Several lines of evidence support a mitochondrial dysfunction in major psychiatric disorders. The objective of this study was to determine whether mitochondrial DNA (mtDNA) expression or content are implicated in the mitochondrial dysfunction observed in schizophrenia (SCH), bipolar disorder (BD), and major depressive disorder (MDD). MtDNA gene expression and mtDNA content (including the MT-ND4 deletion) were measured by RT-qPCR and qPCR, respectively. Post-mortem brain tissue from 60 subjects, divided evenly into four diagnostic groups (SCH, BD, MDD, and control (C)), was analyzed. MT-ND1 gene expression was significantly increased in the BD group compared with the C group. MDD and SCH patients showed a similar pattern of mtDNA expression, which was different from that in BD patients. Similarly, a larger number of MDD and SCH patients tended to have the MT-ND4 gene deleted compared with BD and C subjects. However, no other significant differences were observed in mtDNA gene expression and mtDNA content. Notably, high variability was observed in the mtDNA gene expression and content in each diagnostic group. Previous studies and the present work provide evidence for a role of mtDNA in SCH, BD and MDD. However, further studies with larger patient and control groups as well as by analyzing distinct brain regions are needed to elucidate the role of mtDNA in major psychiatric disorders.

SummaryCarotid atherosclerosis (CA) is one of the most common causes of stroke, and recent studies suggest that pathways initiated by the interaction of the plasma vitamin K-dependent protein GAS6 with the tyrosine kinase receptors TYRO3, AXL and MERTK (TAM) may have a relevant role in atherogenesis. Furthermore, our previous studies indicated an association between GAS6 and stroke. The aim of this study was to analyse the genetic association between SNPs and haplotypes in GAS6-TAM genes and CA. We performed a case-control study with 233 CA patients confirmed by nuclear magnetic resonance angiography and 202 patients who suffered from cardioembolic (non atherogenic) stroke. For all included subjects information on established risk factors was available. Genotyping of 16 selected tagSNPs was performed by real-time PCR, using either FRET or TaqMan probes. Adjusted logistic regression (LR) analyses indicated that rs2289743 in TYRO3 and rs869016 in MERTK were associated to CA, decreasing its risk (OR [95%CI]=0.39 [0.16–0.94] and OR [95%CI]=0.31 [0.14–0.69], respectively). Linkage disequilibrium results were consistent with the haplotype blocks described in HapMap and adjusted LR analyses revealed that the haplotype ACAA in MERTK, containing the minor allele of the associated SNP, was also associated to CA. No association was observed with GAS6 and AXL variants, which suggests that CA is not the mechanism underlying the reported association between GAS6 and stroke. The association between TYRO3 and MERTK variants and carotid atherosclerosis found in this study reinforces a physiological role of the GAS6-TAM pathway in atherogenesis.

Clinical conditions commonly associated with mitochondrial disorders (CAMDs) are often present in autism spectrum disorders (ASD) and intellectual disability (ID). Therefore, the mitochondrial dysfunction hypothesis has been proposed as a transversal mechanism that may function in both disorders. Here, we investigated the presence of conditions associated with mitochondrial disorders and mitochondrial DNA (mtDNA) alterations in 122 subjects who presented ASD with ID (ASD group), 115 subjects who presented ID but not ASD (ID group) and 112 healthy controls (HC group). We assessed in the three study groups the presence of the clinical conditions through a questionnaire and the mtDNA content of two mitochondrial genes, MT-ND1 and MT-ND4, by qPCR. The mtDNA sequences of 98 ASD and 95 ID subjects were obtained by mtDNA-targeted next generation sequencing and analysed through the MToolBox pipeline to identify mtDNA mutations. Subjects with ASD and ID showed higher frequencies of constipation, edema, seizures, vision alterations, strabismus and sphincter incontinence than HCs subjects. ASD and ID subjects showed significantly lower mtDNA content than HCs in both MT-ND1 and MT-ND4 genes. In addition, we identified 49 putative pathogenic variants with a heteroplasmy level higher than 60%: 8 missense, 29 rRNA and 12 tRNA variants. A total of 28.6% of ASD and 30.5% of ID subjects carried at least one putative pathogenic mtDNA mutation. The high frequency of CAMDs, the low mtDNA content and the presence of putative pathogenic mtDNA mutations observed in both ASD and ID subjects are evidence of mitochondrial dysfunction in ASD and ID.