OpenUCT :: Browsing by Author "O'Ryan, Colleen"

Browsing by Author "O'Ryan, Colleen"

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Open Access
ASMT gene polymorphisms are associated with Autism Spectrum Disorder (ASD) symptom severity in a South African population
(2016) De Waal, Margaretha; O'Ryan, Colleen; Roden, Laura
Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterised by behavioural and social impairments. ASD shows evidence of a genetic aetiology, with a large body of research linking ASD to polymorphisms in several different genes and gene families, including those involved in circadian rhythm generation and melatonin biosynthesis. Sleep disorders are highly comorbid with ASD in both children and adults, and range from sleep onset delay, phase shift and sleep disruption. These parasomnias can have a significant impact on the quality of life for persons with ASD and their families, and sleep deprivation can feed into the behavioural deficits in ASD. Melatonin supplementation is often prescribed to assist in alleviating the above mentioned sleep dysfunction. Melatonin is a hormone in the circadian clock system, and is a biochemical signal for darkness to synchronise peripheral cells to the master oscillator. Clinical trials reported that melatonin supplementation at night assists in sleep initiation. However both the mode of action of supplemental melatonin, as well as whether melatonin deficiency is common in ASD, remains unclear. Furthermore, any research on ASD is often hamstrung by the heterogeneous nature of the disorder, necessitating clear phenotyping. This study examines single nucleotide polymorphisms (SNPs) in the gene acetylserotonin methyl transferase (ASMT), which encodes an enzyme in melatonin biosynthesis, in a South African ASD cohort (n=28) and controls (n=6). All participants completed and Autism Diagnostic Observation Schedule-2 assessment that allowed partitioning of the ASD individuals into ASD endophenotypes, to reduce phenotyping heterogeneity. This study found SNPs previously associated with ASD in the promoter and intronic region. Additionally, this study found novel SNPs, and a SNP in a putative transcription factor binding site not previously associated with ASD. The associations found between SNPs and ASD endophenotypes, together with the positions of the SNPs, suggest a potential link between ASMT polymorphisms and ASD symptom severity. Further research, using language assessment tools as well as quantitative measures of melatonin and sleep disruption, may establish the role of melatonin in language impairment in ASD.
Open Access
The biochemical analysis of southern African rhinoceros populations
(1993) O'Ryan, Colleen; Harley, Eric H
The drastic decline in the numbers of the five extant species of rhinoceroses world-wide, mainly as a result of poaching, have placed these species in imminent danger of extinction. This emphasizes the need to understand the relationships among the different species of rhinoceros. The advances in molecular biology have allowed the application of DNA-based genetic techniques to address a number of aspects of rhinoceros biology which have both academic interest and practical value to conservation management. There are four aspects to this study: Firstly, restriction endonuclease maps of mitochondrial DNA were constructed to estimate the time of divergence of Diceros bicornis (black rhinoceros) and Ceratotherium simum (white rhinoceros) from their common ancestor. Secondly, a population genetic study of the relationships among four subspecies of D. bicornis. Thirdly, the application of DNA fingerprinting to examine the intra- and inter-population relatedness in D. bicornis populations. Fourthly, a practical application of PCR to identify the origin of an unknown sample of DNA.
Open Access
The characterization of MHC Class II genes of the Nile crocodile (Crocodylus niloticus) : an investigation of mechanisms that shape genetic diversity in natural populations
(2008) Badenhorst, Lourie; O'Ryan, Colleen; Bishop, Jacqueline
Genes within the Major Histocompatibility Complex (MHC) of vertebrates code for proteins that are involved in antigen recognition and activation of the adaptive immune response. The hallmark of the MHC is the extremely high levels of polymorphism found at loci. A diverse array of mechanisms have been proposed to explain the generation and maintenance of diversity at MHC loci, including the processes of gene conversion, genetic drift and selection; in the presence of many pathogens balancing selection is thought to be the dominant mechanism by which selection operates. Amino acid substitutions within the peptide-binding region (PBR) of MHC genes further supports the hypothesis that positive selection enhances amino acid diversity in the PBR, such that natural selection will favour PBR diversity in natural populations. This study investigated mechanisms that shape genetic diversity of MHC class II genes in a natural population of the Nile crocodile, Crocodylus niloticus. Using PCR-cloning-sequencing methodology, allelic diversity at MHC Class II genes was investigated and provides evidence for at least two Class II 13 gene families in the Nile crocodile. The Crni-OAB family is homologous to classical Class II vertebrate genes; high levels of both allelic and amino acid diversity characterise this gene family and a strong signal of balancing selection acts to maintain functional diversity. The second family, Crni-OBB, most likely represents a non-classical Class II locus in crocodiles and was characterized by reduced levels of diversity. Analysis suggests that Crni-OBB loci have evolved in a divergent manner to those of the Crni-OAB as balancing selection was not detected within the putative PBR. Results from this study suggest that duplication followed by a recombination event has most likely led to the formation of two distinct crocodilian Class II 13 gene families. Secondly, the relative contributions of balancing selection and random genetic drift in the evolution of extant MHC diversity are examined in a natural population of the Nile crocodile. Temporal variation in allele frequencies for MHC and microsatellite loci was assessed in four successive cohorts of crocodiles from the Okavango Delta, Botswana. Results from this study suggest that a combination of short-term neutral forces such as random genetic drift, together with longer-term selection influence variation at Class II loci in the Okavango Nile crocodile. Loci within the MHC of the Nile crocodile appear to be evolving within a dynamic framework of selection, random genetic drift and recombination. This study is the first of its kind to investigate the respective influence of demography and selection on allele frequencies in a natural population of crocodilians.
Metadata only
Cryptic Diversity of African Tigerfish (Genus Hydrocynus) Reveals Palaeogeographic Signatures of Linked Neogene Geotectonic Events
(PLoS, 2011-12-14) Goodier, Sarah; Cotterill, Fenton; O'Ryan, Colleen; Skelton, Paul; de Wit, Maarten
The geobiotic history of landscapes can exhibit controls by tectonics over biotic evolution. This causal relationship positions ecologically specialized species as biotic indicators to decipher details of landscape evolution. Phylogeographic statistics that reconstruct spatio-temporal details of evolutionary histories of aquatic species, including fishes, can reveal key events of drainage evolution, notably where geochronological resolution is insufficient. Where geochronological resolution is insufficient, phylogeographic statistics that reconstruct spatio-temporal details of evolutionary histories of aquatic species, notably fishes, can reveal key events of drainage evolution. This study evaluates paleo-environmental causes of mitochondrial DNA (mtDNA) based phylogeographic records of tigerfishes, genus Hydrocynus, in order to reconstruct their evolutionary history in relation to landscape evolution across Africa. Strong geographical structuring in a cytochrome b (cyt-b) gene phylogeny confirms the established morphological diversity of Hydrocynus and reveals the existence of five previously unknown lineages, with Hydrocynus tanzaniae sister to a clade comprising three previously unknown lineages (Groups B, C and D) and H. vittatus. The dated phylogeny constrains the principal cladogenic events that have structured Hydrocynus diversity from the late Miocene to the Plio-Pleistocene (ca. 0–16 Ma). Phylogeographic tests reveal that the diversity and distribution of Hydrocynus reflects a complex history of vicariance and dispersals, whereby range expansions in particular species testify to changes to drainage basins. Principal divergence events in Hydrocynus have interfaced closely with evolving drainage systems across tropical Africa. Tigerfish evolution is attributed to dominant control by pulses of geotectonism across the African plate. Phylogenetic relationships and divergence estimates among the ten mtDNA lineages illustrates where and when local tectonic events modified Africa's Neogene drainage. Haplotypes shared amongst extant Hydrocynus populations across northern Africa testify to recent dispersals that were facilitated by late Neogene connections across the Nilo-Sahelian drainage. These events in tigerfish evolution concur broadly with available geological evidence and reveal prominent control by the African Rift System, evident in the formative events archived in phylogeographic records of tigerfish.
Open Access
The development of the single-strand conformation polymorphism (SSCP) technique to assess sequence level variation within the major histocompatibility complex (MHC) DRB1 gene in four South African buffalo (Syncerus caffer) populations
(2003) Hedley, Paula; O'Ryan, Colleen
This thesis reports the development of Single-Strand Conformation Polymorphism (SSCP) technique to assess sequence level variation within the Major Histocompatibility Complex (MHC) DRB1 gene in four South African buffalo populations. MHC gene products are involved in the immune response, and so variation within these genes provides information on the immunological fitness of the population under study. The aims of this study were: (i) to develop the SSCP technique; (ii) to investigate the level of genetic variation at the peptide binding region (PBR) of the DRB1 gene in four South African buffalo populations. (iii) This data was then compared to data generated previously in a study on the same populations using microsatellite DNA, (iv) the statistical comparisons were used to assess the appropriateness of SSCP data for population genetic analysis. Levels of heterozygosity, allelic diversity and population differentiation were quantified using MHC DRB1 gene. The amplified region (Exon 2 of the DRB1 gene) showed high levels of variability, with 77 alleles found in the 84 individuals examined using SSCP analyses.
Open Access
Evolution of the African Tigerfish (Genus Hydrocynus) : phylogeographic insights into drainage evolution
(2010) Goodier, Sarah; O'Ryan, Colleen; Cotterill, Woody
Aquatic species,notably fish, can reveal details of drainage evolution, especially where their evolutionary relationships can be reconstructed using phylogeographic methods. In this study, the mitochondrial DNA sequence diversity of the characiform genus, Hydrocynus, which is widespread across tropical Africa, is reconstructed using a phylogenetic framework and divergences are dated using the cytochrome b (cyt) region.
Open Access
Genetic signatures for enhanced olfaction in the African mole-rats
(Public Library of Science, 2014) Stathopoulos, Sofia; Bishop, Jacqueline M; O'Ryan, Colleen
The Olfactory Receptor (OR) superfamily, the largest in the vertebrate genome, is responsible for vertebrate olfaction and is traditionally subdivided into 17 OR families. Recent studies characterising whole-OR subgenomes revealed a ‘birth and death’ model of evolution for a range of species, however little is known about fine-scale evolutionary dynamics within single-OR families. This study reports the first assessment of fine-scale OR evolution and variation in African mole-rats (Bathyergidae), a family of subterranean rodents endemic to sub-Saharan Africa. Because of the selective pressures of life underground, enhanced olfaction is proposed to be fundamental to the evolutionary success of the Bathyergidae, resulting in a highly diversified OR gene-repertoire. Using a PCR-sequencing approach, we analysed variation in the OR7 family across 14 extant bathyergid species, which revealed enhanced levels of functional polymorphisms concentrated across the receptors’ ligand-binding region. We propose that mole-rats are able to recognise a broad range of odorants and that this diversity is reflected throughout their OR7 gene repertoire. Using both classic tests and tree-based methods to test for signals of selection, we investigate evolutionary forces across the mole-rat OR7 gene tree. Four well-supported clades emerged in the OR phylogeny, with varying signals of selection; from neutrality to positive and purifying selection. Bathyergid life-history traits and environmental niche-specialisation are explored as possible drivers of adaptive OR evolution, emerging as non-exclusive contributors to the positive selection observed at OR7 genes. Our results reveal unexpected complexity of evolutionary mechanisms acting within a single OR family, providing insightful perspectives into OR evolutionary dynamics.
Open Access
Investigating genetic diversity at neutral and adaptive DNA markers in the severly bottlenecked Southern white Rhinoceros (Ceratotherium simum simum)
(2009) Coutts, Natalie June; Bishop, Jacqueline; Rachlow, Janet; O'Ryan, Colleen
Open Access
Investigation of DNA methylation at the promoter region of the aralkylamine N-acetyltransferase (AANAT ) gene in South African children with Autism Spectrum Disorder
(2017) Van Wyk, Gerrit; O'Ryan, Colleen; Roden, Laura
Sleep problems and suppressed melatonin production commonly presents with core Autism Spectrum Disorder (ASD) traits. Aralkylamine N-acetyltransferase (AANAT) acts as the penultimate and rate-limiting enzyme in the melatonin biosynthetic pathway, and a study by Hu et al. (2009) reported that AANAT expression was suppressed in an ASD population with severe language impairments. The mechanism responsible for this suppressed expression is unknown. Therefore, the aim of the study was to investigate the genetic and epigenetic features of AANAT in a cohort of South African children with ASD versus children with typical development in combination with a melatonin production study to explore melatonin's contribution to ASD symptomatology. It was expected that meeting this aim would reveal DNA methylation (DNAme) modifications were statistically significant different between case and control participants. Alternatively, that DNAme features would correlate with distinct ASD traits or sleep problems and/or altered melatonin production in case participants. Biological samples and phenotypic data were collected from boys, aged between 6 and 14 years old who were assessed with the Autism Diagnostic Observation Schedule (ADOS-2). The promoter region and gene body of AANAT was sequenced (case n=26, control n=26) and DNAme analysis was performed with the Epityper massARRAY system (case n=19, control n=20). Urinary 6-hydroxymelatonin sulphate (6-OHMS) was quantified with an enzyme-linked immunosorbent assay (case n=4, control n=4). The 6-OHMS investigation was complemented with actigraphy data and a description of sleep behaviour as determined by an abbreviated version of the Children's Sleep Questionnaire. Sequence analysis found no novel single nucleotide polymorphisms and no significant differences between case and control participants. In contrast, a difference (p=0.014) in DNAme at the third CpG site in the promoter region (CpG 3) was identified in case participants assessed with ADOS-2 Module 1 in comparison to case participants assessed with ADOS-2 Modules 2 - and 3. In particular, hypomethylation was more common in participants assessed with Module 1 which is the module used to assess participants with little or no speech abilities. The transcription factor (TF) binding motifs for ZID (zinc finger protein with interaction domain), MEIS1 (Meis homeobox 1) and ZIC1 (zinc finger protein of the cerebellum 1) were identified at or near to CpG 3. These three TFs have known gene ontology terms that relate to neurodevelopment. The age of participants did not correlate with DNAme, and no further statistical significant differences were identified between the DNAme features of case and control participants, nor the correlation analysis of DNAme and ASD traits in case participants. No Module 1 participants volunteered for the 6-OHMS study, and it was therefore not possible to confirm whether DNAme features at CpG 3 correlated with altered melatonin production. The data from the study suggest that hypomethylation at the promoter region of AANAT may be related to speech impairment in ASD, and that epigenetic investigations can uncover molecular underpinnings that correlate to ASD symptomatology. Furthermore, the current study addresses the paucity of molecular information on ASD in Sub-Saharan Africa and thereby contributes to a comprehensive understanding of disease biology. It remains unknown if hypomethylation at AANAT also correlates with suppressed melatonin synthesis in ASD individuals with speech impairments and this need further investigation.
Open Access
An investigation of the sociogenetic structure of the endemic fynbos ant, Camponotus klugii, via the use of microsatellites
(2008) Muna, Natashia; O'Ryan, Colleen
Eusocial insects, in particular ants, demonstrate great variability in their sociogenetic structure with regards to colony organization, queen number, queen mating frequency, levels of relatedness and worker reproduction. Within this study I perform an analysis on two groups of ant nests of the species Campo notus klugii, in order to investigate how the genetic structure may inform us of the sociogenetic structure of the species.
Open Access
Kinship and its consequences in the cooperatively breeding southern pied babbler Turdoides bicolor
(2009) Nelson-Flower, Martha J; O'Ryan, Colleen
Cooperative breeding occurs when more than two individuals help to raise offspring that are not their own, and has been the focus of empirical and theoretical research for over forty years. Of central importance to this work are the fitness costs and benefits of helping, and the factors limiting the reproduction of helpers. To understand these, the genetic relationship between individuals must be known. In this thesis, I use genetic and observational data to explore kinship between individuals in groups of wild Southern Pied Babblers Turdoides bicolor.
Open Access
A macro- and micro-evolutionary investigation of African Camponotus ants
(2002) Eick, Brigitte N; O'Ryan, Colleen; Robertson, Hamish; Harley, Eric
Camponotus than the cytochrome oxidase II gene, based on almost all measures of phylogenetic utility. The primary hypothesis proposed to account for this observation is that these two mitochondrial genes are evolving under different evolutionary constraints. Specifically, the cytochrome oxidase II gene displays greater rate heterogeneity than the cytochrome b gene, thereby decreasing its utility for phylogenetic analyses. Combining sequence data from both genes resulted in more robust phylogenetic hypotheses, with the combined topologies displaying greater congruence with the cytochrome b topologies than those based on cytochrome oxidase II sequence data. The morphological data produced a topology that was congruent with that obtained from molecular data, and provided increased support for certain nodes in the context of a combined molecular-morphological framework. The hypothesis that subgeneric classifications within Camponotus do not accurately reflect phylogenetic relationships was supported by the molecular phylogenies. An exception to this hypothesis was the monophyly of the subgenus Myrmosericus, based on cytochrome b data. The morphological and behavioural data provided support for a monophyletic group comprising the four species assigned to the subgenus Myrmopiromis. However, although these four species associated together in a group based on combined cytochrome oxidase II and cytochrome b sequences, this group was paraphyletic in the combined molecular topology, with two species in subgenus Myrmopsamma also falling within this group.
Open Access
A molecular perspective on the family Testudinidae batsch, 1788
(2002) Cunningham, Jessica; O'Ryan, Colleen; Louis, Edward E; Harley, Eric
The Family Testudinidae have a diverse distribution and, although limited to tropical and subtropical latitudes, are present on all continents with the exception of Australia and Antartica. Their evolutionary history dates back to the late Paleogene at least, and periods of diversification and expansion appear to be closely associated with global climate change, particularly at the border of the Oligocen-Miocene transition.
Open Access
Phylogeny and phylogeography of four southern ocean petrels
(2007) Techow, N M S Mareile; O'Ryan, Colleen; Ryan, Peter G
This thesis investigates the phylogeography of four southern ocean petrel species in an attempt to resolve taxonomic uncertainties and phylogeography in these species. A large proportion of petrel and albatross species are listed as threatened under Red List criteria, in many cases as a result of threats at sea. Most albatrosses and petrels breed in discrete island colonies and exhibit strong natal philopatry. They may thus be expected to show population divergence, but published studies show that this is not always the case. Most studies to date have concentrated on northern hemisphere species, with mostly albatrosses studied within the southern oceans. White-chinned (Procel/aria aequinoctialis), Spectacled (P. conspicillata) and giant petrels (Macronectes giganteus and M. hal/I) are southern ocean species of Procellariiformes. All four species are threatened by accidental mortality in long line and other fisheries, as well as by introduced predators at their breeding colonies. In order to adequately conserve these species, species limits need to be resolved. Taxonomic uncertainties are an important issue in conservation because often only recognised species receive protection. In addition, islands of origin for birds killed at sea need to be identified. This thesis examines the species status of the Spectacled Petrel (Procel/aria conspicillata), which has been separated from the White-chinned Petrel (P. aequinoctialis) based on morphology and vocalisations, as well as examining the taxonomic status of the two forms of giant petrel, and their phylogeography. Cytochrome b was used to confirm the species rank of the Spectacled Petrel. The decision to support separate species status was based on the lack of shared haplotypes, six fixed mutational differences between the closest haplotypes of the White-chinned and Spectacled Petrel and a sequence divergence of 1.74%. Within Procel/aria, Whitechinned and Spectacled Petrels are sister species, closely related to the wide-ranging Grey Petrel. Within the White-chinned Petrel, two regional populations were found corresponding to colonies in the New Zealand region and the Indian/Atlantic Ocean.Evidence of population expansions were detected in both species and both regional populations of the White-chinned Petrel. Between these two regional populations, the greatest genetiC diversity was within the New Zealand regional population. This result is consistent with the White-chinned Petrel originating in the New Zealand area.
Open Access
Phylogeographic analysis reveals strong geographical structuring in the klipspringer, Oreotragus oreotragus
(2008) Le Roex, Nikki; O'Ryan, Colleen
The klipspringer, Oreotragus oreotragus, occurs from the Western Cape of South Africa through to north-east Africa. Anthropological factors such as hunting have eradicated the klipspringer in parts of its former range and efforts have begun to reintroduce klipspringer back into these areas. This has highlighted the need for the proper understanding of the genetic variation, phylogeographic and population structure of the species, as well as the genetic validity of the 11 subspecies designations. Mitochondrial control region and cytochrome b sequence data were used to investigate these topics using blood, faecal and museum specimens. Cytochrome b and control region fragments were amplified in 83 and 60 samples respectively, out of a total sample set of 89 individuals. The generation of authentic mitochondrial DNA control region fragments proved difficult, with both Numt and PCR recombinant sequences identified after amplification. High levels of genetic variation were observed in the klipspringer, with cytochrome b and control region haplotype diversities of 0.78 and 0.98 respectively. Phylogenetic and network analyses showed the distinct geographical clustering of individuals into two major groups, south/south-western (S/SW) and east/north-eastern (E/NE), with the S/SW further split into two divergent groups. This suggests that the two S/SW groups were separated and isolated as a result of shifting climatic conditions in the late Pl iocene/early Pleistocene, after which secondary contact occurred and klipspringer moved upwards from southern Africa to colonise the east. The results from this study have conservation implications with respect to translocation policies, suggesting that translocations should only occur within the geographic groups identified in order to avoid outbreeding depression.
Open Access
Quantification of genetic variation on Island-breeding populations of Procellariiformes : an assessment of the impact of the longline fishing industry on seabirds
(2000) Kelso, Janet; Harley, Eric; O'Ryan, Colleen
The number of albatrosses that are killed on longlines in the Southern ocean is conservatively estimated to be 44 000 birds per annum. These numbers are biologically significant since albatrosses are a prime example of an extreme K-selected species. Ongoing long line fishing in the Southern ocean could lead to a decrease in the size of breeding colonies, and is a cause for major concern as it may impact the long-term survival of these birds. Quantifying genetic variation in threatened populations is a valuable application of molecular biology in conservation. In this study genetic variation was quantified using microsatellite analysis in order to investigate the effects of the longline fisheries on seabird populations. In addition, the feasibility of developing diagnostic markers for determining the provenance of birds forming part of the bycatch was also investigated. The inter-population genetic variance of three species of albatross from four distinct breeding colonies is described. Microsatellite markers were found to be highly variable and provided an assessment of the heterzygosity in the distinct populations, and a measure of the gene flow between these populations. Despite the extreme fidelity that adult albatrosses show to their breeding colonies, relatively low levels of genetic differentiation were observed between the colonies. This suggests that an integrated conservation management strategy could be undertaken successfully.
Open Access
The serotonin transporter gene (SLC6A4) shows differential regulation between children with ASD and typically developing children in a South African population
(2016) Hulley, Michaella; O'Ryan, Colleen
Autism spectrum disorders (ASD) are characterised by impairments in social interaction and communication, and repetitive and compulsive behaviours. The heterogeneous nature of ASD is underpinned by complex genetic networks; hence there is no known single genetic cause of ASD. It is therefore imperative to identify both genetic and epigenetic loci associated with ASD or specifically ASD endophenotypes. This may aid in earlier interventions for ASD if molecular biomarkers were identified. The serotonergic system has a longstanding association with ASD, and the differential expression of the serotonin transporter gene (SLC6A4) is linked to particular ASD traits. This study focuses on a length polymorphic repeat region (5-HTTLPR) upstream of the SLC6A4 promoter, and SLC6A4 promoter DNA methylation. The short variant of 5-HTTLPR is directly linked to lowered SLC6A4 expression and is at higher frequencies in ASD populations. DNA methylation at the promoter of SLC6A4 is also known to affect SLC6A4 expression. This study hypothesis is that there is differential regulation of SLC6A4, through changes in 5-HTTLPR and DNA methylation, between an ASD and control cohort. This differential regulation was also predicted to differ between ASD endophenotypes based on severity levels categorised by ADOS-2 (Autism Diagnostic Observation Schedule-2). ASD children (n=50) were compared to an agematched control group (n=13), all of whom were characterised phenotypically by an ADOS-2 assessment. The 5-HTTLPR and SLC6A4 promoter DNA methylation were analysed using restriction fragment length polymorphic analysis and the EpiTYPER assay, respectively. Significant differences were found in SLC6A4 regulation between the ASD and control group. A significant increase in frequency of individuals homozygous for the 5-HTTLPR long variant in the control group was observed when compared to the ASD cohort (p=0.049); with the long allele conferring reduced risk of ASD. Overall DNA methylation at the SLC6A4 promoter region was significantly decreased in the ASD cohort (p=0.011), the moderate ASD endophenotype (p=0.004), language impaired endophenotype (p=0.003), as well as the more severe socially and repetitive and restricted behaviour groups (p=0.006 and 0.045, respectively), when compared to the control cohort. Reduced levels of DNA methylation at CpG 30 in the target region were found to be significantly associated with higher levels of repetitive behaviour (p=0.001). The data from this study implicates the involvement of the serotonin transporter in overall ASD aetiology, specifically within the language impaired and repetitive and restricted behaviour endophenotypes. The data highlight the importance of maintaining appropriate methylation levels in order to modulate SLC6A4 expression. The regulatory mechanisms that control DNA methylation at the SLC6A4 promoter are unknown and need to be identified to completely understand how dysfunction of the serotonergic system is involved in ASD.
Open Access
Sociogenetic investigation of the southern harvester termite, Microhodotermes viator, via genetic and behavioural bioassays
(2014) Muna, Natashia; O'Ryan, Colleen; Picker, Mike
This thesis presents the first investigation of the population structure of the southern harvester termite, Microhodotermes viator (Family: Hodotermitidae), by assessing the genetic state and behavioural interactions within and between twelve colonies, from four areas across the Western Cape of South Africa. This study also critically debates the relationship between M. viator and heuweltjies (small Mima-like earth mounds), with regards to their origins and age. By critically analysing what is known, and debating the merits and shortcomings of various published hypotheses, this thesis concludes that heuweltjies are unequivocally attributable to the constructions and foraging activities of M. viator. However, the age and longevity of heuweltjies remains contentious. Several studies have attempted to ascertain age, using radiometric carbon dating on the basal calcrete layer found below mature heuweltjies, but there is disparity between results, primarily due to the challenges associated with dating calcrete. Therefore, an alternative method better equipped to mitigate these challenges, such as U-series isochron dating, is suggested for future research.
Open Access
Studies of genetic, gastrointestinal, renal and dietary factors in white and black South African subjects as a possible key to understanding the relative absence of calcium oxalate kidney stone disease in the black population
(2009) Theka, Takalani P; Rodgers, Allen; Ravenscroft, Neil; O'Ryan, Colleen
The incidence of urolithiasis in South Africa's black population is extremely rare «1%) while in the white population it is similar to that of western countries (-15%). The present thesis was aimed at shedding more light on the complex nature of the physicochemical, biochemical and physiological mechanisms in black South Africans which provide this group with a natural protection against urolithiasis in contrast to their white compatriots. Four studies comprise this thesis.
Open Access
The tangled history of olfaction in African mole-rats, Bathyergidae: insights from Olfactory Receptor genes
(2012) Stathopoulos, Sofia; Bishop, Jacqueline M; O'Ryan, Colleen
This thesis reports the first assessment of OR variation in Bathyergidae, and therefore, the first for a family of subterranean mammals. Using a PCR-sequencing approach, 178 unique OR sequences, corresponding to 119 unique OR genes are characterised from 14 mole-rat species. Bathyergidae OR genes are classified using sequence similarity and phylogenetic comparison with more than 50 mammalian OR subgenomes.