Molecular and in silico investigation of a novel ECHS1 gene mutation in a consanguine family with short-chain enoyl-CoA hydratase deficiency and Mt-DNA depletion: effect on trimer assembly and catalytic activity.

Short-chain enoyl-CoA hydratase deficiency (ECHS1D) is a rare congenital metabolic disorder that follows an autosomal recessive inheritance pattern. It is caused by mutations in the ECHS1 gene, which encodes a mitochondrial enzyme involved in the second step of mitochondrial ß-oxidation of fatty acids. The main characteristics of the disease are severe developmental delay, regression, seizures, neurodegeneration, high blood lactate, and a brain MRI pattern consistent with Leigh syndrome. Here, we report three patients belonging to a consanguineous family who presented with mitochondrial encephalomyopathy. Whole-exome sequencing revealed a new homozygous mutation c.619G > A (p.Gly207Ser) at the last nucleotide position in exon 5 of the ECHS1 gene. Experimental analysis showed that normal ECHS1 pre-mRNA splicing occurred in all patients compared to controls. Furthermore, three-dimensional models of wild-type and mutant echs1 proteins revealed changes in catalytic site interactions, conformational changes, and intramolecular interactions, potentially disrupting echs1 protein trimerization and affecting its function. Additionally, the quantification of mtDNA copy number variation in blood leukocytes showed severe mtDNA depletion in all probands.

Vitamin B1 deficiency leads to high oxidative stress and mtDNA depletion caused by SLC19A3 mutation in consanguineous family with Leigh syndrome.

Leigh syndrome (LS) and Leigh-like spectrum are the most common infantile mitochondrial disorders characterized by heterogeneous neurologic and metabolic manifestations. Pathogenic variants in SLC carriers are frequently reported in LS given their important role in transporting various solutes across the blood-brain barrier. SLC19A3 (THTR2) is one of these carriers transporting vitamin-B1 (vitB1, thiamine) into the cell. Targeted NGS of nuclear genes involved in mitochondrial diseases was performed in a patient belonging to a consanguineous Tunisian family with LS and revealed a homozygous c.1264 A > G (p.T422A) variant in SLC19A3. Molecular docking revealed that the p.T422A aa change is located at a key position interacting with vitB1 and causes conformational changes compromising vitB1 import. We further disclosed decreased plasma antioxidant activities of CAT, SOD and GSH enzymes, and a 42% decrease of the mtDNA copy number in patient blood.Altogether, our results disclose that the c.1264 A > G (p.T422A) variant in SLC19A3 affects vitB1 transport, induces a mtDNA depletion and reduces the expression level of oxidative stress enzymes, altogether contributing to the LS phenotype of the patient.

A novel homozygous PIGO mutation associated with severe infantile epileptic encephalopathy, profound developmental delay and psychomotor retardation: structural and 3D modelling investigations and genotype-phenotype correlation.

The PIGO gene encodes the GPI-ethanolamine phosphate transferase 3, which is crucial for the final synthetic step of the glycosylphosphatidylinositol-anchor serving to attach various proteins to their cell surface. These proteins are intrinsic for normal neuronal and embryonic development. In the current research work, a clinical investigation was conducted on a patient from a consanguineous family suffering from epileptic encephalopathy, characterized by severe seizures, developmental delay, hypotonia, ataxia and hyperphosphatasia. Molecular analysis was performed using Whole Exome Sequencing (WES). The molecular investigation revealed a novel homozygous variant c.1132C > T in the PIGO gene, in which a highly conserved Leucine was changed to a Phenylalanine (p.L378F). To investigate the impact of the non-synonymous mutation, a 3D structural model of the PIGO protein was generated using the AlphaFold protein structure database as a resource for template-based tertiary structure modeling. A structural analysis by applying some bioinformatic tools on both variants 378L and 378F models predicted the pathogenicity of the non-synonymous mutation and its potential functional and structural effects on PIGO protein. We also discussed the phenotypic and genotypic variability associated with the PIGO deficiency. To our best knowledge, this is the first report of a patient diagnosed with infantile epileptic encephalopathy showing a high elevation of serum alkaline phosphatase level. Our findings, therefore, widen the genotype and phenotype spectrum of GPI-anchor deficiencies and broaden the cohort of patients with PIGO associated epileptic encephalopathy with an elevated serum alkaline phosphatase level.

Identification of a novel homozygous mutation in NAXE gene associated with early-onset progressive encephalopathy by whole-exome sequencing: in silico protein structure characterization, molecular docking, and dynamic simulation.

Progressive encephalopathy with brain edema and/or leukoencephalopathy, PEBEL1, is a severe neurometabolic disorder characterized by rapidly progressive neurologic deterioration associated with a febrile illness. PEBEL1 is a lethal encephalopathy caused by NAXE gene mutations. Here we report a 6-month-old boy with mitochondrial encephalomyopathy from a consanguineous family. Molecular analysis was performed using whole-exome sequencing followed by segregation analysis. In addition, in silico prediction tools and molecular dynamic approaches were used to predict the structural effect of the mutation. Furthermore, molecular docking of the substrate NADP in both wild-type and mutated NAXE protein was carried out. Molecular analysis revealed the presence of the novel homozygous mutation c.641 T > A (p. Ile214Asn) in the NAXE gene, located at the NAD (P)H hydrate epimerase domain. In addition, bioinformatics analyses and molecular dynamics revealed that p. Ile214Asn mutation could affect the structure, stability, and compactness of the NAXE protein. Moreover, the result of the molecular docking showed that the p. Ile214Asn mutation leads to conformational changes in the catalytic cavity, thus modifying interaction with the substrate and restricting its access. We also compared the phenotype of our patient with those of previously reported cases with PEBEL syndrome. All bioinformatics findings provide evidence that the NAXE variant Asn214 disrupts NAXE protein functionality leading to an insufficient NAD (P)HX repair system and the development of clinical features of PEBEL1 syndrome in our patient. To our knowledge, our case is the 21st case of PEBEL1 patient worldwide and the first case in North Africa.

Mitochondrial disease patients with novel ND4 12058A > C and ND1 m.3911A > G variations: implications for a role in the phenotype following a bioinformatic investigation.

Mitochondrial diseases include a wide group of clinically heterogeneous disorders caused by a dysfunction of the mitochondrial respiratory chain and can be related to mutations in nuclear or mitochondrial DNA genes. In the present report, we performed a whole mitochondrial genome screening in two patients with clinical features of mitochondrial diseases. Mutational analysis revealed the presence of two undescribed heteroplasmic mitochondrial variations, the m.3911A > G (E202G) variant in the MT-ND1 gene found in two patients (P1 and P2) and the m.12058A > C (E433D) pathogenic variant in the MT-ND4 gene present only in patient P2 who had a more severe phenotype. These two substitutions were predicted to be damaging by several bioinformatics tools and lead to amino acid changes in two conserved residues localized in two important functional domains of the mitochondrial subunits of complex I. Furthermore, the 3D modeling suggested that the two amino acid changes could therefore alter the structure of the two subunits and may decrease the stability and the function of complex I. The two described pathogenic variants found in patient P2 could act synergically and alter the complex I function by affecting the proton pumping processes and the energy production and then could explain the severe phenotype compared to patient P1 presenting only the E202G substitution in ND1.

Mutations in aARS genes revealed by targeted next-generation sequencing in patients with mitochondrial diseases.

Mitochondrial diseases are a clinically heterogeneous group of multisystemic disorders that arise as a result of various mitochondrial dysfunctions. Autosomal recessive aARS deficiencies represent a rapidly growing group of severe rare inherited mitochondrial diseases, involving multiple organs, and currently without curative option. They might be related to defects of mitochondrial aminoacyl t-RNA synthetases (mtARS) that are ubiquitous enzymes involved in mitochondrial aminoacylation and the translation process. Here, using NGS analysis of 281 nuclear genes encoding mitochondrial proteins, we identified 4 variants in different mtARS in three patients from unrelated Tunisian families, with clinical features of mitochondrial disorders. Two homozygous variants were found in KARS (c.683C>T) and AARS2 (c.1150-4C>G), respectively in two patients, while two heterozygous variants in EARS2 (c.486-7C>G) and DARS2 (c.1456C>T) were concomitantly found in the third patient. Bio-informatics investigations predicted their pathogenicity and deleterious effects on pre-mRNA splicing and on protein stability. Thus, our results suggest that mtARS mutations are common in Tunisian patients with mitochondrial diseases.

Mutational screening in patients with profound sensorineural hearing loss and neurodevelopmental delay: Description of a novel m.3861A > C mitochondrial mutation in the MT-ND1 gene.

Mitochondrial diseases caused by mitochondrial dysfunction are a clinically and genetically, heterogeneous group of disorders involving multiple organs, particularly tissues with high-energy demand. Hearing loss is a recognized symptom of a number of mitochondrial diseases and can result from neuronal or cochlear dysfunction. The tissue affected in this pathology is most probably the cochlear hair cells, which are essential for hearing function since they are responsible for maintaining the ionic gradients necessary for sound signal transduction. Several mitochondrial DNA mutations have been associated with hearing loss and since mitochondria are crucial for the cellular energy supply in many tissues, most of these mtDNA mutations affect several tissues and will cause syndromic hearing loss. In the present study, we described 2 patients with sensorineural hearing loss and neurodevelopmental delay in whom we tested mitochondrial genes described to be associated with syndromic hearing loss. One of these patients showed a novel heteroplasmic mitochondrial mutation m.3861A > C (W185C) which lead to a loss of stability of the ND1 protein since it created a new hydrogen bund between the unique created cystein C185 and the A182 residue. In the second patient, we detected two novel heteroplasmic variations m.12350C > A (T5N) and m.14351T > C (E108G) respectively in the MT-ND5 and the MT-ND6 genes. The TopPred II prediction for the E108G variation revealed a decrease of the hydrophobicity in the mutated MT-ND6.

Neonatal purulent meningitis in southern Tunisia: Epidemiology, bacteriology, risk factors and prognosis.

OBJECTIVES: To study the epidemiological, clinical and bacteriological aspects and outcome of purulent neonatal meningitis (PNM). METHODOLOGY: Retrospective analysis of 55 cases of PNM hospitalized in the pediatric ward of Hedi Chaker Hospital from 1990 to 2012. Infants less than 29 days of age were included. The diagnosis was made on either the presence of bacteria in the cerebrospinal fluid (CSF) or the combination of pleocytosis >30 cells/mm(3), protein level >1.3 g/l and glucose level <2.2 mmol/l or CSF/blood glucose ratio <0.4. RESULTS: The male:female sex ratio was 1.75. One or more maternal risk factors for infection were found in 24 cases. The main symptoms were fever and poor feeding. Soluble antigen was positive in four cases and cultures had isolated the bacteria in 28 cases. The mortality rate was 40%. The sequelae rate in the survivors was 16.4%. CONCLUSION: This study emphasizes the severity of PNM with high rates of mortality and neurological sequelae.

Ataxia-telangiectasia in the south of Tunisia: A study of 11 cases.

BACKGROUND: Ataxia-telangiectasia (A-T) is a multisystem disorder characterized by progressive neurologic impairment, variable immunodeficiency, impaired organ maturation, X-ray hypersensitivity, oculocutaneous telangiectasia, and a predisposition to malignancy. AIM: We performed this study in order to describe clinical, immunological and molecular features of patients with AT followed in the south of Tunisia Methods: we performed a retrospective study (1996-2012) in the south of Tunisia about all cases of A-T in order to describe their clinical, immunological and molecular features. RESULTS: 11 cases of AT were found. The mean age at onset of symptoms was 20 months with extremes varying from 3 months to 4 years. The median time to diagnosis was 3.6 years (range: 0-12 years).The main clinical feature of cerebellar syndrome, ataxia, was present at diagnosis in 8 patients and occurred at mean ages of 2.8 years. Ocular telangiectasia occurred at a mean age of 3.9 years (extremes: 3 months and 7 years). Recurrent sino-pulmonary infections that affected 7 children occurred at the mean age of 4.3 years. The most common humoral immune abnormality was serum IgA deficiency. Lymphopenia was found in 7 cases and lack of CD4 T in 6 cases. Cytogenetic analyses showed chromosomal instability in all children and a translocation (7-14) in two patients. A molecular diagnosis established in 6 patients from 4 families showed 5 different mutations of ATM gene. After an average decline of 5 years and 6 months, 7 patients died of severe pulmonary infection. Among them, 3 were ATM mutated. CONCLUSION: Morbidity and mortality among patients with A- T are associated with ATM genotype.

Hemolytic anemia and progressive neurologic impairment: think about triosephosphate isomerase deficiency.

We have reported the first Tunisian case of triosephosphate isomerase (TPI) deficiency in a 2-year-old girl. She was the first child of a nonconsanguineous couple. The disease included a neonatal onset of chronic hemolytic anemia, recurrent low-respiratory infections then progressive neurological involvement. The diagnosis was made after her death from the TPI values of her parents who exhibited intermediate enzyme deficiency. Molecular study of TPI genes showed that the father and the mother are heterozygous for Glu105Asp mutation. Pediatricians must be alert to the differential diagnosis in patients having hemolytic anemia and other concomitant manifestations.

[Bacterial meningitis in children: epidemiological data and outcome]. / La méningites purulentes de l'enfant dans le sud Tunisien: aspects épidémiologiques et évolutifs.

BACKGROUND: The bacterial meningitis in children remains a worrisome affection both by its frequency and by its gravity. AIM: describe the epidemiological, clinical and evolutionary data of bacterial meningitis in children aged between 3 months and 15 years. METHODS: we conducted a retrospective study of all cases of bacterial meningitis collected in the department of pediatrics of Hedi Chaker hospital, during a period of 6 years (2006-2011). We analyzed the files retrospectively and we studied the epidemiological data and the outcome. RESULTS: Thirty cases of bacterial meningitis were recorded. The most frequent species were Streptococcus pneumoniae and Haemophilus influenzae followed by Neisseria meningitidis with respectively 43%, 40%, and 6% of cases. The yearly distribution of these bacteria showed an increase of the rate of the bacterial meningitis during the last 2 years. The average age of our patients was 1 year 6months (3 months-13 years). All the patients were vaccinated according to the Tunisian vaccination calendar; and none of them had pneumococcal vaccine or the Hib vaccine. The main clinical manifestations were fever (100 %), seizures (14 %) and vomiting (44 %). Bulging fontanel was noted in 15cas (55 %), somnolence in 11 cases (40 %) and axial hypotonia in 12 cases (44 %). In the outcome, the neurological sequelae were showed in eight patients (26%). CONCLUSION: In our study, H. influenzae and S. pneumoniae were the main microorganisms responsible for bacterial meningitis. We strongly recommend the introduction pneumococcal vaccine in our vaccination calendar.

[Cerebral imaging in epileptic children: study of 140 cases]. / Magerie cérébrale de l'épilepsie de lenfant. Etude de 140 observations.

BACKGROUND: Epilepsy is a chronic disease, often with an onset during childhood and characterized by spontaneous and recurrent seizures. It concerns 0.5-1% of children under 16 years of age. Being much more sensitive than computed tomography, magnetic resonance imaging is the technique of choice to identify an underlying cause. CT scan is used in emergency situations. AIM: To describe cerebral lesions in epilepetic children and to identify predicative factors of abnormal neuroimaging. METHODS: Authors present a retrospective descriptive study of Neuroimaging data of 140 epileptic children evaluated for a period from 2000-2007 in the paediatric departement of Sfax. RESULTS: The mean age at onset of seizures was 3 years. The sex ratio was 1.12. Psychomotor retardation was noted in 75 patients. The seizures were generalized in 75% of case. Neurological examination was abnormal in 73 cases (52%). The main indications for conducting a brain imaging were psychomotor retardation (65 cases) and focal onset seizures (25 cases). Anoxo-ischemic lesions were the most frequent cerebral anomalies followed by brain malformations. Predictors of pathological MRI were an age at onset of seizure <3 years, psychomotor retardation and abnormal neurological examination. CONCLUSION: The morphological imaging is recommended for recent seizures of the child with the exception of idiopathic epilepsies. MRI is the best imaging modality in exploration of epilepsy in this context.

[Primary immune thrombocytopenia in childhood: a regional study in the south of Tunisia]. / Thrombocytopénie immune primaire de L'Enfant: etude régionale dans le sud Tunisien.

BACKGROUND: the primary immune thrombocytopenia (ITP) in children has a favorable evolution in most of cases. aim: describe the epidemiological and therapeutic data and the outcome of primary immune thrombocytopenia in our patients and propose a treatment plan to standardize the management of this disease in our region. methods: We conducted a retrospective study of 140 cases of primary immune thrombocytopenia collected in department of pediatrics and hematology of Hedi Chaker hospital during a period of 15 years. Patients who had a platelet count ≤ 20 000 and / or mucosal or troublesome lifestyle hemorrhage were treated. results: The mean age was 6 years 7 months with extremes varying from 3 months to 15 years. The bleeding manifestations were dominated by cutaneous bleeding in the form of petechiae or bruise (100%). Epistaxis and gingivorragia were noted in 32,9% and 25,7% of the cases respectively. The most of patient were treated with corticosteroids (79%). Intravenous immunoglobulin was associated with corticosteroids in 7%. An acute ITP occurred in 94 cases (67%) and a chronic ITP in 30 cases (21%). CONCLUSION: In the recently diagnosed ITP, the response delay under association Intravenous immunoglobulin and corticoids is shorter than that of corticoids alone, but the high cost of Intravenous immunoglobulin associated with their immediate side effects compels us to recommend corticoids as a first line of treatment.

Nephropathic infantile form of cystinosis about one case.

Cystinosis is the major cause of inherited Fanconi syndrome, and should be suspected in young children with a failure to thrive and with signs of renal proximal tubular damage. This is a study of a case report of cystinosis revealed by a growth failure and chronic dehydration. A 9-month-old boy was referred to our department for evaluation of polyuria and polydipsia. Clinical examination showed dehydration and enlarged wrists and rachitic rosaries. The presence of metabolic acidosis, hypokalemia, hypochloremia with proteinuria, polyuria, and hypercalciuria was suggestive of inherited Fanconi syndrome. The diagnosis of cystinosis was confirmed by an increased leukocyte cystine level.

Arterial ischemic stroke in children: 22 cases from southern Tunisia.

The aim of this study is to review the cases of arterial ischemic stroke (AIS) in children in our department to evaluate the clinical and neuroimaging features, the etiologies and the treatment. This study retrospectively reviewed the records of all children aged between 1 month and 16 years who were admitted from 2000 to 2010 for AIS in the pediatrics department of Hedi Chaker University hospital in Sfax, Tunisia. Twenty-two children were enrolled. The average age at stroke was 3 years and 2 months. Cardiac disease (27%) and moyamoya disease (18%) were the most common etiologies. Adverse outcome after childhood stroke includes death in 9%, recurrence in 18% and neurologic deficits in 45%.

Resistant invasive aspergillosis in an autosomal recessive chronic granulomatous disease.

Chronic granulomatous disease (CGD) is an inherited immunodeficiency characterized by severe bacterial and fungal infections. Invasive aspergillosis and other rare mold diseases are the leading causes of mortality. We report one case of CGD revealed by retropharyngeal abscess. On evolution, the patient developed an invasive aspergillosis resistant to treatment.

Miliary tuberculosis mimicking COVID-19 multisystemic inflammatory syndrome in children.

Miliary tuberculosis (TB) is a severe form of disseminated TB. In pediatrics, many cases are missed because the symptomatology of TB mimics common childhood diseases. We present the case of a 6-year-old girl with no remarkable history who had recurrent fever for 3 months. She was initially diagnosed with, and treated for, refractory multisystem inflammatory syndrome in children (MIS-C). When the study was extended to other differential diagnoses, thoraco-abdominopelvic computed tomography revealed miliary pulmonary nodules in addition to lymph nodes and spleen lesions. Magnetic resonance imaging of the brain revealed multiple tuberculomas. The tuberculin test results were positive. The course of the disease was favorable under quadruple therapy.

Clinical, functional and genetic analysis of twenty-four patients with chronic granulomatous disease - identification of eight novel mutations in CYBB and NCF2 genes.

Chronic granulomatous disease is an inherited disorder in which phagocytes lack a functional NADPH oxidase and cannot produce superoxide anions. The most common form is caused by mutations in CYBB encoding gp91phox. We investigated 24 CGD patients and their families. Twenty-one mutations in CYBB were classified as X91(0), X91(+) or X91(-) variants according to cytochrome b (558) expression. Point mutations in encoding regions represented 50 % of the mutations found in CYBB, splice site mutations 27 %, deletions and insertions 23 %. Eight mutations in CYBB were novel leading to X91(0)CGD cases. Two of these were point mutations: c493G>T and a double mutation c625C>G in exon 6 and c1510C>T in exon 12 leading to a premature stop codon at Gly165 in gp91phox and missense mutations His209Arg/Thr503Ile respectively. Two novel splice mutations in 5'intronic regions of introns 1 and 6 were found. A novel deletion/insertion c1024_1026delCTG/insT results in a frameshift introducing a stop codon at position 346 in gp91phox. The last novel mutation was the insertion of a T at c1373 leading to a frameshift and a premature stop codon at position 484 in gp91phox. For the first time the precise size of two large mutations in CYBB was determined by array-comparative genomic hybridization and carriers' status were evaluated by multiplex ligation-dependent probe amplification assay. No clear correlation between clinical severity and CYBB mutations could be established. Of three mutations in CYBA, NCF1 and NCF2 leading to rare autosomal recessive CGD, one nonsense mutation c29G>A in exon 1 of NCF2 was new.

Febrile seizures: an epidemiological and outcome study of 482 cases.

INTRODUCTION: Febrile seizures (FSs) are the most common type of seizures seen in children. After the first FS, 3 to 12% of children develop epilepsy, and 30% of these patients present with recurrent FS. The purpose of this study was to describe the epidemiological aspects of FS in order to better define the long-term outcomes in children with first FS and to identify the risk factors associated with the recurrence of FS as well as the development of epilepsy. METHODS: A retrospective study of 482 children with FS was conducted from January of 2004 to December of 2009 in the pediatric department of Hedi Chaker University Hospital in Sfax, Tunisia. The medical records for each patient were first collected and then analyzed at a later time. RESULTS: The study included 482 children. Simple FSs were found in 55.2% of children, and complex FSs were observed in 44.8%. The mean duration for follow-up examinations was 2 years and 4 months, and ranged from 1 to 5 years. No deaths or permanent neurological deficits due to FSs were observed, and only six children (1%) developed epilepsy. A total of 57 children (11.7%) developed recurrent seizures. Our findings suggest that a family history of FS, young age at onset, and a low degree of fever were predictive of recurrent FSs. CONCLUSION: Children with FSs encounter a minor risk of mortality and morbidity. While recurrent seizures are observed in these children, only a minority of these patients develop epilepsy.