Localisation of the putative magnetoreceptive protein Cryptochrome 1b in the retinae of migratory birds and homing pigeons

Cryptochromes are ubiquitously expressed in various animal tissues including the retina. Some cryptochromes are involved in regulating circadian activity. Cryptochrome proteins have also been suggested to mediate the primary mechanism in light-dependent magnetic compass orientation in birds. Cryptochrome 1b (Cry1b) exhibits a unique carboxy terminus exclusively found in birds so far, which might be indicative for a specialised function. Cryptochrome 1a (Cry1a) is so far the only cryptochrome protein that has been localised to specific cell types within the retina of migratory birds. Here we show that Cry1b, an alternative splice variant of Cry1a, is also expressed in the retina of migratory birds, but it is primarily located in other cell types than Cry1a. This could suggest different functions for the two splice products. Using diagnostic bird-specific antibodies (that allow for a precise discrimination between both proteins), we show that Cry1b protein is found in the retinae of migratory European robins (Erithacus rubecula), migratory Northern Wheatears (Oenanthe oenanthe) and pigeons (Columba livia). In all three species, retinal Cry1b is localised in cell types which have been discussed as potentially well suited locations for magnetoreception: Cry1b is observed in the cytosol of ganglion cells, displaced ganglion cells, and in photoreceptor inner segments. The cytosolic rather than nucleic location of Cry1b in the retina reported here speaks against a circadian clock regulatory function of Cry1b and it allows for the possible involvement of Cry1b in a radical-pair-based magnetoreception mechanism

Extending systemC to support mixed discrete-continuous system modeling and simulation

Systems on chip are more and more heterogeneous and include software, analog/RF and digital hardware, and non-electronic components such as sensors or actuators. The design and the verification of such systems require appropriate modeling means to deal with the increasing complexity and to achieve efficient simulation. SystemC is providing a modeling and simulation framework that supports digital (discrete) hardware and software systems from abstract specifications to register transfer level models. In the paper, we are proposing a way to extend the capabilities of SystemC to support mixed discrete-continuous systems by implementing a synchronous dataflow (SDF) model of computation (MoC). The SDF MoC is used to embed continuous-time behavior in SDF modules and to support the synchronization with the existing SystemC kernel. The paper presents an overview of the architecture and the syntax of the proposed extensions and gives modeling examples with simulation results

Cryptochrome 1a localisation in light- and dark-adapted retinae of several migratory and non-migratory bird species: no signs of light-dependent activation

The magnetic compass of birds seems to be based on light-dependent radical-pair processes in the eyes. Cryptochromes are currently the only candidate proteins known in vertebrates that may serve as the primary radical-pair-based magnetoreceptor molecules. Previous immunohistochemical studies have suggested that cryptochrome 1a (Cry1a) is localised in the photoreceptor outer segments of the ultraviolet/violet (UV/V) cones, and it has been claimed that differences in Cry1a antibody staining intensities show that Cry1a is activated by light and that this should make Cry1a the most likely magnetoreceptive candidate molecule. Here, we present an independent study of Cry1a distribution within retinae of several bird species, ranging from non-migratory domestic chicken and rock pigeon to night-migratory passerines, using both the previously used antibody and two newly generated antibodies, one against the same epitope as the originally used antibody and one against a different epitope of Cry1a. We confirm the UV/V cone outer segment localisation of Cry1a in all the tested bird species. In some stainings, we found Cry1a immunoreactivity as a distinct punctate pattern throughout the whole length of the UV/V cone outer segments. These dots with a diameter of around 170 nm might suggest that many Cry1a molecules accumulate in distinct spots in the UV/V cone outer segments. However, we did not see any notable difference in Cry1a immunoreactivity between light- and dark-adapted retinae. We find no evidence whatsoever that a C-terminal antibody against Cry1a labels only a light-activated form of the Cry1a protein

Localisation of cryptochrome 2 in the avian retina.

Cryptochromes are photolyase-related blue-light receptors acting as core components of the mammalian circadian clock in the cell nuclei. One or more members of the cryptochrome protein family are also assumed to play a role in avian magnetoreception, but the primary sensory molecule in the retina of migratory birds that mediates light-dependent magnetic compass orientation has still not been identified. The mRNA of cryptochrome 2 (Cry2) has been reported to be located in the cell nuclei of the retina, but Cry2 localisation has not yet been demonstrated at the protein level. Here, we provide evidence that Cry2 protein is located in the photoreceptor inner segments, the outer nuclear layer, the inner nuclear layer and the ganglion cell layer in the retina of night-migratory European robins, homing pigeons and domestic chickens. At the subcellular level, we find Cry2 both in the cytoplasm and the nucleus of cells residing in these layers. This broad nucleic expression rather points to a role for avian Cry2 in the circadian clock and is consistent with a function as a transcription factor, analogous to mammalian Cry2, and speaks against an involvement in magnetoreception

Cryptochrome 1a localisation in light- and dark-adapted retinae of several migratory and non-migratory bird species: no signs of light-dependent activation.

The magnetic compass of birds seems to be based on light-dependent radical-pair processes in the eyes. Cryptochromes are currently the only candidate proteins known in vertebrates that may serve as the primary radical-pair-based magnetoreceptor molecules. Previous immunohistochemical studies have suggested that cryptochrome 1a (Cry1a) is localised in the photoreceptor outer segments of the ultraviolet/violet (UV/V) cones, and it has been claimed that differences in Cry1a antibody staining intensities show that Cry1a is activated by light and that this should make Cry1a the most likely magnetoreceptive candidate molecule. Here, we present an independent study of Cry1a distribution within retinae of several bird species, ranging from non-migratory domestic chicken and rock pigeon to night-migratory passerines, using both the previously used antibody and two newly generated antibodies, one against the same epitope as the originally used antibody and one against a different epitope of Cry1a. We confirm the UV/V cone outer segment localisation of Cry1a in all the tested bird species. In some stainings, we found Cry1a immunoreactivity as a distinct punctate pattern throughout the whole length of the UV/V cone outer segments. These dots with a diameter of around 170 nm might suggest that many Cry1a molecules accumulate in distinct spots in the UV/V cone outer segments. However, we did not see any notable difference in Cry1a immunoreactivity between light- and dark-adapted retinae. We find no evidence whatsoever that a C-terminal antibody against Cry1a labels only a light-activated form of the Cry1a protein

Evaluation of Retinoids for Induction of the Redundant Gene <i>ABCD2</i> as an Alternative Treatment Option in X-Linked Adrenoleukodystrophy

<div><p>X-linked adrenoleukodystrophy (X-ALD), the most common peroxisomal disorder, is a clinically heterogeneous disease that can manifest as devastating inflammatory cerebral demyelination (CALD) leading to death of affected males. Currently, the only curative treatment is allogeneic hematopoietic stem cell transplantation (HSCT). However, HSCT is only effective when performed at an early stage because the inflammation may progress for eighteen months after HSCT. Thus, alternative treatment options able to immediately halt the progression are urgently needed. X-ALD is caused by mutations in the <i>ABCD1</i> gene, encoding the peroxisomal membrane protein ABCD1, resulting in impaired very long-chain fatty acid metabolism. The related ABCD2 protein is able to functionally compensate for <i>ABCD1</i>-deficiency both <i>in vitro</i> and <i>in vivo</i>. Recently, we demonstrated that of the cell types derived from CD34⁺ stem cells, predominantly monocytes but not lymphocytes are metabolically impaired in X-ALD. As <i>ABCD2</i> is virtually not expressed in these cells, we hypothesize that a pharmacological up-regulation of <i>ABCD2</i> should compensate metabolically and halt the inflammation in CALD. Retinoids are anti-inflammatory compounds known to act on <i>ABCD2</i>. Here, we investigated the capacity of selected retinoids for <i>ABCD2</i> induction in human monocytes/macrophages. In THP-1 cells, 13-<i>cis</i>-retinoic acid reached the highest, fivefold, increase in ABCD2 expression. To test the efficacy of retinoids <i>in vivo</i>, we analyzed ABCD2 mRNA levels in blood cells isolated from acne patients receiving 13-<i>cis</i>-retinoic acid therapy. In treated acne patients, ABCD2 mRNA levels were comparable to pre-treatment levels in monocytes and lymphocytes. Nevertheless, when primary monocytes were <i>in vitro</i> differentiated into macrophages and treated with 13-<i>cis</i>-retinoic acid, we observed a fourfold induction of <i>ABCD2</i>. However, the level of ABCD2 induction obtained by retinoids alone is probably not of therapeutic relevance for X-ALD. In conclusion, our results suggest a change in promoter accessibility during macrophage differentiation allowing induction of ABCD2 by retinoids.</p></div

13CRA mediates a modest induction of <i>ABCD2</i> in differentiated human macrophages <i>in vitro</i>.

<p>(A) ABCD1, ABCD2, ABCD3, and, as a reference for normalization, HPRT mRNA levels were detected by qRT-PCR after treatment of <i>in vitro</i> differentiated macrophages with 2.5, 5 and 7 µM of 13CRA for 24 h. The results are shown as fold-induction of ABCD1-3/HPRT relative to solvent (DMSO)-treated cells. (B) As a control for the differentiation of monocytes into macrophages, LXRα expression was quantified and depicted as copy numbers of LXRα mRNA normalized to HPRT mRNA levels. (C) ABCD2 mRNA levels were similar in monocytes and M-CSF-differentiated macrophages. Values represent means ± SEM of three independent treatments. qRT-PCR analyses were performed in two technical replicates. * <i>p</i><0.05; ** <i>p</i><0.01; *** <i>p</i><0.001; <i>ns</i>, not significant.</p

UVM-SystemC-AMS based framework for the correct by construction design of MEMS in their real heterogeneous application context

Each new embedded system tends to integrate more sensors with tight software-driven control, digitally assisted analog circuits, and heterogeneous structure. A more responsive simulation environment is needed to support the co-design and verification of such complex architectures including all its digital hardware/software and analog/multi-physical aspects using Multi-Disciplinary Virtual Prototyping (MDVP). Taking a Micro-Electro-Mechanical System (MEMS) vibration sensor as an example, we introduce a reusable framework based on the state-of-the-art technologies SystemC AMS, Finite Elements/Reduced-Order modeling, and UVM to design, simulate, and verify such systems in their real application context

A complex regulatory network operates at the human <i>ABCD2</i> promoter.

<p>Activation and inhibition of the <i>ABCD2</i> gene are indicated. Nucleotide positions relative to the translational start site are indicated below the sequence. SREBP = sterol regulatory element (SRE)-binding proteins; LXR = liver X receptor; TR = thyroid hormone receptor; RXR = retinoid X receptor; RAR = retinoic acid receptor; TCF-4 = T-cell factor 4; Sp-1/3 = specificity protein 1/3; DR = direct repeat spaced by 1/2/4 or 5 nucleotides; TBE 1/3 = TCF binding element; 22R-HC = 22(R)-hydroxycholesterol; 9/13CRA = 9/13-<i>cis</i>-retinoic acid; T3 = triiodothyronine; 4-PBA = 4-phenylbutyrate; SAHA = suberoylanilide hydroxamic acid.</p