Gene expression during early development and genetic variation among recently evolved sympatric Arctic charr (Salvelinus alpinus) morphs in Lake Þingvallavatn, Iceland

The four morphs of Arctic charr (Salvelinus alpinus) in Lake Þingvallavatn, Iceland, which differ in many phenotypic traits related to morphology, life history, and feeding ecology, are believed to have evolved locally within the lake after the retreat of the Ice-age glacier. The principal aims of the study were to get a handle on the molecular mechanisms underlying the phenotypic differences and assess genetic differentiation among the morphs. Gene expression during early development was surveyed to look for differential expression of genes thereby identifying developmental processes affecting divergent phenotypes. Genetic variation among the morphs was studied and patterns of biological function (gene ontology) and genomic position of highly differentiated variants were examined. Both candidate gene and transcriptome-wide profiling (RNA-sequencing) approaches were used. The results reveal both differentiation in expression and genetic composition of the sympatric morphs. Gene expression differences in multiple genes and biological pathways were discovered, pointing to substantial differentiation of morphs and that many genes may have been under selection. However, RNA degradation during sample handling created technical problems that complicated data analysis. The transcriptome-wide profiling was nonetheless useful as it revealed expression differences in genes relating to extra-cellular matrix formation and skeletogenesis and highlights differentiation in more biological pathways. The data show extensive genome-wide differentiation in allele frequencies, pointing to reproductive isolation of the morphs and/or natural selection operating on multiple parts of the genome. Strong genetic differentiation among morphs was for example discovered in immunological genes using a candidate gene approach and in genes involved in collagen metabolism and environmental sensing, by gene ontology enrichment tests of differentiated variants in the transcriptome. The expression differences in embryos and the clear genetic differentiation of the morphs suggest that they have advanced along "the speciation continuum" towards becoming reproductively isolated.Fjögur afbrigði bleikju (Salvelinus alpinus) finnast í Þingvallavatni. Afbrigðin eru talin hafa þróast innan vatnsins frá lokum síðustu ísaldar og eru ólík hvað varðar m.a. stærð, útlit, lífsferla og fæðuöflun. Meginmarkmið verkefnisins var að auka skilning á hvaða sameinda- og þroskunarferlar liggja að baki mismunandi svipgerð afbrigðanna og meta erfðafræðilega aðgreiningu þeirra á milli. Könnuð var genatjáning í snemmþroskun í leit að mismunandi tjáðum genum sem gætu þannig bent á hvaða ferlar móta þroskun ólíkra svipgerða. Erfðabreytileiki meðal afbrigðanna var metinn og athugað hvort að erfðaset með mikinn mun í tíðni samsæta, meðal afbrigða, fyndust í genum með svipuð líffræðileg hlutverk og/eða væru bundin við ákveðna staði innan erfðamengisins. Tvenns konar aðferðarfræði var beitt, í fyrsta lagi að kanna áhugaverð gen með sértækum aðferðum og í öðru lagi að rannsaka allt umritunarmengið (RNA-raðgreiningu). Niðurstöðurnar afhjúpa ólíka genatjáningu og erfðamun milli afbrigðanna. Munur í tjáningu finnst á genum í mörgum líffræðilegum ferlum sem bendir til töluverðar aðgreiningar afbrigðanna og að mögulega hafi mörg gen verið undir náttúrulegu vali. RNA-niðurbrot í sýnum, líklega vegna tæknilegra vandkvæða í meðhöndlun þeirra, hækkaði flækjustig greininga á RNA-raðgreiningargögnum. Greining umritunarmengisins var engu að síður gagnleg þar sem tjáningarmunur fannst í genum sem tengjast myndun utanfrumugrindar og beinmyndun. Gögnin sýna mikinn mun í tíðni samsæta meðal afbrigða og var mikinn mun að finna víða í erfðamenginu. Það getur bent til æxlunarlegrar einangrunar afbrigðanna og/eða náttúrulegs vals á mörgum litningasvæðum. Mikill erfðamunur fannst til dæmis í genum tengdum ónæmiskerfinu með sértækum aðferðum og aðgreinandi erfðabreytileiki í genum tengdum kollagen-efnaskiptum og umhverfisskynjum (sjón, heyrn) var áberandi í umritunarmenginu. Genatjáningarmunur í fóstrum og skýr munur í erfðasamsetningu afbrigðanna bendir til að þau séu komin áleiðis inn á "veg tegundamyndunar"

Mastoiditis in children in Iceland

Neðst á síðunni er að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenINTRODUCTION: Mastoiditis is an infection in the mastoid process and is a complication of otitis media. Studies have revealed that the incidence might be increasing with altered antibiotic usage. The aim of the current study was to describe the epidemiology, clinical symptoms and treatment of mastoiditis in Iceland during the last two decades with special emphasis on children and to study possible correlations between antibiotic use and incidence of mastoiditis. PATIENTS AND METHODS: Information on patients diagnosed with mastoiditis during the period 1984-2002 at The Children's Hospital Iceland, The Department of Paediatrics, Landakoti and Landspitali--University Hospital Iceland was gathered and clinical data were recorded from patients records of children diagnosed with mastoiditis during 1999-2002. Information on antibiotic use during the years 1989-2002 was obtained from the Ministry of Health in Iceland. RESULTS: Eighty-four patients were diagnosed with mastoiditis during the period 1984-2002. Of those, 52 (62%) were children less than 18 years of age. The mean age of those children was 2 years and 8 months. Boys were 58%. Twenty six (50%) of the children were less than three years old. During the years 1999-2002, a total of 28 children were diagnosed; the mean age was 2 years and 2 months. Fifteen children (54%) sought medical attention within a week prior to admission to hospital and had been diagnosed with otitis media. Eleven children (73%) were appropriately treated with antibiotics prior to the diagnosis of mastoiditis but four (27%) received no antibiotics. During the period 1989-2002, a statistically significant correlation was detected between decreased antibiotic use among children and increasing incidence of mastoiditis (r=-0.68; p=0.007). DISCUSSION: Following changes in guidelines for antibiotic prescriptions for otitis media in Iceland during the nineties, antibiotic use in children decreased at the same time as the incidence for mastoiditis increased. It is uncertain, however, if a causal relationship exists. It is important to diagnose and appropriately treat otitis media, while staying alert for serious complications, especially in young children.Inngangur: Stikilbólga er sýking í stikilholrýmum gagnaugabeins og fylgikvilli miðeyrnabólgu. Erlendar rannsóknir benda til að síðustu ár hafi nýgengi aukist með breyttri notkun sýklalyfja við miðeyrnabólgu. Tilgangur rannsóknarinnar var að skoða faraldsfræði, einkenni og meðferð stikilbólgu á Íslandi síðustu 20 ár með sérstaka áherslu á börn með stikilbólgu, ásamt fylgni sýklalyfjanotkunar við nýgengi stikilbólgu. Sjúklingar og aðferðir: Upplýsingar um þá sem greindust með stikilbólgu á árunum 1984-2002 á Barnaspítala Hringsins, Landakoti og Landspítala (áður Borgarspítali og Sjúkrahús Reykjavíkur) voru skráðar og sjúkraskrár þeirra sem greindust á árunum 1999-2002 voru skoðaðar. Hjá heilbrigðisráðuneytinu fengust upplýsingar um sýklalyfjanotkun á Íslandi á tímabilinu 1989-2002. Niðurstöður: Alls greindust 84 með stikilbólgu á árunum 1984-2002, þar af 52 börn (62%). Miðaldur þeirra var 2 ár og 8 mánuðir. Drengir voru 58%. Tuttugu og sex (50%) börn voru yngri en 3 ára. Á árunum 1999-2002 greindust 28 börn, miðaldur var 2 ár og 2 mánuðir. Fimmtán börn (54%) leituðu til læknis innan viku fyrir innlögn og greindust með miðeyrnabólgu. Ellefu börn (73%) fengu viðeigandi sýklalyf en fjögur (27%) fengu ekki meðferð fyrir innlögn. Á tímabilinu 1989-2002 var marktæk fylgni á milli minnkandi notkunar sýklalyfja hjá börnum og vaxandi nýgengis stikilbólgu (r =-0,68; p = 0,007). Ályktanir: Í kjölfar breyttra ráðlegginga um sýklalyfjanotkun við miðeyrnabólgu á Íslandi sem birtar voru upp úr 1990 dró úr notkun sýklalyfja hjá börnum og nýgengi stikilbólgu jókst en óvíst er hvort um beint orsakasamhengi er að ræða. Mikilvægt er að greina miðeyrnabólgu og meðhöndla á réttan hátt, og vera vakandi fyrir alvarlegum fylgikvillum, einkum hjá ungum börnum

Klínískar leiðbeiningar um áhættumat og forvarnir hjarta- og æðasjúkdóma

Hægt er að lesa greinina í heild sinni með því að smella á hlekkinn View/OpenHjarta- og æðasjúkdómar eru algengasta orsök ótímabærs heilsubrests og dauðsfalla á Vesturlöndum. Það er því mikilvægt að meðferð og forvarnir gegn þessum sjúkdómum séu markvissar. Markmið þessara leiðbeininga er að auðvelda heilbrigðisstarfsfólki forvarnarstarf vegna hjartaog æðasjúkdóma með það að leiðarljósi að: hindra myndun æðakölkunar minnka líkur á að æðakölkun valdi skemmdum í líffærum fækka áföllum (sjúkdómstilfellum eða ótímabærum dauða) af völdum hjarta- og æðasjúkdóm

Differentiation at the MHCIIα and Cath2 Loci in Sympatric Salvelinus alpinus Resource Morphs in Lake Thingvallavatn

Publisher's versionNorthern freshwater fish may be suitable for the genetic dissection of ecological traits because they invaded new habitats after the last ice age (∼10.000 years ago). Arctic charr (Salvelinus alpinus) colonizing streams and lakes in Iceland gave rise to multiple populations of small benthic morphotypes, often in sympatry with a pelagic morphotype. Earlier studies have revealed significant, but subtle, genetic differentiation between the three most common morphs in Lake Thingvallavatn. We conducted a population genetic screen on four immunological candidate genes Cathelicidin 2 (Cath2), Hepcidin (Hamp), Liver expressed antimicrobial peptide 2a (Leap-2a), and Major Histocompatibility Complex IIα (MHCIIα) and a mitochondrial marker (D-loop) among the three most common Lake Thingvallavatn charr morphs. Significant differences in allele frequencies were found between morphs at the Cath2 and MHCIIα loci. No such signal was detected in the D-loop nor in the other two immunological genes. In Cath2 the small benthic morph deviated from the other two (FST = 0.13), one of the substitutions detected constituting an amino acid replacement polymorphism in the antimicrobial peptide. A more striking difference was found in the MHCIIα. Two haplotypes were very common in the lake, and their frequency differed greatly between the morphotypes (from 22% to 93.5%, FST = 0.67). We then expanded our study by surveying the variation in Cath2 and MHCIIα in 9 Arctic charr populations from around Iceland. The populations varied greatly in terms of allele frequencies at Cath2, but the variation did not correlate with morphotype. At the MHCIIα locus, the variation was nearly identical to the variation in the two benthic morphs of Lake Thingvallavatn. The results are consistent with a scenario where parts of the immune systems have diverged substantially among Arctic charr populations in Iceland, after colonizing the island ∼10.000 years ago.The Palsson laboratory is supported by Icelandic Research foundation and the University of Iceland research fund. Icelandic research foundation (grant of excellence: nr 100204011) to S.S. Sigurdsson, A. Palsson, B.K. Kristjansson, Zophonias O. Jonsson and Ian A. Johnston paid for part of this work. Kalina H. Kapralova and Johannes Gudbrandsson were supported by the University of Iceland doctoral fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer ReviewedRitrýnt tímari

Differential gene expression during early development in recently evolved and sympatric Arctic charr morphs

Phenotypic differences between closely related taxa or populations can arise through genetic variation or be environmentally induced, leading to altered transcription of genes during development. Comparative developmental studies of closely related species or variable populations within species can help to elucidate the molecular mechanisms related to evolutionary divergence and speciation. Studies of Arctic charr (Salvelinus alpinus) and related salmonids have revealed considerable phenotypic variation among populations and in Arctic charr many cases of extensive variation within lakes (resource polymorphism) have been recorded. One example is the four Arctic charr morphs in the ∼10,000 year old Lake Thingvallavatn, which differ in numerous morphological and life history traits. We set out to investigate the molecular and developmental roots of this polymorphism by studying gene expression in embryos of three of the morphs reared in a common garden set-up. We performed RNA-sequencing, de-novo transcriptome assembly and compared gene expression among morphs during an important timeframe in early development, i.e., preceding the formation of key trophic structures. Expectedly, developmental time was the predominant explanatory variable. As the data were affected by some form of RNA-degradation even though all samples passed quality control testing, an estimate of 3′-bias was the second most common explanatory variable. Importantly, morph, both as an independent variable and as interaction with developmental time, affected the expression of numerous transcripts. Transcripts with morph effect, separated the three morphs at the expression level, with the two benthic morphs being more similar. However, Gene Ontology analyses did not reveal clear functional enrichment of transcripts between groups. Verification via qPCR confirmed differential expression of several genes between the morphs, including regulatory genes such as AT-Rich Interaction Domain 4A (arid4a) and translin (tsn). The data are consistent with a scenario where genetic divergence has contributed to differential expression of multiple genes and systems during early development of these sympatric Arctic charr morphs.he project was funded by The Icelandic Center for Research (grant number: 100204011) to Sigurður S. Snorrason, Arnar Pálsson, Zophonías O. Jónsson and Bjarni K. Kristjánsson. The University of Iceland Doctoral Fund to Jóhannes Guðbrandsson and University of Iceland research fund to Arnar Pálsson, Sigurður S. Snorrason and Zophonías O. Jónsson. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer Reviewe

Extensive genetic differentiation between recently evolved sympatric Arctic charr morphs

Publisher's version (útgefin grein)The availability of diverse ecological niches can promote adaptation of trophic specializations and related traits, as has been repeatedly observed in evolutionary radiations of freshwater fish. The role of genetics, environment, and history in ecologically driven divergence and adaptation, can be studied on adaptive radiations or populations showing ecological polymorphism. Salmonids, especially the Salvelinus genus, are renowned for both phenotypic diversity and polymorphism. Arctic charr (Salvelinus alpinus) invaded Icelandic streams during the glacial retreat (about 10,000 years ago) and exhibits many instances of sympatric polymorphism. Particularly, well studied are the four morphs in Lake Þingvallavatn in Iceland. The small benthic (SB), large benthic (LB), planktivorous (PL), and piscivorous (PI) charr differ in many regards, including size, form, and life history traits. To investigate relatedness and genomic differentiation between morphs, we identified variable sites from RNA‐sequencing data from three of those morphs and verified 22 variants in population samples. The data reveal genetic differences between the morphs, with the two benthic morphs being more similar and the PL‐charr more genetically different. The markers with high differentiation map to all linkage groups, suggesting ancient and pervasive genetic separation of these three morphs. Furthermore, GO analyses suggest differences in collagen metabolism, odontogenesis, and sensory systems between PL‐charr and the benthic morphs. Genotyping in population samples from all four morphs confirms the genetic separation and indicates that the PI‐charr are less genetically distinct than the other three morphs. The genetic separation of the other three morphs indicates certain degree of reproductive isolation. The extent of gene flow between the morphs and the nature of reproductive barriers between them remain to be elucidated.This project was supported by The Icelandic Center for Research (RANNIS #100204011) to SSS and coworkers, The University of Iceland Doctoral Fund to JG and University of Iceland research fund to AP, SSS and ZOJ.Peer reviewe

Transcriptional dynamics of a conserved gene expression network associated with craniofacial divergence in Arctic charr

Background Understanding the molecular basis of craniofacial variation can provide insights into key developmental mechanisms of adaptive changes and their role in trophic divergence and speciation. Arctic charr (Salvelinus alpinus) is a polymorphic fish species, and, in Lake Thingvallavatn in Iceland, four sympatric morphs have evolved distinct craniofacial structures. We conducted a gene expression study on candidates from a conserved gene coexpression network, focusing on the development of craniofacial elements in embryos of two contrasting Arctic charr morphotypes (benthic and limnetic). Results Four Arctic charr morphs were studied: one limnetic and two benthic morphs from Lake Thingvallavatn and a limnetic reference aquaculture morph. The presence of morphological differences at developmental stages before the onset of feeding was verified by morphometric analysis. Following up on our previous findings that Mmp2 and Sparc were differentially expressed between morphotypes, we identified a network of genes with conserved coexpression across diverse vertebrate species. A comparative expression study of candidates from this network in developing heads of the four Arctic charr morphs verified the coexpression relationship of these genes and revealed distinct transcriptional dynamics strongly correlated with contrasting craniofacial morphologies (benthic versus limnetic). A literature review and Gene Ontology analysis indicated that a significant proportion of the network genes play a role in extracellular matrix organization and skeletogenesis, and motif enrichment analysis of conserved noncoding regions of network candidates predicted a handful of transcription factors, including Ap1 and Ets2, as potential regulators of the gene network. The expression of Ets2 itself was also found to associate with network gene expression. Genes linked to glucocorticoid signalling were also studied, as both Mmp2 and Sparc are responsive to this pathway. Among those, several transcriptional targets and upstream regulators showed differential expression between the contrasting morphotypes. Interestingly, although selected network genes showed overlapping expression patterns in situ and no morph differences, Timp2 expression patterns differed between morphs. Conclusion Our comparative study of transcriptional dynamics in divergent craniofacial morphologies of Arctic charr revealed a conserved network of coexpressed genes sharing functional roles in structural morphogenesis. We also implicate transcriptional regulators of the network as targets for future functional studies.This project was supported by The Icelandic Centre for Research (RANNIS/IRF, grant 100204) and The University of Iceland Research Fund.Peer Reviewe

Fylgikvillar í miðtaugakerfi af völdum sýkinga í miðeyra og skútum

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenOtitis media and sinusitis are common diseases. Between 1981 and 1990 eight patients were treated at Borgarspitalinn for serious central nervous system complications from infections of the middle ear and sinuses. Twelve complications were found in these 8 patients. Cerebral abscess was the most common and serious complication and caused death in one patient. With the advent of broad-spectrum antibiotics the clinical course of middle ear disease and sinusitis has been altered. The clinician may be falsely assured that administration of antibiotics will result in complete resolution of these diseases while unsuspected complications can go undetected.Miðeyrna- og skútabólga (otitis media-sinusitis paranasalis) eru tíðir sjúkdómar og fylgja gjarnan í kjölfar veirusýkinga í efri öndunarvegum. Fyrir daga sýklalyfja gátu þessir sjúkdómar tekið á sig hastarlega mynd og valdið alvarlegum sýkingum í aðlægum líffærum svo og í miðtaugakerfi (1). Meðferð og gangur miðeyma- og skútabólgu breyttist mjög við tilkomu sýklalyfja fyrir miðja 20. öldina (2). Alvarlegir fylgikvillar þessara sjúkdóma hafa orðið æ sjaldgæfari. Kynslóð lækna hefur alist upp án þess að kynnast þeim fylgikvillum í miðtaugakerfi, sem miðeyrna- og skútabólgur geta leitt til. Notkun sýklalyfja getur á hinn bóginn dulið og dregið á langinn sjúkdómsmynd þessara fylgikvilla (3). Ofangreindir þættir kunna að valda því að þeir greinast síður í tæka tíð. Grein þessi er rituð með það fyrir augum að minna lækna á alvarlegar hliðar þessara sjúkdóma. Jafnframt verður athuguð tíðni fylgikvilla af völdum sýkinga í miðeyra og skútum og grunnatriði í meðhöndlun þeirra