Color discrimination requires the input of different photoreceptor cells that are sensitive to different wavelengths of light. The Drosophila visual system contains multiple classes of photoreceptor cells that differ in anatomical location, synaptic connections, and spectral sensitivity. The Rh5 and Rh6 opsins are expressed in nonoverlapping sets of R8 cells and are the only Drosophila visual pigments that remain uncharacterized. In this study, we ectopically expressed Rh5 and Rh6 in the major class of photoreceptor cells (R1-R6) and show them to be biologically active in their new environment. The expression of either Rh5 or Rh6 in "blind" ninaE(17) mutant flies, which lack the gene encoding the visual pigment of the R1-R6 cells, fully rescues the light response. Electrophysiological analysis showed that the maximal spectral sensitivity of the R1-R6 cells is shifted to 437 or 508 nm when Rh5 or Rh6, respectively, is expressed in these cells. These spectral sensitivities are in excellent agreement with intracellular recordings of the R8p and R8y cells measured in Calliphora and Musca. Spectrophotometric analyses of Rh5 and Rh6 in vivo by microspectrophotometry, and of detergent-extracted pigments in vitro, showed that Rh5 is reversibly photoconverted to a stable metarhodopsin (lambda(max) = 494 nm), whereas Rh6 appears to be photoconverted to a metarhodopsin (lambda(max) = 468 nm) that is less thermally stable. Phylogenetically, Rh5 belongs to a group of short-wavelength-absorbing invertebrate visual pigments, whereas Rh6 is related to a group of long-wavelength-absorbing pigments and is the first member of this class to be functionally characterized.

Objectives The primary aim of this systematic review is to objectively evaluate the test performance characteristics of three-dimensional echocardiography (3DE) in measuring left ventricular (LV) volumes and ejection fraction (EF). Background Despite its growing use in clinical laboratories, the accuracy of 3DE has not been studied on a large scale. It is unclear if this technology offers an advantage over traditional two-dimensional (2D) methods. Methods We searched for studies that compared LV volumes and EF measured by 3DE and cardiac magnetic resonance (CMR) imaging. A subset of those also compared standard 2D methods with CMR. We used meta-analyses to determine the overall bias and limits of agreement of LV end-diastolic volume (EDV), end-systolic volume (ESV), and EF measured by 3DE and 2D echocardiography (2DE). Results Twenty-three studies (1,638 echocardiograms) were included. The pooled biases ± 2 SDs for 3DE were −19.1 ± 34.2 ml, −10.1 ± 29.7 ml, and − 0.6 ± 11.8% for EDV, ESV, and EF, respectively. Nine studies also included data from 2DE, where the pooled biases were −48.2 ± 55.9 ml, −27.7 ± 45.7 ml, and 0.1 ± 13.9% for EDV, ESV, and EF, respectively. In this subset, the difference in bias between 3DE and 2D volumes was statistically significant (p = 0.01 for both EDV and ESV). The difference in variance was statistically significant (p < 0.001) for all 3 measurements. Conclusions Three-dimensional echocardiography underestimates volumes and has wide limits of agreement, but compared with traditional 2D methods in these carefully performed studies, 3DE is more accurate for volumes and more precise in all 3 measurements.

Background Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited genetic myocardial disease characterized by fibrofatty replacement of the myocardium and a predisposition to cardiac arrhythmias and sudden death. We evaluated the cardiomyopathy gene titin (TTN) as a candidate ARVC gene because of its proximity to an ARVC locus at position 2q32 and the connection of the titin protein to the transitional junction at intercalated disks. Methods and Results All 312 titin exons known to be expressed in human cardiac titin and the complete 3’ untranslated region were sequenced in 38 ARVC families. Eight unique TTN variants were detected in 7 families including a prominent Thr2896Ile mutation that showed complete segregation with the ARVC phenotype in one large family. The Thr2896IIe mutation maps within a highly conserved immunoglobulin-like fold (Ig10 domain), located in titin’s spring region. Native gel electrophoresis, NMR, intrinsic fluorescence, and proteolysis assays of wildtype and mutant Ig10 domains revealed that the Thr2896IIe exchange reduces the structural stability and increases the propensity towards degradation of the Ig10 domain. The phenotype of TTN variant carriers was characterized by history of sudden death (5/7 families), progressive myocardial dysfunction causing death or heart transplant (8/14 cases), frequent conduction disease (11/14), and incomplete penetrance (86%). Conclusions Our data provide evidence that titin mutations can cause ARVC, a finding that further expands the origin of the disease beyond desmosomal proteins. Structural impairment of the titin spring is a likely cause of ARVC and constitutes a novel mechanism underlying myocardial remodeling and sudden cardiac death.

Mutations in SCN5A were detected in 1.7% of DCM families. Two-thirds (6 of 9) of all reported DCM mutations in SCN5A localize to the highly conserved homologous S3 and S4 transmembrane segments, suggesting a shared mechanism of disruption of the voltage-sensing mechanism of this channel leading to DCM. Not surprisingly, SCN5A mutation carriers show a strong arrhythmic pattern that has clinical and diagnostic implications.

OBJECTIVES The purpose of this study was to assess the phenotype of Filamin C (FLNC) truncating variants in dilated cardiomyopathy (DCM) and understand the mechanism leading to an arrhythmogenic phenotype. BACKGROUND Mutations in FLNC are known to lead to skeletal myopathies, which may have an associated cardiac component. Recently, the clinical spectrum of FLNC mutations has been recognized to include a cardiac-restricted presentation in the absence of skeletal muscle involvement. METHODS A population of 319 U.S. and European DCM cardiomyopathy families was evaluated using whole-exome and targeted next-generation sequencing. FLNC truncation probands were identified and evaluated by clinical examination, histology, transmission electron microscopy, and immunohistochemistry. RESULTS A total of 13 individuals in 7 families (2.2%) were found to harbor 6 different FLNC truncation variants (2 stopgain, 1 frameshift, and 3 splicing). Of the 13 FLNC truncation carriers, 11 (85%) had either ventricular arrhythmias or sudden cardiac death, and 5 (38%) presented with evidence of right ventricular dilation. Pathology analysis of 2 explanted hearts from affected FLNC truncation carriers showed interstitial fibrosis in the right ventricle and epicardial fibrofatty infiltration in the left ventricle. Ultrastructural findings included occasional disarray of Z-discs within the sarcomere. Immunohistochemistry showed normal plakoglobin signal at cell–cell junctions, but decreased signals for desmoplakin and synapse-associated protein 97 in the myocardium and buccal mucosa. CONCLUSIONS We found FLNC truncating variants, present in 2.2% of DCM families, to be associated with a cardiac-restricted arrhythmogenic DCM phenotype characterized by a high risk of life-threatening ventricular arrhythmias and a pathological cellular phenotype partially overlapping with arrhythmogenic right ventricular cardiomyopathy.

Taste buds are assemblies of elongated epithelial cells, which are innervated by gustatory nerves that transmit taste information to the brain stem. Taste cells are continuously renewed throughout life via proliferation of epithelial progenitors, but the molecular regulation of this process remains unknown. During embryogenesis, sonic hedgehog (SHH) negatively regulates taste bud patterning, such that inhibition of SHH causes the formation of more and larger taste bud primordia, including in regions of the tongue normally devoid of taste buds. Here, using a Cre-lox system to drive constitutive expression of SHH, we identify the effects of SHH on the lingual epithelium of adult mice. We show that misexpression of SHH transforms lingual epithelial cell fate, such that daughter cells of lingual epithelial progenitors form cell type-replete, onion-shaped taste buds, rather than non-taste, pseudostratified epithelium. These SHH-induced ectopic taste buds are found in regions of the adult tongue previously thought incapable of generating taste organs. The ectopic buds are composed of all taste cell types, including support cells and detectors of sweet, bitter, umami, salt and sour, and recapitulate the molecular differentiation process of endogenous taste buds. In contrast to the well-established nerve dependence of endogenous taste buds, however, ectopic taste buds form independently of both gustatory and somatosensory innervation. As innervation is required for SHH expression by endogenous taste buds, our data suggest that SHH can replace the need for innervation to drive the entire program of taste bud differentiation.

Despite the high reported accuracy of exercise echocardiography in the detection of coronary artery disease, factors that compromise its sensitivity and specificity are less clear. This study examined the results of 179 post-treadmill stress echocardiograms in 150 consecutive patients who also underwent cardiac catheterization and in 29 normal persons at low risk for coronary artery disease. Of 114 patients who had significant coronary stenoses at angiography, 96 had an abnormal exercise echocardiogram (overall sensitivity 84%). False negative results correlated with the performance of submaximal exercise, single-vessel disease and moderate (50% to 70% diameter) stenoses. After the exclusion of seven patients performing submaximal exercise, the sensitivity was 90%. In 54 patients without previous infarction performing maximal exercise, the sensitivity was 87%, higher in patients with multivessel coronary disease (96%) than in those with single-vessel disease (79%). After the exclusion of patients with nondiagnostic results, due either to the performance of submaximal stress or the presence of electrocardiographic (ECG) changes at rest, exercise echocardiography had a higher sensitivity than did exercise electrocardiography (87% vs. 63%, p = 0.01). In 36 patients without significant coronary disease, exercise echocardiography had an overall specificity of 86%. After the exclusion of patients with a nondiagnostic test, exercise echocardiography had a specificity of 82% compared with 74% specificity for exercise electrocardiography (p = NS). Similarly, of the 29 normal subjects, 93% had a normal exercise echocardiogram and 97% had a normal exercise ECG (p = NS). Similarly, of the 29 normal subjects, 93% had a normal exercise echocardiogram and 97% had a normal exercise ECG (p = NS). Age, gender, body weight and image quality did not significantly influence the accuracy of exercise echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)

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