Clinical impact of acquired risk factors in TTN-mediated dilated cardiomyopathy

Background/Introduction

Truncating variants in TTN-encoded titin (TTNtvs) underlie ∼25% of familial dilated cardiomyopathy (DCM) cases. In addition, TTNtvs are over-represented in alcoholic, peripartum, and chemotherapy-induced CM suggesting that risk factors may play a substantive role in the penetrance and expressivity of TTN-mediated DCM.

Purpose

To determine the prevalence and clinical impact of risk factors for TTN-mediated DCM within a single center cohort of unrelated patients with pathogenic (P)/likely pathogenic (LP) TTNtvs.

Methods

In this retrospective study, an institutionally developed natural language processing algorithm was used to identify all TTNtv-positive patients evaluated clinically between 01/2012 and 12/2019. Each TTNtv was then mapped to the TTN reference sequence (NM_133378.4) and classified according to a strict interpretation of the 2015 American College of Medical Genetics and Genomics (ACMG) guidelines. After exclusion of individuals with complex congenital heart disease, ischemic heart disease, and those without ACMG P/LP TTNtvs, available medical records were reviewed for risk factors such as long-term heavy alcohol consumption (>80 grams/day), cardiotoxic chemotherapy exposure, morbid obesity (body mass index >40), biopsy/imaging-confirmed myocarditis, peripartum/tachycardia-mediated CM, and valvular heart disease.

Results

Overall, 33 ACMG P/LP TTNtv-positive patients were identified (40% female; mean age at presentation 45±16 years; mean LVEF at presentation 38%±17%). Of note, 17/33 (52%) presented with heart failure (HF) and 4/33 (12%) presented with sustained ventricular arrhythmias (VAs). The remaining 12 (36%) TTNtv-positive patients presented with incidentally detected asymptomatic left ventricular systolic dysfunction (n=9) or as a result of genetic cascade screening (n=3). In comparison to TTNtv-positive patients with non-HF presentations, those with HF had worse left ventricular function (mean LVEF: 26% ± 11% vs 51% ±12%; p<0.001) and were more likely to have ≥1 risk factor [11/17 (65%) vs 4/16 (25%); p=0.04]. Unexpectedly, the 7 TTNtv-positive patients that presented with (n=4) or subsequently developed (n=3) sustained VAs were younger at the time of presentation (34±13 years vs 48±15 years; p=0.04) and displayed a similar degree of left ventricular dysfunction to those without sustained VAs (mean LVEF: 42% ± 17% vs 36% ± 17%; p=ns). Interestingly, the only risk factor over-represented amongst those with sustained VAs was bileaflet mitral valve prolapse [3/7 (43%) vs 0/26 (0%); p=0.006].

Conclusion

The majority of TTNtv-positive patients (14/23; 61%) with a history of HF and/or sustained VAs possessed ≥1 acquired risk factor providing further evidence that gene-environment interaction(s) exert a crucial role in the manifestation of TTN-mediated disease.

Funding Acknowledgement

Type of funding source: None

P4172Prevalence and potential genetic determinants of young sudden unexplained death victims with suspected arrhythmogenic mitral valve prolapse

Background

Mitral valve prolapse (MVP) is largely considered a benign condition. Recently, arrhythmogenic MVP, a sudden cardiac death (SCD)-predisposing condition characterized clinically by frequent/complex ventricular arrhythmias likely secondary to prolapsing leaflet-induced fibrosis of the left ventricle (LV), has emerged as an underappreciated cause of sudden unexplained death in the young (SUDY).

Objective

To determine the prevalence and potential genetic underpinnings of suspected arrhythmogenic MVP in a referral cohort of SUDY cases.

Methods

In this retrospective necropsy study, the medical records, autopsy reports, and whole exome molecular autopsy (WEMA) results for 77 SUDY victims (27 females; average age at death 20.6±8.9 years) were reviewed. Evidence of myxomatous MVP and concomitant LV pathology were noted. Variants detected in the pre-specified 164 WEMA gene panel with a frequency <0.001 in public exomes were classified using the 2015 American College of Medical Genetics (ACMG) guidelines.

Results

Overall, 6/77 (7.8%; 2 females; average age at death 20.7±6.9 years) SUDY cases had MVP as the lone abnormal post-mortem finding. The majority had bileaflet involvement (5/6; 83%) and microscopic LV fibrosis (5/6; 83%). Two SUDY cases (33%) were diagnosed with MVP by echocardiography prior to death. No gross hypertrophy, myocyte disarray, or fibrofatty replacement was noted. Unexpectedly, an ACMG pathogenic/likely pathogenic (P/LP) was more likely to be detected in SUDY cases with MVP than those without [3/6 (50%) vs 9/71 (13%); p<0.05]. Interestingly, the three variants identified in MVP-positive SUDY cases localized to genes associated previously with a cardiomyopathy/channelopathy predisposition (p.E1518fsX25-DMD, p.S285N-RYR2, and p.R109X-TTN).

Conclusion

This WEMA series provides additional evidence that the combination of bileaflet MVP and microscopic LV fibrosis underlies an unexpected number of SUDY cases. Whether P/LP variants in cardiomyopathy/channelopathy-susceptibility genes function as contributing factors or if unrelated, but poorly understood, molecular mechanisms account for the distinct cardiomyopathy-like phenotype observed in arrhythmogenic MVP requires further investigation.

New Media in Medical Education

ln 1984 the American Association of Medical Colleges´ Panel on the General Professional Education of the Physician challenged the medical community to take a leadership position in the effective application of information science and computer technology to medical education. The medical education community has risen to that challenge through the use of microcomputer technology and optical disc media including the recently developed fully integrated Hypermedia environment to enhance the learning environment.

Ngi and Internet2: accelerating the creation of tomorrow's internet

Internet2 is a consortium of leading U.S. universities working in partnership with industry and the U.S. government's Next Generation Internet (NGI) initiative to develop a faster, more reliable Internet for research and education including enhanced, high-performance networking services and the advanced applications that are enabled by those services [1]. By facilitating and coordinating the development, deployment, operation, and technology transfer of advanced, network-based applications and network services, Internet2 and NGI are working together to fundamentally change the way scientists, engineers, clinicians, and others work together. [http://www.internet2.edu] The NGI Program has three tracks: research, network testbeds, and applications. The aim of the research track is to promote experimentation with the next generation of network technologies. The network testbed track aims to develop next generation network testbeds to connect universities and federal research institutions at speeds that are sufficient to demonstrate new technologies and support future research. The aim of the applications track is to demonstrate new applications, enabled by the NGI networks, to meet important national goals and missions [2]. [http://www.ngi.gov/] The Internet2/NGI backbone networks, Abilene and vBNS (very high performance Backbone Network Service), provide the basis of collaboration and development for a new breed of advanced medical applications. Academic medical centers leverage the resources available throughout the Internet2 high-performance networking community for high-capacity broadband and selectable quality of service to make effective use of national repositories. The Internet2 Health Sciences Initiative enables a new generation of emerging medical applications whose architecture and development have been restricted by or are beyond the constraints of traditional Internet environments. These initiatives facilitate a variety of activities to foster the development and deployment of emerging applications that meet the requirements of clinical practice, medical and related biological research, education, and medical awareness throughout the public sector. Medical applications that work with high performance networks and supercomputing capabilities offer exciting new solutions for the medical industry. Internet2 and NGI,strive to combine the expertise of their constituents to establish a distributed knowledge system for achieving innovation in research, teaching, learning, and clinical care.

Murine retroviral vector producer cells survival and toxicity in the peritoneal cavity of dogs

Retroviral vector producer cells (VPC) can effectively transfer genes in vivo. To develop a safe method to target gene delivery into intraperitoneal tumors, we have examined the toxicity of intraperitoneal (i.p.) infusion of retroviral VPC in a xenogeneic canine model. Mongrel dogs were injected intraperitoneally (i.p.) with 2 x 10(9) murine LTKOSN.2 VPC. The animals did not demonstrate acute toxicity and tolerated the i.p. infusion of the cells without difficulty. Starting 7 days after i.p. injection, the dogs received intravenous injections of ganciclovir (GCV) twice daily (5 mg/kg) for 7 days. The treatment dogs underwent peritoneal washings on days 3, 7 and 14 after their initial infusion of cells to study the persistence of the VPC. GCV treatment did not cause significant toxicities. Dogs underwent serial blood tests to evaluate bone marrow, renal, liver and immunological function. Complete blood counts, electrolytes and renal function remained normal throughout the study. Although, transient mild elevations occurred of serum alkaline phosphate, the remaining hepatic enzymes remained normal. Histologic examination of tissues from animals sacrificed after the i.p. administration of the VPC revealed no tissue destruction of the normal peritoneal lining. The dogs mounted an antibody response to the murine VPC that was first observed 7 days post injection. PCR analysis of selected tissues after GCV administration did not reveal persistent vector sequences. These results demonstrated that the injection of xenogeneic VPC is not accompanied by significant adverse effects over a 1 month period following administration into the canine peritoneal cavity. These data support the potential clinical application of the VPC in Phase I clinical trials in humans.

A kinase/phosphatase system involving the protooncogene Lck is necessary for inducible modulation of Sob 1 during T cell activation

The phosphotyrosine containing protein Sob 1 regulates inducibility of a DNA binding complex (Band A) at the SRE of c-fos during T cell activation. In the present study, Sob 1 was regulated by activation of T cells through the T cell antigen receptor. Inhibition of protein tyrosine kinases (PTK) inactivated Sob 1 function and allowed the Band A DNA-protein complex to form. Inhibition of protein tyrosine phosphatases (PTP) caused constitutive activation of Sob 1 function and prevented induction of Band A at the SRE. Thus, Sob 1 is regulated by a constitutive PTP/PTK system. J.CaM 1 cells that lack a functional form of the PTK Lck are unable to induce Band A through the T cell antigen receptor. J.CaM 1 cells reconstituted with Lck seem to induce Band A normally. Thus, functional Lck is required for regulation of Sob 1.

Importance of learned resourcefulness to weight loss and early success during maintenance: preliminary evidence

The present study examined the importance of learned resourcefulness skills as measured by Rosenbaum's Self-Control Schedule (SCS) (Behav Ther 1980; 11: 109-121) to weight loss following a self-control program. Twenty-two women signed up for the 5-week self-control program. Participants' weight was recorded at the first and final session of the program, and at a 4-week follow-up. Results indicated that low resourceful women were more likely to drop out of the self-control program than high resourceful women. Although both the high and low resourceful women who completed the program lost the same amount of weight, only the high resourceful subjects continued to lose weight at follow-up. In contrast, the low resourceful women regained lost weight. Results point to the importance of learned resourcefulness for maintenance of weight loss following a self-control weight program.

New mammalian chloride channel identified by expression cloning

Ion channels selectively permeable to chloride ions regulate cell functions as diverse as excitability and control of cell volume. Using expression cloning techniques, a complementary DNA from an epithelial cell line has been isolated, sequenced and its putative structure examined by site-directed mutagenesis. This cDNA, encoding a 235-amino-acid protein, gave rise to a chloride-selective outward current when expressed in Xenopus oocytes. The expressed, outwardly rectifying chloride current was calcium-insensitive and was blocked by nucleotides applied to the cell surface. Mutation of a putative nucleotide-binding site resulted in loss of nucleotide block but incurred dependence on extracellular calcium concentration. The unusual sequence of this putative channel protein suggests a new class of ion channels not related to other previously cloned chloride channels.

Dopamine D1 receptor stimulation of cyclic AMP accumulation in COS-1 cells

Dopamine is shown to stimulate cAMP accumulation in COS-1 cells via endogenously expressed dopamine D1 receptors. A dissociation of dopamine and beta-adrenoceptor responses is demonstrated by the use of selective antagonists and different desensitization patterns following exposure of the cells to dopamine or the beta-adrenoceptor agonist, isoproterenol. The dopamine response in COS-1 cells exhibits a pharmacological profile similar to that found in dopamine D1 tissues such as rat striatum and fish retina. The presence of DARPP-32 (dopamine- and cAMP-regulated phosphoprotein, Mr 32,000) immunoreactivity in COS-1 cells is shown by Western blotting and is consistent with the endogenous expression of a dopamine D1 receptor in these cells. It is concluded that a dopamine D1 receptor is expressed in COS-1 cells and the implications of this are discussed.

A68930: a potent agonist selective for the dopamine D1 receptor

A68930, (1R,3S)-1-aminomethyl-5,6-dihydroxy-3-phenylisochroman HCl, is a potent (EC50 = 2.5 nM), partial (intrinsic activity = 66% of dopamine) agonist in the fish retina dopamine-sensitive adenylate cyclase model of the D1 dopamine receptor. In the rat caudate-putamen model of the D1 dopamine receptor, A68930 is a potent (EC50 = 2.1 nM) full agonist. In contrast, A68930 is a much weaker (EC50 = 3920 nM) full agonist in a biochemical model of the dopamine D2 receptor. The orientation of the 3-phenyl substituent in the molecule is critical for the affinity and selectivity of the molecule towards the dopamine D1 receptor. A68930 also displays weak alpha 2-agonist activity but the molecule is virtually inactive at the alpha 1- and beta-adrenoceptors. When tested in rats bearing a unilateral 6-OHDA lesion of the nigro-neostriatal neurons, A68930 elicits prolonged (greater than 20 h) contralateral turning that is antagonized by dopamine D1 receptor selective doses of SCH 23390 but not by D2 receptor selective doses of haloperidol. In this lesioned rat model, A68930 increases 2-deoxyglucose accumulation in the lesioned substantia nigra, pars reticulata. When tested in normal rats, A68930 elicits hyperactivity and, at higher doses, produces a forelimb clonus.

AuthorBase: a database of authoring systems software

A working prototype database of authoring system software was developed as part of a study of authoring software conducted by the National Library of Medicine. The database and development issues ranging from the scope of the database to what information to document are described. The protype demonstrates that records of reasonable integrity can be derived from vendor supplied information as long as users understand the database is only an initial starting point in searching for authoring software and a resource for becoming generally familiar with the technology.

A-69024: a non-benzazepine antagonist with selectivity for the dopamine D-1 receptor

A-69024 HBr, 1-(2-bromo-4,5-dimethoxybenzyl)-7-hydroxy-6-methoxy-2-methyl-1,2,3,4- tetrahydroisoquinoline hydrobromide, is a selective antagonist of the dopamine D-1 receptor. A-69024 HBr shows an apparent affinity toward the D-1 receptor (identified using [125I]SCH 23390) of 12.6 (4.15-38.3) nM (mean (90% CL), n = 3); the apparent affinity toward the D-2 receptor (identified using [3H]spiroperidol is 1 290 (1,200-1,380) nM (n = 3); using [125I]lysergic acid diethylamine to identify the 5-HT1C receptor gives apparent affinity of 17,800 (9,700-32,600) nM (n = 3). In assays of adenylate cyclase activity, A-69024 HBr antagonizes the D-1 receptor with a calculated affinity of 43.9 (17.5-110) nM (n = 5), while the molecule antagonizes the D-2 receptor with a calculated affinity greater than 400 nM. Behavioral studies demonstrate that A-69024 HBr (5 mg/kg s.c.) is able to block both amphetamine-induced locomotor activity and apomorphine-induced stereotypy. Furthermore, A-69024 HBr blocks SF&F 38393-, but not quinpirole-, induced rotation in rats having unilateral 6-hydroxydopamine lesions of the substantia nigra. When administered at behaviorally effective doses. A-69024 HBr neither increases the concentration of serum prolactin nor potentiates dihydroxyphenylalanine (DOPA) accumulation in the caudate-putamen of rats pretreated with the DOPA decarboxylase inhibitor NSD 1015. Because A-69024 is a dopamine receptor antagonist discriminating between the D-1 and D-2 receptors, it may be a useful research tool.

Beta-adrenergic blockade in children

Beta-adrenergic blockers are often used in children to treat a variety of cardiovascular and noncardiovascular medical problems. The clinical experiences with beta-blockers in neonates, children, and adolescents are discussed in this comprehensive review.

Perception of expiratory flow by asthmatics and non-asthmatics during rest and exercise

Perception of respiratory function may be an important factor in self-management of asthma. Previous research has suggested that asthmatics may not accurately perceive pulmonary functioning. The perception of normal and asthmatic individuals was assessed using a magnitude production procedure in a series of three studies, proceeding from normal individuals during rest, then submaximal exercise, to a comparison of normal and asthmatic adolescents during rest and submaximal exercise. At rest there were no differences between males and females, adults and adolescents, or asthmatics and non-asthmatics. However, there were significant differences in perception between rest and exercise for all groups. These findings suggest that a breakdown in perception does not occur during submaximal exercise in patients with asthma.

Asthma and bacterial sinusitis in children

Signs, symptoms, and radiographic abnormalities of sinusitis are frequent in children with asthma; it is not known whether sinus inflammation is associated with bacterial infection or other mechanisms. Eight asthmatic patients with exacerbation of asthma despite bronchodilator therapy were studied after maxillary sinusitis was confirmed by radiographs. All had cough, wheezing, nasal stuffiness, rhinorrhea and were afebrile. Four patients had headaches, and two had facial pain. Maxillary sinus aspirates were obtained, and bacterial cultures were positive in five: Branhamella catarrhalis (2), nontypeable Hemophilus influenzae (2), Streptococcus pneumoniae (1). Nose and throat cultures did not correlate with sinus cultures. All patients received bronchodilators, and four of eight patients received steroids. All were treated for 14 to 28 days with antibiotics during which seven of the eight patients improved clinically including all with positive sinus cultures. Asthma-symptoms diary scores were kept by five; all demonstrated improvement. Pulmonary-function tests improved in five of seven patients after the antibiotic and asthma therapy including the four patients with positive cultures. Sinus radiographs cleared in three, improved in three, and were unchanged in two patients after antibiotic therapy.

Sample Performance of the Grille Spectrometer

The grille spectrometer observed the setting and rising sun 18 times during the Spacelab 1 mission. In addition to solar absorption lines, many of which had not been observed before, atmospheric spectral absorptions due to carbon monoxide and carbon dioxide were observed at heights tangent to the thermosphere (greater than 85 kilometers), and absorptions due to ozone, water, methane, and nitrous oxide were observed in the mesosphere (greater than 50 kilometers). The strongly coupled molecules NO-NO(2) and HC1-HF were observed as pairs in the stratosphere. Methane is presented as an example of the instrumental operations because of the characteristic aspect of the Q branch of its v(3) band.

Analysis of the prognosis of minimal and occult breast cancers

Of 296 occult breast cancers diagnosed at Kaiser-Permanente Medical Center, Los Angeles, in the last ten years, 80 were classified as minimal and 167 as nonminimal. Minimal cancers were intraductal, lobular in situ, or invasive and 0.5 cm or less in diameter. In the occult-minimal group, no woman had axillary node metastases, and there were no recurrences. In the occult-nonminimal group, 26% of the patients had axillary nodal involvement, with a recurrence rate of 13% and a mortality of 11.6%. Occult breast cancers differed significantly between minimal and nonminimal tumors in both treatment and prognosis. Nonminimal cancers should be treated as any palpable carcinoma. More conservative approaches could be considered for the minimal group, but prospective controlled studies should be done to determine the long-term risks of such treatment.