Analysis of Whole Exome Sequencing with Cardiometabolic Traits Using Family-Based Linkage and Association in the IRAS Family Study.

Ann Hum Genet. 2017 Mar;81(2):49-58

Authors: Tabb KL, Hellwege JN, Palmer ND, Dimitrov L, Sajuthi S, Taylor KD, Ng MC, Hawkins GA, Chen YI, Brown WM, McWilliams D, Williams A, Lorenzo C, Norris JM, Long J, Rotter JI, Curran JE, Blangero J, Wagenknecht LE, Langefeld CD, Bowden DW

Abstract
Family-based methods are a potentially powerful tool to identify trait-defining genetic variants in extended families, particularly when used to complement conventional association analysis. We utilized two-point linkage analysis and single variant association analysis to evaluate whole exome sequencing (WES) data from 1205 Hispanic Americans (78 families) from the Insulin Resistance Atherosclerosis Family Study. WES identified 211,612 variants above the minor allele frequency threshold of ≥0.005. These variants were tested for linkage and/or association with 50 cardiometabolic traits after quality control checks. Two-point linkage analysis yielded 10,580,600 logarithm of the odds (LOD) scores with 1148 LOD scores ≥3, 183 LOD scores ≥4, and 29 LOD scores ≥5. The maximal novel LOD score was 5.50 for rs2289043:T>C, in UNC5C with subcutaneous adipose tissue volume. Association analysis identified 13 variants attaining genome-wide significance (P < 5 × 10(-08) ), with the strongest association between rs651821:C>T in APOA5 and triglyceride levels (P  =  3.67 × 10(-10) ). Overall, there was a 5.2-fold increase in the number of informative variants detected by WES compared to exome chip analysis in this population, nearly 30% of which were novel variants relative to the Database of Single Nucleotide Polymorphisms (dbSNP) build 138. Thus, integration of results from two-point linkage and single-variant association analysis from WES data enabled identification of novel signals potentially contributing to cardiometabolic traits.

PMID: 28067407 [PubMed - indexed for MEDLINE]

Slowly progressive d-bifunctional protein deficiency with survival to adulthood diagnosed by whole-exome sequencing.

J Neurol Sci. 2017 Jan 15;372:6-10

Authors: Matsukawa T, Koshi KM, Mitsui J, Bannai T, Kawabe M, Ishiura H, Terao Y, Shimizu J, Murayama K, Yoshimura J, Doi K, Morishita S, Tsuji S, Goto J

Abstract
d-Bifunctional protein (DBP) deficiency is an autosomal recessive disorder of peroxisomal fatty acid oxidation caused by mutations in HSD17B4. It is typically fatal by the age of two years with symptom onset during the neonatal period, and survival until late childhood is rare. We herein report the case of a patient with DBP deficiency surviving until adulthood, who showed severe sensorineural deafness, disturbances in language acquisition, slowly progressive cerebellar ataxia, and peripheral neuropathy. This patient, in whom findings of prior investigations were nondiagnostic, had been followed up as having an early-onset spinocerebellar degeneration of unknown etiology. Whole-exome sequencing analysis at the age of 36 showed two heterozygous variants in the gene HSD17B4, which encodes DBP in this patient. A panel of peroxisomal investigations showed normal levels of very long chain fatty acids (VLCFAs) in plasma and elevated serum phytanic acid levels. Recently, an increasing number of patients with DBP deficiency surviving until adolescence/adulthood have been reported, in whom abnormalities in the levels of VLCFAs and other peroxisomal metabolites are marginal or nonexistent. Genetic analysis of HSD17B4 should be considered in adult patients with cerebellar ataxia, peripheral neuropathy, and pyramidal signs in addition to sensorineural auditory disturbance since childhood.

PMID: 28017249 [PubMed - indexed for MEDLINE]

Polymerase ε (POLE) ultra-mutation in uterine tumors correlates with T lymphocyte infiltration and increased resistance to platinum-based chemotherapy in vitro.

Gynecol Oncol. 2017 Jan;144(1):146-152

Authors: Bellone S, Bignotti E, Lonardi S, Ferrari F, Centritto F, Masserdotti A, Pettinella F, Black J, Menderes G, Altwerger G, Hui P, Lopez S, de Haydu C, Bonazzoli E, Predolini F, Zammataro L, Cocco E, Ferrari F, Ravaggi A, Romani C, Facchetti F, Sartori E, Odicino FE, Silasi DA, Litkouhi B, Ratner E, Azodi M, Schwartz PE, Santin AD

Abstract
OBJECTIVE: Up to 12% of all endometrial-carcinomas (EC) harbor DNA-polymerase-ε-(POLE) mutations. It is currently unknown whether the favorable prognosis of POLE-mutated EC is derived from their low metastatic capability, extraordinary number of somatic mutations thus imparting immunogenicity, or a high sensitivity to chemotherapy.
METHODS: Polymerase-chain-reaction-amplification and Sanger-sequencing were used to test for POLE exonuclease-domain-mutations (exons 9-14) 131 EC. Infiltration of CD4+ and CD8+ T-lymphocytes (TIL) and PD-1-expression in POLE-mutated vs POLE wild-type EC was studied by immunohistochemistry (IHC) and the correlations between survival and molecular features were investigated. Finally, primary POLE-mutated and POLE-wild-type EC cell lines were established and compared in-vitro for their sensitivity to chemotherapy.
RESULTS: Eleven POLE-mutated EC (8.5%) were identified. POLE-mutated tumors were associated with improved progression-free-survival (P<0.05) and displayed increased numbers of CD4+ (44.5 vs 21.8; P=0.001) and CD8+ (32.8 vs 13.5; P<0.001) TILs when compared to wild-type POLE EC. PD-1 receptor was overexpressed in TILs from POLE-mutated vs wild-type-tumors (81% vs 28%; P<0.001). Primary POLE tumor cell lines were significantly more resistant to platinum-chemotherapy in-vitro when compared to POLE-wild-type tumors (P<0.004).
CONCLUSIONS: POLE ultra-mutated EC are heavily infiltrated with CD4+/CD8+ TIL, overexpress PD-1 immune-check-point (i.e., features consistent with chronic antigen-exposure), and have a better prognosis when compared to other molecular subtypes of EC patients. POLE-mutated tumor-cell lines are resistant to platinum-chemotherapy in-vitro suggesting that the better prognosis of POLE-patients is not secondary to a higher sensitivity to chemotherapy but likely linked to enhanced immunogenicity.

PMID: 27894751 [PubMed - indexed for MEDLINE]

Drugs for Children.

Clin Pharmacol Ther. 2017 Jun;101(6):704-706

Authors: Ito S

Abstract
The "Therapeutic Orphan" status of children is gradually improving, but our efforts to eliminate off-label/off-evidence use must be sustained for safer and more effective pediatric drug therapy. This is even more important in resource-scarce settings, because of the increasing child population in those regions. The juncture of pediatric pharmacology and global child health represents an emerging field of clinical pharmacology illuminating a crucial societal need on a global scale.

PMID: 28510298 [PubMed - indexed for MEDLINE]

Evaluation of the Safety of Drugs and Biological Products Used During Lactation: Workshop Summary.

Clin Pharmacol Ther. 2017 Jun;101(6):736-744

Authors: Wang J, Johnson T, Sahin L, Tassinari MS, Anderson PO, Baker TE, Bucci-Rechtweg C, Burckart GJ, Chambers CD, Hale TW, Johnson-Lyles D, Nelson RM, Nguyen C, Pica-Branco D, Ren Z, Sachs H, Sauberan J, Zajicek A, Ito S, Yao LP

Abstract
This report serves as a summary of a 2-day public workshop sponsored by the US Food and Drug Administration (FDA) to discuss the safety of drugs and biological products used during lactation. The aim of the workshop was to provide a forum to discuss the collection of data to inform the potential risks to breastfed infants with maternal use of medications during lactation. Discussions included the review of current approaches to collect data on medications used during lactation, and the considerations for future approaches to design and guide clinical lactation studies. This workshop is part of continuing efforts to raise the awareness of the public for women who choose to breastfeed their infants.

PMID: 28510297 [PubMed - indexed for MEDLINE]

Adverse Drug Reactions in Children: The Double-Edged Sword of Therapeutics.

Clin Pharmacol Ther. 2017 Jun;101(6):725-735

Authors: Elzagallaai AA, Greff M, Rieder MJ

Abstract
Adverse drug reactions (ADRs) represent a major health problem worldwide, with high morbidity and mortality rates. ADRs are classified into Type A (augmented) and Type B (bizarre) ADRs, with the former group being more common and the latter less common but often severe and clinically more problematic due to their unpredictable nature and occurrence at any dose. Pediatric populations are especially vulnerable to ADRs due to the lack of data for this age group from the drug development process and because of the wide use of off-label and unlicensed use of drugs. Children are more prone to specific types of ADRs because of the level of maturity of body systems involved in absorption, metabolism, transportation, and elimination of drugs. This state-of-the-art review provides an overview of definitions, classifications, epidemiology, and pathophysiology of ADRs and discusses the available evidence for related risk factors and causes of ADRs in the pediatric population.

PMID: 28295234 [PubMed - indexed for MEDLINE]

Impulse control disorders and levodopa-induced dyskinesias in Parkinson's disease: an update.

Lancet Neurol. 2017 Mar;16(3):238-250

Authors: Voon V, Napier TC, Frank MJ, Sgambato-Faure V, Grace AA, Rodriguez-Oroz M, Obeso J, Bezard E, Fernagut PO

Abstract
Dopaminergic medications used in the treatment of patients with Parkinson's disease are associated with motor and non-motor behavioural side-effects, such as dyskinesias and impulse control disorders also known as behavioural addictions. Levodopa-induced dyskinesias occur in up to 80% of patients with Parkinson's after a few years of chronic treatment. Impulse control disorders, including gambling disorder, binge eating disorder, compulsive sexual behaviour, and compulsive shopping occur in about 17% of patients with Parkinson's disease on dopamine agonists. These behaviours reflect the interactions of the dopaminergic medications with the individual's susceptibility, and the underlying neurobiology of Parkinson's disease. Parkinsonian rodent models show enhanced reinforcing effects of chronic dopaminergic medication, and a potential role for individual susceptibility. In patients with Parkinson's disease and impulse control disorders, impairments are observed across subtypes of decisional impulsivity, possibly reflecting uncertainty and the relative balance of rewards and losses. Impairments appear to be more specific to decisional than motor impulsivity, which might reflect differences in ventral and dorsal striatal engagement. Emerging evidence suggests impulse control disorder subtypes have dissociable correlates, which indicate that individual susceptibility predisposes towards the expression of different behavioural subtypes and neurobiological substrates. Therapeutic interventions to treat patients with Parkinson's disease and impulse control disorders have shown efficacy in randomised controlled trials. Large-scale studies are warranted to identify individual risk factors and novel therapeutic targets for these diseases. Mechanisms underlying impulse control disorders and dyskinesias could provide crucial insights into other behavioural symptoms in Parkinson's disease and addictions in the general population.

PMID: 28229895 [PubMed - indexed for MEDLINE]

Essential Medicines for Children.

Clin Pharmacol Ther. 2017 Jun;101(6):718-720

Authors: Hoppu K

Abstract
The World Health Organization (WHO) defines Essential Medicines as those that satisfy the priority healthcare needs of the population. The right to essential medicines has been considered an important component of the right to health. In the name of equity, children should also have access to appropriate, available, affordable, and quality essential medicines they need, but children's essential medicines are too often missing.

PMID: 28182281 [PubMed - indexed for MEDLINE]

Improving Medicine Use for Children: A Global Imperative.

Clin Pharmacol Ther. 2017 Jun;101(6):715-717

Authors: MacLeod SM

Abstract
Professionals committed to optimal medical care of children recognize the need to increase future availability of thoroughly validated medicinal treatments. This will only be achieved through expanded efforts of pediatric clinical pharmacologists and clinical pharmacists equipped with the necessary skills in relevant research and educational methods. Recent research has demonstrated a shortfall in the human resource pool, particularly in low- and lower-middle-income countries where a majority of children under 14 years of age reside.

PMID: 28127760 [PubMed - indexed for MEDLINE]

Advantageous use of HepaRG cells for the screening and mechanistic study of drug-induced steatosis.

Toxicol Appl Pharmacol. 2016 Jul 01;302:1-9

Authors: Tolosa L, Gómez-Lechón MJ, Jiménez N, Hervás D, Jover R, Donato MT

Abstract
Only a few in vitro assays have been proposed to evaluate the steatotic potential of new drugs. The present study examines the utility of HepaRG cells as a cell-based assay system for screening drug-induced liver steatosis. A high-content screening assay was run to evaluate multiple toxicity-related cell parameters in HepaRG cells exposed to 28 compounds, including drugs reported to cause steatosis through different mechanisms and non-steatotic compounds. Lipid content was the most sensitive parameter for all the steatotic drugs, whereas no effects on lipid levels were produced by non-steatotic compounds. Apart from fat accumulation, increased ROS production and altered mitochondrial membrane potential were also found in the cells exposed to steatotic drugs, which indicates that all these cellular events contributed to drug-induced hepatotoxicity. These findings are of clinical relevance as most effects were observed at drug concentrations under 100-fold of the therapeutic peak plasmatic concentration. HepaRG cells showed increased lipid overaccumulation vs. HepG2 cells, which suggests greater sensitivity to drug-induced steatosis. An altered expression profile of transcription factors and the genes that code key proteins in lipid metabolism was also found in the cells exposed to drugs capable of inducing liver steatosis. Our results generally indicate the value of HepaRG cells for assessing the risk of liver damage associated with steatogenic compounds and for investigating the molecular mechanisms involved in drug-induced steatosis.

PMID: 27089845 [PubMed - indexed for MEDLINE]

Ultra-rare genetic variation in common epilepsies: a case-control sequencing study.

Lancet Neurol. 2017 Feb;16(2):135-143

Authors: Epi4K consortium, Epilepsy Phenome/Genome Project

Abstract
BACKGROUND: Despite progress in understanding the genetics of rare epilepsies, the more common epilepsies have proven less amenable to traditional gene-discovery analyses. We aimed to assess the contribution of ultra-rare genetic variation to common epilepsies.
METHODS: We did a case-control sequencing study with exome sequence data from unrelated individuals clinically evaluated for one of the two most common epilepsy syndromes: familial genetic generalised epilepsy, or familial or sporadic non-acquired focal epilepsy. Individuals of any age were recruited between Nov 26, 2007, and Aug 2, 2013, through the multicentre Epilepsy Phenome/Genome Project and Epi4K collaborations, and samples were sequenced at the Institute for Genomic Medicine (New York, USA) between Feb 6, 2013, and Aug 18, 2015. To identify epilepsy risk signals, we tested all protein-coding genes for an excess of ultra-rare genetic variation among the cases, compared with control samples with no known epilepsy or epilepsy comorbidity sequenced through unrelated studies.
FINDINGS: We separately compared the sequence data from 640 individuals with familial genetic generalised epilepsy and 525 individuals with familial non-acquired focal epilepsy to the same group of 3877 controls, and found significantly higher rates of ultra-rare deleterious variation in genes established as causative for dominant epilepsy disorders (familial genetic generalised epilepsy: odd ratio [OR] 2·3, 95% CI 1·7-3·2, p=9·1 × 10(-8); familial non-acquired focal epilepsy 3·6, 2·7-4·9, p=1·1 × 10(-17)). Comparison of an additional cohort of 662 individuals with sporadic non-acquired focal epilepsy to controls did not identify study-wide significant signals. For the individuals with familial non-acquired focal epilepsy, we found that five known epilepsy genes ranked as the top five genes enriched for ultra-rare deleterious variation. After accounting for the control carrier rate, we estimate that these five genes contribute to the risk of epilepsy in approximately 8% of individuals with familial non-acquired focal epilepsy. Our analyses showed that no individual gene was significantly associated with familial genetic generalised epilepsy; however, known epilepsy genes had lower p values relative to the rest of the protein-coding genes (p=5·8 × 10(-8)) that were lower than expected from a random sampling of genes.
INTERPRETATION: We identified excess ultra-rare variation in known epilepsy genes, which establishes a clear connection between the genetics of common and rare, severe epilepsies, and shows that the variants responsible for epilepsy risk are exceptionally rare in the general population. Our results suggest that the emerging paradigm of targeting of treatments to the genetic cause in rare devastating epilepsies might also extend to a proportion of common epilepsies. These findings might allow clinicians to broadly explain the cause of these syndromes to patients, and lay the foundation for possible precision treatments in the future.
FUNDING: National Institute of Neurological Disorders and Stroke (NINDS), and Epilepsy Research UK.

PMID: 28102150 [PubMed - indexed for MEDLINE]

Ending a Diagnostic Odyssey: Family Education, Counseling, and Response to Eventual Diagnosis.

Pediatr Clin North Am. 2017 Feb;64(1):265-272

Authors: Basel D, McCarrier J

Abstract
Genomic sequencing is the diagnostic test of choice for families with undiagnosed or rare diseases seeking an explanation for their child's complex medical concerns. The desire to find answers can easily bias interpretation of sequencing results, and thus the counseling process is designed to facilitate informed decision making and set realistic expectations for possible outcomes. The patient case examples serve to highlight the various challenges and complexities encountered with the clinical application of genomic sequencing and to reflect some of the data that has been accrued during the past 5 years of clinical experience.

PMID: 27894449 [PubMed - indexed for MEDLINE]

C14orf93 (RTFC) is identified as a novel susceptibility gene for familial nonmedullary thyroid cancer.

Biochem Biophys Res Commun. 2017 Jan 22;482(4):590-596

Authors: Liu C, Yu Y, Yin G, Zhang J, Wen W, Ruan X, Li D, Zhang S, Cai W, Gao M, Chen L

Abstract
The genetic causes for familial nonmedullary thyroid cancer (FNMTC) remain largely unknown. Through genetic linkage analysis and exome sequencing, C14orf93 (RTFC), PYGL, and BMP4 were identified as susceptibility gene candidates in a FNMTC family. By examining the expression and the oncogenic functions of these candidate genes, PYGL and BMP4 were excluded. We further characterized the functions of the uncharacterized gene RTFC in thyroid cancer. RTFC promotes thyroid cancer cell survival under starving conditions, and thyroid cancer cell migration. The R115Q, V205M and G209D RTFC mutants enhance the colony forming capacity of thyroid cancer cells, and are able to transform normal thyroid cells. In summary, our data suggest the roles of RTFC in thyroid carcinogenesis.

PMID: 27864143 [PubMed - indexed for MEDLINE]

Analysis of Mutations in AARS2 in a Series of CSF1R-Negative Patients With Adult-Onset Leukoencephalopathy With Axonal Spheroids and Pigmented Glia.

JAMA Neurol. 2016 Dec 01;73(12):1433-1439

Authors: Lynch DS, Zhang WJ, Lakshmanan R, Kinsella JA, Uzun GA, Karbay M, Tüfekçioglu Z, Hanagasi H, Burke G, Foulds N, Hammans SR, Bhattacharjee A, Wilson H, Adams M, Walker M, Nicoll JA, Chataway J, Fox N, Davagnanam I, Phadke R, Houlden H

Abstract
Importance: Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a frequent cause of adult-onset leukodystrophy known to be caused by autosomal dominant mutations in the CSF1R (colony-stimulating factor 1) gene. The discovery that CSF1R mutations cause ALSP led to more accurate prognosis and genetic counseling for these patients in addition to increased interest in microglia as a target in neurodegeneration. However, it has been known since the discovery of the CSF1R gene that there are patients with typical clinical and radiologic evidence of ALSP who do not carry pathogenic CSF1R mutations. These patients include those in whom the pathognomonic features of axonal spheroids and pigmented microglia have been found. Achieving a genetic diagnosis in these patients is important to our understanding of this disorder.
Objective: To genetically characterize a group of patients with typical features of ALSP who do not carry CSF1R mutations.
Design, Settings, and Participants: In this case series study, 5 patients from 4 families were identified with clinical, radiologic, or pathologic features of ALSP in whom CSF1R mutations had been excluded previously by sequencing. Data were collected between May 2014 and September 2015 and analyzed between September 2015 and February 2016.
Main Outcomes and Measures: Focused exome sequencing was used to identify candidate variants. Family studies, long-range polymerase chain reaction with cloning, and complementary DNA sequencing were used to confirm pathogenicity.
Results: Of these 5 patients, 4 were men (80%); mean age at onset of ALSP was 29 years (range, 15-44 years). Biallelic mutations in the alanyl-transfer (t)RNA synthetase 2 (AARS2) gene were found in all 5 patients. Frameshifting and splice site mutations were common, found in 4 of 5 patients, and sequencing of complementary DNA from affected patients confirmed that the variants were loss of function. All patients presented in adulthood with prominent cognitive, neuropsychiatric, and upper motor neuron signs. Magnetic resonance imaging in all patients demonstrated a symmetric leukoencephalopathy with punctate regions of restricted diffusion, typical of ALSP. In 1 patient, brain biopsy demonstrated axonal spheroids and pigmented microglia, which are the pathognomonic signs of ALSP.
Conclusions and Relevance: This work indicates that mutations in the tRNA synthetase AARS2 gene cause a recessive form of ALSP. The CSF1R and AARS2 proteins have different cellular functions but overlap in a final common pathway of neurodegeneration. This work points to novel targets for research and will lead to improved diagnostic rates in patients with adult-onset leukoencephalopathy.

PMID: 27749956 [PubMed - indexed for MEDLINE]

Hereditary breast and ovarian cancer: new genes in confined pathways.

Nat Rev Cancer. 2016 09;16(9):599-612

Authors: Nielsen FC, van Overeem Hansen T, Sørensen CS

Abstract
Genetic abnormalities in the DNA repair genes BRCA1 and BRCA2 predispose to hereditary breast and ovarian cancer (HBOC). However, only approximately 25% of cases of HBOC can be ascribed to BRCA1 and BRCA2 mutations. Recently, exome sequencing has uncovered substantial locus heterogeneity among affected families without BRCA1 or BRCA2 mutations. The new pathogenic variants are rare, posing challenges to estimation of risk attribution through patient cohorts. In this Review article, we examine HBOC genes, focusing on their role in genome maintenance, the possibilities for functional testing of putative causal variants and the clinical application of new HBOC genes in cancer risk management and treatment decision-making.

PMID: 27515922 [PubMed - indexed for MEDLINE]

An investigation of the association of genetic susceptibility risk with somatic mutation burden in breast cancer.

Br J Cancer. 2016 Sep 06;115(6):752-60

Authors: Zhu B, Mukherjee A, Machiela MJ, Song L, Hua X, Shi J, Garcia-Closas M, Chanock SJ, Chatterjee N

Abstract
BACKGROUND: Genome-wide association studies have reported nearly 100 common germline susceptibility loci associated with the risk for breast cancer. Tumour sequencing studies have characterised somatic mutation profiles in breast cancer patients. The relationship between breast cancer susceptibility loci and somatic mutation patterns in breast cancer remains largely unexplored.
METHODS: We used single-nucleotide polymorphism (SNP) genotyping array data and tumour exome sequencing data available from 638 breast cancer patients of European ancestry from The Cancer Genome Atlas (TCGA) project. We analysed both genotype data and, when necessary, imputed genotypes for 90 known breast cancer susceptibility loci. We performed linear regression models to investigate possible associations between germline risk variants with total somatic mutation count (TSMC), as well as specific mutation types. We examined individual SNP genotypes, as well as a multi-SNP polygenic risk score (PRS). Models were statistically adjusted for age at diagnosis, stage, oestrogen-receptor (ER) and progesterone-receptor (PR) status of breast cancer. We also performed stratified analyses by ER and PR status.
RESULTS: We observed a significant inverse association (P=8.75 × 10(-6); FDR=0.001) between the risk allele in rs2588809 of the gene RAD51B and TSMC across all breast cancer patients, for both ER(+) and ER(-) tumours. This association was also evident for different types of mutations. The PRS analysis for all patients, with or without rs2588809, showed a significant inverse association (P=0.01 and 0.04, respectively) with TSMC. This inverse association was significant in ER(+) patients with the ER(+)-specific PRS (P=0.02), but not among ER(-) patients for the ER(-)-specific PRS (P=0.39).
CONCLUSIONS: We observed an inverse association between common germline risk variants and TSMC, which, if confirmed, could provide new insights into how germline variation informs our understanding of somatic mutation patterns in breast cancer.

PMID: 27467053 [PubMed - indexed for MEDLINE]

Neuromuscular endplate pathology in recessive desminopathies: Lessons from man and mice.

Neurology. 2016 Aug 23;87(8):799-805

Authors: Durmuş H, Ayhan Ö, Çırak S, Deymeer F, Parman Y, Franke A, Eiber N, Chevessier F, Schlötzer-Schrehardt U, Clemen CS, Hashemolhosseini S, Schröder R, Hemmrich-Stanisak G, Tolun A, Serdaroğlu-Oflazer P

Abstract
OBJECTIVE: To assess the clinical, genetic, and myopathologic findings in 2 cousins with lack of desmin, the response to salbutamol in one patient, and the neuromuscular endplate pathology in a knock-in mouse model for recessive desminopathy.
METHODS: We performed clinical investigations in the patients, genetic studies for linkage mapping, exome sequencing, and qPCR for transcript quantification, assessment of efficacy of (3-month oral) salbutamol administration by muscle strength assessment, 6-minute walking test (6MWT), and forced vital capacity, analysis of neuromuscular endplate pathology in a homozygous R349P desmin knock-in mouse by immunofluorescence staining of the hind limb muscles, and quantitative 3D morphometry and expression studies of acetylcholine receptor genes by quantitative PCR.
RESULTS: Both patients had infantile-onset weakness and fatigability, facial weakness with bilateral ptosis and ophthalmoparesis, generalized muscle weakness, and a decremental response over 10% on repetitive nerve stimulation. Salbutamol improved 6MWT and subjective motor function in the treated patient. Genetic analysis revealed previously unreported novel homozygous truncating desmin mutation c.345dupC leading to protein truncation and consequent fast degradation of the mutant mRNA. In the recessive desminopathy mouse with low expression of the mutant desmin protein, we demonstrated fragmented motor endplates with increased surface areas, volumes, and fluorescence intensities in conjunction with increased α and γ acetylcholine receptor subunit expression in oxidative soleus muscle.
CONCLUSIONS: The patients were desmin-null and had myopathy, cardiomyopathy, and a congenital myasthenic syndrome. The data from man and mouse demonstrate that the complete lack as well as the markedly decreased expression of mutant R349P desmin impair the structural and functional integrity of neuromuscular endplates.

PMID: 27440146 [PubMed - indexed for MEDLINE]

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