Characterization of mtDNA variation in a cohort of South African paediatric patients with mitochondrial disease

Mitochondrial disease can be attributed to both mitochondrial and nuclear gene mutations. It has a heterogeneous clinical and biochemical profile, which is compounded by diversity of the genetic background. Disease-based epidemiological information has expanded significantly in recent decades, but little information is known that clarifies the aetiology in African patients. The aim of this study was to investigate mitochondrial DNA variation and pathogenic mutations in muscle of diagnosed paediatric patients from South Africa. A cohort of 71 South African paediatric patients was included and a high-throughput nucleotide sequencing approach was used to sequence full-length muscle mtDNA. The average coverage of the mtDNA genome was 81 ± 26 per position. After assigning haplogroups, it was determined that although the nature of non-haplogroup defining variants was similar in African and non-African haplogroup patients, the number of substitutions were significantly higher in African patients. We describe previously reported disease-associated and novel variants in this cohort. We observed a general lack of commonly reported syndrome-associated mutations, which supports clinical observations and confirms general observations in African patients when using single mutation screening strategies based on (predominantly non-African) mtDNA disease-based information. It is finally concluded that this first extensive report on muscle mtDNA sequences in African paediatric patients highlights the need for a full length mtDNA sequencing strategy, which applies to all populations where specific mutations is not present. This, in addition to nuclear DNA gene mutation and pathogenicity evaluations, will be required to better unravel the aetiology of these disorders in African patients.http://www.nature.com/ejhg/index.htm

A case for genomic medicine in South African paediatric patients with neuromuscular disease

DATA AVAILABILITY STATEMENT : The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author/s.Paediatric neuromuscular diseases are under-recognised and under-diagnosed in Africa, especially those of genetic origin. This may be attributable to various factors, inclusive of socioeconomic barriers, high burden of communicable and non-communicable diseases, resource constraints, lack of expertise in specialised fields and paucity of genetic testing facilities and biobanks in the African population, making access to and interpretation of results more challenging. As new treatments become available that are effective for specific sub-phenotypes, it is even more important to confirm a genetic diagnosis for affected children to be eligible for drug trials and potential treatments. This perspective article aims to create awareness of the major neuromuscular diseases clinically diagnosed in the South African paediatric populations, as well as the current challenges and possible solutions. With this in mind, we introduce a multi-centred research platform (ICGNMD), which aims to address the limited knowledge on NMD aetiology and to improve genetic diagnostic capacities in South African and other African populations.The National Health Laboratory Services (NHLS) of South Africa; the South African Medical Research Council (SAMRC), The genetics of Neuromuscular Diseases in South African patient populations: the ICGNMD study as well as the National Research Foundation (NRF) of South Africa.https://www.frontiersin.org/journals/pediatricsam2023Paediatrics and Child Healt

An investigation into the origin of acyl-amino acid conjugation in the human and bovine metabolism

PhD (Biochemistry), North-West University, Potchefstroom CampusGlycine conjugation and subsequent excretion of carboxylic acids of endogenous and exogenous origin is a normal detoxication process. A wide variety of short- and medium-chain, mono and dicarboxyl, acylglycine conjugates are also excreted in the urine of patients suffering from various metabolic disorders. The formation of these conjugates is catalyzed by glycine N-acyltransferase (EC 2.3.1.13). During the last two decades acylarnino acid conjugates with amino acid moieties other than glycine have also been detected in the urine of patients with metabolic disorders. These include propionylalanine, propionylglutamic acid, benzoylalanine, isovalerylalanine, isovalerylglutamic acid, and 3-methylcrotonylglutamic acid. This study investigated the conjugation of benzoyl-CoA with the aliphatic and acidic amino acids as well as their amides by glycine N-acyltransferase. Bovine and human glycine N-acyltransferase was purified from liver mitochondria in a five-step strategy and conjugation was investigated using these preparations in addition to mitochondrial lysates. A new electrospray ionization tandem mass spectrometry-based method was developed to characterize as well as quantify benzoylamino acid conjugation. Bovine glycine N-acyltransferase conjugated benzoyl-CoA with glycine (KmGiy = 6.2 mM), asparagine (KmAsn = 129 mM), glutamine (KmGJn = 353 mM), alanine (KmAJa = 1573 mM), and glutamic acid (KmGiu = 1148 mM) in a sequential mechanism. Benzoyl conjugation with serine was also detected. Human glycine N-acyltransferase, on the other hand, showed a less diverse amino acid substrate utilization and conjugated benzoyl-CoA with glycine (KmGiy = 6.4 mM), alanine (KmAJa = 998 mM), as well as glutamic acid. The results indicated that, compared to glycine, all other amino acids conjugated with benzoyl-CoA at much lower rates, which explains the relative low levels of the newly detected conjugates in urine. Inhibition of human and bovine glycine N-acyltransferase by benzoylamino acid conjugates other than glycine were much lower compared to benzoylglycine and it is unlikely to have an inhibitory effect on glycine N-acyltransferase in vivo. A human liver cDNA clone was obtained using bovine N-terminal sequence data which shared a strong homology (82 % ) with bovine GNAT cDNA as well as bovine glutarnine N-phenylacetyltransferase cDNA (77 %). Attempts to express the cDNA in E.coli were not successful and the identity of this cDNA could therefore not be confirmed.Doctora

Combined tarsal and carpal tunnel syndrome in Mucolipidosis Type III : a case study and review

Mucolipidosis type III (MLIII) (MIM# 252600) is an uncommon autosomal recessive disorder that results from uridine 5'-diphosphate-N-acetylglucosamine: lysosomal hydrolase N-acetyl-1-phosphotransferase or UDP-GlcNAc 1-phophotransferase deficiency. Clinical manifestations include developmental delay, short stature and other structural abnormalities. Less common clinical features, such as carpal tunnel syndrome, claw hand deformities, trigger fingers, and claw toes have previously been reported, but no specific association with tarsal tunnel syndrome has been reported in the literature. Tarsal tunnel syndrome is caused by entrapment of the posterior tibialis nerve in the tunnel formed by the medial malleolus of the ankle and the flexor retinaculum. It causes pain in the heel and sole of the foot as well as abnormal sensation in the distribution area of nervus tibialis posterior. In adults, the most common cause described is a ganglion. The phenomenon is rare in children and the published series are small. This case report portrays the presentation of a young girl with breath-holding spells secondary to painful bilateral tarsal tunnel syndrome and trigger fingers subsequently diagnosed with MLIII

An overview of a cohort of South African patients with mitochondrial disorders

Mitochondrial disorders are frequently encountered inherited diseases characterized by unexplained multisystem involvement with a chronic, intermittent, or progressive nature. The objective of this paper is to describe the profile of patients with mitochondrial disorders in South Africa. Patients with possible mitochondrial disorders were accessed over 10 years. Analyses for respiratory chain and pyruvate dehydrogenase complex enzymes were performed on muscle. A diagnosis of a mitochondrial disorder was accepted only if an enzyme activity was deficient. Sixtythree patients were diagnosed with a mitochondrial disorder, including 40 African, 20 Caucasian, one mixed ancestry, and two Indian patients. The most important findings were the difference between African patients and other ethnicities: respiratory chain enzyme complexes CI+III or CII+III deficiencies were found in 52.5% of African patients, being of statistical significance (p value=0.0061). They also presented predominantly with myopathy (p value= 0.0018); the male:female ratio was 1:1.2. Twenty-five (62.5%) African patients presented with varying degrees of a myopathy accompanied by a myopathic face, high palate, and scoliosis. Fourteen of these 25 also had ptosis and/or progressive external ophthalmoplegia. No patients of other ethnicities presented with this specific myopathic phenotype. Caucasian patients (16/20) presented predominantly with central nervous system involvement. Of the South African pediatric neurology patients, Africans are more likely to present with myopathy and CII+III deficiency, and Caucasian patients are more likely to present with encephalopathy or encephalomyopath

Glycation of fibrinogen in uncontrolled diabetic patients and the effects of glycaemic control on fibrinogen glycation

Evidence exists for a relationship between glycaemic control and macrovascular disease. Non-enzymatic glycation of proteins may explain this relationship in part. We investigated the effect of blood glucose control, under out-patient conditions, on fibrinogen glycation as well as the relationship between glycated fibrinogen and glycaemic control using a new sensitive method for the measurement of glycated fibrinogen.The authors would like to thank the volunteers who took part in the study for their willingness and effort. We would also like to thank Sr. Dorothy Kekana for her hard work in recruiting subjects and in the execution of the intervention. Many thanks also to Dr. Rustem Litvinov and Dr. Robert Ariëns, for their expertise and input in analytic experiments and results. The study was funded by research funds from the North-West University and the University of Pretoria. Insulin was provided by Sanofi-Aventis, South Africa and Novo-Nordisk, South Africa and glucometers by Roche Diagnostics

Glycaemic control improves fibrin network characteristics in type 2 diabetes : a purified fibrinogen model

Diabetic subjects have been shown to have altered fibrin network structures.One proposed mechanism for this is non-enzymatic glycation of fibrinogen due to high blood glucose.We investigated whether glycaemic control would result in altered fibrin network structures due to decreased fibrinogen glycation. Twenty uncontrolled type 2 diabetic subjects were treated with insulin in order to achieve glycaemic control. Twenty age- and body mass index (BMI)-matched non-diabetic subjects were included as a reference group. Purified fibrinogen, isolated from plasma samples was used for analysis.There was a significant decrease in fibrinogen glycation (6.81 to 5.02 mol glucose/mol fibrinogen) with a corresponding decrease in rate of lateral aggregation (5.86 to 4.62) and increased permeability (2.45 to 2.85 x 10–8 cm2) and lysis rate (3.08 to 3.27 μm/min) in the diabetic subjects after glycaemic control.These variables correlated with markers of glycaemic control. Fibrin clots of non-diabetic subjects had a significantly higher ratio of inelastic to elastic deformation than the diabetic subjects (0.10 vs. 0.09). Although there was no difference in median fiber diameter between diabetic and non-diabetic subjects, there was a small increase in the proportion of thicker fibers in the diabetic samples after glycaemic control. Results from SDS-PAGE indicated no detectable difference in factor XIIIa-crosslinking of fibrin clots between uncontrolled and controlled diabetic samples. Diabetic subjects may have altered fibrin network formation kinetics which contributes to decreased pore size and lysis rate of fibrin clots. Achievement of glycaemic control and decreased fibrinogen glycation level improves permeability and lysis rates in a purified fibrinogen model