Heiko Harten

Osnabrück University | UOS · Developmental Biology / Zoology

Muscle contraction depends on strictly controlled Ca²⁺ transients within myocytes. A major player maintaining these transients is the sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase, SERCA. Activity of SERCA is regulated by binding of micropeptides and impaired expression or function of these peptides results in cardiomyopathy. To date, it is not kn...

The Bowditch effect or staircase phenomenon is the increment or reduction of contractile force when heart rate increases, defined as either a positive or negative staircase. The healthy and failing human heart both show positive or negative staircase, respectively, but the causes of these distinct cardiac responses are unclear. Different experiment...

ELife digest The hormone insulin and similar molecules called insulin-like peptides act as signals to control many processes in the body, including growth, stress responses and aging. Disrupting these signaling pathways can cause many diseases, with diabetes being the most common of these. Although the roles of the signaling pathways have been well...

According to a classic tenet, sugar transport across animal membranes is restricted to monosaccharides. Here, we present the first report of an animal sucrose transporter, SCRT, which we detected in Drosophila melanogaster at each developmental stage. We localized the protein in apical membranes of the late embryonic hindgut as well as in vesicular...

Drosophila nephrocytes are specialised cells that share critical functional, morphological, and molecular features with mammalian podocytes. Accordingly, nephrocytes represent a preferred invertebrate model for human glomerular disease. Here, we established a method for cell-specific isolation of the two types of Drosophila nephrocytes, garland and...

Drosophila, like all insects, has an open circulatory system for the distribution of haemolymph and its components. The circulation of the haemolymph is essentially driven by the pumping activity of the linear heart. The heart is constructed as a tube into which the haemolymph is sucked and pumped forward by rhythmic contractions running from the p...

Neprilysins are highly conserved ectoenzymes that hydrolyze and thus inactivate signaling peptides in the extracellular space. Herein, we focus on Neprilysin 4 from Drosophila melanogaster and evaluate the existing knowledge on the physiological relevance of the peptidase. Particular attention is paid to the role of the neprilysin in regulating fee...

Introduction: Transmembrane protein 43 (TMEM43) is localized in the nuclear envelope and endoplasmic reticulum (ER). TMEM43- c.1073C>T, p.S358L leads to a rare fully penetrant type 5 arrhythmogenic right ventricular cardiomyopathy (ARVC5). The molecular pathomechanism of ARVC5 is not well understood. Methods: TurboID cloned to N- and C-terminal of...

Within a cell, vesicles play a crucial role in the transport of membrane material and proteins to a given target membrane, and thus regulate a variety of cellular functions. Vesicular transport occurs by means of, among others, endocytosis, where cargoes are taken up by the cell and are processed further upon vesicular trafficking, i.e. transported...

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a severe cardiac disease that leads to heart failure or sudden cardiac death (SCD). For the pathogenesis of ARVC, various mutations in at least eight different genes have been identified. A rare form of ARVC is associated with the mutation TMEM43 p.S358L, which is a fully penetrant variant i...

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): DFG Objectives TMEM43 encodes for a transmembrane protein located in the ER membrane and the nuclear rim. TMEM43 has predicted four transmembrane domains. The missense variant TMEM43 p.S358L is fully penetrant in males and associated w...

Appropriate cardiac performance depends on a tightly controlled handling of Ca²⁺ in a broad range of species, from invertebrates to mammals. The role of the Ca²⁺ ATPase, SERCA, in Ca²⁺ handling is pivotal, and its activity is regulated, inter alia, by interacting with distinct proteins. Herein, we give evidence that 4E binding protein (4E-BP) is a...

The neprilysin (M13) family of metalloendopeptidases comprises highly conserved ectoenzymes that cleave and thereby inactivate many physiologically relevant peptides in the extracellular space. Impaired neprilysin activity is associated with numerous human diseases. Here, we present a comprehensive list and classification of M13 family members in D...

Endosome biogenesis in eukaryotic cells is critical for nutrient uptake and plasma membrane integrity. Early endosomes initially contain Rab5, which is replaced by Rab7 on late endosomes prior to their fusion with lysosomes. Recruitment of Rab7 to endosomes requires the Mon1-Ccz1 guanosine exchange factor (GEF). Here, we show that full function of...

Tetraspanin-2A (Tsp2A) is an integral membrane protein of smooth septate junctions in Drosophila melanogaster. To elucidate its structural and functional roles in Malpighian tubules, we used the GAL4/UAS system to selectively knockdown Tsp2A in principal cells of the tubule. Tsp2A localizes to smooth septate junctions (sSJ) in Malpighian tubules in...

Septate junctions (SJs) are occluding cell-cell junctions that have roles in paracellular permeability and barrier function in the epithelia of invertebrates. Arthropods have two types of SJs, pleated SJs (pSJs) and smooth SJs (sSJs). In Drosophila melanogaster, sSJs are found in the midgut and Malpighian tubules, but the functions of sSJs and thei...

Neuropeptides and peptide hormones serve as critical regulators of numerous biological processes, including development, growth, reproduction, physiology, and behaviour. In mammals, peptidergic regulatory systems are complex and often involve multiple peptides that act at different levels and relay to different receptors. To improve the mechanistic...

Somatic muscles are formed by the iterative fusion of myoblasts into muscle fibres. This process is driven by the recurrent recruitment of proteins to the cell membrane to induce F-actin nucleation at the fusion site. Although various proteins involved in myoblast fusion have been identified, knowledge about their sub-cellular regulation is rather...

In Drosophila, formation of the cardiac extracellular matrix (ECM) starts during embryogenesis. Assembly and incorporation of structural proteins such as Collagen IV, Pericardin, and Laminin A, B1, and B2 into the cardiac ECM is critical to the maintenance of heart integrity and functionality and, therefore, to longevity of the animal. The cardiac...

The biomechanical properties of extracellular matrices (ECMs) are critical to many biological processes, including cell-cell communication and cell migration and function. The correct balance between stiffness and elasticity is essential to the function of numerous tissues, including blood vessels and the lymphatic system, and depends on ECM consti...

Drosophila harbors a simple tubular heart that ensures hemolymph circulation within the body. The heart is built by a few different cell types, including cardiomyocytes that define the luminal heart channel and ostia cells that constitute openings in the heart wall allowing hemolymph to enter the heart chamber. Regulation of flow directionality wit...

In many polychaete species filamentous, pectinate or arborescence branchiae may be present. In species with well-developed parapodia, such as Amphinomidae and Eunicidae, they are often associated with the notopodia. Mostly they arise close to the dorsal cirrus. Whereas the branchiae are regarded as the main site for respiration, the cirri function...

Size and weight measurements.3rd instar larvae where grouped into genotype-specific cohorts of 10 individuals. The weights of at least five cohorts per genotype were averaged to calculate the mean weight of one respective larva. P values marked in bold indicate statistically significant deviations from the respective controls.For size measurements,...

Feeding assay.Depicted are dye intensities (no. of detected pixels) within the intestines of animals of the indicated genotype. At least six individuals per genotype and time point were analyzed. P values marked in bold indicate statistically significant deviations from the respective controls.DOI: http://dx.doi.org/10.7554/eLife.19430.010

Lethality assay.Depicted are the percentages of animals of a specific stage that do not develop into the next stage. valuesmarked in bold indicate statistically significant deviations from the respective controls.DOI: http://dx.doi.org/10.7554/eLife.19430.004

Chemical shifts and detected changes of significantly affected metabolites.Significant changes are based on correlations with predictive scores from cross validated OPLS-DA models (Q2 = 0.95 and 0.74, respectively). A cutoff value for R2 corresponding to p<0.05 with Bonferroni correction for an assumed number of 100 metabolites was used.DOI: http:/...

Ammonia is a toxic waste product from protein metabolism and needs to be either converted into less toxic molecules or, in the case of fish and aquatic invertebrates, excreted directly as is. In contrast to fish, very little is known regarding the ammonia excretion mechanism and the participating excretory organs in marine invertebrates. In the cur...

Hand proteins belong to the highly conserved family of basic Helix-Loop-Helix transcription factors and are critical to distinct developmental processes, including cardiogenesis and neurogenesis in vertebrates. In Drosophila melanogaster a single orthologous hand gene is expressed with absence of the respective protein causing semilethality during...

The ability of many insects to walk on vertical smooth surfaces such as glass or even on the ceiling has fascinated biologists for ages and has led to the discovery of highly specialized adhesive organs located at the distal end of the animals' legs. So far, research has primarily focused on structural and ultrastructural investigations leading to...

The neuronal microtubule-associated protein Tau is expressed in different variants, and changes in Tau isoform composition occur during development and disease. Here, we investigate a potential role of the multivalent tau mRNA-binding proteins G3BP1 and IMP1 in regulating neuronal tau expression. We demonstrate that G3BP1 and IMP1 expression induce...

Polarity of cardiac cells. (A–D) Localization of the cell adhesion protein FasIII (A,B) and the cortex protein αSpectrin in stage 17 embryonic hearts (C, D). Both proteins predominantly localize to the apical and lateral membranes of cardiomyocytes. This distribution is not changed in homozygous lohMB05750 (E–H) and prcMB03017 mutants (I–L). (TIF)

Fat body derived Prc contributes to heart integrity. (A–F) Induced knock down of prc activity by expression of the IR line VDRC100357 (C, D) and the specific IR line VDRC41320 (E, F), either under the control of handC-Gal4 (C, E) or prc-Gal4 (D, F). The expression of both hairpins under the control of either driver results in a pericardial cell det...

Accumulation of the tracer dye uranin in the head of an injected wild type pharate adult. Anterior is to the top. (MP4)

loh maps to the second chromosome and is identical to CG6232. (A–B) Cardiac phenotype initially identified in the EMS allele loh1. Homozygous mutant first instar larvae display a detachment of pericardial cells (arrowhead) from the heart tube (visualized by handC-GFP). (C–F) Transheterozygous third instar larvae used for mapping of loh1. The allele...

Life span of mutants. Life span curves of control (white1118) or homozygous lohMB05750 and prcMB03017 mutants indicate a reduction of life time upon mutation of either loh or prc. (TIF)

Heart autonomous function of loh. (A) RT-PCR showing lohA transcript levels in control embryos compared to homozygous lohMB05750 embryos. Transcripts are massively reduced in the mutants, leading to decreased protein levels (compare to Figure 4D). (B–D) Induced knock down of loh activity by expression of the IR line VDRC31020 (C) targeting both tra...

ECM formation in loh and prc mutants and generated revertants. (A, B) Prc mis-localizes in homozygous loh1 and lohMI02765 stage 17 embryos very similar to the phenotype observed in lohMB05750 (compare to Figure 6B). (C) PCR using oligonucleotides flanking the inserted minos elements in lohMB05750 or prcMB03017. The chosen reaction conditions only a...

Heart beat pattern in a wild type semi-dissected third instar larva. Anterior is to the left. (MP4)

Specificity of the anti-Loh antibody. (A–C) Stage 17 embryos stained against Loh. A cardiac signal is present in control and heterozygous Df(2L)Exel7048/CyO,Kr>GFP embryos (arrowheads), but absent from homozygous deficient animals (C). (TIF)

Overexpression and localization of LohA. (A) Total protein extracts from third instar larvae. Immunoblots probed against Loh or Prc. The ectopic overexpression of LohA does not induce alterations in Prc protein levels. (B) Optical section through the fat body of a prc>LohA third instar larva stained against Loh (red), βPS integrin (green) and GFP (...

Heart beat pattern in a transheterozygous lohMB05750/Df(2L)Exel7048 semi-dissected third instar larva. Anterior is to the left. (MP4)

Heart beat pattern in a transheterozygous prcMB03017/Df(3L)vin6 semi-dissected third instar larva. Anterior is to the left. (MP4)

Author Summary Cellular adhesion and tissue integrity in multicellular organisms strongly depend on the molecular network of the extracellular matrix (ECM). The number, topology and function of ECM molecules are highly diverse in different species, or even in single matrices in one organism. In our study we focus on the protein class of ADAMTS-like...

The Hand basic helix-loop-helix transcription factors play an important role in the specification and patterning of various tissues in vertebrates and invertebrates. Here, we have investigated the function of Hand in the development of the Drosophila wing hearts which consist of somatic muscle cells as well as a mesodermally derived epithelium. We...

In aquatic invertebrates, metabolic nitrogenous waste is excreted predominately as ammonia. Very little is known, however, of the underlying mechanisms of ammonia excretion, particularly in freshwater species. Our results indicate that in the non-parasitic freshwater planarian Schmidtea mediterranea, ammonia excretion depends on acidification of th...

Neprilysins (Neps) are membrane-bound M13 endopeptidases responsible for the activation and/or inactivation of peptide signalling events on cell surfaces. By hydrolysing their respective substrates, mammalian Neps are crucial to the metabolism of numerous bioactive peptides, especially in the nervous, immune, cardiovascular and inflammatory systems...

Here we report on the generation and in vivo analysis of a series of loss-of-function mutants for the Drosophila ArfGEF, Gartenzwerg. The Drosophila gene gartenzwerg (garz) encodes the orthologue of mammalian GBF1. garz is expressed ubiquitously in embryos with substantially higher abundance in cells forming diverse tubular structures such as saliv...

ADAM metalloproteases are membrane bound glycoproteins that control many biological processes during development and differentiation, mainly by acting as ectodomain sheddases. The Drosophila genome contains five genes that code for classical ADAM proteins which are characterized by a highly conserved domain structure with the respective catalytic d...

In this study participation of cation/proton exchangers (NHE) in ammonia uptake in the medial midgut of Manduca sexta larvae was investigated employing a modified Ussing chamber. There was a mean inward net ammonia (NH₃ + NH₄+) flux of 194 ± 17 nmol cm⁻² h⁻¹ across the isolated epithelium under conditions of 0.1 mmol L⁻¹ ammonia on both sides of th...

A Disintegrin And Metalloprotease (ADAM) proteins belong to the metzincin superfamily of metalloproteases that are known to play important roles in several physiological and developmental processes including myoblast fusion, tumor necrosis factor-α release or fertilization. They are characterized by a typical domain structure with a proteolytically...

Proteins belonging to the family of neprilysins are typically membrane bound M13 endopeptidases responsible for the inactivation and/or activation of peptide signaling events on cell surfaces. Mammalian neprilysins are known to be involved in the metabolism of various regulatory peptides especially in the nervous, immune, cardiovascular and inflamm...

The goal of this study was to identify and characterize the hypothesized apical cation/H(+) exchanger responsible for K(+) and/or Na(+) secretion in the renal (Malpighian) tubules of the yellow fever mosquito Aedes aegypti. From Aedes Malpighian tubules, we cloned "AeNHE8," a full-length cDNA encoding an ortholog of mammalian Na(+)/H(+) exchanger 8...

The midgut of the tobacco hornworm, Manduca sexta, actively secretes potassium ions. This can be measured as short-circuit current (I(sc)) with the midgut mounted in an Ussing chamber and superfused with a high-K(+) saline containing as its major osmolyte 166 mM sucrose. Iso-osmotic substitution of sucrose by non-metabolisable compounds (mannitol,...

In lepidopteran larvae, three transport mechanisms are involved in the active and electrogenic K(+) secretion that occurs in the epithelial goblet cells of the midgut. These consist of (i) basolateral K(+) channels, allowing K(+) entry from the haemolymph into the cytosol, (ii) apical electrogenic K(+)/2H(+) antiporters, which are responsible for s...