Coordinated control of adiposity and growth by anti-anabolic kinase ERK7

Energy storage and growth are coordinated in response to nutrient status of animals. How nutrient-regulated signaling pathways control these processes in vivo remains insufficiently understood. Here, we establish an atypical MAP kinase, ERK7, as an inhibitor of adiposity and growth in Drosophila. ERK7 mutant larvae display elevated triacylglycerol (TAG) stores and accelerated growth rate, while overexpressed ERK7 is sufficient to inhibit lipid storage and growth. ERK7 expression is elevated upon fasting and ERK7 mutant larvae display impaired survival during nutrient deprivation. ERK7 acts in the fat body, the insect counterpart of liver and adipose tissue, where it controls the subcellular localization of chromatin-binding protein PWP1, a growth-promoting downstream effector of mTOR. PWP1 maintains the expression of sugarbabe, encoding a lipogenic Gli-similar family transcription factor. Both PWP1 and Sugarbabe are necessary for the increased growth and adiposity phenotypes of ERK7 loss-of-function animals. In conclusion, ERK7 is an anti-anabolic kinase that inhibits lipid storage and growth while promoting survival on fasting conditions.Peer reviewe

Identification of sugar responsive transcription factors in silico

In order to survive, all organism require sugars, amino acids and lipids, which are used for energy and growth. The nutritional needs of an organism vary tremendously between species, depending on their environment and physiological period. Despite dietary differences, every organism must maintain their metabolic homeostasis, otherwise they will suffer harmful – and eventually deadly – complications. For example, excess sugar consumption has been linked to metabolic diseases such as metabolic syndrome and type II diabetes. The maintenance of metabolic homeostasis requires regulation and sensing of nutrient levels. Amino acids, lipids and sugars are sensed and monitored through distinct mechanisms that initiate transcriptional responses, which then activate corresponding downstream pathways. Intracellular sugars are sensed by the highly conserved transcription factor ChREBP and Mondo, which heterodimerize with Mlx. The complex then binds to the carbohydrate response elements of their target genes, regulating a variety of metabolic pathways, including glycolysis and lipogenesis. However, despite recent discoveries of new sugar sensors, our understanding of the ChREBP/Mondo-Mlx network remains incomplete. As metabolic regulation, including sugar sensing, is highly conserved between mammals and Drosophila, this organism has been widely used in in vivo studies. Drosophila provides an extensive genetic toolkit, lack of genetic redundancy and a fully sequenced, annotated genome. These features make Drosophila an optimal model for sugar sensing studies. Genome-wide sequencing allows researchers to study organisms’ entire genome at once. However, the organization and analysis of such a large amount of data requires computational methods. A variety of strategies, carried out by computational algorithms, have been developed to best analyze different types of biological data. The focus of this thesis is on usage of in silico methods to uncover novel genetic regulators in sugar sensing. By using in silico methods for both pre-existing and novel data we identified two new sugar responsive members of the Mondo-Mlx sugar sensing network in Drosophila: transcription factors Grain and Clockwork orange (Cwo). Further, we revealed that Grain converges on lipid metabolism with Sugarbabe, a previously known sugar responsive transcription factor. While binding to overlapping genomic sites, Grain contributes to lipogenic gene expression mainly on a low sugar diet, and Sugarbabe under high sugar conditions. We also uncovered tissue-specificity of the sugar-inducible expression of Grain, and established Cwo as a regulatory link between Mondo-Mlx and Myc, both in Drosophila and mouse hepatocytes. We also describe the connection between ChREBP, DEC1 and DEC2 (mammalian orthologs of Cwo) in the regulation of ribosome biogenesis. Lastly, we demonstrate reprogramming of carbohydrate pathways in a relatively short evolutionary timeframe within closely related species. Finally, we identified genes involved in genomic variation of sugar tolerance. All results were achieved through a close co-operation between computational and experimental research. In conclusion, the results of this thesis highlight the potential of computational analyses in driving the identification of new candidate regulators of sugar responsive gene regulation.Jokainen eliö tarvitsee energiaa kasvaakseen ja selviytyäkseen. Tämä edellyttää sokerien, amino- ja rasvahappojen tuotantoa ja/tai saamista ravinnosta. Eri lajien ravintoaineiden tarpeet vaihtelevat todella paljon, ja riippuvat niin eliön elinympäristöstä kuin kasvuvaiheesta. Ravintoaineiden tarpeista riippumatta jokaisen eliön on säädeltävä ja ylläpidettävä aineenvaihdunnallista tasapainoaan, sillä epäonnistuminen johtaa vahingollisiin – jopa kuolettaviin – seurauksiin. Esimerkiksi sokerin liikakäyttö on yhdistetty aineenvaihdunnallisiin sairauksiin kuten metaboliseen syndroomaan ja II-tyypin diabetekseen. Aineenvaihdunnallisen tasapainon säilyttäminen vaatii ravintoaineiden aistintaa ja säätelyä. Amino-, rasvahappojen ja sokerien valvonta ja säätely tapahtuu erilaisten mekanismien kautta, jotka vuorostaan säätelevät ja käynnistävät transkriptionaalisia vasteita ja biologisia reittejä. Evolutiivisesti säilyneet transkriptiofaktori ChREBP ja Mondo ovat pääosin vastuussa solunsisäisestä sokerin aistinnasta. Yhdessä sitoutumiskumppaninsa Mlx:n kanssa ne sitoutuvat kohdegeeneihinsä säädellen useita metabolisia reittejä, kuten glykolyysiä ja lipogeneesiä. Uusia sokerisäätelijöitä on viime aikoina tunnistettu, mutta siitä huolimatta ymmärryksemme ChREBP/Mondo-Mlx säätelyverkosta on vajavainen. Aineenvaihdunnan säätely, mukaan lukien sokerisäätely, on evolutiivisesti hyvin säilynyt nisäkkäiden ja banaanikärpäsen (Drosophila) välillä. Banaanikärpäselle on myös kehitetty suuri määrä geneettisiä työkaluja sekä sen genomi on täysin sekvensoitu. Näistä syistä banaanikärpänen onkin laajasti käytetty malliorganismi, ja soveltuu hyvin myös sokerisäätelyn tutkimukseen. Genominlaajuinen sekvensointi mahdollistaa koko eliön perimän tutkimuksen kerralla. Kuitenkin näin suuren datamäärän analysointi vaatii laskennallisia metodeja. Laskennallisilla metodeilla toteutettavia erilaisia strategioita on kehitetty erityyppisten biologisten datojen analysointiin. Tässä väitöskirjassa keskitytään uusien geneettisten säätelijöiden löytämiseen sokerisäätelyssä laskennallisia (in silico) metodeja käyttäen. Käyttämällä in silico -metodeja sekä olemassa olevaan että väitöskirjaa varten tuotettuun dataan, tunnistimme kaksi uutta sokerisäätelijää Mondo-Mlx säätelyverkossa banaanikärpäsessä: transkriptiofaktorit Grain ja Clockwork orange (Cwo). Osoitamme että Grain ja Sugarbabe, tunnettu sokerisäätelijä, säätelevät yhdessä rasvametaboliaa. Grain säätelee rasvametaboliaa matalan verensokerin aikana, kun taas Sugarbabe osallistuu säätelyyn korkean verensokerin aikana. Lisäksi osoitimme Cwo:n toimivan ribosomien biogeneesissä säätelijänä Mondo-Mlx:n ja Myc:n välillä niin banaanikärpäsessä kuin hiiressäkin. Selvitimme myös yhteyden ChREBP, DEC1 ja DEC2 (nisäkkäiden Cwo ortologi) välillä ribosomien biogeneesissä. Lopuksi osoitimme hiilihydraattien säätelymekanismien uudelleenohjelmoinnin olevan mahdollista suhteellisen lyhyellä evolutiivisella aikavälillä läheisten lajien välillä. Viimeiseksi tunnistimme sokerisäätelyn perinnölliseen säätelyyn osallistuvia geenejä. Kaikki nämä tulokset saavutettiin laskennallisen ja kokeellisen tutkimuksen tiiviinä yhteistyönä. Johtopäätöksenä tämän väitöskirjan tulokset korostavat laskennallisten menetelmien mahdollisuuksia uusien geneettisten sokerisäätelijöiden tunnistamisessa

Stem Cell Intrinsic Hexosamine Metabolism Regulates Intestinal Adaptation to Nutrient Content

The intestine is an organ with an exceptionally high rate of cell turnover, and perturbations in this process can lead to severe diseases such as cancer or intestinal atrophy. Nutrition has a profound impact on intestinal volume and cellular architecture. However, how intestinal homeostasis is maintained in fluctuating dietary conditions remains insufficiently understood. By utilizing the Drosophila midgut model, we reveal a novel stem cell intrinsic mechanism coupling cellular metabolism with stem cell extrinsic growth signal. Our results show that intestinal stem cells (ISCs) employ the hexosamine biosynthesis pathway (HBP) to monitor nutritional status. Elevated activity of HBP promotes Warburg effectlike metabolic reprogramming required for adjusting the ISC division rate according to nutrient content. Furthermore, HBP activity is an essential facilitator for insulin signaling-induced ISC proliferation. In conclusion, ISC intrinsic hexosamine synthesis regulates metabolic pathway activities and defines the stem cell responsiveness to niche-derived growth signals.Peer reviewe

Psychiatric symptoms and couple satisfaction in parents of newborns before and during the COVID‐19 pandemic—A comparison of two prospective studies

Abstract Aims To assess anxiety, depression, perceived stress, couple satisfaction and life satisfaction of parents of healthy newborns in two cohorts in 2015 and in 2020 during the COVID‐19 pandemic. Design A prospective follow‐up study. Methods We enrolled 60 parents of healthy newborns (n = 30 dyads) in 2015 and 60 parents (n = 30 dyads) in 2020. Both parents completed six valid and reliable questionnaires independently 1–2 days and 12 months after delivery: Beck Anxiety Inventory, Beck Depression Inventory‐II, Edinburgh Postnatal Depression Scale, Perceived Stress Scale, Couple Satisfaction Index and Life Satisfaction Scale‐4. Results Anxiety was more common but couple satisfaction better in both parents during the COVID‐19 pandemic than in 2015. Depressive symptoms and perceived stress were similarly low, and life satisfaction was similarly high in both cohorts, indicating ample parental resilience. There was a moderate positive association between previous mental health disorders and parental anxiety after delivery during the COVID‐19 pandemic

Metabolic gene regulation by Drosophila GATA transcription factor Grain

Nutrient-dependent gene regulation critically contributes to homeostatic control of animal physiology in changing nutrient landscape. In Drosophila, dietary sugars activate transcription factors (TFs), such as Mondo-Mlx, Sugarbabe and Cabut, which control metabolic gene expression to mediate physiological adaptation to high sugar diet. TFs that correspondingly control sugar responsive metabolic genes under conditions of low dietary sugar remain, however, poorly understood. Here we identify a role for Drosophila GATA TF Grain in metabolic gene regulation under both low and high sugar conditions. De novo motif prediction uncovered a significant over-representation of GATA-like motifs on the promoters of sugar-activated genes in Drosophila larvae, which are regulated by Grain, the fly ortholog of GATA1/2/3 subfamily. grain expression is activated by sugar in Mondo-Mlx-dependent manner and it contributes to sugar-responsive gene expression in the fat body. On the other hand, grain displays strong constitutive expression in the anterior midgut, where it drives lipogenic gene expression also under low sugar conditions. Consistently with these differential tissue-specific roles, Grain deficient larvae display delayed development on high sugar diet, while showing deregulated central carbon and lipid metabolism primarily on low sugar diet. Collectively, our study provides evidence for the role of a metazoan GATA transcription factor in nutrient-responsive metabolic gene regulation in vivo.Peer reviewe

Sugar-responsive inhibition of Myc-dependent ribosome biogenesis by Clockwork orange

The ability to feed on a sugar-containing diet depends on a gene regulatory network controlled by the intra-cellular sugar sensor Mondo/ChREBP-Mlx, which remains insufficiently characterized. Here, we present a genome-wide temporal clustering of sugar-responsive gene expression in Drosophila larvae. We identify gene expression programs responding to sugar feeding, including downregulation of ribosome biogenesis genes, known targets of Myc. Clockwork orange (CWO), a component of the circadian clock, is found to be a mediator of this repressive response and to be necessary for survival on a high-sugar diet. CWO expres-sion is directly activated by Mondo-Mlx, and it counteracts Myc through repression of its gene expression and through binding to overlapping genomic regions. CWO mouse ortholog BHLHE41 has a conserved role in repressing ribosome biogenesis genes in primary hepatocytes. Collectively, our data uncover a cross-talk between conserved gene regulatory circuits balancing the activities of anabolic pathways to main-tain homeostasis during sugar feeding.Peer reviewe