. Among nuclear DNA (nDNA) genes POLG was sequenced in 41 patients, TWNK (C10orf2) in 13 patients, and RNASEH1 in 2 patients. Total of 27 patients were included in the chronic progressive external ophthalmoplegia (CPEO) group, 24 in the CPEO+ group. Twenty-six patients had mitochondrial encephalomyopathy (ME), six patients Kearns-Sayre syndrome (KSS), and one patient sensory ataxic neuropathy, dysarthria, ophthalmoparesis (SANDO) syndrome. Genetic analysis of nDNA genes revealed the presence of pathogenic or possibly pathogenic variants in the POLG gene in nine patients, the TWNK gene in five patients and the RNASEH1 gene in two patients. Detailed patients' history and careful assessment of family history are essential in the diagnostic work-up. Genetic studies of both mtDNA and nDNA are necessary for the final diagnosis of progressive external ophthalmoplegia and for genetic counseling.

MRI findings in SANDO variety of the ataxia-neuropathy spectrum with a novel mutation in POLG (c.3287G>T): A case report

Sensory ataxic neuropathy with dysarthria and ophthalmoparesis (SANDO) is an adult onset sensory ataxic neuropathy, dysarthria and chronic progressive external ophthalmoplegia associated with mutations in POLG1. We report a 38-year-old woman with a history of progressive gait instability and bilateral ptosis. Neurological examination found ataxia, ophthalmoplegia, and dysarthria. MRI showed bilateral thalamic and cerebellar lesions. A POLG related disorder was suspected and after DNA sequencing a SANDO with a novel mutation in POLG was confirmed.

Mitochondrial respiratory chain disorders in the Old Order Amish population

The Old Order Amish populations in the US are one of the Plain People groups and are descendants of the Swiss Anabaptist immigrants who came to North America in the early eighteenth century. They live in numerous small endogamous demes that have resulted in reduced genetic diversity along with a high prevalence of specific genetic disorders, many of them autosomal recessive. Mitochondrial respiratory chain deficiencies arising from mitochondrial or nuclear DNA mutations have not previously been reported in the Plain populations. Here we present four different Amish families with mitochondrial respiratory chain disorders. Mutations in two mitochondrial encoded genes leading to mitochondrial respiratory chain disorder were identified in two patients. In the first case, MELAS syndrome caused by a mitochondrial DNA (mtDNA) mutation (m.3243A>G) was identified in an extended Amish pedigree following a presentation of metabolic strokes in the proband. Characterization of the extended family of the proband by a high resolution melting assay identified the same mutation in many previously undiagnosed family members with a wide range of clinical symptoms. A MELAS/Leigh syndrome phenotype caused by a mtDNA mutation [m.13513G>A; p.Asp393Asn] in the ND5 gene encoding the ND5 subunit of respiratory chain complex I was identified in a patient in a second family. Mutations in two nuclear encoded genes leading to mitochondrial respiratory chain disorder were also identified in two patients. One patient presented with Leigh syndrome and had a homozygous deletion in the NDUFAF2 gene, while the second patient had a homozygous mutation in the POLG gene, [c.1399G>A; p.Ala467Thr]. Our findings identify mitochondrial respiratory chain deficiency as a cause of disease in the Old Order Amish that must be considered in the context of otherwise unexplained systemic disease, especially if neuromuscular symptoms are present.

The POLG Polyglutamine Tract Variants in Iranian Patients with Multiple Sclerosis

OBJECTIVE

Multiple Sclerosis (MS) is a common disease of the central nervous system. The interaction between inflammatory and neurodegenerative processes typically results in irregular neurological disturbances followed by progressive disability. Mitochondrial dysfunction has been implicated in neurodegenerative disorders. The DNA polymerase-gamma (POLG) gene, which encodes the catalytic subunit of enzyme responsible for directing mtDNA replication, contains a poly glutamine tract (poly-Q) in the N-terminal, encoded by a CAG sequence in exon 2.

MATERIALS & METHODS

We analyzed the POLG trinucleotide repeats in 40 Iranian patients with MS (27 females and 13 males with an age range of 18-55); and 47 healthy age, gender, and ethnic matched controls were chosen by PCR-SSCP analysis.

RESULTS

Our results indicated that the most common allele in patients had 10 consecutive CAG repeats (10Q). Other alleles of 11and 12 trinucleotide repeats were detected. We did not find any difference between the CAG repeat length distribution in controls and MS patients.

CONCLUSION

No correlation was observed in the POLG gene CAG repeat with pathogenesis of MS, but it looks that other point mutations in POLG gene may have an important role in the disease's pathogenesis and produced more significant results.

The POLG Gene Polymorphism in Iranian Varicocele-Associated Infertility Patients

OBJECTIVES

Varicocele is associated with impaired testicular function and male infertility, but the molecular mechanisms by which fertility is affected have not been satisfactorily explained. The aim of our study was to investigate whether or not the polymerase gamma (POLG) polymorphism is associated with Iranian varicocele patients.

MATERIALS AND METHODS

We determined the POLG CAG repeat length in DNA samples extracted from 40 varicocele patients and 30 control subjects by PCR-denature polyacrylamide gel electrophoresis and sequencing.

RESULTS

The distribution of the CAG repeat length in varicocele patients showed no notable difference from that in control subjects, but we found a significant statistical inverse correlation between 10/10 and 10/#10 genotypes and varicocele grade.

CONCLUSION

These findings indicate that POLG CAG repeats may affects the varicocele grade, but the mechanisms remain to be elucidated.