David C. Klein - US grants

AANAT as the Timezyme: "Arylalkylamine N-acetyltransferase controls daily changes in melatonin production by the pineal gland and thereby plays a unique role in biological timing in vertebrates. Arylalkylamine N-acetyltransferase is also expressed in the retina, where it may play other roles in addition to signaling, including neurotransmission and detoxification. Large changes in activity reflect cyclic 3',5'-adenosine monophosphate-dependent phosphorylation of arylalkylamine N-acetyltransferase, leading to formation of a regulatory complex with 14-3-3 proteins. This activates the enzyme and prevents proteosomal proteolysis. The conserved features of regulatory systems that control arylalkylamine N-acetyltransferase are a circadian clock and environmental lighting." From (1)[unreadable] [unreadable] Evolution of AANAT: "The melatonin rhythm-generating enzyme, arylalkylamine N-acetyltransferase (AANAT) is known to have recognizable ancient homologs in bacteria and fungi, but not in other eukaryotes. Analysis of new cDNA and genomic sequences has identified several additional homologs in other groupings. First, an AANAT homolog has been found in the genome of the cephalochordate amphioxus, representing the oldest homolog in chordates. Second, two AANAT homologs have been identified in unicellular green algae. The homologs in amphioxus, unicellular green algae, fungi and bacteria are similarly primitive in that they lack sequences found in vertebrate AANATs that are involved in regulation and that facilitate binding and catalysis. In addition, all these sequences are intronless. These features are consistent with horizontal transfer of the AANAT ancestor from bacteria to green algae, fungi and chordates. Lastly, a third AANAT gene has been found in teleost fish, suggesting that AANAT genes serve multiple functions in addition to melatonin synthesis." From (2)[unreadable] [unreadable] [unreadable] Adaptive control of melatonin synthesis: "Pineal melatonin synthesis increases at night in all vertebrates, due to an increase in the activity of arylalkylamine N-acetyltransferase (AANAT). Melatonin is also synthesized in the retina of some vertebrates and it is generally assumed that patterns of pineal and retinal AANAT activity and melatonin production are similar, i.e. they exhibit a high-at-night pattern. However, the situation in fish is atypical because in some cases retinal melatonin increases during the day, not the night. Consistent with this, we now report that light increases the activity and abundance of the AANAT expressed in trout retina, AANAT1, at a time when the activity and abundance of pineal AANAT, AANAT2, decreases. Likewise, exposure to darkness causes retinal AANAT protein and activity to decrease coincident with increases in the pineal gland. Rhythmic changes in retinal AANAT protein and activity are 180 degrees out of phase with those of retinal AANAT1 mRNA; all appear to be driven by environmental lighting, not by a circadian oscillator. The atypical high-during-the-day pattern of retinal AANAT1 activity may reflect an evolutionary adaptation that optimizes an autocrine/paracrine signaling role of melatonin in photoadaptation and phototransduction; alternatively, it might reflect an adaptation that broadens and enhances aromatic amine detoxification in the retina.?"(From 4)[unreadable] [unreadable] Posttranslational control of AANAT via 14-3-3 interaction in the retina: "14-3-3 proteins are a ubiquitous, highly conserved family of chaperone proteins involved in signal transduction, regulation of cell cycle, intracellular trafficking/targeting, cytoskeletal structure, and transcription. Although 14-3-3 proteins are among the most abundant proteins in the CNS, very little is known about their functional roles in the vertebrate retina. In the present study, we demonstrated that photoreceptors express 14-3-3 protein(s) and identified a 14-3-3 binding partner in photoreceptor cells, the melatonin-synthesizing enzyme arylalkylamine N-acetyltransferase (AANAT). Importantly, our data demonstrate that the binding of 14-3-3 to AANAT is regulated by light, with dramatic functional consequences. During the night in darkness, retinal AANAT is phosphorylated and forms a complex with 14-3-3 proteins with an apparent molecular weight of approximately 90 kDa. Phosphorylation of AANAT facilitates the binding of enzyme to 14-3-3 proteins. Within the complex, AANAT is catalytically activated and protected from dephosphorylation and degradation. Light disrupts the AANAT/14-3-3 complex, leading to catalytic inactivation, dephosphorylation, and proteolytic degradation of the enzyme. In the presence of the proteasome inhibitor, lactacystin, light results in the formation of a high molecular weight complex (>150 kDa), which may represent an intermediate in the AANAT degradation process. These findings provide new insight into the roles of 14-3-3 proteins in photoreceptor cells and to the mechanisms controlling melatonin synthesis in the vertebrate retina." (From 3) [unreadable] [unreadable] Development of an AANAT inhibitor: "Serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase, AANAT) regulates the daily rhythm in the production of melatonin and is therefore an attractive target for pharmacologic modulation of the synthesis of this hormone. Previously prepared bisubstrate analogs show potent inhibition of AANAT but have unfavorable pharmacokinetic properties due to the presence of phosphate groups which prevents transfer across the plasma membrane. Here, we examine a bis-pivaloyloxymethylene (POM)-tryptamine-phosphopantetheine prodrug (2) and its biotransformations in vitro by homogenates and pineal cells. Compound 2 is an efficient porcine liver esterase substrate for POM cleavage in vitro although cyclization of the phosphate moiety is a potential side product. Tryptamine phosphopantetheine (3) is converted to tryptamine-coenzyme A (CoA) bisubstrate analog (1) by human phosphoribosyl pyrophosphate amidotransferase (PPAT) and dephosphocoenzyme A kinase (DPCK) in vitro. Compound 2 was found to inhibit melatonin production in rat pineal cell culture. It was also found that the POM groups are readily removed to generate 3; however, further processing to tryptamine-CoA (1) is much slower in pineal extracts or cell culture. Implications for CoA prodrug development based on the strategy used here are discussed."From (5).[unreadable] [unreadable] Differential affinities of 14-3-3 proteins for phosphorylated AANAT(pAANAT): Work in progress has revealed that all 14-3-3 proteins do not exhibit the same affinity for pAANAT. Notably, the gamma isoform appears to represent a subgroup of 14-3-3 proteins that bind two molecules of pAANAT, based on indirect binding experiments. This work is being extended in attempts to confirm this indirect indication by producing crystals of pAANAT and 14-3-3 gamma.[unreadable] [unreadable] The essential role of an AANAT proline: The available evidence indicates that AANAT is a structurally stable except for one loop, termed Loop 1, which appears to be highly mobile. In one configuration, acetylate products can easily exit the active site and in another configuration the unacetylated products are tightly bound to the enzyme. We have determined that a proline in the middle of Loop 1 plays an unpredicted role in promoting the mobility of Loop 1. It appears that this proline divides Loop 1 into two semi-independent sequences which interact with each other and prevent formation of a single stable structure, thereby enhancing the mobility of the Loop 1. This novel finding has broad significance in understanding the movement of floppy loops in other proteins. The presence of this proline is highly conserved in vertebrates and represents one of the structural changes which occured during he course of evolution of AANAT.

Evolution of pineal gland: "The defining feature of the pineal gland is the capacity to function as a melatonin factory that operates on a approximately 24 h schedule, reflecting the unique synthetic capacities of the pinealocyte. Melatonin synthesis is typically elevated at night and serves to provide the organism with a signal of nighttime. Melatonin levels can be viewed as hands of the clock. Issues relating to the evolutionary events leading up to the immergence of this system have not received significant attention. When did melatonin synthesis appear in the evolutionary line leading to vertebrates? When did a distinct pineal gland first appear? What were the forces driving this evolutionary trend? As more knowledge has grown about the pinealocyte and the relationship it has to retinal photoreceptors, it has become possible to generate a plausible hypothesis to explain how the pineal gland and the melatonin rhythm evolved. At the heart of the hypothesis is the melatonin rhythm enzyme arylalkylamine N-acetyltransferase (AANAT). The advances supporting the hypothesis will be reviewed here and expanded beyond the original foundation;the hypothesis and its implications will be addressed." From (1) AANAT E-Box: "Arylalkylamine N-acetyltransferase (Aanat) is the penultimate enzyme in the serotonin-N-acetylserotonin-melatonin pathway. It is nearly exclusively expressed in the pineal gland and the retina. A marked rhythm of Aanat gene expression in the rat pineal is mediated by cyclic AMP response elements located in the promoter and first intron. Intron 1 also contains E-box elements, which mediate circadian gene expression in other cells. Here we examined whether these elements contribute to rhythmic Aanat expression in the pineal gland. This was done using transgenic rats carrying Aanat transgenes with mutant E-box elements. Circadian expression of Aanat transgenes was not altered by these mutations. However, these mutations enhanced ectopic expression establishing that the intronic Aanat E-box elements contribute to the gene's pineal specific expression. A similar role of the Aanat E-box has been reported in zebrafish, indicating that Aanat E-box mediated silencing is a conserved feature of vertebrate biology." From (2). "In all ..... species, AANAT activity is regulated at the post-translational level and, to a variable degree, also at the transcriptional level. Here, the transcriptional regulation of pineal aanat (aanat2) of the gilthead seabream (Sparus aurata) was investigated. Real-time polymerase chain reaction quantification of aanat2 mRNA levels in the pineal gland collected throughout the 24-h cycle revealed a rhythmic expression pattern. In cultured pineal glands, the amplitude was reduced, but the daily rhythmic expression pattern was maintained under constant illumination, indicating a circadian clock-controlled regulation of seabream aanat2 In NIH-3T3 cells, the seabream aanat2 promoter was activated by a synergistic action of BMAL/CLOCK and orthodenticle homeobox 5 (OTX5). Promoter sequence analyses revealed the presence of the photoreceptor conserved element and an extended E-box (i.e. the binding sites for BMAL/CLOCK and OTX5 that have been previously associated with pineal-specific and rhythmic gene expression). These results suggest that seabream aanat2 is a clock-controlled gene that is regulated by conserved mechanisms." (From 3) NeuroD: "NeuroD1/BETA2, a member of the bHLH transcription factor family, is known to influence the fate of specific neuronal, endocrine and retinal cells. We report here that NeuroD1 mRNA is highly abundant in the developing and adult rat pineal gland. Pineal expression begins in the 17-day embryo at which time it is also detectable in other brain regions. Expression in the pineal gland increases during the embryonic period and is maintained thereafter at levels equivalent to those found in the cerebellum and retina. In contrast, NeuroD1 mRNA decreases markedly in non-cerebellar brain regions during development. Pineal NeuroD1 levels are similar during the day and night, and do not appear to be influenced by sympathetic neural input. Gene expression analysis of the pineal glands from neonatal NeuroD1 knockout mice identifies 127 transcripts that are down-regulated (>twofold, p <0.05) and 16 that are up-regulated (>twofold, p <0.05). According to quantitative RT-PCR, the most dramatically down-regulated gene is kinesin family member 5C ( approximately 100-fold) and the most dramatically up-regulated gene is glutamic acid decarboxylase 1 ( approximately fourfold). Other impacted transcripts encode proteins involved in differentiation, development, signal transduction and trafficking. These findings represent the first step toward elucidating the role of NeuroD1 in the rodent pinealocyte." From (4). Crx/Otx: "Otx2 is a vertebrate homeobox gene, which has been found to be essential for the development of rostral brain regions and appears to play a role in the development of retinal photoreceptor cells and pinealocytes. In this study, the temporal expression pattern of Otx2 was revealed in the rat brain, with special emphasis on the pineal gland throughout late embryonic and postnatal stages. Widespread high expression of Otx2 in the embryonic brain becomes progressively restricted in the adult to the pineal gland. Crx (cone-rod homeobox), a downstream target gene of Otx2, showed a pineal expression pattern similar to that of Otx2, although there was a distinct lag in time of onset. Otx2 protein was identified in pineal extracts and found to be localized in pinealocytes. Total pineal Otx2 mRNA did not show day-night variation, nor was it influenced by removal of the sympathetic input, indicating that the level of Otx2 mRNA appears to be independent of the photoneural input to the gland. Our results are consistent with the view that pineal expression of Otx2 is required for development and we hypothesize that it plays a role in the adult in controlling the expression of the cluster of genes associated with phototransduction and melatonin synthesis." From (5) Pax4: "Pax 4 is a homeobox gene encoding a transcription factor that is essential for embryonic development of the endocrine pancreas. In the pancreas, Pax4 counters the effects of the related Pax6 protein, which is also involved in development of the retina and the pineal gland. In this study, we report that Pax4 is strongly expressed in the pineal gland and retinal photoreceptors of the rat. Pineal and retinal Pax4 mRNA is low in the fetus and increases postnatally;Pax6 exhibits an inverse pattern of expression, being very strongly expressed in both tissues in the fetus. In the adult, the abundance of Pax4 mRNA exhibits a diurnal rhythm in both the pineal gland and retina with maximal levels occurring late in the day. Sympathetic denervation of the pineal gland by superior cervical ganglionectomy prevents the nocturnal decrease in pineal Pax4 mRNA but does not alter the pattern of retinal Pax4 expression. Norepinephrine is released by sympathetic nerves in the pineal gland at night;in the present study, we found that treatment with adrenergic agonists suppresses pineal Pax4 expression in vivo and in vitro. Norepinephrine is known to elevate pineal cyclic AMP;here it was found that treatment with a cyclic AMP mimic reduces pineal Pax4 mRNA. These findings suggest that the nocturnal decrease in pineal Pax4 mRNA is controlled by an adrenergic-cyclic AMP mechanism and that Pax4 may function to mediate adrenergic control of circadian gene expression in the pineal gland." (Rath et al., in preparation). Eya2. Eya2, The homolog of the Drosophila gene eyeless has been identified in the pineal gland and retina. Efforts are underway to characterize the gene products, expression pattern and function.

Analysis of global gene expression: Studies are in progress which have characterized gene expression in the pineal gland. The first stage has involved analysis of the rat pineal gland: "The rodent pineal transcriptome was investigated ..... using microarray gene expression. Comparison of midday and midnight expression profiles revealed that a global >2-fold change in the expression of 1000 genes, 2/3 of which increase at night. Among these, 400 increase >4- fold in expression; studies in organ culture reveal that in nearly all cases, the expression of the highly upregulated genes is induced by treatment with NE or cyclic nucleotide analogs. These findings are consistent with the conclusion that NE-cyclic nucleotide signaling is the primary mechanism responsible for the nocturnal increase in gene expression. However, it is also clear that other mechanisms are involved, because a small number of highly rhythmic genes are not induced or are weakly induced by NE treatment. Comparison of the level of gene expression in the pineal gland to the median expression in other tissues indicates that a set of > 300 genes are expressed >8- fold higher in the pineal gland. A significant subset of the most highly expressed genes encode proteins involved in melatonin synthesis and the control of this process, including signalling via adrenergic receptors and second messengers including cyclic nucleotides, Ca++ and phospholipids. Clusters of highly expressed genes are associated with the cellular biology of thyroid hormone, retinoid acid, glutamate biology; and, with metal ion homeostasis, membrane trafficking, and the immune response. Other highly and/or rhythmically expressed genes also encode transcription factors, ion channels, transporters, receptors, regulatory molecules and secreted products that have not previously appeared in the pineal literature. Comparison of the pineal gene expression profile to that of several other tissues adds to the evidence that the pineal gland is most similar to the retina by expanding the number of genes that are highly expressed exclusively in these two tissues. This study indicates that control of pineal biology is significantly more complex than previously thought, that the number of highly expressed genes in the pineal gland and retina is higher than previously thought, and also provides molecular evidence to suspect that the gland might function outside of the highly conserved role it plays in melatonin production." From (Bailey et al, in preparation).[unreadable] The work on the rodent pineal gland is being followed up with similar work on the pineal gland of the monkey and human, so as to determine the similarity of the patterns of gene expression in these three tissues.[unreadable] The results of the analysis of the rodent pineal gland has triggered a number of studies, some of which have been published, which have focused on genes that have been highlighted by the microarray studies. An example is detailed in HD000095-37. [unreadable] [unreadable] Control of dopamine signal transduction in the pineal gland: Dopamine plays a broad role in biology through actions mediated by specific G-protein coupled receptors. "We have discovered that the expression of the gene that encodes the dopamine D4 receptor (Drd4), can change rapidly. Drd4 mRNA increases 20-fold at night in the pineal gland and retina to levels that are >10-fold higher than those in other tissues The abundance of pineal Drd4 transcripts is controlled by the well described circadian regulatory system that controls pineal function. In vitro studies indicate that Drd4 is induced by an And gate mechanism which is activated by adrenergic /cyclic AMP signaling and is dependent on thyroid hormone (T3). These findings point to an important role of dopamine/Drd4 signalling in the pineal gland and retina. On a more general level, it appears reasonable to consider that dopamine/D4R signaling in other tissues could reflect the interaction of cyclic AMP and T3."(From Kim et al, in preparation[unreadable] [unreadable] Control of cyclic AMP degradation: "The pineal gland is a photoneuroendocrine transducer that influences circadian and circannual dynamics of many physiological functions via the daily rhythm in melatonin production and release. Melatonin synthesis is stimulated at night by a photoneural system through which pineal adenylate cyclase is adrenergically activated, resulting in an elevation of cAMP. cAMP enhances melatonin synthesis through actions on several elements of the biosynthetic pathway. cAMP degradation also appears to increase at night due to an increase in phosphodiesterase (PDE) activity, which peaks in the middle of the night. Here, it was found that this nocturnal increase in PDE activity results from an increase in the abundance of PDE4B2 mRNA (approximately 5-fold; doubling time, approximately 2 h). The resulting level is notably higher (>6-fold) than in all other tissues examined, none of which exhibit a robust daily rhythm. The increase in PDE4B2 mRNA is followed by increases in PDE4B2 protein and PDE4 enzyme activity. Results from in vivo and in vitro studies indicate that these changes are due to activation of adrenergic receptors and a cAMP-dependent protein kinase A mechanism. Inhibition of PDE4 activity during the late phase of adrenergic stimulation enhances cAMP and melatonin levels. The evidence that PDE4B2 plays a negative feedback role in adrenergic/cAMP signaling in the pineal gland provides the first proof that cAMP control of PDE4B2 is a physiologically relevant control mechanism in cAMP signaling." From (1)[unreadable] [unreadable] Control of circadian rhythms by the Ptprn and Ptprn2. We have participated in an effort to describe the role that two synaptic vesicle proteins play in circadian biology. "We have found that synaptic vesicle proteins islet antigen 2(IA-2, Ptprn) and islet antigen 2-beta (IA-2-B, Ptprn2) are essential for circadian rhythms in activity, blood pressure, heart rate and temperature. IA-2 and IA-2-B are expressed in the suprachiasmatic nucleus (SCN), the master circadian oscillator in mammals the SCN of animals lacking these genes exhibit patterns of electrical activity which indicate that electrical activity of the SCN is not coherently rhythmic and that total activity is markedly reduced. IA-2 and IA-2-B may act in the SCN to facilitate cell-cell communication, as is required for the synchronization of individual oscillating cells, resulting in coherent circadian output." From Kim et al (in preparation)

Pineal FceRIalpha : This exciting development started with finding made by microarray (J Biol Chem. 2007 Nov 9;282(45):32758-64). This revealed that amoung the many genes that increase in expression at night, was the gene encoding the alpha subunit of the high affinity IgE (FceRI) receptor, which has been characterized as mediating IgE-mediated allergic responses and to play a central role in controlling Mast cell activation by the antigen/IgE complex. This gene is known to be expressed in mast cells, basophils, eosinophils, monocytes, Langerhans cells, platelets, and neutrophils. The expression of this gene in the pineal gland has not been reported and the finding of high expression in this tissue was of interest in the context of report that the pineal gland impacts the immune system and through this interaction might impact immune function broadly, including autoimmune disease, immune response to pathogens and the immune reponse to cancer cells. This was studied in collaboration with other NIH investigators and extramural scientists, in an attempt to better understand expression of this gene and the functional role IgE receptor plays in the pineal gland. As described, it was found that the FceRIalpha and FceRIgammapolypeptides are expressed in the pinealocyte, the melatonin secreting cell of the pineal gland. Moreover, Fcer1a mRNA levels increase 100-fold at night to levels that are higher than in other tissues examined. Pineal FcepsilonRIalpha protein also increases markedly at night from nearly undetectable daytime levels. Our studies indicate that pineal Fcer1a mRNA levels are controlled by a well-described neural pathway that controls pineal function;this pathway includes the master circadian oscillator in the suprachiasmatic nucleus and passes through central and peripheral structures. The circadian expression of FceRIalpha in the pineal gland is driven by this neural circuit via an adrenergic/cyclic AMP mechanism. Expression of FceRIa was found to be higher in the pineal gland than in all tissues examined except for a rat basophilic leukemia cell line, making the pineal gland a valuable model for future study of the biology of this receptor. Pineal FceRIalpha and FceRIgamma may represent a previously unrealized molecular link between the neuroendocrine and immune systems. Phagocytic cells in the pineal perifascular space: "The perivascular space of the rat pineal gland is known to contain phagocytic cells that are immunoreactive for leukocyte antigens, and thus they appear to belong to the macrophage/microglial cell line. These cells also contain MHC class II proteins. We investigated this cell type in the pineal gland of mice. Actively phagocytosing cells with a prominent lysosomal system were found in the pericapillary spaces of the mouse pineal gland following intravenous injection of horseradish peroxidase. The cells also exhibited strong acid phosphatase activity. Perivascular cells were immunopositive for MHC class II protein and for CD68, a marker of monocytes/phagocytes. This study verifies that perivascular phagocytes with antigen-presenting properties are present in the mouse pineal gland." From Chronobiology International. 23:393-401.

Analysis of global gene expression: Studies are in progress which have characterized gene expression in the pineal gland. The first stage has involved analysis of the rat pineal gland: The rodent pineal transcriptome was investigated using microarray gene expression. Comparison of midday and midnight expression profiles revealed that a global >2-fold change in the expression of 1000 genes, 2/3 of which increase at night. Among these, 400 increase >4- fold in expression; studies in organ culture reveal that in nearly all cases, the expression of the highly upregulated genes is induced by treatment with NE or cyclic nucleotide analogs. These findings are consistent with the conclusion that NE-cyclic nucleotide signaling is the primary mechanism responsible for the nocturnal increase in gene expression. However, it is also clear that other mechanisms are involved, because a small number of highly rhythmic genes are not induced or are weakly induced by NE treatment. Comparison of the level of gene expression in the pineal gland to the median expression in other tissues indicates that a set of > 300 genes are expressed >8- fold higher in the pineal gland. A significant subset of the most highly expressed genes encode proteins involved in melatonin synthesis and the control of this process, including signalling via adrenergic receptors and second messengers including cyclic nucleotides, Ca++ and phospholipids. Clusters of highly expressed genes are associated with the cellular biology of thyroid hormone, retinoid acid, glutamate biology; and, with metal ion homeostasis, membrane trafficking, and the immune response. Other highly and/or rhythmically expressed genes also encode transcription factors, ion channels, transporters, receptors, regulatory molecules and secreted products that have not previously appeared in the pineal literature. Comparison of the pineal gene expression profile to that of several other tissues adds to the evidence that the pineal gland is most similar to the retina by expanding the number of genes that are highly expressed exclusively in these two tissues. This study indicates that control of pineal biology is significantly more complex than previously thought, that the number of highly expressed genes in the pineal gland and retina is higher than previously thought, and also provides molecular evidence to suspect that the gland might function outside of the highly conserved role it plays in melatonin production. The work on the rodent pineal gland is being followed up with similar work on the pineal gland of the monkey and human, so as to determine the similarity of the patterns of gene expression in these three tissues. This work is being extended using RNA Seq technology, with focus on miRNA and long noncoding RNAs in addition to annotated genes. Long noncoding RNAs (From Coon et al, PNAS, 2012): Long noncoding RNAs (lncRNAs) play a broad range of biological roles, including regulation of expression of genes and chromosomes. Here, we present evidence that lncRNAs are involved in vertebrate circadian biology. Differential night/day expression of 112 lncRNAs (0.3 to >50 kb) occurs in the rat pineal gland, which is the source of melatonin, the hormone of the night. Approximately one-half of these changes reflect nocturnal increases. Studies of eight lncRNAs with 2- to >100-fold daily rhythms indicate that, in most cases, the change results from neural stimulation from the central circadian oscillator in the suprachiasmatic nucleus (doubling time = 0.5-1.3 h). Light exposure at night rapidly reverses (halving time = 9-32 min) levels of some of these lncRNAs. Organ culture studies indicate that expression of these lncRNAs is regulated by norepinephrine acting through cAMP. These findings point to a dynamic role of lncRNAs in the circadian system. MicroRNAs: MicroRNAs (miRNAs) play a broad range of roles in biological regulation. In this study rat pineal miRNAs were profiled for the first time and their importance evaluated by focusing on the main function of the pineal gland, melatonin synthesis. Next-generation sequencing and related methods revealed the miRNA population is dominated by a small group of miRNAs: 75% is accounted for by 10 miRNAs; miR-182 represents 28%. In addition to miR-182, miR-183 and miR-96 are also highly enriched in the pineal gland, a distinctive pattern also found in the retina. This effort also identified previously unrecognized miRNAs and other small non-coding RNAs. Pineal miRNAs do not exhibit a marked night/day difference in abundance with few exceptions (eg. 2-fold night/day differences in the abundance of miR-96 and miR-182); this contrasts sharply with the dynamic 24-hour pattern that characterizes the pineal transcriptome. During development, the abundance of most pineal-enriched miRNAs increases; however, there is a marked decrease in at least one, miR-483. miR-483 is a likely regulator of melatonin synthesis, based on the following: it inhibits melatonin synthesis by pinealocytes in culture; it acts via predicted binding sites in the 3-prime UTR of arylalkylamine N-acetyltransferase (Aanat), the penultimate enzyme in melatonin synthesis; and, it exhibits a developmental profile opposite to that of Aanat transcripts. These observations support the hypothesis that miR-483 suppresses Aanat mRNA levels during development and that the developmental decrease in miR-483 abundance promotes melatonin synthesis.

Action of Fra-2: FRA-2/FOSL2 is a basic region-leucine zipper motif transcription factor that is widely expressed in mammalian tissues. The functional repertoire of this factor is unclear, partly due to a lack of knowledge of genomic sequences that are targeted. Here, we identified novel, functional FRA-2 targets across the genome through expression profile analysis in a knockdown transgenic rat. In this model, a nocturnal rhythm of pineal gland FRA-2 is suppressed by a genetically encoded, dominant negative mutant protein. Bioinformatic analysis of validated sets of FRA-2-regulated and -nonregulated genes revealed that the FRA-2 regulon is limited by genomic target selection rules that, in general, transcend core cis-sequence identity. However, one variant AP-1-related (AP-1R) sequence was common to a subset of regulated genes. The functional activity and protein binding partners of a candidate AP-1R sequence were determined for a novel FRA-2-repressed gene, Rgs4. FRA-2 protein preferentially associated with a proximal Rgs4 AP-1R sequence as demonstrated by ex vivo ChIP and in vitro EMSA analysis; moreover, transcriptional repression was blocked by mutation of the AP-1R sequence, whereas mutation of an upstream consensus AP-1 family sequence did not affect Rgs4 expression. Nocturnal changes in protein complexes at the Rgs4 AP-1R sequence are associated with FRA-2-dependent dismissal of the co-activator, CBP; this provides a mechanistic basis for Rgs4 gene repression. These studies have also provided functional insight into selective genomic targeting by FRA-2, highlighting discordance between predicted and actual targets. Future studies should address FRA-2-Rgs4 interactions in other systems, including the brain, where FRA-2 function is poorly understood. (From Davies et al 2011) cAMP control of AANAT transcription: Arylalkylamine N-acetyltransferase (AANAT) is the key regulatory enzyme controlling the daily rhythm of melatonin biosynthesis. In chicken retinal photoreceptor cells, Aanat transcription and AANAT activity are regulated in part by cAMP-dependent mechanisms. The purpose of this study was to identify regulatory elements within the chicken Aanat promoter responsible for cAMP-dependent induction. Photoreceptor-enriched retinal cell cultures were transfected with a luciferase reporter construct containing up to 4 kb of 5'-flanking region and the first exon of Aanat. Forskolin treatment stimulated luciferase activity driven by the 4 kb promoter construct and by all 5'-deletion constructs except the smallest, Aanat (-217 to +120)luc. Maximal basal and forskolin-stimulated expression levels were generated by the Aanat (-484 to +120)luc construct. This construct lacks a canonical cyclic AMP-response element (CRE), but contains two other potentially important elements in its sequence: an eight times TTATT repeat (TTATT(8) ) and a CRE-like sequence. Electrophoretic mobility shift assays, luciferase reporter assays, chromatin immunoprecipitation, and siRNA experiments provide evidence that these elements bind c-Fos, JunD, and CREB to enhance basal and forskolin-stimulated Aanat transcription. We propose that the CRE-like sequence and TTATT(8) elements in the 484 bp proximal promoter interact to mediate cAMP-dependent transcriptional regulation of Aanat. (From Haque et al 2011)3) Control of membrane potential: Perforated patch clamp recording was used to study the control of membrane potential (V(m)) and spontaneous electrical activity in the rat pinealocyte by norepinephrine. Norepinephrine did not alter spiking frequency. However, it was found to act through (1B)-adrenoreceptors in a concentration-dependent manner (0.1-10 m) to produce a biphasic change in V(m). The initial response was a hyperpolarization (13 mV from a resting potential of -46 mV) due to a transient (5 sec) outward K(+) current (50 pA). This current appears to be triggered by Ca(2+) released from intracellular stores, based on the observation that it was also seen in cells bathed in Ca(2+)-deficient medium. In addition, pharmacological studies indicate that this current was dependent on phospholipase C (PLC) activation and was in part mediated by bicuculline methiodide and apamin-sensitive Ca(2+)-controlled K(+) channels. The initial transient hyperpolarization was followed by a sustained depolarization (4 mV) due to an inward current (10 pA). This response was dependent on PLC-dependent activation of Na(+)/Ca(2+) influx but did not involve nifedipine-sensitive voltage-gated Ca(2+) channels. Together, these results indicate for the first time that activation of (1B)-adrenoreceptors initiates a PLC-dependent biphasic change in pinealocyte V(m) characterized by an initial transient hyperpolarization mediated by a mixture of Ca(2+)-activated K(+) channels followed by a sustained depolarization mediated by a Ca(2+)-conducting nonselective cation channel. (From Zemkova et al 2011)

Signficant progress has been made in the development of an LC-MS/MS assay that detects day time levels of N-acetyltryptamine and melatonin in human plasma. The assay used deuterated internal standards to monitor recovery and to provide a basis for quantitatin. Theprinciples of this assay provide the basis for a high-throughput automated method. Initial studies have established that N-acetyltryptamine is present in blood and that it exhibits significant variation amoung volunteers who have provided blood through the NIH Blood Bank Research Donor Program. Limited results precludes further comment.