Dissertation submitted to the Faculty of Science, University of the Witswatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. May 2015 in Johannesburg / Claudins are a large gene family found in all vertebrates. Claudins encode tetraspan membrane proteins, involved in the structure and function of the tight junctions. This association of cells leads to the formation of the epithelial sheet which is involved in many functions such as embryo morphogenesis. The NCBI database shows 27 claudins identified in humans; 23 in mice and 17 in Xenopus. This suggests that an increase in gene family size may correlate with the evolution of more complex vertebrates. In this study claudins from the most basal extant vertebrate, the sea lamprey, were investigated. RNA used to build up the lamprey genome by Jeramiah Smith (Smith et al., 2012), was used for lamprey claudin sequences. Additionally this study identified 2 more claudins (Cldn B & Cldn F). The phylogenetic tree constructed using claudins from higher vertebrate model organisms and the invertebrates Ciona intestinalis and Drosophila melanogaster; showed that lamprey claudins are evolutionarily more distantly related to their orthologs in higher vertebrates. Furthermore some claudins in lamprey did not show any homologs in higher vertebrates and vice versa, indicating the emergence of novel members in higher vertebrates. However lamprey Cldn A was found to be homologous to CLDN 3 in higher vertebrates. This is interesting since CLDN 3 is involved in the development of two vertebrate specific traits; one of which is the ear placode. Thus Cldn A (renamed Cldn 3B), was made a focus of this study. RNA in situ hybridization using probes designed from individual UTRs showed localised expression of Cldn 3B in the ear placode, pharyngeal pouch, pericardial cavity and the fin fold whereas Cldn B (renamed Cldn 8B) was mostly expressed in the pharyngeal pouch and ear placode much like its orthologs in higher vertebrates. Knockout experiments showed that Cldn 3B is involved in sealing and expansion of the ear placode and pharyngeal arches during development whereas Cldn 8B is involved in determining ear placode development. Thus claudins are seen to be heavily involved in the morphology of vertebrate specific traits therefore an expansion in this gene family would affect the complexity of vertebrates during evolution.

Thesis (MsCMedSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The gastrointestinal morphology and the distribution of the different types of mucin secreting goblet cells were investigated in three mammalian insectivorous species, namely A. spinosissimus, C. cyanea and A. hottentotus. The aim of the study was to provide a comprehensive morphological comparison between the different species. Another aim was to illustrate and compare the distribution of mucins (neutral, sulfo- and sialomucins) in the gastrointestinal tracts (GITs) of these species, in order to better understand the quality of the biofilm in the GIT. Mucins secreted onto the surface of the GIT have an effect on the colonisation of microflora in the mucosal layer, constructing a biofilm which protects the GIT surface from opportunistic pathogens. The shape, proportional length, and proportional surface areas of the different gastrointestinal regions were recorded and compared in the three species. Histochemical staining methods were used to detect and to distinguish between neutral, sulfo- and sialomucins. The number of goblet cells in the GIT containing each of the above mucins in the epithelium lining the surface or crypts was quantified, and the data expressed as the number of neutral, sulfo- or sialomucin containing goblet cells per mm2 of the surface or crypt epithelium. In all three species the stomach was uncompartmentalised. The internal aspect of the stomach in A. spinosissimus was hemi-glandular, containing stratified squamous epithelium in the fundus, with glandular epithelium in the body and pyloric region. However, C. cyanea and A. hottentotus had wholly glandular stomachs. A. spinosissimus was the only species studied that had a caecum which demonstrated transverse mucosal folds and V-shaped mucosal folds in the proximal colon. Both C. cyanea and A. hottentotus had villi up to the distal part of the GIT. Longitudinal mucosal folds were present in the distal colon. The GITs of both C. cyanea and A. hottentotus showed little morphological differentiation namely a simple, glandular stomach and the lack of a caecum. Mixed (neutral and acid) mucins and mixed acid (sulfo- and sialomucins) mucin secreting goblet cells were prominent mucin cell types in all three mammalian insectivorous species. Despite these general similarities, marked differences were observed in the qualitative expression and distribution of the three types of mucins throughout the GIT. The overall similarity between the three insectivores and other distantly related mammalian species suggests that mixed mucin secreting goblet cell types are prominent contributors to the maintenance of the intestinal biofilm in the majority of mammals, irrespective of their diet or taxonomy. / AFRIKAANSE OPSOMMING: Die bestudering van die morfologie van die spysverteringskanaal (SVK) en die verspreiding van die verskillende musien produserende bekerselle was in drie insek-etende soogdier spesies uitgevoer, naamlik in A. spinosissimus, C. cyanea en A. hottentotus. Die doel van die studie was om „n omvattende morfologiese vergelyking te maak tussen die drie spesies, sowel as om die verspreiding van die verskillende musiene te beskryf in die SVK. Kennis van die verspreiding van die verskillende tipes musiene (neutral, sulfaat en nie-sulfaat bevattende musiene) kan moontlik inligting verskaf aangaande die kwaliteit van die biofilm in the SVK. Die laasgenoemde musiene wat gesekreteer word op die oppervlak van die SVK, bepaal die kolonisasie van die mikroflora in die mukosale laag wat „n biofilm vorm en die SVK beskerm teen patogene. Die vorm, proportionele lengte en proportionele oppervlaks areas van die verskillende SVK gebiede is opgeteken, waarna dit vergelyk is tussen die drie insektivore spesies. Histochemiese kleurings tegnieke is gebruik om die musiene waar te neem en om te onderskei tussen die neutraal, sulfaat en nie-sulfaat bevattende musiene. Die aantal beker selle wat elk van die bogenoemde musiene bevat het, is getel in die oppervlaks epiteel- en kript areas van die SVK. Hierdie data is weergegee as die aantal neutraal, sulfaat en nie-sulfaat bevattende beker selle per oppervlaks epiteel- of kript area (mm2). Die vorm van die maag in al drie spesies was eenvoudig en nie gekompartementaliseer nie. Die interne aspek van die maag in A. spinosissimus het meerlagige plaveisel epiteel in die fundus gehad en klieragtige epiteel in die liggaam en pilorus gedeeltes. Daarbenewens het C. cyanea en A. hottentotus slegs klieragtige epiteel in die maag gehad. A. spinosissimus was die enigste spesie in hierdie studie wat „n sekum gehad het met dwars voue, asook V-vormige mukosale voue in die proksimale kolon. Beide C. cyanea en A. hottentotus het villi tot in die distale gedeelte van die SVK gehad. Longitudinale mukosale voue was teenwoordig in die distale gedeelte van die kolon. Die SVK van beide C. cyanea en A. hottentotus het min morfologiese differensiasie getoon deurdat die spesies „n eenvoudige, klieragtige maag gehad het en geen sekum nie. Gemenge (neutral en suur) musiene asook gemengde suur (sulfaat en nie-sulfaat bevattende) musiene was die dominante musien tipes in the SVK van al drie insek-etende soogdier spesies. Ten spyte van die algemene ooreenkomste, was daar merkwaardige verskille in die getalle en verspreiding van die verskillende musiene in die SVK. Die algemene ooreenkomste tussen die drie insektivore soogdier spesies met soogdiere van ander families, stel voor dat die gemende musien sekreterende beker selle „n prominente bydrae maak tot die onderhoud van die biofilm in the SVK in die meerderheid van soogdiere, ongeag van hul dieet of spesie klassifikasie.

"June 2003" Includes bibliographical references (leaves 408-457)

"June 2003" / Includes bibliographical references (leaves 408-457) / [26], 457 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Anatomical Sciences, 2003