Robea Ballo

Multiple epiphyseal dysplasia, ribbing type: A novel point mutation in the COMP gene in a South African family

Multiple epiphyseal dysplasia is broadly categorised into the more severe Fairbank and the milder Ribbing types. In this paper we document mild MED in a South African kindred, and demonstrate that heterozygosity for a mutation in the cartilage oligomeric matrix protein (COMP) gene causes the condition. The mutation, C1594G, implies a N523K substitution, altering a residue at the carboxyl-terminal end of the calmodulin-like region of COMP. The identification of this mutation demonstrates that the spectrum of manifestations from mild MED through pseudoachondroplasia can all be produced by structural mutations in COMP.

X-linked spastic paraplegia: evidence for homogeneity with a variable phenotype

Hereditary spastic paraplegia (HSP) is rarely inherited in an X‐linked recessive mode in pure and complicated forms. Recently, molecular linkage studies have suggested that these variant X‐linked HSP conditions result from locus heterogeneity. In this paper we report on the clinical and linkage analysis of a kindred with complicated X‐linked HSP. The finding in this family of a map location of the putative HSP gene in the same region as that documented for the pure HSP gene provides evidence that allelic mutations might also be responsible for the variable phenotype encountered in these X‐linked disorders.

X-linked mixed deafness with stapes fixation in a Mauritian kindred: Linkage to Xq probe pDP34

Molecular linkage analysis was undertaken on a large Mauritian kindred with X-linked mixed deafness, stapes fixation, and perilymphatic gusher (X-LDSF). DNA probe pDP34 (DXYS1) was tightly linked to the disorder, with a lod score of 6.32 at zero recombination. This observation indicates that the gene for this form of deafness maps to the Xq13-q21.1 region and has important implications for carrier screening and antenatal diagnosis.

Stickler-like syndrome due to a dominant negative mutation in the COL2A1 gene

The type II collagenopathies include a wide spectrum of phenotypes ranging from mild spondylo epiphyseal dysplasia (SED) to severe achondrogenesis/hypochondrogenesis. Several attempts have been made at providing phenotype-genotype correlations in this group of disorders. In this report we discuss a South African family in which four members have a phenotype resembling Stickler syndrome type 1. Ocular problems and conductive deafness predominate, while skeletal changes resemble those of a mild form of multiple epiphyseal dysplasia (MED). In distinction to the classical form of Stickler syndrome, the affected persons have stubby digits. DNA analysis of the exons of the COL2A1 gene documented a C-T transversion in exon 39, resulting in an Arg704Cys substitution in the triple helical domain of the type II collagen peptide; this nontermination mutation may be indicative of further heterogeneity in the Stickler group of disorders or of a new syndrome amongst the type II collagenopathies.

Spinocerebellar ataxia type 7 in South Africa: Epidemiology, pathogenesis and therapy.

Disorders of the nervous system represent a significant proportion of the global burden of non-communicable diseases, due to the trend towards ageing populations. The Department (now Division) of Human Genetics at the University of Cape Town (UCT) has been involved in pioneering research into these diseases since the appointment of Prof. Peter Beighton as Head of Department in 1972. Beightons emphasis on understanding the genetic basis of disease laid the groundwork for investigations into several monogenic neurodegenerative conditions, including Huntingtons disease and the polyglutamine spinocerebellar ataxias (SCAs). In particular, SCA7, which occurs at an unusually high frequency in the South African (SA) population, was identified as a target for further research and therapeutic development. Beginning with early epidemiological surveys, the SCA7 project progressed to molecular genetics-based investigations, leading to the identification of a founder effect in the SA SCA7 patient population in the mid-2000s. Capitalising on the founder haplotype shared by many SCA7 patients, UCT researchers went on to develop the first population-specific gene-silencing approach for the disease. More recently, efforts have shifted to the development of a more accurate model to decipher the precise mechanisms of neurodegeneration, using induced pluripotent stem cells derived from SA SCA7 patients. In many ways, the SA SCA7 journey reflects the legacy and vision of Prof. Peter Beighton, and his efforts to establish world-class, collaborative research into diseases affecting the African continent.

Genotyping of alcohol dehydrogenase type 2 and 3 using a two-buffer polyacrylamide gel electrophoresis system.

Abstract Genetic polymorphisms in the alcohol dehydrogenase genes, ADH2 and ADH3, have been shown to affect individual susceptibility to diseases such as alcoholism and oesophageal cancer. Although several PCR-based methods for genotyping these enzymes have been previously developed, the two-buffer polyacrylamide gel electrophoresis system has the ability to rapidly resolve all classes of point mutations within 2–3 hours instead of the conventional overnight separation. The success of this technique is partly attributable to a discontinuous two-phase buffer system and horizontal flatbed gel electrophoresis rather than conventional vertical gels. Using a modification of this system, we were able to detect all of the known polymorphisms within ADH2 exons 3 and 9 and ADH3 exon 8, as well as a rare variant within ADH2 exon 9. This method is rapid, cost-effective, and is ideal for large scale screening programmes.

Duchenne muscular dystrophy in the Western Cape, South Africa: Where do we come from and where are we going?

Duchenne muscular dystrophy (DMD) is one of the most common and severe of the inherited dystrophies, with an incidence of 1 in 3 500 live, male births worldwide. Becker muscular dystrophy (BMD) has a lower incidence of 1:14 000 - 18 000 boys and a milder progression and longer life expectancy. Over the last two decades, better understanding of the underlying disease aetiology as well as major advances in medical technology have brought about significantly improved genetic diagnosis and clinical care for B/DMD patients. Exciting developments in the field of gene-based therapies have once again put B/DMD in the limelight, with renewed focus on the importance of comprehensive genetic testing protocols. We present a historical overview of the medical and molecular service for B/DMD offered over the last three decades in South Africa, specifically in the Western Cape, from a clinical as well as a laboratory perspective.

Transcriptional and electrophysiological aberrations in an induced pluripotent stem cell-derived model of spinocerebellar ataxia type 7

Spinocerebellar ataxia type 7 (SCA7) is an inherited neurodegenerative disease caused by a polyglutamine repeat expansion in the ATXN7 gene. Patients with this disease suffer from a degeneration of their cerebellar Purkinje neurons and retinal photoreceptors that result in a progressive ataxia and loss of vision. As with many neurodegenerative diseases, studies of pathogenesis have been hindered by a lack of disease-relevant models. To this end, we have generated induced pluripotent stem cells (iPSCs) from a cohort of SCA7 patients in South Africa. First, we differentiated the SCA7 affected iPSCs into neurons which showed evidence of a transcriptional phenotype affecting components of STAGA (ATXN7 and KAT2A) and the heat shock protein pathway (DNAJA1 and HSP70). We then performed electrophysiology on the SCA7 iPSC-derived neurons and found that these cells show features of functional aberrations. Lastly, we were able to differentiate the SCA7 iPSCs into retinal photoreceptors that also showed similar transcriptional aberrations to the SCA7 neurons. Our findings demonstrate that iPSC-derived neurons and photoreceptors from SCA7 patients express molecular and electrophysiological differences that are indicative of impaired neuronal health. We hope that these findings will contribute towards the ongoing efforts to establish the cell-derived models of neurodegenerative diseases that are needed to develop patient-specific treatments.Spinocerebellar ataxia type 7 (SCA7) is an inherited neurodegenerative disease that is characterised by ataxia and visual loss. It results from a degeneration of cerebellar Purkinje neurons and retinal photoreceptors caused by a polyglutamine repeat expansion in the ATXN7 gene, a component of the STAGA transcription co-activator complex. As with many neurodegenerative diseases, studies of pathogenesis have been hindered by a lack of disease-relevant models. To this end, we have generated the first induced pluripotent stem cells (iPSCs) from South African SCA7 patients, where the disease occurs at an unusually high frequency as a result of a founder effect. These iPSCs were capable of differentiation into neural and retinal cells, and showed evidence of a transcriptional phenotype affecting components of STAGA (ATXN7 and KAT2A) and the heat shock protein pathway (DNAJA1 and HSP70). Functionally, SCA7 iPSC-derived neurons exhibited more negative resting membrane potentials and increased input resistance compared to controls, suggesting reduced excitability in response to synaptic input. These results provide the first evidence of a disease phenotype in SCA7 iPSC-derived cells, establishing a valuable model for the study of neurodegenerative diseases and the development of population-specific therapies.

The rise of developmental genetics – a historical account of the fusion of embryology and cell biology with human genetics and the emergence of the Stem Cell Initiative

Genetics and cell biology are very prominent areas of biological research with rapid advances being driven by a flood of theoretical, technological and informational knowledge. Big biology and small biology continue to feed off each other. In this paper, we provide a brief overview of the productive interactions that have taken place between human geneticists and cell biologists at UCT, and credit is given to the enabling environment created led by Prof. Peter Beighton. The growth of new disciplines and disciplinary mergers that have swept away division of the past to make new exciting syntheses are discussed. We show how our joint research has benefitted from worldwide advances in developmental genetics, cloning and stem cell technologies, genomics, bioinformatics and imaging. We conclude by describing the role of the UCT Stem Cell Initiative and show how we are using induced pluripotent cells to carry out disease-in-the- dish studies on retinal degeneration and fibrosis.

Towards guidelines for informed consent for prospective stem cell research

Stem cell science is advancing at an unprecedented rate, with thousands of research papers being published every year and many clinical trials for a wide range of conditions underway as registered on ClinicalTrials.gov. This rapidly expanding and alluring field has brought with it ever more complex and multifaceted ethical issues, many of which require new guidelines, consent protocols and even change in legislation, since they do not fit comfortably in the existing bioethical regulations and protocols. Keeping up with the ethical implications of stem cell research is daunting to the expert and non-expert. We review the various types of stem cells and then focus on multipotent and pluripotent cell types, since it is these cell types that bring with them the greatest research and therapeutic potential, while concurrently delivering novel ethical conundrums. Certain key considerations are currently lacking and what is needed is how to obtain permission from individuals who donate their biological material for both scientific inquiry and eventually, for their potential therapeutic utility.