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X-linked adrenoleukodystrophy (X-ALD) affects the nervous system white matter and adrenal cortex secondary to mutations in the ABCD1 gene that encodes a peroxisomal membrane protein: the adrenoleukodystrophy protein. The disease is characterized by high concentrations of very long-chain fatty acids in plasma, adrenal, testicular and nervous tissues. Various types of mutations have been identified in the ABCD1 gene: point mutations, insertions, and deletions. To date, more than 40 point mutations have been reported at the splice junctions of the ABCD1 gene; only few functional studies have been performed to explore these types of mutations. In this study, we have identified de novo splice site mutation c.1780+2T>G in ABCD1 gene in an X-ALD Tunisian patient. Sequencing analysis of cDNA showed a minor transcript lacking exon 7 and a major transcript with a partial intron 7 retention due to activation of a new intronic cryptic splice site. Both outcomes lead to frameshifts with premature stop codon generation in exon 8 and intron 7 respectively. To the best of our knowledge, the current study demonstrates that a single splicing mutation affects the ABCD1 transcripts and the ALDP protein function.

Background: X-linked adrenoleukodystrophy (X-ALD) is a recessive neurodegenerative disorder that affects the brain's white matter and is associated with adrenal insufficiency. It is characterized by an abnormal function of the peroxisomes, which leads to an accumulation of very long-chain fatty acids (VLCFA) in plasma and tissues, especially in the cortex of the adrenal glands and the white matter of the central nervous system, causing demyelinating disease and adrenocortical insufficiency (Addison's disease). X-ALD is caused by a mutation in the ABCD1 gene (ATP-binding cassette, subfamily D, member 1), which encodes the adrenoleukodystrophy protein involved in the transport of fatty acids into the peroxisome for degradation. Objective: We report here a disease-related variant in the ABCD1 gene in a 19-year-old Tunisian boy with childhood cerebral adrenoleukodystrophy. Methods: The diagnosis was based on clinical symptoms, high levels of VLCFA in plasma, typical MRI pattern and molecular analysis. Results: Molecular analysis by direct sequencing of the ABCD1 gene showed the presence of a novel missense mutation c.284C>A (p.Ala95Asp) occurring in the transmembrane domain in the proband, his mother and his sister. Conclusion: Using bioinformatic tools we suggest that this novel variant may have deleterious effects on adrenoleukodystrophy protein structure and function.

Apoptosis of skeletal muscle fibers is a well-known event occurring in patients suffering from muscular dystrophies. In this study, we hypothesized that functional polymorphisms in genes involved in the mitochondrial apoptotic pathway might modulate the apoptotic capacity underlying the muscle loss and contributing to intrafamilial and interfamilial variable phenotypes in LGMD2C (Limb Girdle Muscular Dystrophy type 2C) patients sharing the same c.521delT mutation in SGCG gene. Detection of apoptosis was confirmed on muscle biopsies taken from LGMD2C patients using the TUNEL method. We genotyped then ten potentially functional SNPs in TP53, BCL-2 and BAX genes involved in the mitochondrial apoptotic pathway. Potential genotype-dependent Bcl-2 and p53 protein expressed in skeletal muscle was investigated using western blot and ELISA assays. The result showed that muscle cells carrying the TP53-R72R and TP53-16 bp del/del genotypes displayed an increased p53 level which could be more effective in inducing apoptosis by activation of the pro-apoptotic gene expression. In addition, the BCL2-938 AA genotype was associated with increased Bcl-2 protein expression in muscle from LGMD2C patients compared to -938CC genotype, while there was no evidence of significant difference in the BAX haplotype. Our findings suggest that increased Bcl-2 protein expression may counteract pro-apoptotic pathways and thus reduce the muscle loss. To the best of our knowledge, this is a pioneer study evaluating the role of apoptotic BCL-2 and TP53 genes in contributing to the phenotypic manifestation of c.521delT mutation in LGMD2C patients. Larger studies are needed to validate these findings.

Recessive mutations of CAPN3 gene are reported to be responsible for limb girdle muscular dystrophy type 2A (LGMD2A). In all, 15-25% of intronic nucleotide changes identified in this gene were investigated by in silico analysis, but occasionally supported by experimental data or reported in some cases as a polymorphism. We report here genetic and transcriptional analyses in three Tunisian patients belonging to the same consanguineous family sharing the same mutation c.1194-9 A>G and Alu repeats insertion in intron 7 of CAPN3 gene. Reverse transcriptase-PCR experiments performed on total RNA from the patient's muscle biopsy showed retention of the eight last nucleotides of intron 9 in the CAPN3 transcript lacking the first seven exons. Our results provide evidence regarding the potential involvement of Alu elements in aberrant processing of pre-mRNA owing to the disruption of pre-existing intronic splicing regulatory elements. We also demonstrated variable mRNA alternative splicing among tissues and between LGMD2A patients. A deep intronic variation and rearrangement have been reported in the literature as causing genetic diseases in humans. However, this is the first report on a potential pathogenic CAPN3 gene mutation resulting from an Alu insertion.

In this study, we detected new sequence variations in LAMA2 and SGCG genes in 5 ethnic populations, and analysed their effect on enhancer composition and mRNA structure. PCR amplification and DNA sequencing were performed and followed by bioinformatics analyses using ESEfinder as well as MFOLD software. We found 3 novel sequence variations in the LAMA2 (c.3174+22_23insAT and c.6085 +12delA) and SGCG (c. (*) 102A/C) genes. These variations were present in 210 tested healthy controls from Tunisian, Moroccan, Algerian, Lebanese and French populations suggesting that they represent novel polymorphisms within LAMA2 and SGCG genes sequences. ESEfinder showed that the c. (*) 102A/C substitution created a new exon splicing enhancer in the 3'UTR of SGCG genes, whereas the c.6085 +12delA deletion was situated in the base pairing region between LAMA2 mRNA and the U1snRNA spliceosomal components. The RNA structure analyses showed that both variations modulated RNA secondary structure. Our results are suggestive of correlations between mRNA folding and the recruitment of spliceosomal components mediating splicing, including SR proteins. The contribution of common sequence variations to mRNA structural and functional diversity will contribute to a better study of gene expression.

Primary hyperoxaluria type 1 (PH1) is a severe autosomal recessive inherited disorder of glyoxylate metabolism caused by mutations in the AGXT gene on chromosome 2q37.3 that encodes the hepatic peroxisomal enzyme alanine:glyoxylate aminotransferase. These mutations are found throughout the entire gene and cause a wide spectrum of clinical severity. Rare in Europe, PH1 is responsible for 13% of the end stage renal failure in the Tunisian child. In the present work, we identified the double mutation c.32C>T (Pro11Leu) and c.731T>C (p.Ile244Thr) in AGXT gene in five unrelated Tunisian families with PH1 disease. Our results provide evidence regarding the potential involvement of c.32C>T, originally described as common polymorphism, on the resulting phenotype. We also reported an extreme intrafamilial heterogeneity in clinical presentation of PH1. Despite the same genetic background, the outcome of the affected members differs widely. The significant phenotypic heterogeneity observed within a same family, with a same genotype, suggests the existence of relevant modifier factors.

Pelizaeus Merzbacher disease and Pelizaeus Merzbacher like disease (PMLD) are hypomyelinating leucodystrophies of the central nervous system (CNS) with a very similar phenotype. PMD is an X-linked recessive condition caused by mutations, deletion duplication or triplication of the proteolipid protein 1 gene (PLP1). However, PMLD is a recessive autosomal hypomyelinating leukodystrophy caused by mutations of the GJC2 gene. In this study, we analyzed 5 patients belonging to 4 Tunisian families. Direct sequencing of GJC2 gene in all probands showed the same homozygous founder mutation c.-167A>G localized in the promoter region. We also generated two microsatellite markers GJC2 195GT and GJC2 76AC closed to the GJC2 gene to confirm the presence of a founder effect for this mutation. Haplotype study showed that the c.-167A>G promoter mutation occurred in a specific founder haplotype in Tunisian population. The identification of this founder mutation has important implications towards genetic counseling in relatives of these families and the antenatal diagnosis.

Azoospermia factor (AZF) deletions were associated with severe oligospermia and azoospermia with testicular histologies varying from maturation arrest (MA) to Sertoli cell-only (SCO) phenotypes. Abnormal androgen receptor (AR) structure or function has also been implicated in male infertility. To assess the contribution of these genetic defects to azoospermic patients, 19 Tunisian men with SCO (n = 13) or MA (n = 6) were enrolled in this study. Using immunohistochemistry method, we evaluated the expression of AR in testicular biopsy for the two phenotypes. PCR with primers flanking the AR-(CAG)n region and direct sequencing were used to determine AR-(CAG)n length. And PCR amplification of 14 sequence-tagged sites (STSs) located at Yq was used to determine the rate and extent of Y microdeletions. We found a significant difference of the AR expression between SCO and MA cases. Hence, this expression in the testis depends on the status of spermatogenesis. However, we did not find any relationship between the (CAG) repeat and the testicular histology (neither for SCO nor MA). On the other hand, we found a high frequency of AZF deletions (46.2%) in SCOS and in MA (50%). The present results also suggest the contribution of Y chromosome microdeletions in SCO and MA pathogenesis.

Mitochondrial encephalopathy, lactic acidosis and strokelike episodes (MELAS) syndrome is a mitochondrial disorder characterized by a wide variety of clinical presentations and a multisystemic organ involvement. In this study, we report a Tunisian girl with clinical features of MELAS syndrome who was negative for the common m.3243A>G mutation, but also for the reported mitochondrial DNA (mtDNA) mutations and deletions. Screening of the entire mtDNA genome showed several known mitochondrial variants besides to a novel transition m.1640A>G affecting a wobble adenine in the anticodon stem region of the tRNA(Val). This nucleotide was conserved and it was absent in 150 controls suggesting its pathogenicity. In addition, no mutations were found in the nuclear polymerase gamma-1 gene (POLG1). These results suggest further investigation nuclear genes encoding proteins responsible for stability and structural components of the mtDNA or to the oxidative phosphorylation machinery to explain the phenotypic variability in the studied family.

AIMS The preponderance of experimental data from clinical and animal models demonstrates an adverse effect of varicocele on spermatogenesis. The review of the literature shows that there may be an underlying genetic etiology in varicocele. Here, we explore the Yq microdeletions among infertile men to evaluate their involvement in varicocele development and sperm production defect. RESULTS Microdeletions of 14 sequence-tagged-sites in the Yq11 region were screened in 210 infertile men using polymerase chain reaction techniques. Out of 210 infertile men, 69 (33%) men were with varicocele. Our results showed that the risk to develop varicocele is increased among infertile men with spermatogenesis (oligo-normospermia) (odds ratio = 3.57, confidence interval 95%: 1.49-8.84). However, we did not find any relationship between Y chromosome microdeletions and varicocele appearance (p = 0.73). In addition, a significant association was found between Y microdeletions and oligospermia (p

LGMD (limb-girdle muscular dystrophy) and CMD (congenital muscular dystrophy) are two common forms of neuromuscular disorders which are distinguishable by their age of onset but with probably a similar underlying pathway. In the present study, we report immunohistochemical, Western-blot and genetic analyses in a large consanguineous Tunisian family with two branches, including seven patients sharing similar LGMD2 phenotype in one branch and one CMD patient in the other branch. Linkage analyses were compatible with the LGMD2A locus in one branch and the MDC1A (muscular dystrophy congenital type 1A) locus in the other branch. This result was supported by deficiency in merosin and calpain3 in the CMD patient and LGMD patients respectively. Mutation analysis revealed two distinct mutations: a c.8005delT frameshift deletion in exon 56 of the LAMA2 (laminin-α2) gene (MDC1A) was found in the CMD patient and a new homozygous mutation c.1536+1G>T in the donor splice site of intron 12 of the CAPN3 (calpain3) gene (LGMD2A) was found in the LGMD patients. RT–PCR (reverse transcription–PCR) performed on total RNA from a LGMD2A patient's muscle biopsy showed complete retention of intron 12 in CAPN3 cDNA, generating a PTC (premature termination codon) that potentially elicits degradation of the nonsense mRNA by NMD (nonsense-mediated mRNA decay). Our results indicate that mRNA analysis is necessary to clarify the primary effect of genomic mutations on splicing efficiency that alters mRNA processing and expression level.

Generalized epilepsy with febrile seizure plus (GEFS+) is an autosomal dominant disorder. In the literature, 5 responsible genes were identified and 2 novel susceptibility loci for GEFS+ at 2p24 and 8p23-p21 were reported, indicating the genetic heterogeneity of this disorder. The aim of this report is to identify the responsible loci in a large affected Tunisian family by performing a 10cM density genome-wide scan. The highest multipoint logarithm of odds (LOD) score (1.04) was found for D5S407 in the absence of recombination. Two other interesting regions were found around marker D19S210 (LOD=0.799) and D7S484 (LOD=0.61) markers. To fine map these loci, additional markers in 2 regions on 5q13.3 and 7p14.2 were analyzed and positive LOD scores for both loci were obtained. Sequencing of the Sodium channel subunit beta-1 gene (SCN1B) (19q13.1) showed the absence of any causal mutation. Our findings emphasized the genetic heterogeneity of febrile seizures.

We undertook in this study the first successful prenatal diagnoses of MDC1A and LGMD2C forms in Africa, with a subsequent postnatal clinical follow-up of the newborns. Genetic and molecular studies were performed on cultured amniotic fluid cells after exclusion of maternal cell contamination. Immunofluorescence on the patients' muscle biopsies was performed so as to study the expression of muscular laminins. Results showed that normal and affected fetuses were diagnosed according to the presence or the absence of the responsible mutation in LAMA2 or SGCG genes. Postnatal molecular and clinical outcome was concordant with all prenatal diagnoses. However, a patient with MDC1A form of congenital muscular dystrophy who was diagnosed as affected was normal at birth, and developed later clinical features different from those observed in his severely affected elder brother. This intrafamilial clinical variability in two siblings occurring with the same mutation in LAMA2 gene emphasizes the importance of the postnatal follow-up in the confirmation of prenatal diagnosis, and suggests that other genetic or epigenetic factors can monitor the course of the MDC1A form.

Background Airway inflammation is an important characteristic of asthma and has been associated with airway remodelling and bronchial hyperreactivity. The mucosal microenvironment composed of structural cells and highly specialised extracellular matrix is able to amplify and promote inflammation. This microenvironment leads to the development and maintenance of a specific adaptive response characterized by Th2 and Th17. Bronchial fibroblasts produce multiple mediators that may play a role in maintaining and amplifying this response in asthma. Objective To investigate the role of bronchial fibroblasts obtained from asthmatic subjects and healthy controls in regulating Th17 response by creating a local micro-environment that promotes this response in the airways. Methods Human bronchial fibroblasts and CD4+T cells were isolated from atopic asthmatics and non-atopic healthy controls. CD4+T were co-cultured with bronchial fibroblasts of asthmatic subjects and healthy controls. RORc gene expression was detected by qPCR. Phosphorylated STAT-3 and RORγt were evaluated by western blots. Th17 phenotype was measured by flow cytometry. IL-22, IL17, IL-6 TGF-β and IL1-β were assessed by qPCR and ELISA. Results Co-culture of CD4+T cells with bronchial fibroblasts significantly stimulated RORc expression and induced a significant increase in Th17 cells as characterized by the percentage of IL-17+/CCR6+ staining in asthmatic conditions. IL-17 and IL-22 were increased in both normal and asthmatic conditions with a significantly higher amount in asthmatics compared to controls. IL-6, IL-1β, TGF-β and IL-23 were significantly elevated in fibroblasts from asthmatic subjects upon co-culture with CD4+T cells. IL-23 stimulates IL-6 and IL-1β expression by bronchial fibroblasts. Conclusion Interaction between bronchial fibroblasts and T cells seems to promote specifically Th17 cells profile in asthma. These results suggest that cellular interaction particularly between T cells and fibroblasts may play a pivotal role in the regulation of the inflammatory response in asthma.