Adult-onset mitochondrial movement disorders: a national picture from the Italian Network

Introduction

Both prevalence and clinical features of the various movement disorders in adults with primary mitochondrial diseases are unknown.

Methods

Based on the database of the “Nation-wide Italian Collaborative Network of Mitochondrial Diseases”, we reviewed the clinical, genetic, neuroimaging and neurophysiological data of adult patients with primary mitochondrial diseases (n = 764) where ataxia, myoclonus or other movement disorders were part of the clinical phenotype.

Results

Ataxia, myoclonus and movement disorders were present in 105/764 adults (13.7%), with the onset coinciding or preceding the diagnosis of the mitochondrial disease in 49/105 (46.7%). Ataxia and parkinsonism were the most represented, with an overall prevalence at last follow-up of 59.1% and 30.5%, respectively. Hyperkinetic movement disorders were reported in 15.3% at last follow-up, being the less common reported movement disorders. The pathogenic m.8344A > G and POLG variants were always associated with a movement disorder, while LHON variants and mtDNA single deletions were more commonly found in the subjects who did not present a movement disorder. The most common neuroimaging features were cortical and/or cerebellar atrophy, white matter hyperintensities, basal ganglia abnormalities and nigro-striatal degeneration. Almost 70% of patients with parkinsonism responded to dopaminergic therapy, mainly levodopa, and 50% with myoclonus were successfully treated with levetiracetam.

Conclusion

Movement disorders, mainly ataxia and parkinsonism, are important findings in adult primary mitochondrial diseases. This study underlies the importance of looking for a mitochondrial etiology in the diagnostic flowchart of a movement disorder and may help direct genetic screening in daily practice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10697-1.

AAV9-based gene therapy partially ameliorates the clinical phenotype of a mouse model of Leigh syndrome

Leigh syndrome (LS) is the most common infantile mitochondrial encephalopathy. No treatment is currently available for this condition. Mice lacking Ndufs4, encoding NADH: ubiquinone oxidoreductase iron-sulfur protein 4 (NDUFS4) recapitulates the main findings of complex I (cI)-related LS, including severe multisystemic cI deficiency and progressive neurodegeneration. In order to develop a gene therapy approach for LS, we used here an AAV2/9 vector carrying the human NDUFS4 coding sequence (hNDUFS4). We administered AAV2/9-hNDUFS4 by intravenous (IV) and/or intracerebroventricular (ICV) routes to either newborn or young Ndufs4-/- mice. We found that IV administration alone was only able to correct the cI deficiency in peripheral organs, whereas ICV administration partially corrected the deficiency in the brain. However, both treatments failed to improve the clinical phenotype or to prolong the lifespan of Ndufs4-/- mice. In contrast, combined IV and ICV treatments resulted, along with increased cI activity, in the amelioration of the rotarod performance and in a significant prolongation of the lifespan. Our results indicate that extraneurological organs have an important role in LS pathogenesis and provide an insight into current limitations of adeno-associated virus (AAV)-mediated gene therapy in multisystem disorders. These findings warrant future investigations to develop new vectors able to efficiently target multiple organs.

Role of neuronal and inducible nitric oxide synthases in the guinea pig ileum myenteric plexus during in vitro ischemia and reperfusion

BACKGROUND

Intestinal ischemia and reperfusion (I/R) injury leads to abnormalities in motility, namely delay of transit, caused by damage to myenteric neurons. Alterations of the nitrergic transmission may occur in these conditions. This study investigated whether an in vitro I/R injury may affect nitric oxide (NO) production from the myenteric plexus of the guinea pig ileum and which NO synthase (NOS) isoform is involved.

METHODS

The distribution of the neuronal (n) and inducible (i) NOS was determined by immunohistochemistry during 60 min of glucose/oxygen deprivation (in vitro ischemia) followed by 60 min of reperfusion. The protein and mRNA levels of nNOS and iNOS were investigated by Western-immunoblotting and real time RT-PCR, respectively. NO levels were quantified as nitrite/nitrate.

KEY RESULTS

After in vitro I/R the proportion of nNOS-expressing neurons and protein levels remained unchanged. nNOS mRNA levels increased 60 min after inducing ischemia and in the following 5 min of reperfusion. iNOS-immunoreactive neurons, protein and mRNA levels were up-regulated during the whole I/R period. A significant increase of nitrite/nitrate levels was observed in the first 5 min after inducing I/R and was significantly reduced by N(ω) -propyl-l-arginine and 1400 W, selective inhibitors of nNOS and iNOS, respectively.

CONCLUSIONS & INFERENCES

Our data demonstrate that both iNOS and nNOS represent sources for NO overproduction in ileal myenteric plexus during I/R, although iNOS undergoes more consistent changes suggesting a more relevant role for this isoform in the alterations occurring in myenteric neurons following I/R.

Protein kinase C modulates NMDA receptors in the myenteric plexus of the guinea pig ileum during in vitro ischemia and reperfusion

BACKGROUND

Ischemic episodes lead to profound functional and structural alterations of the gastrointestinal tract which may contribute to disorders of intestinal motility. Enhancement of glutamate overflow and the consequent activation of NMDA (N-methyl-D-aspartate) receptors may participate to such changes by modulating different enteric neurotransmitter systems, including cholinergic motor pathways.

METHODS

The molecular mechanism/s underlying activation of NMDA receptors in the guinea pig ileum were investigated after glucose/oxygen deprivation (in vitro ischemia) and during reperfusion.

KEY RESULTS

The number of ileal myenteric neurons positive for NR1, the functional subunit of NMDA receptors, and its mRNA levels were unchanged after in vitro ischemia/reperfusion. In these conditions, the protein levels of NR1, and of its phosphorylated form by protein kinase C (PKC), significantly increased in myenteric neurons, whereas, the levels of NR1 phosphorylated by protein kinase A (PKA) did not change, with respect to control values. Spontaneous glutamate overflow increased during in vitro ischemia/reperfusion. In these conditions, the NMDA receptor antagonists, D(-)-2-amino-5-phosphonopentanoic acid [(D)-AP5] (10 μmol L(-1)) and 5,7-dichlorokynurenic acid (5,7-diClKyn acid) (10 μmol L(-1)) and the PKC antagonist, chelerythrine (1 μmol L(-1)), but not the PKA antagonist, H-89 (1 μmol L(-1)), were able to significantly depress the increased glutamate efflux.

CONCLUSIONS & INFERENCES

The present data suggest that in the guinea pig ileum during in vitro ischemia/reperfusion, NR1 protein levels increase. Such event may rely upon posttranscriptional events involving NR1 phosphorylation by PKC. Increased NR1 levels may, at least in part, explain the ability of NMDA receptors to modulate a positive feedback on ischemia/reperfusion-induced glutamate overflow.

MGMT methylation in diffuse large B-cell lymphoma: validation of quantitative methylation-specific PCR and comparison with MGMT protein expression

AIMS

(1) To validate a quantitative real time methylation specific PCR assay (MethyLight) for the detection of O6-methylguanine-DNA methyltransferase (MGMT) gene methylation status (MS) in diffuse large B-cell lymphoma (DLBCL). (2) To determine the immunohistochemical (IHC) expression of the MGMT protein and correlate it with MS. Both IHC and MethyLight results were compared with patient's outcome.

METHODS

71 patients with primary nodal DLBCL were studied. MGMT immunoreactivity was detected using a specific monoclonal antibody. The MS of MGMT gene was analysed in 52/71 DLBCL using MethyLight. A selected subset of 40 DLBCL was also analysed using qualitative methylation-specific PCR (MSP). Statistical analysis of overall survival (OS), lymphoma-specific survival (LSS) and progression free survival (PFS) was performed according to IHC and MS results.

RESULTS

19/71 DLBCLs (27%) were MGMT-negative at IHC; all were analysed, together with 33/52 MGMT-positive DLBCLs. MethyLight showed a better performance than MSP. There was a good correlation between the presence of MGMT expression and the unmethylated status; the absence of IHC expression was poorly correlated with the presence of methylation. Better OS, LSS and PFS was found in DLBCLs with MGMT gene methylation. DLBCLs not expressing MGMT at IHC showed a longer PFS.

CONCLUSIONS

The quantitative real-time methylation-specific PCR assay for the detection of MGMT gene hypermethylation has been validated for the first time in DLBCL. Immunohistochemistry seems to represent an useful preliminary test to identify unmethylated cases; MS analysis may be performed in non-immunoreactive cases to identify truly methylated DLBCLs, which bear a better prognosis.