The role of RREB1 in human pancreatic beta cell development and function

Human genetics can be used as a tool to gain insights into fundamental aspects of human development, physiology and pathophysiology. Genome-wide association studies have uncovered multiple independent signals which alter risk for type 2 diabetes (T2D) and influence related glycaemic traits at the RREB1 locus. Fine-mapping revealed that one of these signals is driven by a common coding variant rs9379084 (p.D1171N), highlighting RREB1 as the causal transcript. Little is known about the function of the zinc finger transcription factor (TF) RREB1 in glucose homeostasis and how changes in its expression and/or activity might alter diabetes risk. The aim of my thesis was to determine the role of RREB1 in human beta cell development and function through transcriptomic and cellular phenotyping of genome-edited human induced pluripotent stem cells (hiPSCs) and EndoC-βH1 beta cells. To investigate the effect of loss of RREB1 on islet cell development I generated RREB1 knockout (KO) hiPSC lines using CRISPR/Cas9 and differentiated them along the pancreatic endocrine lineage. Gene expression profiling revealed that loss of RREB1 had a positive impact on the generation of endocrine precursors (EPs). Endocrine progenitor markers (NEUROG3, NKX2.2, NEUROD1) were significantly up-regulated, while pancreas progenitor marker genes (CPA2, NOTCH1) were markedly down-regulated in hiPSC-derived RREB1 KO EPs. RREB1-depleted EndoC-βH1 cells, generated using either RNA interference-mediated knock-down or CRISPR/Cas9-mediated KO of RREB1, were characterised by reduced INS expression and insulin content, whilst, gene expression profiling pointed to a positive effect of loss of RREB1 on the differentiation state of mature beta cells. Significant up-regulation of genes implicated in beta cell function, connectivity and maturity (GCK, SNAP25, GJD2, UCN3 ) was accompanied by simultaneous down-regulation of beta cell disallowed genes (PDGFRA, IGFBP4). RREB1 ChIP-Seq analysis in EndoC-βH1 cells identified a subset of these as direct RREB1 target genes and revealed an enrichment of RREB1 binding sites in islet active promoters, highlighting RREB1 as novel transcriptional activator and repressor in endocrine cells. RREB1 cis-regulated genes were enriched for target genes of the beta cell forbidden TF REST, pointing to a potential cooperative action of these two TFs in endocrine gene regulation. Transcriptional activities of RFX2 and RFX3 were significantly up-regulated in developing and mature RREB1 KO beta cells. While RFX2 was identified as direct RREB1 target gene showing markedly increased transcript levels in RREB1-deficient beta cells, the mechanism underlying up-regulation of RFX3 motif activity remained unclear. To explore the impact of the RREB1 T2D-associated alleles on beta cell development, I generated allele-specific hiPSC lines using CRISPR/Cas9. Characterisation of differentiated hiPSCs homozygous for the RREB1 T2D-associated coding variant p.N1171 suggested that the T2D protective allele acted as a gain-of-function allele, negatively affecting beta cell differentiation. How this is compatible with a protective effect on T2D risk requires further investigation. Overall, characterisation of two complimentary RREB1 KO models showed a novel role for RREB1 in beta cell development and function, contributing to the growing list of studies aiming to facilitate biological insights from T2D-associated genes.</p

The value of in vitro studies in a case of neonatal diabetes with a novel Kir6.2-W68G mutation.

Journal ArticleThis is an open access article available at http://onlinelibrary.wiley.com/doi/10.1002/ccr3.370/fullIn infants, especially with novel previously undescribed mutations of the KATP channel causing neonatal diabetes, in vitro studies can be used to both predict the response to sulphonylurea treatment and support a second trial of glibenclamide at higher than standard doses if the expected response is not observed

Applied Resiliency and Suicide Prevention: a Strengths-based, Risk- Reduction Framework

Book Summary: This inspiring resource presents theories, findings, and interventions from Positive Suicidology, an emerging strengths-based approach to suicide prevention. Its synthesis of positive psychology and suicidology theories offers a science-based framework for promoting wellbeing to complement or, if appropriate, replace traditional deficit-driven theories and therapies used in reducing suicidal thoughts and behaviors. Coverage reviews interpersonal, intrapersonal, and societal risk factors for suicide, and identifies protective factors, such as hope and resilience, that can be enhanced in therapy. From there, chapters detail a palette of approaches and applications of Positive Suicidology, from the powerful motivating forces described in Self-Determination Theory to meaning-building physical and social activities. Among the topics covered: Future-oriented constructs and their role in suicidal ideation and enactment. Gratitude as a protective factor for suicidal ideation and behavior: theory and evidence. Considering race and ethnicity in the use of positive psychological approaches to suicide. The Six R’s framework as mindfulness for suicide prevention. Community-based participatory research and empowerment for suicide prevention. Applied resiliency and suicide prevention: a strengths-based, risk-reduction framework. Psychotherapists, counselors, social workers, psychiatrists, and health psychologists, as well as educators, clergy and healthcare professionals, will find A Positive Psychological Approach to Suicide an invaluable source of contemporary evidence-based strategies for their prevention and intervention efforts with suicidal clients

Withdrawal of Antidementia Drugs in Older People: Who, When and How?

The evidence base to guide withdrawal of antidementia medications in older people with dementia is limited; while some randomised controlled studies have considered discontinuation of cholinesterase inhibitors, no such studies examining discontinuation of the N-Methyl-D-aspartate receptor antagonist memantine have been conducted to date. The purpose of this opinion article was to summarise the existing evidence on withdrawal of cholinesterase inhibitors and memantine, to highlight the key considerations for clinicians when making these prescribing decisions and to offer guidance as to when and how treatment might be discontinued. Until the evidence-base is enhanced by the findings of large scale randomised controlled discontinuation trials of ChEIs and memantine which use multiple, clinically relevant cognitive, functional and behavioural outcome measures, clinicians’ prescribing decisions involve balancing the risks of discontinuation with side-effects and costs of continued treatment. Such decisions must be highly individualised and patient-centred