Browsing by Author "Heckmann, Jeannine M"
Now showing 1 - 10 of 10
Results Per Page
Sort Options
- ItemOpen AccessEvolution of sensory neuropathy after initiation of antiretroviral therapy(2018) Centner, Chad; Heckmann, Jeannine MIntroduction: We studied the evolution of sensory neuropathy after antiretroviral therapy (ART) in human immunodeficiency virus–infected South Africans. Methods: Enrolment commenced before ART with 6-monthly follow-ups for 24 months. Symptomatic distal sensory polyneuropathy (SDSP) was defined as one symptom and sign. Symptom/sign scores were compared between visits. Results: We enrolled 184 participants. Pre-ART, 16% had SDSP. After 18 months of ART, pain prevalence decreased in those with pre-ART SDSP (odds ratio [OR], 0.09; 95% confidence interval [95%CI], 0.03-0.29). Symptoms improved in 50% ever experiencing pain (mean improvement=-4.5 on 11-point scale). Participants SDSP-free pre-ART developed SDSP at a rate of 18 per 100 person-years. After 24 months, 18% had SDSP. Stavudine (60% of cohort) did not predict incident SDSP, but associated with increased prevalence of reduced/absent reflexes at 18 months (OR, 2.24; 95% CI, 1.08-4.65). Conclusions: Painful symptoms improved during ART. Evolving sensory neuropathy was due to increasing small and large fiber dysfunction.
- ItemOpen AccessExome sequencing identifies novel dysferlin mutation in a family with pauci-symptomatic heterozygous carriers(BioMed Central, 2018-06-07) Jalali-Sefid-Dashti, Mahjoubeh; Nel, Melissa; Heckmann, Jeannine M; Gamieldien, JunaidBackground We investigated a South African family of admixed ancestry in which the first generation (G1) developed insidious progressive distal to proximal weakness in their twenties, while their offspring (G2) experienced severe unexpected symptoms of myalgia and cramps since adolescence. Our aim was to identify deleterious mutations that segregate with the affected individuals in this family. Methods Exome sequencing was performed on five cases, which included three affected G1 siblings and two pauci-symptomatic G2 offspring. As controls we included an unaffected G1 sibling and a spouse of one of the G1 affected individuals. Homozygous or potentially compound heterozygous variants that were predicted to be functional and segregated with the affected G1 siblings, were further evaluated. Additionally, we considered variants in all genes segregating exclusively with the affected (G1) and pauci-symptomatic (G2) individuals to address the possibility of a pseudo-autosomal dominant inheritance pattern in this family. Results All affected G1 individuals were homozygous for a novel truncating p.Tyr1433Ter DYSF (dysferlin) mutation, with their asymptomatic sibling and both pauci-symptomatic G2 offspring carrying only a single mutant allele. Sanger sequencing confirmed segregation of the variant. No additional potentially contributing variant was found in the DYSF or any other relevant gene in the pauci-symptomatic carriers. Conclusion Our finding of a truncating dysferlin mutation confirmed dysferlinopathy in this family and we propose that the single mutant allele is the primary contributor to the neuromuscular symptoms seen in the second-generation pauci-symptomatic carriers.
- ItemOpen AccessHIV-associated sensory neuropathy in an African cohort a longitudinal study of risk factors predisposing to antiretroviral induced painful neuropathy(2013) Van der Watt, Johan J; Heckmann, Jeannine M; Dandara, Collet; Wilkinson, Robert JDistal sensory polyneuropathy (DSP) amongst human immunodeficiency virus (HIV)-infected patients is frequently a painful and disabling condition. HIV-associated DSP is either a consequence of HIV (HIV-DSP) or antiretroviral-induced toxic neuropathy (ATN). The purpose of this research was to investigate the characteristics of HIV-associated DSP over the first 24 weeks of starting cART in an African community-based cohort. Apart from studying the longitudinal association of candidate risk factors based on previous reports, we focused on two additional aspects. Firstly, the Nacetyltransferase 2 (NAT2) genotype, which determines an individual's acetylation status, influences the risk for isoniazid (INH)-associated neuropathy.
- ItemOpen AccessInvestigating the functionality of African-specific variants in the TGFB1 regulatory region and their potential role in HIV-associated kidney complications(2016) Buys, Joy-Mari; Heckmann, Jeannine M; Prince, Sharon; Nel, MelissaTransforming growth factor beta-1 (TGF-β1) is a cytokine involved in immune modulation and tissue regeneration and has a polymorphic TGFB1 promoter. African-specific single nucleotide polymorphisms (SNPs) have been identified in the TGFB1 promoter and they occur at higher frequencies in South Africans with African-genetic ancestry (≈17%) compared with West and East African genomes (<5%). However, the functional significance of these SNPs has only been partially explored. In this study it was hypothesized that higher frequencies of immunemediated disease complications in South Africans, such as HIV-associated nephropathy (HIVAN), may be influenced by functional genetic variations in TGFB1. To address this, the African-specific TGFB1 haplotypes containing singular, or combinations of, -1287 G>A (rs11466314), -1154 C>T (rs35318502), -387 C>T (rs11466316) and -14 G>A (rs9282871) were investigated for their effect on TGFB1 promoter activity. Briefly, an extended TGFB1 regulatory region driving a luciferase reporter was used as a template to generate six TGFB1 promoter haplotypes (referred to as H-1 through H-6 in this thesis) by site-directed mutagenesis and luciferase activity was used to measure promoter activity. The functional TGFB1 -1347 C>T variant was also investigated (H-5 and H-6 containing -1347 C and T alleles, respectively) because all four of the African variants more frequently co-occurred with the previously reported "lower expressing" TGFB1 -1347 C variant (H-1 through H- 4). Transient transfection of the TGFB1 promoter reporter constructs in two renal cell lines (RCC4+VHL and Caki- 2) showed no difference between -1347 C (H-5) and T (H-6) basal promoter activity. Having at least one African variant resulted in ~5-fold loss of basal TGFB1 promoter activity in renal cells when compared to the most common haplotype (H-5) (p<0.05). The repressive effect is mainly attributed to the -387 T variant (H-1) as the addition of other African variants on this haplotype showed no additional TGFB1 promoter repression. The repressive effect of the TGFB1 -387 T variant was maintained even after in-vitro treatment of transfected renal cells with recombinant human TGF-β1 (rhTGF-β1). To determine whether the African-specific TGFB1 promoter haplotypes (H-AFR), containing TGFB1 -387 T and tested in luciferase assays, also impact on endogenous TGF-β1 protein levels, western blot analysis was performed on human dermal fibroblasts from patients who had been genotyped. Similar to the promoter studies, basal TGF- β1 protein levels in cells with the H-AFR were ~47% lower compared to cells without (p=0.04) and no difference was seen in response to hrTGF-β1. Interestingly, when western blots were screened for phosphorylated Smad3 (pSmad3) protein levels, as an indicator of the activated TGF-β1 canonical pathway, similar pSmad3 levels were observed under basal and hrTGF-β1 stimulated conditions for all haplotypes (p>0.05). The possible interaction of HIV tat on the African TGFB1 promoter variants was also assessed. Luciferase activity was measured after co-transfecting renal RCC4+VHL and HT1080 fibroblast cells with a HIV Tat expression vector and the H-6, H-5 and H-AFR promoter luciferase constructs. Results showed that the promoter activity for all TGFB1 haplotypes was upregulated in the renal cells (≥1.6-fold; p<0.001). The same result was, however, only observed for TGFB1 haplotypes H-5 and H-AFR in the fibroblast cells (≥1.4-fold; p<0.01). This is interesting because no difference was seen between TGFB1 H-5 and H-6 basal promoter activity. To investigate whether histopathological severity of HIVAN correlated with TGF-β1 staining patterns, immunohistochemistry was performed on 20 renal biopsies from patients with HIVAN. A semi-quantitative "histo" score (H-score) was calculated by multiplying the percentage of positive cells with the intensity of the stain before comparing the scores with control biopsies (HIV-negative, n=3 and HIV-positive without HIVAN, n=3). Compared to the HIV-positive controls the kidney tubules of HIVAN biopsies had higher H-scores. Strikingly, the interstitium of HIVAN samples stained much more prominently (17/18) than both control groups suggesting that TGF-β1 staining in the renal interstitium appear to be specific for HIVAN. In conclusion this study shows that the African-specific haplotypes effect basal TGFB1 promoter activity and TGF-β1 protein levels. However, they do not seem to affect the cytoplasmic TGF-β1/pSmad3 protein levels in response to rhTGF-β1 autocrine stimulation. Immunohistochemistry results suggest that TGF-β1 pathway may be prominently dysregulated in the renal interstitium of HIVAN cases.
- ItemOpen AccessA modular and adjustable ptosis crutch as a non-surgical solution to elevating the upper eyelid of myasthenia gravis patients(2017) Findlay, Megan; Sivarasu, Sudesh; Heckmann, Jeannine MMyasthenia Gravis (MG) is a treatable autoimmune disorder that affects the neuromuscular junction. MG is characterised by fatigable muscle weakness of voluntary skeletal muscles with the most commonly affected muscles being the eye and facial muscles. Patients of African genetic ancestry, particularly juveniles, are more likely to develop ocular muscle complications of MG compared to their European counterparts. MG ophthalmoplegic complications include persistent difficulty with moving the eyes and blepharoptosis, despite treatment. Blepharoptosis, or ptosis, describes the condition of a lowered upper eyelid(s), beyond its normal anatomic position. Surgical correction of ptosis is often contraindicated in MG patients with severe weakness of the muscles involved in eye closure and in patients with active disease. In these cases, a non-surgical solution to elevating the ptotic eyelid above the visual axis is required. Objective: To design a patient specific, modular and low cost ptosis crutch to elevate the eyelid(s) of myasthenia gravis patients. The ptosis crutch should be low cost, modular and adjustable in nature. Method: 16 MG patients (42 ± 23 years) volunteered to participate in the pre-design phase of the project. Initial eye measurements of each participant were taken using photographic measurement. A bottomup approach was followed for the design of the ptosis crutch. 3D CAD models of the modular ptosis crutch were created in SolidWorks, according to the measured dimensions and the predefined design parameters. The ptosis crutch was prototyped using 3D printing. Eightyseven design failures were observed before the final design was realised. A design feedback loop lead to the discovery of a device that satisfied the specified requirements. The final ptosis crutch was tested, in the clinical setting, on 12 MG patients (43 ± 24 years). Results: The ptosis crutch was designed to fit onto the superior border of the spectacle frame. The ptosis crutch is adjustable along the x- axis to cater for the inter-individual variability of globe protrusion. The crutch bar is adjusted along the z-axis and elevated the ptotic eyelid by 1.96mm (±1.11mm). All of the participants indicated that they would be interested in using the ptosis crutch on a long-term basis. Conclusion: The immediate feedback on the ptosis crutch from the MG patients has shown a positive outcome for the device. Future work will include obtaining long term feedback on the ptosis crutch from all of the users as well as investigating manufacturing methods using materials with increased durability.
- ItemOpen AccessMotor neuron disease in an African population: A review of current literature and a case series of the flail arm variant in the Western Cape(2018) Cross, Helen; Heckmann, Jeannine MBackground: Motor neuron disease (MND) is a devastating neurodegenerative disorder, with recognised phenotypic subtypes. Although prevalent in all parts of the world, little is described in the literature with regards motor neuron disease as it occurs in African populations. Aims: This study had two main aims: to conduct a systematic review of the current available literature on motor neuron disease in persons of African genetic descent, and to describe the clinical phenotype in a subgroup of MND patients with the flail arm (FA) variant seen at Groote Schuur Hospital MND clinic. Methods: In order to identify the current published knowledge of motor neuron disease in African populations, a systematic literature review was conducted using Pubmed and Google Scholar. For the case series description, patients presenting to the Groote Schuur Hospital MND clinic with a phenotype of restricted proximal upper limb, lower motor neuron involvement for at least 12 months after symptom onset, during the time period of March 2014 to September 2016, were considered for inclusion. A full clinical description of each case, including history, examination and electrophysiological findings, was conducted. Results: Review of the available literature on MND as it occurs in persons with African ancestry revealed that little is well described. Although there are a few original studies, all are small and most are out-dated. Some trends emerged, including younger age at onset of disease, tendency to longer survival, and possibly more frequent presentation with bilateral upper limb involvement. Six cases of FA variant of MND, representing 13% of the MND clinic cohort seen over the 2.5 years given time period, all with African genetic ancestry by self-categorization, are reported illustrating the various previously described features of this phenotype. Even within these few cases, there is variation in presentation and disease course. Conclusions: More research is required on African populations to address the questions surrounding MND as it occurs in Africans, including phenotypic and genetic similarities or differences to other populations. Although controversy surrounding exact case definition of the FA variant of MND remains, it does represent a unique phenotype, and seems to occur in patients of African genetic ancestry in a similar manner to that described in Caucasian populations.
- ItemOpen AccessPlasma cytokine profiles in HIV-1 infected patients developing neuropathic symptoms shortly after commencing antiretroviral therapy: a case-control study(2014-02-10) Van der Watt, Johan J; Wilkinson, Katalin A; Wilkinson, Robert J; Heckmann, Jeannine MAbstract Background In patients infected with human immunodeficiency virus 1 (HIV-1) neuropathic symptoms may develop within weeks of starting combination antiretroviral therapy (cART). This timing coincides with the occurrence of immune reconstitution inflammatory syndrome. Our objective was to investigate the longitudinal association of plasma cytokine and soluble receptor concentrations with incident neuropathic symptoms within 12 weeks of starting programme-based cART in a nested case-control study. Methods One hundred and twenty adults without neuropathic symptoms and about to initiate cART were followed longitudinally for 24 weeks after cART initiation. Subjects were examined for peripheral neuropathy at baseline (pre-cART) and 2-, 4-, 12- and 24 weeks thereafter. Individuals developing neuropathic symptoms within 12 weeks of starting cART were matched in a nested case-control design with those remaining symptom-free for at least 24 weeks. Plasma was collected at each visit. Cytokines and soluble receptors were quantified using multiplex immunometric assays. Results Incident neuropathic symptoms occurred in 32 (27%) individuals within 12 weeks of starting cART for the first time. Cytokine concentrations increased at 2 weeks, irrespective of symptom-status, returning to baseline concentrations at 12 weeks. Compared to the control group, the symptomatic group had higher baseline levels of interleukin-1 receptor (IL-1R)-antagonist. The symptomatic group also showed greater increases in soluble interleukin-2 receptor-alpha and tumour necrosis factor (TNF) receptor-II levels at week 2 and soluble interleukin-6 receptor levels at week 12. Ratios of pro-inflammatory- vs anti-inflammatory cytokines were higher for TNF-alpha/IL-4 (p = 0.022) and interferon-gamma/IL-10 (p = 0.044) in those developing symptoms. After 24 weeks of cART, the symptomatic group showed higher CD4+ counts (p = 0.002). Conclusions The initiation of cART in previously treatment naïve individuals was associated with a cytokine 'burst’ between 2- and 4 weeks compared with pre-cART levels. Individuals developing neuropathic symptoms within 12 weeks of starting cART showed evidence of altered cytokine concentrations even prior to initiating cART, most notably higher circulating IL-1R-antagonist levels, and altered ratios of “pain-associated” cytokine and soluble receptors shortly after cART initiation.
- ItemOpen AccessProfiling of patient-specific myocytes identifies altered gene expression in the ophthalmoplegic subphenotype of myasthenia gravis(BioMed Central, 2019-01-29) Nel, Melissa; Prince, Sharon; Heckmann, Jeannine MBackground: While extraocular muscles are affected early in myasthenia gravis (MG), but respond to treatment, we observe a high incidence of treatment-resistant ophthalmoplegia (OP-MG) among MG subjects with African genetic ancestry. Previously, using whole exome sequencing, we reported potentially functional variants which associated with OP-MG. The aim of this study was to profile the expression of genes harbouring the OP-MG associated variants using patient-derived subphenotype-specific ‘myocyte’ cultures. Methods From well-characterised MG patients we developed the ‘myocyte’ culture models by transdifferentiating dermal fibroblasts using an adenovirus expressing MyoD. These myocyte cultures were treated with homologous acetylcholine receptor antibody-positive myasthenic sera to induce muscle transcripts in response to an MG stimulus. Gene expression in myocytes derived from OP-MG (n = 10) and control MG subjects (MG without ophthalmoplegia; n = 6) was quantified using a custom qPCR array profiling 93 potentially relevant genes which included the putative OP-MG susceptibility genes and other previously reported genes of interest in MG and experimental autoimmune myasthenia gravis (EAMG). Results OP-MG myocytes compared to control MG myocytes showed altered expression of four OP-MG susceptibility genes (PPP6R2, CANX, FAM136A and FAM69A) as well as several MG and EAMG genes (p < 0.05). A correlation matrix of gene pair expression levels revealed that 15% of gene pairs were strongly correlated in OP-MG samples (r > 0.78, p < 0.01), but not in control MG samples. OP-MG susceptibility genes and MG-associated genes accounted for the top three significantly correlated gene pairs (r ≥ 0.98, p < 1 × 10− 6) reflecting crosstalk between OP-MG and myasthenia pathways, which was not evident in control MG cells. The genes with altered expression dynamics between the two subphenotypes included those with a known role in gangliosphingolipid biosynthesis, mitochondrial metabolism and the IGF1-signalling pathway. Conclusion Using a surrogate cell culture model our findings suggest that muscle gene expression and co-expression differ between OP-MG and control MG individuals. These findings implicate pathways not previously considered in extraocular muscle involvement in myasthenia gravis and will inform future studies.
- ItemOpen AccessA review of the genetic spectrum of hereditary spastic paraplegias, inherited neuropathies and spinal muscular atrophies in Africans(2022-03-24) Mahungu, Amokelani C; Monnakgotla, Nomakhosazana; Nel, Melissa; Heckmann, Jeannine MBackground Genetic investigations of inherited neuromuscular disorders in Africans, have been neglected. We aimed to summarise the published data and comment on the genetic evidence related to inherited neuropathies (Charcot-Marie-Tooth disease (CMT)), hereditary spastic paraplegias (HSP) and spinal muscular atrophy (SMA) in Africans. Methods PubMed was searched for relevant articles and manual checking of references and review publications were performed for African-ancestry participants with relevant phenotypes and identified genetic variants. For each case report we extracted phenotype information, inheritance pattern, variant segregation and variant frequency in population controls (including up to date frequencies from the gnomAD database). Results For HSP, 23 reports were found spanning the years 2000–2019 of which 19 related to North Africans, with high consanguinity, and six included sub-Saharan Africans. For CMT, 19 reports spanning years 2002–2021, of which 16 related to North Africans and 3 to sub-Saharan Africans. Most genetic variants had not been previously reported. There were 12 reports spanning years 1999–2020 related to SMN1-SMA caused by homozygous exon 7 ± 8 deletion. Interestingly, the population frequency of heterozygous SMN1-exon 7 deletion mutations appeared 2 × lower in Africans compared to Europeans, in addition to differences in the architecture of the SMN2 locus which may impact SMN1-SMA prognosis. Conclusions Overall, genetic data on inherited neuromuscular diseases in sub-Saharan Africa, are sparse. If African patients with rare neuromuscular diseases are to benefit from the expansion in genomics capabilities and therapeutic advancements, then it is critical to document the mutational spectrum of inherited neuromuscular disease in Africa. Highlights Review of genetic variants reported in hereditary spastic paraplegia in Africans Review of genetic variants reported in genetic neuropathies in Africans Review of genetic underpinnings of spinal muscular atrophies in Africans Assessment of pathogenic evidence for candidate variants
- ItemOpen AccessTreatment-resistant ophthalmoplegia in Myasthenia gravis: extraocular muscle pathology, the role of TGFβ1 and the derivation of induced pluripotency towards 'disease-in-a-dish' modeling(2016) Rautenbach, Robyn Marié; Heckmann, Jeannine M; Ballo, RobeaMyasthenia gravis (MG) is an autoimmune disease in which pathogenic antibodies target specific neuromuscular junction proteins, most frequently acetylcholine receptors (AChR). Among those without detectable AChR-antibodies, a subgroup of patients has antibodies directed against muscle-specific tyrosine kinase (MuSK). In MG the pathogenic antibodies result in failure of neuromuscular transmission with consequent fatiguable skeletal muscle weakness. MG frequently affects the extraocular muscles (EOMs) early in the course of the disease, resulting in diplopia and ptosis, which is usually reversible with treatment. A treatment-resistant ophthalmoplegia and ptosis occurs as a complication of MG in a distinct subset of cases referred to as OP-MG. The EOMs are highly specialised muscle tissue with a unique physiological and immunological microenvironment with a large satellite cell niche, a distinct muscle fibroblast population, different transcriptional and cellular signaling pathways and fewer intrinsic complement regulatory proteins to protect them against antibody- activated complement-mediated damage. We hypothesised that in OP-MG, there is a differential response of the EOMs to the underlying MG disease process(es) on a genetic and molecular level, resulting in abnormal myofibre homeostasis. We aimed to report descriptive clinical-pathological data pertaining to EOM function and histopathological and ultrastructural EOM tissue analysis of a patient with OP- MG versus that of a non-MG control (both consented to EOM donation at ocular realignment surgery). EOM tissue from an OP-MG individual with AChR- and MuSK- antibody negative MG, demonstrated predominantly myopathic pathology and ultrastructural evidence of mitochondrial stress. The OP-MG EOM findings differ from the control EOM, which showed normal muscle histopathology in a patient undergoing strabismus surgery for a sensory exotropia in a non-seeing eye (loss of retinal stimulus for fusion) and a similar duration of deviation. These OP-MG findings appear to better correlate with previously reported histology/ultrastructure in limb muscle in MuSK-positive MG rather than AChR-positive MG. We next focussed on transforming growth factor beta-1 (TGFβ1) as a critical cytokine involved in muscle repair. An auto-induction pathway in muscle allows TGFβ1 expression to influence the transdifferentiation of satellite cells into myofibroblasts or myoblasts. In orbital fibroblasts, TGFβ1 has also been shown to upregulate decay accelerating factor (DAF), a complement regulatory protein expressed at lower levels in EOMs than other muscles, which should protect against complement-mediated injury. We established OP-MG and control-MG phenotype-specific dermal fibroblast cell lines and performed immunoblotting to evaluate TGFβ1-induced Smad3 phosphorylation and Daf expression in mouse myotubes. We demonstrated repression of phosphorylated-Smad3, a marker of the canonical TGFβ1 pathway, in OP-MG versus control MG fibroblasts after treatment with TGFβ1. We also demonstrated that TGFβ1 significantly upregulates Daf expression levels in mouse myoblasts. Taken together, these results suggest that OP-MG fibroblasts (and possibly myofibroblasts) are likely to be more susceptible to complement-mediated damage and abnormal myofibrogenesis due to their altered response to TGFβ1 stimulation and secondary DAF upregulation. Finally we investigated the feasability of establishing an in vitro disease model for MG or OP-MG by reprogramming dermal fibroblasts into disease phenotype-specific induced pluripotent stem (iPS) cells. We successfully generated and characterised iPS cells for one individual. However, this process was very labour-intensive, cost-inefficient and time-consuming, taking approximately four months to establish pluripotency in a single patient and thereby limited its further application(s). In conclusion, the EOM ultrastructural findings of an OP-MG case are novel and show similar findings to those described in limb skeletal muscle of MuSK-positive MG patients. The TGFβ1 pathway appears to be differentially regulated in OP-MG compared to control-MG cases and this may impact DAF upregulation in the EOMs in MG patients. Finally, our group is exploring an alternative method of establishing a 'disease-in-a-dish' model that is more cost-effective and practically feasible than the iPS cell route.