Whole exome sequencing identifies genetic variants in inherited thrombocytopenia with secondary qualitative function defects.

Inherited thrombocytopenias are a heterogeneous group of disorders characterized by abnormally low platelet counts which can be associated with abnormal bleeding. Next-generation sequencing has previously been employed in these disorders for the confirmation of suspected genetic abnormalities, and more recently in the discovery of novel disease-causing genes. However its full potential has not yet been exploited. Over the past 6 years we have sequenced the exomes from 55 patients, including 37 index cases and 18 additional family members, all of whom were recruited to the UK Genotyping and Phenotyping of Platelets study. All patients had inherited or sustained thrombocytopenia of unknown etiology with platelet counts varying from 11×109/L to 186×109/L. Of the 51 patients phenotypically tested, 37 (73%), had an additional secondary qualitative platelet defect. Using whole exome sequencing analysis we have identified "pathogenic" or "likely pathogenic" variants in 46% (17/37) of our index patients with thrombocytopenia. In addition, we report variants of uncertain significance in 12 index cases, including novel candidate genetic variants in previously unreported genes in four index cases. These results demonstrate that whole exome sequencing is an efficient method for elucidating potential pathogenic genetic variants in inherited thrombocytopenia. Whole exome sequencing also has the added benefit of discovering potentially pathogenic genetic variants for further study in novel genes not previously implicated in inherited thrombocytopenia.

Home-based Extended Rehabilitation for Older people (HERO): study protocol for an individually randomised controlled multi-centre trial to determine the clinical and cost-effectiveness of a home-based exercise intervention for older people with frailty as extended rehabilitation following acute illness or injury, including embedded process evaluation.

BACKGROUND: The majority of older people (> 65 years) in hospital have frailty and are at increased risk of readmission or death following discharge home. In the UK, following acute hospitalisation, around one third of older people with frailty are referred on for rehabilitation, termed 'intermediate care' services. Although this rehabilitation can reduce early readmission to hospital (< 30 days), recipients often do not feel ready to leave the service on discharge, suggesting possible incomplete recovery. Limited evidence suggests extended rehabilitation is of benefit in several conditions and there is preliminary evidence that progressive physical exercise can improve mobility and function for older people with frailty, and slow progression to disability. Our aim is to evaluate the effectiveness of the Home-based Older People's Exercise (HOPE) programme as extended rehabilitation for older people with frailty discharged home from hospital or intermediate care services after acute illness or injury. METHODS: A multi-centre individually randomised controlled trial, to evaluate the clinical and cost-effectiveness of the HOPE programme. This individualised, graded and progressive 24-week exercise programme is delivered by NHS physiotherapy teams to people aged 65 and older with frailty, identified using the Clinical Frailty Scale, following discharge from acute hospitalisation and linked intermediate care rehabilitation pathways. The primary outcome is physical health-related quality of life, measured using the physical component summary score of the modified Short Form 36- item health questionnaire (SF36) at 12 months. Secondary outcomes include self-reported physical and mental health, functional independence, death, hospitalisations, care home admissions. Plans include health economic analyses and an embedded process evaluation. DISCUSSION: This trial seeks to determine if extended rehabilitation, via the HOPE programme, can improve physical health-related quality of life for older people with frailty following acute hospitalisation. Results will improve awareness of the rehabilitation needs of older people with frailty, and provide evidence on the clinical and cost-effectiveness of the targeted exercise intervention. There is potential for considerable benefit for health and social care services through widespread implementation of trial findings if clinical and cost-effectiveness is demonstrated. TRIAL REGISTRATION: ISRCTN 13927531 . Registered on April 19, 2017.

Diversity and impact of rare variants in genes encoding the platelet G protein-coupled receptors.

Platelet responses to activating agonists are influenced by common population variants within or near G protein-coupled receptor (GPCR) genes that affect receptor activity. However, the impact of rare GPCR gene variants is unknown. We describe the rare single nucleotide variants (SNVs) in the coding and splice regions of 18 GPCR genes in 7,595 exomes from the 1,000-genomes and Exome Sequencing Project databases and in 31 cases with inherited platelet function disorders (IPFDs). In the population databases, the GPCR gene target regions contained 740 SNVs (318 synonymous, 410 missense, 7 stop gain and 6 splice region) of which 70 % had global minor allele frequency (MAF) < 0.05 %. Functional annotation using six computational algorithms, experimental evidence and structural data identified 156/740 (21 %) SNVs as potentially damaging to GPCR function, most commonly in regions encoding the transmembrane and C-terminal intracellular receptor domains. In 31 index cases with IPFDs (Gi-pathway defect n=15; secretion defect n=11; thromboxane pathway defect n=3 and complex defect n=2) there were 256 SNVs in the target regions of 15 stimulatory platelet GPCRs (34 unique; 12 with MAF< 1 % and 22 with MAF≥ 1 %). These included rare variants predicting R122H, P258T and V207A substitutions in the P2Y12 receptor that were annotated as potentially damaging, but only partially explained the platelet function defects in each case. Our data highlight that potentially damaging variants in platelet GPCR genes have low individual frequencies, but are collectively abundant in the population. Potentially damaging variants are also present in pedigrees with IPFDs and may contribute to complex laboratory phenotypes.

SLFN14 mutations underlie thrombocytopenia with excessive bleeding and platelet secretion defects.

Inherited thrombocytopenias are a group of disorders that are characterized by a low platelet count and are sometimes associated with excessive bleeding that ranges from mild to severe. We evaluated 36 unrelated patients and 17 family members displaying thrombocytopenia that were recruited to the UK Genotyping and Phenotyping of Platelets (GAPP) study. All patients had a history of excessive bleeding of unknown etiology. We performed platelet phenotyping and whole-exome sequencing (WES) on all patients and identified mutations in schlafen 14 (SLFN14) in 12 patients from 3 unrelated families. Patients harboring SLFN14 mutations displayed an analogous phenotype that consisted of moderate thrombocytopenia, enlarged platelets, decreased ATP secretion, and a dominant inheritance pattern. Three heterozygous missense mutations were identified in affected family members and predicted to encode substitutions (K218E, K219N, and V220D) within an ATPase-AAA-4, GTP/ATP-binding region of SLFN14. Endogenous SLFN14 expression was reduced in platelets from all patients, and mutant SLFN14 expression was markedly decreased compared with that of WT SLFN14 when overexpressed in transfected cells. Electron microscopy revealed a reduced number of dense granules in affected patients platelets, correlating with a decreased ATP secretion observed in lumiaggregometry studies. These results identify SLFN14 mutations as cause for an inherited thrombocytopenia with excessive bleeding, outlining a fundamental role for SLFN14 in platelet formation and function.