Chip-based mtDNA mutation screening enables fast and reliable genetic diagnosis of OXPHOS patients.

PURPOSE: Oxidative phosphorylation is under dual genetic control of the nuclear and the mitochondrial DNA (mtDNA). Oxidative phosphorylation disorders are clinically and genetically heterogeneous, which makes it difficult to determine the genetic defect, and symptom-based protocols which link clinical symptoms directly to a specific gene or mtDNA mutation are falling short. Moreover, approximately 25% of the pediatric patients with oxidative phosphorylation disorders is estimated to have mutations in the mtDNA and a standard screening approach for common mutations and deletions will only explain part of these cases. Therefore, we tested a new CHIP-based screening method for the mtDNA. METHODS: MitoChip (Affymetrix) resequencing was performed on three test samples and on 28 patient samples. RESULTS: Call rates were 94% on average and heteroplasmy detection levels varied from 5-50%. A genetic diagnosis can be made in almost one-quarter of the patients at a potential output of 8 complete mtDNA sequences every 4 days. Moreover, a number of potentially pathogenic unclassified variants (UV) were detected. CONCLUSIONS: The availability of long-range PCR protocols and the predominance of single nucleotide substitutions in the mtDNA make the resequencing CHIP a very fast and reliable method to screen the complete mtDNA for mutations.     

Baf60c is a component of the neural progenitor-specific BAF complex in developing retina

Remodeling of the chromatin network plays an important role regulating embryonic development as well as differentiation. The SWI/SNF complex is an ATP-dependent chromatin-remodeling complex. It consists of several proteins, including an ATPase subunit, either Brg1 or Brm. Two subunits of this complex, Baf53a and Baf45, have been previously identified as being neural progenitor-specific. In this study, we show that Baf60c, another important part of this large complex, acts in a similar neural progenitor-specific manner. We show that during development Baf60c is expressed in neural progenitors in human retinas as well as mouse retina, cortex and spinal cord. Baf60c expression is lost during neural differentiation and its overexpression keeps the progenitors in a proliferative state through its interaction with the Notch pathway. Finally, we show that Baf60c is re-expressed in the Müller glial cells that re-enter the cell cycle after neurotoxic damage.     

Clamp loading,unloading and intrinsic stability of the PCNA, β and gp45 sliding clamps of human,E. coli and T4 replicases

Background: The high speed and processivity of replicative DNA polymerases reside in a processivity factor which has been shown to be a ring-shaped protein. This protein (‘sliding clamp’) encircles DNA and tethers the catalytic unit to the template. Although in eukaryotic, prokaryotic and bacteriophage-T4 systems, the processivity factors are ring-shaped, they assume different oligomeric states. The Escherichia coli clamp (the β subunit) is active as a dimer while the eukaryotic and T4 phage clamps (PCNA and gp45, respectively) are active as trimers. The clamp can not assemble itself on DNA. Instead, a protein complex known as a clamp loader utilizes ATP to assemble the ring around the primer-template. This study compares properties of the human PCNA clamp with those of E. coli and T4 phage. Results: The PCNA ring is a stable trimer down to a concentration below 100 nm (K_d ≈ 21 nm ). On DNA, the PCNA clamp slides freely and dissociates from DNA slowly (t_1/2 ≈ 24 min). β is more stable in solution (K_d < 60 pm ) and on DNA (t_1/2 ≈ 1 h) than PCNA which may be explained by its simpler oligomeric state. The T4 gp45 clamp is a much less stable trimer than PCNA (K_d ≈ 250 nm ) and requires association with the polymerase to stabilize it on DNA as observed previously. The consequence of this cooperation between clamp and polymerase is that upon finishing a template and dissociation of the polymerase from DNA, the gp45 clamp spontaneously dissociates from DNA without assistance. However, the greater stability of the PCNA and β clamps on DNA necessitates an active process for their removal. The clamp loaders (RF-C and γ complex) were also capable of unloading their respective clamps from DNA in the presence of ATP. Conclusions: The stability of the different clamps in solution correlates with their stability on DNA. Thus, the low stability of the T4 clamp explains the inability to isolate gp45 on DNA. The stability of the PCNA and β clamps predicts they will require an unloading factor to recycle them on and off DNA during replication. The clamp loaders of PCNA and β double as clamp unloaders presumably for the purpose of clamp recycling.     

Autocrine growth of human blymphocytes: Maintained response to autostimulatory factors is the special feature of immortalization by Epstein-Barr virus—A hypothesis

The autocrine growth profile of human B lymphocytes transformed with Epstein-Barr virus (EBV) was found to comprise three distinct components: a B-cell growth factor (BCGF); an interleukin-1 (IL-1)-like activity; an activity requiring cell-to-cell contact for its action. Observations on the inhibition of the EBV-carrying Daudi lymphoma line by α-interferon indicated that loss of response to these autostimulatory factors was underlying growth cessation. Furthermore, a putative for BCGF was found to be down-regulated on B cells stimulated with non-transforming mitogens but constitutively expressed following EBV-transformation. Taken together with recent evidence that normal B cells produce autostimulatory factors, these findings suggest that the special feature of autocrine growth by EBV-immortalized cells is a maintenance of what should normally be a transient phenotype, possibly through deregulation of receptor expression. This hypothesis is discussed.     

Effects of Advertising: A Qualitative Analysis of Young Adults’ Engagement with Social Media About Food

Young adults are constantly exposed to energy-dense, nutrient-poor food and beverages, particularly through advertising. Exposure can influence poor food choices and negatively impact health. This study aimed to understand young adults’ attitudes and experiences associated with food-related advertisements, particularly on social media. This qualitative analysis involved n = 166 Australian 18 to 24-year-olds who were involved in a four-week online conversation on different areas relating to health, social media, and eating. Inductive thematic analysis was utilised on two forums on the recall and perceptions of food-related advertisements. Young adults commonly mentioned aspects of the marketing mix (promotion, product, price, and place) in food advertisements. Participants were more readily able to recall energy-dense, nutrient-poor food advertisements compared to healthy food-related advertisements. Digital advertisements were often discussed alongside the use of ad-blockers and algorithms which tailored their social media viewing to what they like. Participants felt constant exposure to unhealthy food advertisements hindered their ability to realise healthy eating behaviours and created feelings of guilt. This current analysis highlights the need to provide an advertising environment that appropriately motivates healthy eating and a food environment that allows healthy food to be the affordable and convenient option.     

Psycho-Behavioural Segmentation in Food and Nutrition: A Systematic Scoping Review of the Literature

Inadequate dietary intakes are a key modifiable risk factor to reduce the risk of developing non-communicable diseases. To encourage healthy eating and behaviour change, innovative public health interventions are required. Social marketing, in particular segmentation, can be used to understand and target specific population groups. However, segmentation often uses demographic factors, ignoring the reasons behind why people behave the way they do. This review aims to explore the food and nutrition related research that has utilised psycho-behavioural segmentation. Six databases from were searched in June 2020. Inclusion criteria were: published 2010 onwards, segmentation by psycho-behavioural variables, outcome related to food or nutrition, and healthy adult population over 18 years. 30 studies were included; most were quantitative (n = 28) and all studies used post-hoc segmentation methods, with the tools used to segment the population varying. None of the segments generated were targeted in future research. Psycho-behavioural factors are key in understanding people’s behaviour. However, when used in post-hoc segmentation, do not allow for effective targeting as there is no prior understanding of behaviours that need to change within each segment. In future, we should move towards hybrid segmentation to assist with the design of interventions that target behaviours such as healthy eating.