Browsing by Author "Greenberg, Jacquie"

Now showing 1 - 20 of 25
  • Thumbnail Image
    Item
    Open Access
    Apoptosis in Haematopoietic progenitors
    (2009) Rossouw, Sophia Catherine; Greenberg, Jacquie
    Introduction: Intracranial pressure (ICP) monitoring is a cornerstone of care for patients with severe traumatic brain injury (TBI). The primary goal of ICP treatment is to preserve brain oxygenation, and since brain oxygenation is usually not measured, the control of ICP is used as a surrogate marker. However studies indicating that cerebral hypoxia/ischemia may occur in the face of adequate ICP and cerebral perfusion pressure (CPP) suggest that the interaction between ICP and brain oxygenation is poorly understood and warrants further investigation. This is of particular importance in the context of children in whom the interpretation of relationships between intracranial factors is even more complex due to changing physiological norms with age. To date little scientific data exists in children and treatment threshold values are often extrapolated from adult guidelines. This study aims to better understand the relationship between ICP and brain oxygenation measured as brain tissue oxygen tension (PbtO2) in a large paediatric cohort suffering from severe TBI. Specifically analysis 1) investigated ICP and PbtO2 profiles over time following TBI, 2) examined the relationship between ICP and PbtO2 from time-linked paired observations, 3) explored various critical thresholds for ICP and PbtO2, and 4) interrogated digital data trends depicting the relationship between ICP and PbtO2. The level of agreement between hourly recorded and high frequency electronic data for ICP and PbtO2 was also evaluated. Method: Paired ICP and PbtO2 data from 75 children with severe TBI were tested with correlation and regression. Additional analyses controlled for mean arterial pressure (MAP), arterial partial pressure of oxygen (PaO2), CPP, arterial partial pressure of carbon dioxide (PaCO2) and haemoglobin (Hb) using multivariate logistic regression analysis and general estimating equations. Various thresholds for ICP were examined; these included age-related thresholds to account for the potential influence of age. Receiver-operating curves (ROCs) were used to graphically demonstrate the relationships between various thresholds of ICP and various definitions of low PbtO2. These were constructed for pooled and individual patient data. Interrogation of electronically recorded data allowed for case illustrations examining the relationship between ICP and PbtO2 at selected time points. Hourly and electronic data were compared using Bland and Altman plots and by contrasting the frequency of ICP and PbtO2 perturbations recorded with each system. 5 Result: Analyses using over 8300 hours of paired observations revealed a weak relationship between ICP and PbtO2, with an initially positive but weak slope (r = 0.05) that trended downwards only at higher values of ICP. Controlling for inter-individual differences, as well as MAP, CPP, PaO2, PaCO2 and Hb did not strengthen this association. This poor relationship was further reflected in the examination of threshold ICP values with ROCs, no singular critical ICP threshold for compromised brain oxygenation was discernible. Using age-based thresholds did not improve this relationship and individual patient ROCs demonstrated inter-individual heterogeneity in the relationship between ICP and PbtO2. However, it was clear that in individual patients ICP did exhibit a strong negative relationship with PbtO2 at particular time points, but various different relationships between the 2 variables were also demonstrated. A high level of agreement was found between hourly and electronic data. Conclusion: These results suggest that the relationship between ICP and PbtO2 is highly complex. Although the relationship in individual children at specific time points may be strong, pooled data for the entire cohort of patients, and even for individual patients, suggest only a weak relationship. This is likely because several other factors affect PbtO2 outside of ICP, and some factors affect both independently of each other. These results suggest that more study should be directed at optimising ICP thresholds for treatment in children. The use of complimentary monitoring modalities may assist in this task. Depending on the adequacy of measures of brain perfusion, metabolism or oxygenation, it is possible that targeting a range of ICP values in individual patients may be appropriate; however this would require detailed investigation.
  • Thumbnail Image
    Item
    Open Access
    At-risk individual's perspectives of Spinocerebellar Ataxia (SCA) Presymptomatic Testing (PT)
    (2021) Lloyd, Deanah; Wessels, Tina-Marie; Greenberg, Jacquie
    Since the introduction of presymptomatic testing for Spinocerebellar Ataxia in South Africa, no research has looked at the impact, perceptions or acceptance of such testing within this diverse population. Despite the relatively high frequencies of late onset autosomal dominant conditions in South Africa, the uptake of presymptomatic testing by those at-risk of inheriting these conditions has been lower than that seen internationally. This research project sought to understand these low levels of utilisation, by exploring the perceptions of those at-risk of inheriting Spinocerebellar Ataxia towards presymptomatic testing. In depth semi-structured interviews were conducted with six individuals at-risk of inheriting Spinocerebellar Ataxia. The interviews were transcribed verbatim and thematically analysed. The four themes that emerged from the data included: 1) Caregiving, 2) Relationships, 3) Being At-Risk and 4) Presymptomatic Testing (PT) Perceptions. These themes explore the significant and long-lasting burdens faced both physically and emotionally by the affected individual as well as their relatives. With no currently available way of preventing or curing the condition, those atrisk described being left with a sense of hopelessness and anxiety about their future. The at-risk individuals' perceptions and fears were often linked to their and their family's experiences of the condition. Additionally, their perceptions of presymptomatic testing, although positive, did not correlate with testing utilisation amongst the participants. As such, the current underutilisation of presymptomatic testing in South Africa was found to be due to the at-risk individuals' fears of the result and its' perceived consequences, rather than a negative perception of presymptomatic testing. This is significant as it indicates that the current lack of uptake of presymptomatic testing is due to external factors unrelated to the test itself. As such, genetic counsellors should focus their efforts on counselling the individual through their fears as opposed to primarily offering presymptomatic testing. Although these findings contribute to our understanding of this previous understudied population, they cannot be extrapolated to apply to the entire South African at-risk population due to the small sample size of the study. This knowledge however, may assist in improving the presymptomatic testing process by providing greater insight into the population's experiences and perspectives. Thus, it is recommended that future studies explore ways that genetic counselling sessions and the presymptomatic testing process could be altered to incorporate this knowledge.
  • Thumbnail Image
    Item
    Open Access
  • Thumbnail Image
    Item
    Open Access
    Detailed investigation of the unstable (CAG) repeat and the immediate surrounding region of the IT15 gene in some South African families with Huntington disease
    (2005) Scholefield, Janine; Greenberg, Jacquie; Goliath, Rene
    The primary aim of this study was to investigate the origins of the HD mutation in South Africa (SA) by constructing a single nucleotide polymorphism (SNP) haplotype around the IT15 gene and to determine how many haplotypes there are in SA. Haplotypes were created by genotyping 6 SNPs in a total of 15 HD families. These families were comprised of seven Caucasian, 6 Mixed Ancestry and two Black African families.
  • Thumbnail Image
    Item
    Open Access
    Development of a SCA7 patient-derived lymphoblast cell model for testing RNAi knock-down of the disease-causing gene
    (2011) Berkowitz, Danielle Claire; Greenberg, Jacquie; Scholefield, Janine; Weinberg, Marco
    Spinocerebellar ataxia type 7 (SCA7) is an inherited neurodegenerative disease caused by the expansion of a CAG repeat within the ataxin-7 gene. The South African SCA7 population has been shown to have arisen due to a founder effect, and a single nucleotide polymorphism (SNP) within ataxin-7 has been linked to the SCA7 mutation in all South African patients genotyped to date. Recently, this SNP has been exploited in a potential allele-specific RNA interference (RNAi) based therapy, in order to knock down the expression of the mutant transcript in heterozygous patients. Although this approach has been tested in an artificial cellbased model of SCA7, focus has shifted towards testing the therapy in SCA7 patient-derived transformed lymphoblast cell lines
  • Thumbnail Image
    Item
    Open Access
    Exploration of the impact of genetic counselling and patient support group involvement on retinal degenerative disorders (RDD) patients: a qualitative study
    (2018) Goliath, Rene; Wessels, Tina-Marié; Greenberg, Jacquie
    This study explored the experiences of individuals within the clinical genetic service in South Africa, with inherited retinal disease. Methods: This qualitative research was based on a grounded theory approach. Semi-structured interviews were carried out after obtaining approval from the University of Cape Town Research and Ethics committees as well as from study participants themselves. Ten willing individuals were interviewed using an open-ended question guide to extract information about their experiences with vision loss including but not exclusively, concerning participants knowledge about their condition, ability to make decisions and their adaptation experiences. Interviews were audio recorded, transcribed verbatim and a reiterative thematic analysis performed on the raw data. Results: A range of themes and sub-themes emerged from the data that marked participants' experiences from the time of onset of vision loss. The main broad themes include "a roller coaster journey," "learning how to survive," "a genetic condition affecting the back of the eye, and "paving the way forward." Conclusions: The four themes presented in an almost linear fashion, marking a journey patients experienced from the onset of symptoms to the time of the interview. The initial stage of their journey was marked by difficulties and challenges exacerbated by the psychopathological responses reported in this dissertation. This stage was perceived to be prolonged and often extended into adulthood. The messages from the data support a view that the diverse and extended nature of this initial period was due to the limited support this group of participants received from the low vision specialists they consulted with. A significant impression of frustration and disillusionment was experienced by participants on not receiving information and guidance from these health care providers. Various mechanisms of support and control positively influenced patients' learning how to cope and survive their journey with visual impairment. Coping, learning what their condition is, what the causes are and the risks involved for future generations, empowered the participants in this study to obtain a view of a future for themselves and to make relevant decisions and choices necessary to realise the way ahead. Taken together though, continued education was deemed worthwhile.
  • Thumbnail Image
    Item
    Open Access
    A Founder Mutation in MYO7A Underlies a Significant Proportion of Usher Syndrome in Indigenous South Africans: Implications for the African Diaspora
    (Association for Research in Vision and Ophthalmology (ARVO), 2015-10) Roberts, Lisa; George, Siddiqah; Greenberg, Jacquie; Ramesar, Raj
    PURPOSE. Research over the past 25 years at the University of Cape Town has led to the identification of causative mutations in 17% of the 1416 families in the Retinal Degenerative Diseases (RDD) biorepository in South Africa. A low rate of mutation detection has been observed in patients of indigenous African origin, hinting at novel genes and mutations in this population. Recently, however, data from our translational research program showed two unrelated indigenous African families with Usher syndrome (USH), with the same homozygous MYO7A mutation. Therefore, the extent to which this mutation contributes toward the disease burden in South Africa was investigated. METHODS. Cohorts of unrelated indigenous South African probands with different RDD diagnoses were tested for the MYO7A c.6377delC mutation. Familial cosegregation analysis was performed for homozygous probands, clinical data were evaluated, and SNP haplotypes were analyzed. RESULTS. This homozygous MYO7A mutation underlies a remarkable 43% of indigenous African USH cases investigated in this study, the majority of which (60%) were diagnosed clinically with Type 2 USH. All homozygotes shared a common haplotype. This mutation does not appear to cause nonsyndromic vision loss. CONCLUSIONS. Of interest is the origin of this common mutation relevant to the Bantu population migration into southern Africa. Further investigation of the phenotype may elucidate the disease biology, and perhaps reveal a larger cohort with the same mutation, with which to assess the impact of environmental and genetic modifiers and evaluate therapeutic trials.
  • Thumbnail Image
    Item
    Open Access
    The genetic basis of human athletic performance
    (2003) Bekker, Jan Pieter Ignatius; Greenberg, Jacquie
    Research has suggested an association between the angiotensen-I converting enzyme (aCE) insertion/deletion (I/D) polymorphism and endurance performance, skeletal and cardiac muscle hypertrophy and performance in power associated sporting events. The nitric oxide synthase (ecNOS) G894T polymorphism is associated with endurance training induced decreased submaximal diastolic blood pressure and nitric oxide is a direct modulator of ACE activity.
  • Thumbnail Image
    Item
    Open Access
    Hereditary nonpolyposis colorectal cancer : comprehension of a cancer risk in conjuction with a genetic risk
    (2007) Bruwer, Zandré; Futter, Merle; Greenberg, Jacquie; Vivian, Lauraine
    The purpose of this study was to explore the level of understanding of the predictive test result and subsequent impact of testing for a predisposition to HNPCC. Using a qualitative research design, in-depth interviews were conducted with ten individuals (all mutationpositive and asymptomatic for CRC) subsequent to the disclosure of their predictive test result. The use of personal interviews could construct rich descriptions of the circumstances faced by these individuals, following their predictive testing for HNPCC.
  • Thumbnail Image
    Item
    Open Access
    Hereditary nonpolyposis colorectal cancer : factors contributing to adherence and non-adherence to surveillance for mutation carriers in rural areas of the Northern and Western Cape Brenda Julie Kruger.
    (2005) Kruger, Brenda Julie; Greenberg, Jacquie; Vivian, Lauraine
    The aim of this study was to explore possible factors that may affect non-adherence and adherence to surveillance guidelines for mutation positive individuals who are at high risk of developing CRC in the areas of the Northern Cape of South Africa. The study took place in rural, impoverished areas of the Northern Cape of South Africa and used a qualitative, exploratory research design to prospectively study the participants.
  • Thumbnail Image
    Item
    Open Access
    An investigation into the level of genetic knowledge and family communication regarding genetic risk in parents of children with cystic fibrosis
    (2007) Schoeman, Mardelle; Futter, Merle; Greenberg, Jacquie
    The aims of the present study were to determine the level of genetic knowledge of parents with a child with cystic fibrosis; to determine the impact of the birth of a child with cystic fibrosis upon subsequent reproductive choices and to investigate family communication about genetic risk. A qualitative approach was selected as it aims to understand, attempts to make sense of and provides descriptions that portray the richness and complexity of ordinary events from the perspective of the participants.
  • Thumbnail Image
    Item
    Open Access
  • Thumbnail Image
    Item
    Open Access
    An investigation into the understanding of basic genetic inheritance amongst amaXhosa caregivers of patients with Haemophilia
    (2009) Solomon, Gabriele Anna Eva; Greenberg, Jacquie; Penn, Claire; Vivian, Lauraine
    This study sought to explore the level of understanding of basic genetic inheritance among isiXhosa-speaking caregivers of patients with the genetic bleeding disorder haemophilia. Haemophilia A and B are X-linked recessive inherited, lifelong bleeding disorders that are caused by deficiencies in blood clotting factors. The condition predominantly affects males, while females are carriers and usually unaffected. These bleeding disorders have a profound impact on the daily life of the affected individual, on carrier mothers and close family. Education is vital to enable women to appreciate the implications of being a carrier and to fully inform them and their partners of the implications for a prospective child. Socio-economic and language issues in South Africa are a major barrier to communication and an obstacle to good medical care for first-language Xhosa speakers. In order to provide culturally-sensitive, effective genetic counselling and to improve communication between health care service providers and first-language Xhosa speakers, it is important to explore the intrinsic knowledge and basic understanding of this cultural group. The study used an exploratory qualitative research design. Ten participants were recruited amongst first-language Xhosa speaking mothers or caregivers of patients with haemophilia residing in townships near Cape Town. Qualitative data were generated from transcribed and translated audiorecords of ten semi-structured interviews, conducted in Xhosa by an interpreter as well as from participant observation notes by the investigator. Results suggest that the participants had a very limited understanding of the clinical management and cause of haemophilia. Information given by health care providers did not appear to be assimilated and participants remained unsure as to the implications of haemophilia. In spite of frequent visits to clinics there appeared to be limited understanding of the medical treatment and genetic consequences of haemophilia, which suggests that communication between health care providers and participants was inadequate. While treatment and care by health care service providers was fully accepted, several participants believe that traditional practices would provide more satisfactory explanations regarding the cause of the condition. Awareness by all role players of v different cultural beliefs and of how illness is interpreted by first-language Xhosa speakers might improve communication between health care service providers and isiXhosa speakers.
  • Thumbnail Image
    Item
    Open Access
    A molecular investigation of Huntington disease; origins of the mutation and current prevalence in South Africa
    (2015) Baine, Fiona Eugenie Kebirungi; Greenberg, Jacquie; Hayden Michael
    Huntington disease (HD) is a devastating neurodegenerative condition characterised by a triad of symptoms: behavioural/psychiatric changes, cognitive decline and movement disorder. The dominantly inherited disease-causing mutation is an expanded trinucleotide (CAG) repeat in the Huntingtin(HTT) gene. Clinical symptoms are believed to be the result of degeneration of specific neuronal populations that are susceptible to the presence of a toxic expanded protein product. The disease is incurable and following the onset of symptoms, is progressively debilitating over 10-20 years and eventually fatal. Although typical epidemiological studies of prevalence are challenging for a genetic disorder such as HD, family studies and various other methods of ascertainment have been used to estimate its occurrence in different populations. Prevalence is therefore known to vary geographically; population-specific haplotypes have been hypothesised to be the basis of this variation between ethnic groups. High prevalence estimates for populations with European ancestry led to the supposition that the HD mutation was introduced to different regions by Europeans. In South Africa, a survey in the 1970s estimated that the prevalence of HD in the white and coloured subpopulations was similar at 2 per 100 000 individuals; while that in the black subpopulation was significantly lower, at less than 0.01 per 100 000 individuals. Molecular genetic analyses have since revealed links between the white and coloured subpopulations which would explain the similarity in prevalence; however, our knowledge of the genetics of HD in the black subpopulation, has been sorely lacking. This study provides, for the first time, a comprehensive analysis of the HTT gene in an African population. An evaluation of the normal distribution of CAG-tract sizes highlighted significant differences between the subpopulations. Haplotype analysis identified population-specific disease-associated haplotypes, confirming distinct origins of the HD mutation in the different subpopulations. In a coloured family with the rare juvenile form of the disease, DNA sequencing revealed no novel variants within the immediate vicinity of the CAG-tract that could be associated with the observed instability. This indicates that genome-wide analyses may be more useful in identifying factors related to repeat instability and future investigations are planned for a cohort of South African patients affected by juvenile onset HD.
  • Thumbnail Image
    Item
    Open Access
    The molecular investigation of Stargardt disease in South Africa
    (2003) September, Alison; Greenberg, Jacquie; Ramesar, Raj; Callaghan, R; Kerr, Ian; Linton, K
    Hereditary macular degeneration describes a group of conditions causing macular pathology. Stargardt disease (STGD) is the most common inherited juvenile macular dystrophy characterised by severed reduction of central visual acuity and normal peripheral vision. The ABCA4 (adenosine triphosphate binding cassette transporter) gene is the only gene implicated in the autosomal recessive (ar) form of the STGD phenotype, while one genetic locus and one gene have been shown to be causative of the autosomal dominant form.
  • Thumbnail Image
    Item
    Open Access
    A molecular investigation of the novel gene underlying autosomal dominant retinitis pigmentosa in a South African family
    (1999) Bardien-Kruger, Soraya; Greenberg, Jacquie; Beighton, Peter; Ramesar, Rajkumar
    The inherited retinal degenerative disorders are a common cause of severe visual handicap in the W estem world. Retinitis pigmentosa (RP) is a group of retinopathies in which a primary feature is a progressive loss of photoreceptor and retinal pigment epithelium function. Over the last decade, investigations into the patho-physiology of RP have identified numerous disease-causing genes and loci (for a current listing refer to the web site http://www.sph.uth.tmc.edu/Retnet/). A study of a South African family with an autosomal dominant form of RP (adRP) forms the basis of this dissertation. In this family, comprising 44 individuals, the first manifestation of visual disturbance is usually evident between 20 and 30 years of age. Subsequently, another South African adRP family, consisting of 25 members, was also incorporated into this investigation. Genetic linkage analysis facilitated the mapping of the disease phenotype in the two South African adRP families to a 10 cM interval on chromosome 17q22. This novel locus, designated RP17, is the eighth identified for adRP. Haplotype construction in the two kindreds, in conjunction with multipoint analyses subsequently fine mapped RP17 to a 1 cM region between microsatellite markers D17S1604 and D17S948. Although the two families are from ethnically diverse population groups, they share the same disease-associated haplotype spanning 12 cM, which suggests that the disorder may be caused by the same pathogenic mutation in the same gene. The positional cloning approach was utilised in an endeavour to identify the RP17 gene and an attempt was made to construct a physical map of the 1 cM critical region. A contig consisting of seven yeast artificial chromosome (YAC) clones was assembled using sequence-tagged-site (STS) content mapping. In order to close a gap in the YAC contig, a bacterial artificial chromosome (BAC) library was screened and the vectorette PCR technique was used to verify overlapping sequences. This contig should provide a useful tool for the purpose of isolating genes or transcription units within the RP17 critical interval. In this regard, purified YAC DNA was isolated using pulsed-field gel electrophoresis and the cDNA selection technique was employed to generate a transcription map. This approach was applied to YAC 75Ic12 using a foetal brain cDNA library, and two rounds of selection were performed to create a sub-library for enriched cDNAs derived from this clone. Screening for the presence of contaminating sequences in the 480 transformants revealed that (i) approximately 7% of the selected clones contain COT-1 DNA and (ii) none of the clones were contaminated with yeast AB1380 DNA. Ten randomly chosen clones were sequenced and subjected to BLASTN analysis, which revealed the presence of a 23 bp contaminant, known genes as well as novel transcripts. In order to optimise efforts to isolate the adRP gene, four positional candidates residing on 17q were screened for evidence implicating them in the adRP phenotype in the two 17q22-linked families. The genes investigated were: PDEG (gamma subunit of rod phosphodiesterase), TIMP2 (tissue inhibitor of metalloproteinases-2), PKCA (protein kinase C alpha) and retinal fascin. These candidates were chosen on the basis of (i) mapping to 17q, (ii) expression in the retina and/or (iii) potential involvement in the rod phototransduction pathway. Recombination events between the adRP locus and a single strand conformation polymorphism (SSCP) in PDEG, and a restriction fragment length polymorphism (RFLP) in TIMP2 provided evidence for the exclusion of these candidate genes. A novel SSCP detected in the promoter region of retinal fascin was genotyped in the two adRP families and showed a lack of co-segregation with the disease locus. Furthermore, direct DNA sequencing of the coding regions as well as the promoter region of retinal fascin in RP affected family members did not reveal any pathogenic mutations. In addition, data is provided which suggests that PKCA does not reside on any of the YACs and BACs encompassing the RP17 critical interval. This gene is therefore unlikely to be responsible for the adRP phenotype in the two RP17-linked families. Ultimately, the work reported in this thesis may contribute to the body of knowledge on inherited retinal degenerative disorders. Moreover, this investigation should provide the basis for further study of the aetiology of RP in all families linked to the RP17 locus on chromosome 17q22. The immediate application of these molecular findings is the potential for pre-symptomatic testing of at-risk members from the two adRP kindreds.
  • No Thumbnail Available
    Item
    Open Access
    Mutation analysis of important retinal candidate genes: progression from research to diagnostic service
    (2006) Roberts, Lisa Jane; Greenberg, Jacquie; Ramesar, Raj
    Approximately one third of all human inherited disease includes defects of the eye. Retinal degenerative disorders (RDDs) are a group of diseases characterised by photoreceptor cell death in the retina and consequent vision loss. The Division of Human Genetics at the University of Cape Town (UCT) has samples archived in the RDD DNA database from over 1000 South African families. The research in this Division currently involves mutation screening of retinal candidate genes, with the goal of identifying the causative genetic mutation in each of the families registered in the database, in order to facilitate future therapeutic intervention. The purpose of this study was to determine the distribution and clinical utility of mutations in important candidate genes in a subset of South African RDD patients. To this end, three important retinal candidate genes were selected and screened in appropriate patient cohorts. The mutation analysis included screening for large deletions which is a novel approach in the study of RDDs. The screening of Rhodopsin (RHO) in 61 individuals, retinitis pigmentosa 1 (RP1) in 70 individuals and retinal pigment epithelium-specific protein 65kDa (RPE65) in 87 individuals led to the identification of 10 families for whom a molecular diagnostic service can now be provided. For most families the amount of useful information available without further research is minimal, however for four of the families, therapeutic interventions may be possible, now or in the near future. In addition to the pathogenic mutations found, 17 single nucleotide polymorphisms (SNPs) were identified during this study. Furthermore, a significant association between ethnicity and the frequency of the high and low risk alleles of two of these SNPs (that may modify the phenotype of RDDs) was shown. This information may be useful in providing diagnostic or prognostic indicators in the future. The utility of RDD research should not be trivialised as it identifies families who may benefit from current interventions or be eligible for possible therapeutic trials, eliminates gene candidates in families, and is necessary for understanding the disease (which in itself is a requirement for development of therapies).
  • Thumbnail Image
    Item
    Open Access
    Novel cell models for the study of spinocerebellar ataxia type 7 pathogenesis and therapy in a South African patient cohort
    (2012) Watson, Lauren; Greenberg, Jacquie; Wood, Matthew
    Spinocerebellar ataxia type 7 (SCA7) is a dominantly-inherited neurodegenerative disease, resulting from a CAG trinucleotide repeat expansion in the ataxin-7 gene. The Ataxin-7 protein is known to play a role in transcriptional regulation through association with cellular histone acetylation complexes, and several studies have highlighted the role of transcriptional dysregulation, caused by the presence of mutant Ataxin-7, in the neuronal dysfunction that precedes the onset of disease symptoms.This study aimed to establish patient-derived cell models of SCA7, for use in the investigation of pathogenesis (with particular reference to transcriptional alterations), and in the evaluation of previously-developed therapies for the disease.The high prevalence of SCA7 in the South African population, as a result of a founder effect, makes this disease particularly amenable to allele-specific RNA interference (RNAi)-based therapy. Thus, this study also evaluated the feasibility of these cell models as a vehicle to test previously-developed RNAi therapeutics, using the alteration of expression of key transcripts as a phenotypic marker. SCA7 patient and control dermal fibroblasts were reprogrammed to pluripotency by retroviral transduction. The resultant induced pluripotent stem cell (iPSC) lines were characterised with respect to endogenous markers of pluripotency, differentiation capacity and transgene silencing. These cells were then subjected to neuronal differentiation, the success of which was confirmed by the expression of early neuronal markers.
  • Thumbnail Image
    Item
    Open Access
    A pilot study of how individuals with inherited retinal degenerative disorders perceived being part of a genetic research programme
    (2005) Basson, Frieda; Greenberg, Jacquie; Futter, Merle
    Includes bibliographical references.
  • Thumbnail Image
    Item
    Open Access
    RNAi based allele-specific silencing of the disease-causing gene in black South African patients with SCA7
    (2008) Scholefield, Janine; Greenberg, Jacquie
    The polyglutamine disorders are a subgroup of inherited neurodegenerative disorders with a common mutation which confers toxicity via a polyglutamine tract in the protein leading ultimately to various forms of neurodegeneration. One of these disorders, spinocerebellar ataxia 7 (SCA7) exists at a higher frequency in South Africa, than elsewhere in the world, and a founder effect has been demonstrated in South Africa, such that every patient tested thus far is linked to a common ancestor. The manipulation of RNA interference (RNAi) has been used with increasing success to selectively knockdown the expression of disease-causing genes at the RNA level. Thus, the possibility of applying this method to SCA7 in South Africa was considered. However, the wild-type allele of ataxin-7 is likely to be necessary for cellular function therefore a form of allele-specific silencing is required, such as a SNP linked to the mutation.