Preoblikovanje medceličnih stikov v nevretenčarskih epitelih med morfogenezo integumenta in prebavnega sistema

Kunčič, Katja (author), Žnidaršič, Nada (mentor)

Medcelični stiki so kompleksne proteinske povezave med membranami sosednjih celic in so ključni za organizacijo celic v tkivu. Vedno več raziskav dokazuje, da so medcelični stiki dinamični kompleksi, ki se lahko preoblikujejo v skladu s spremembami v arhitekturi in delovanju tkiv. Podatki o strukturnem preoblikovanju medceličnih stikov izhajajo skoraj izključno iz analiz vretenčarskih tkiv. Največje spremembe v organizaciji in arhitekturi epitelov potekajo med embrionalnim razvojem, v skladu z morfogenezo različnih organov. Kljub spremembam velikosti, oblike in strukture epitelnih celic, mora biti zagotovljena vloga epitela kot pregrade ter njegova vloga v transportu snovi, pri čemer imajo ključno vlogo medcelični stiki. V nalogi smo analizirali strukturne spremembe adherentnih in septiranih stikov v epidermisu, v epitelu prebavnih žlez in v epitelu črevesa v povezavi z diferenciacijo tkiv med razvojem pri členonožcu Porcellio scaber. Epidermis in črevesni epitel sta ektodermalna epitela, epitel prebavnih žlez pa je endodermalnega izvora, zato smo lahko primerjali tvorbo in preoblikovanje stikov v izvorno različnih epitelih. Preoblikovanje stikov smo analizirali v izbranih fazah embrionalnega (S13 in S16) in postembrionalnega razvoja (marzupijske in postmarzupijske manke). Histološko organizacijo epitelov smo analizirali s svetlobno mikroskopijo, ultrastrukturno zgradbo medceličnih stikov pa s presevno elektronsko mikroskopijo. Adherentni stiki, ki so ključni za mehansko stabilizacijo, imajo podobno strukturo od faze srednjega embrija do odraslih živali. Ugotovili smo, da se nekoliko spremeni pozicija adherentnega stika v epidermisu, ki se v pozni embriogenezi pomakne bolj subapikalno. V epidermalnem in črevesnem epitelu se med razvojem izrazito spremeni ultrastruktura septiranih stikov. Posamezne septe so prvič razvidne v fazi poznega embrija tako pri epidermalnem kot pri črevesnem epitelu. Za diferenciacijo septiranih stikov med razvojem je značilno, da tvorbi posameznih sept sledi oblikovanje krajših nizov sept in na koncu tvorba diferenciranega stika iz daljših in neprekinjenih nizov sept. Nizi sept se začnejo intenzivno daljšati na prehodu živali iz embrionalne v postembrionalno fazo. Septirani stiki v epitelu prebavne žleze so pri vseh analiziranih fazah strukturno podobni, med diferenciacijo epitela je razvidno podaljšanje teh stikov. V fazi levitve pozne marzupijske manke se spremeni oblika epidermalnih celic, iz ploščate v kubično. Ultrastruktura adherentnih stikov v ektodermalnih epitelih ostane med levitvijo mank nespremenjena, septirani stiki pa se preoblikujejo v krajše in prekinjene nize sept. Pri septiranih stikih endodermalnega epitela prebavnih žlez med levitvijo manke nismo opazili sprememb. Rezultati kažejo, da na preoblikovanje medceličnih stikov vplivajo procesi razvoja organizma in tudi druge večje fiziološke spremembe, kot je levitev.

• Language: Slovenian
• Keywords: adherentni stiki, septirani stiki, ultrastruktura medceličnih stikov, nevretenčarski epitel, Porcellio scaber
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2020
• PID: 20.500.12556/RUL-119980
• COBISS.SI-ID: 30222083
• Publication date in RUL: 14.09.2020

Secondary language

• Language: English
• Title: Cell junctions remodeling in invertebrate epithelia during integument and digestive system morphogenesis

Abstract

Cell junctions are complex protein connections between the plasma membranes of neighbouring cells and are essential for the organization of cells in tissue. An increasing number of studies show that cell junctions are dynamic complexes that can be modified in relation to changes in architecture and function of tissue. Data on structural reorganization of cell junctions derives almost exclusively from vertebrate cells and tissue. Organization and architecture of epithelia change mostly during embryonic development in relation to morphogenesis of different organs. The function of epithelium as a barrier and the role in material transport must be maintained at tissue level during changes in cell size, shape and structure. Cell junctions have a key role in the maintenance of epithelial integrity and in the regulation of transepithelial transport. We have analysed structural changes of cell junctions in selected invertebrate epithelia in relation to tissue differentiation during development. Ultrastructural characteristics of adherens and septate junctions in ectodermal (epidermis, hindgut) and endodermal (digestive glands) epithelia of the arthropod Porcellio scaber were determined and compared. Embryonic developmental stages (S13 and S16) and postembryonic stages (marsupial mancae and postmarsupial mancae) were included in the study. Histological architecture of epithelia was imaged by light microscopy and ultrastructural characterization was performed by transmission electron microscopy. Our results show that the position of the adherens junction in epidermis changes slightly during development. In late-stage embryo it becomes slightly more subapically located. The structure of adherens junction does not change much from mid-stage embryo to adult animals. The ultrastructure of septate junctions clearly changes in epidermal and hindgut epithelium during development. Individual septa are first observed in late-stage embryo in both epithelia. The differentiation of septate junctions during development is characterized by formation of individual septa, followed by formation of short strings of septa, until the formation of long and continuous junctions. Strings of septa begin to lengthen intensively during the transition from embryonic to postembryonic phase. In midgut epithelium the septate junctions are similar in all developmental stages. They become slightly longer during differentiation. During moulting of late marsupial manca the shape of epidermal cells changes from squamous to cubical. The ultrastructure of adherens junction in ectodermal epithelia does not change during moulting phase while the septate junctions remodel into shorter and discontinuous strings of septa. We did not observe any changes in septate junction ultrastructure in the endodermal epithelium of digestive glands. Results show that the remodelling of cell junctions is affected by developmental processes as well as major physiological changes like moulting.

• Keywords: adherens junctions, septate junctions, ultrastructure of intercellular junctions, invertebrate epithelia, Porcellio scaber