Cavitating and tigroid-like leukoencephalopathy in a case of NDUFA2-related disorder

Calcium stress reduces the reproductive capacity and pathogenicity of the pine wood nematode (Bursaphelenchus xylophilus) by inhibiting oxidative phosphorylation reaction

The continuous use of chemical pesticides to control nematodes could result in the developing of pesticide-resistant nematodes. Novel nucleic acid pesticides are becoming the focus of pesticide research due to their strong specificity, high efficiency, and environmental friendliness. However, the limited known biochemical targets restrict the development of target pesticides for nematodes. The calcium stress experiments on pine wood nematodes (PWN) showed that 100 mmol/L Ca2+ resulted in longitudinal depression on the PWN body wall, reduced oviposition, and increased corrected mortality. To enrich the biological targets of nematode pesticides, we further investigated the response mechanism of PWN to calcium stress at the molecular level. Differentially expressed gene analysis showed that genes involved in the oxidative phosphorylation (OXPHOS) pathway were significantly enriched. RNA interference results of 6 key genes belonging to four mitochondrial complex I (BXNDUFA2), III (BXQCR8), IV (BXCOX17), V (BXV-ATPaseB, BXV-ATPaseE, BXV-ATPaseε) in non-stressed nematodes showed reduction in PWN oviposition, population size, feeding ability, and pathogenicity. The BXNDUFA2 gene interference had the highest inhibitory impact by decreasing the oviposition from 31.00 eggs to 6.75 eggs and PWN population size from 8.27 × 103 nematodes to 1.64 × 103 nematodes, respectively. Interestingly, RNA interference of these 6 key genes in calcium-stressed nematodes also led to increased mortality and decreased oviposition of PWN. In summary, calcium stress inhibited the reproductive capacity of PWN by down-regulating key genes BXNDUFA2, BXQCR8, BXV-ATPaseB, BXV-ATPaseE, BXV-ATPaseε, and BXCOX17, thereby reducing the pathogenicity. The current results enrich the RNAi targets in PWN and provide a scientific basis for developing novel nucleic nematicides.

Respirasome Proteins Are Regulated by Sex-Hormone Interactions in the Brain

The existence of sex differences in disease incidence is attributed, in part, to sex differences in metabolism. Uncovering the precise mechanism driving these differences is an extraordinarily complex process influenced by genetics, endogenous hormones, sex-specific lifetime events, individual differences and external environmental/social factors. In fact, such differences may be subtle, but across a life span, increase susceptibility to a pathology. Whilst research persists in the hope of discovering an elegant biological mechanism to underpin sex differences in disease, here, we show, for the first time, that such a mechanism may be subtle in nature but influenced by multiple sex-specific factors. A proteomic dataset was generated from a gonadectomized mouse model treated with Tibolone, a menopausal hormone therapy. Following functional enrichment analysis, we identified that Alzheimer's disease and the electron transport chain-associated pathways were regulated by sex-hormone interactions. Specifically, we identified that the expression of three respirasome proteins, NDUFA2, NDUFA7 and UQCR10, is significantly altered by compounding factors that contribute to sex differences. These proteins function in bioenergetics and produce reactive oxygen species, which are each dysregulated in many diseases with sex differences in incidence. We show sex-specific reprogrammed responses to Tibolone following gonadectomy, which primarily influence the expression of proteins contributing to metabolic pathways. This further infers that metabolic differences may underpin the observed sex differences in disease, but also that hormone therapy research now has potential in exploring sex-specific interventions to produce an effective method of prevention or treatment.

Tongue Root Cyst as a Manifestation of the Variant m.3243A>G

There are indications that the frequency of cyst formation is increased in mitochondrial disorders (MIDs). Cysts can be found in various organs of MID patients but tongue root cysts have not been reported as a manifestation of a MID.

In a 56-year-old male with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) manifesting with recurrent stroke-like episodes, seizures, cognitive impairment, ataxia, psychiatric abnormalities, bilateral visual impairment, bilateral hypoacusis, pre-diabetes, hyperlipidemia, myopathy, and lactic acidosis, an asymptomatic, pre-epiglottic cyst with 1 cm in diameter and protein-rich content in the right tongue root was accidentally detected on ultrasound and confirmed by MRI at the age of 50 years. The patient did not complain about dysarthria or dysphagia but had a mild cerebellar speech. The cyst was confirmed on an MRI six years later, without having changed in diameter, extension, or symptomatology. Due to the atypical location, a branchiogenic cyst was excluded. In conclusion, tongue root cysts may be a manifestation of the m.3243A>G variant.

Mitochondrial disorders of the OXPHOS system

Mitochondrial disorders are among the most frequent inborn errors of metabolism, their primary cause being the dysfunction of the oxidative phosphorylation system (OXPHOS). OXPHOS is composed of the electron transport chain (ETC), formed by four multimeric enzymes and two mobile electron carriers, plus an ATP synthase [also called complex V (cV)]. The ETC performs the redox reactions involved in cellular respiration while generating the proton motive force used by cV to synthesize ATP. OXPHOS biogenesis involves multiple steps, starting from the expression of genes encoded in physically separated genomes, namely the mitochondrial and nuclear DNA, to the coordinated assembly of components and cofactors building each individual complex and eventually the supercomplexes. The genetic cause underlying around half of the diagnosed mitochondrial disease cases is currently known. Many of these cases result from pathogenic variants in genes encoding structural subunits or additional factors directly involved in the assembly of the ETC complexes. Here, we review the historical and most recent findings concerning the clinical phenotypes and the molecular pathological mechanisms underlying this particular group of disorders.

Analysis of Human Mutations in the Supernumerary Subunits of Complex I

Complex I is the largest member of the electron transport chain in human mitochondria. It comprises 45 subunits and requires at least 15 assembly factors. The subunits can be divided into 14 "core" subunits that carry out oxidation-reduction reactions and proton translocation, as well as 31 additional supernumerary (or accessory) subunits whose functions are less well known. Diminished levels of complex I activity are seen in many mitochondrial disease states. This review seeks to tabulate mutations in the supernumerary subunits of humans that appear to cause disease. Mutations in 20 of the supernumerary subunits have been identified. The mutations were analyzed in light of the tertiary and quaternary structure of human complex I (PDB id = 5xtd). Mutations were found that might disrupt the folding of that subunit or that would weaken binding to another subunit. In some cases, it appeared that no protein was made or, at least, could not be detected. A very common outcome is the lack of assembly of complex I when supernumerary subunits are mutated or missing. We suggest that poor assembly is the result of disrupting the large network of subunit interactions that the supernumerary subunits typically engage in.

Cavitating and tigroid-like leukoencephalopathy in a case of NDUFA2-related disorder

Biallelic variants in nuclear gene NDUFA2 have been reported so far in only three children with variable presentations including Leigh syndrome or leukoencephalopathy. Herein, we report a further female child affected by NDUFA2‐related disorder presenting with cavitating and tigroid‐like pattern of leukodystrophy and without systemic biochemical abnormalities of mitochondrial disorders.