Mutations in the PTEN-induced kinase 1 (PINK1) gene have recently been implicated in autosomal recessive early onset Parkinson Disease (1, 2). To investigate the role of PINK1 in neurodegeneration, we designed human and murine neuronal cell lines expressing either wild-type PINK1 or PINK1 bearing a mutation associated with Parkinson Disease. We show that under basal and staurosporine-induced conditions, the number of terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL)-positive cells was lower in wild-type PINK1 expressing SH-SY5Y cells than in mock-transfected cells. This phenotype was due to a PINK1-mediated reduction in cytochrome c release from mitochondria, which prevents subsequent caspase-3 activation. We show that overexpression of wild-type PINK1 strongly reduced both basal and staurosporine-induced caspase 3 activity. Overexpression of wild-type PINK1 also reduced the levels of cleaved caspase-9, caspase-3, caspase-7, and activated poly(ADP-ribose) polymerase under both basal and staurosporine-induced conditions. In contrast, Parkinson disease-related mutations and a kinase-inactive mutation in PINK1 abrogated the protective effect of PINK1. Together, these results suggest that PINK1 reduces the basal neuronal pro-apoptotic activity and protects neurons from staurosporine-induced apoptosis. Loss of this protective function may therefore underlie the degeneration of nigral dopaminergic neurons in patients with PINK1 mutations.

Mice homozygous for a defect in the PTCD2 (pentatricopeptide repeat domain protein 2) gene were generated in order to study the role of this protein in mitochondrial RNA metabolism. These mice displayed specific but variable reduction of ubiquinol–cytochrome c reductase complex activity in mitochondria of heart, liver and skeletal muscle due to a decrease in the expression of mitochondrial DNA-encoded cytochrome b, the catalytic core of the complex. This reduction in mitochondrial function has a profound effect on the myocardium, with replacement of ventricular cardiomyocytes by fibro-fatty tissue. Northern blotting showed a reduction in the mRNA for the mitochondrial DNA encoded proteins cytochrome b (cytb) and ND5 (NADH dehydrogenase subunit 5) and an elevation in a combined pre-processed ND5-CYTB transcript. This suggests that the PTCD2 protein is involved in processing RNA transcripts involving cytochrome b derived from mitochondrial DNA. This defines the site for PTCD2 action in mammalian mitochondria and suggests a possible role for dysfunction of this protein in the aetiology of heart failure.

Context: Pyruvate dehydrogenase phosphatase (PDP) deficiency has been previously reported as an enzymopathy, but the genetic basis for such a defect has never been established. Objective: The aim of this study was to identify the cause of the defect in two patients who presented with PDP deficiency. Patients: We studied two brothers of consanguineous parents who presented with neonatal hypotonia, elevated lactate, and less than 25% native pyruvate dehydrogenase complex (PDHc) activity in skin fibroblasts compared with controls. The activity of the complex could be restored to normal values by preincubation of the cells with dichloroacetate or by treating cell extracts with calcium. Results: These two individuals were found to be homozygous for a 3-bp deletion in the coding sequence of the PDP isoform 1 (PDP1), which removes the amino acid residue leucine from position 213 of the protein. A recombinant version of this protein was synthesized and found to have a very reduced (<5%) ability to activate purified PDHc. Reduced steady-state levels of PDP1 in the patient’s fibroblasts coupled with the low catalytic activity of the mutant PDP1 resulted in native PDHc activity being reduced, but this could be corrected by the addition of recombinant PDP1 (wild type). Conclusion: We have identified mutations in PDP1 in two brothers with PDP deficiency and have proven that the mutation is disease-causing. This is the first demonstration of human disease due to a mutation in PDP1.

Background: The usage of whole-slide images has recently been gaining a foothold in medical education, training, and diagnosis. Objectives: The first objective of the current study was to compare academic performance on virtual microscopy (VM) and light microscopy (LM) for learning pathology, anatomy, and histology in medical and dental students during the COVID-19 period. The second objective was to gather insight into various applications and usage of such technology for medical education. Materials and methods: Using the keywords “virtual microscopy” or “light microscopy” or “digital microscopy” and “medical” and “dental” students, databases (PubMed, Embase, Scopus, Cochrane, CINAHL, and Google Scholar) were searched. Hand searching and snowballing were also employed for article searching. After extracting the relevant data based on inclusion and execution criteria, the qualitative data were used for the systematic review and quantitative data were used for meta-analysis. The Newcastle Ottawa Scale (NOS) scale was used to assess the quality of the included studies. Additionally, we registered our systematic review protocol in the prospective register of systematic reviews (PROSPERO) with registration number CRD42020205583. Results: A total of 39 studies met the criteria to be included in the systematic review. Overall, results indicated a preference for this technology and better academic scores. Qualitative analyses reported improved academic scores, ease of use, and enhanced collaboration amongst students as the top advantages, whereas technical issues were a disadvantage. The performance comparison of virtual versus light microscopy meta-analysis included 19 studies. Most (10/39) studies were from medical universities in the USA. VM was mainly used for teaching pathology courses (25/39) at medical schools (30/39). Dental schools (10/39) have also reported using VM for teaching microscopy. The COVID-19 pandemic was responsible for the transition to VM use in 17/39 studies. The pooled effect size of 19 studies significantly demonstrated higher exam performance (SMD: 1.36 [95% CI: 0.75, 1.96], p < 0.001) among the students who used VM for their learning. Students in the VM group demonstrated significantly higher exam performance than LM in pathology (SMD: 0.85 [95% CI: 0.26, 1.44], p < 0.01) and histopathology (SMD: 1.25 [95% CI: 0.71, 1.78], p < 0.001). For histology (SMD: 1.67 [95% CI: −0.05, 3.40], p = 0.06), the result was insignificant. The overall analysis of 15 studies assessing exam performance showed significantly higher performance for both medical (SMD: 1.42 [95% CI: 0.59, 2.25], p < 0.001) and dental students (SMD: 0.58 [95% CI: 0.58, 0.79], p < 0.001). Conclusions: The results of qualitative and quantitative analyses show that VM technology and digitization of glass slides enhance the teaching and learning of microscopic aspects of disease. Additionally, the COVID-19 global health crisis has produced many challenges to overcome from a macroscopic to microscopic scale, for which modern virtual technology is the solution. Therefore, medical educators worldwide should incorporate newer teaching technologies in the curriculum for the success of the coming generation of health-care professionals.