Prevalence of comorbid asthma in Tunisian patients with COVID-19: clinical features and outcomes.

INTRODUCTION: The coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has resulted in around 1 million COVID-19 infection cases and over 29,000 deaths in Tunisia thus far. There is great variability in the prevalence of asthma among patients with COVID-19, but the impact of asthma on patients with COVID-19 is not clear. We sought to describe the clinical features of Tunisian patients with COVID-19 and to compare asthmatic and non-asthmatic patients. METHODOLOGY: This retrospective study included 675 Tunisian patients who were hospitalized with COVID-19. Clinical characteristics were collected from medical records. Bivariate analyses and multivariate regression models were used to assess the associations between asthma and the risk of severe symptoms, including death/recovery. RESULTS: The prevalence of asthma in the sample was 14.5%. The results show that asthmatic patients with COVID-19 have significantly less severe symptoms and better outcomes than non-asthmatic patients. CONCLUSIONS: Asthma was not found to be associated with higher severity or worse prognosis among patients with COVID-19 in Tunisia.

Genetic analysis of Tunisian families with Usher syndrome type 1: toward improving early molecular diagnosis.

PURPOSE: Usher syndrome accounts for about 50% of all hereditary deaf-blindness cases. The most severe form of this syndrome, Usher syndrome type I (USH1), is characterized by profound congenital sensorineural deafness, vestibular dysfunction, and retinitis pigmentosa. Six USH1 genes have been identified, MYO7A, CDH23, PCDH15, USH1C, SANS, and CIB2, encoding myosin VIIA, cadherin-23, protocadherin-15, harmonin, scaffold protein containing ankyrin repeats and a sterile alpha motif (SAM) domain, and calcium- and integrin-binding member 2, respectively. METHODS: In the present study, we recruited four Tunisian families with a diagnosis of USH1, together with healthy unrelated controls. Affected members underwent detailed audiologic and ocular examinations. We used the North African Deafness (NADf) chip to search for known North African mutations associated with USH. Then, we selected microsatellite markers covering USH1 known loci to genotype the DNA samples. Finally, we performed DNA sequencing of three known USH1 genes: MYO7A, PCDH15, and USH1C. RESULTS: Four biallelic mutations, all single base changes, were found in the MYO7A, USH1C, and PCDH15 genes. These mutations consist of a previously reported splicing defect c.470+1G>A in MYO7A, three novel variants, including two nonsense (p.Arg3X and p.Arg134X) in USH1C and PCDH15, respectively, and one frameshift (p.Lys615Asnfs*6) in MYO7A. CONCLUSIONS: We found a remarkable genetic heterogeneity in the studied families with USH1 with a variety of mutations, among which three were novel. These novel mutations will be included in the NADf mutation screening chip that will allow a higher diagnosis efficiency of this extremely genetically heterogeneous disease. Ultimately, efficient molecular diagnosis of USH in a patient's early childhood is of utmost importance, allowing better educational and therapeutic management.

Molecular Analysis of Libyan Families with Allgrove Syndrome: Geographic Expansion of the Ancestral Mutation c.1331+1G>A in North Africa.

BACKGROUND/AIMS: Allgrove syndrome is a rare autosomal recessive disorder characterized by alacrima, achalasia, and adrenal insufficiency. It is caused by mutations of the AAAS gene located on chromosome 12q13 encoding the WD-repeat protein ALADIN. The c.1331+1G>A mutation is one of the most common mutations described in the literature and was identified in Tunisian and Algerian populations. Herein, we describe the clinical and genetic profile of two families from Libya in North Africa associated with Allgrove syndrome. METHODS: Two unrelated families clinically diagnosed with Allgrove syndrome were evaluated for sequence variations in the AAAS gene. Blood samples were collected, and isolated DNA derived from the subjects was amplified. The entire sequence of the AAAS gene was analyzed by PCR-RFLP and direct sequencing. RESULTS: Molecular analysis revealed the major homozygous mutation (c.1331+1G>A) in all patients. The presence of a major mutation in Tunisia, Algeria and, as discovered in this report, in Libya in patients with Allgrove syndrome suggests the existence of an ancestral mutation and a founder effect in North Africa. CONCLUSIONS: The findings allow for a fast genetic counseling in North African families with Allgrove syndrome. To the best of our knowledge, this is the first report of Allgrove syndrome in Libya.

Clinical and molecular analysis of isovaleric acidemia patients in the United Arab Emirates reveals remarkable phenotypes and four novel mutations in the IVD gene.

Isovaleric acidemia (IVA) is an autosomal recessive inborn error of leucine metabolism caused by deficiency of mitochondrial isovaleryl-CoA dehydrogenase (IVD). Accumulation of isovaleryl-CoA derivatives to toxic levels results in clinical symptoms of the disease. Here, we investigate the clinical and molecular features of Arab patients with IVA. Patients from five unrelated families were evaluated clinically and for defects in the IVD gene. Four novel mutations (p.F382fs, p.R392H, p.R395Q and p.E408K) have been identified with p.R395Q occurring in two families. In addition, molecular modeling of the identified missense mutations predicted their damaging effects on the protein and computational analysis of the p.F382fs mutation predicted the disruption of a 3' splicing site resulting in inactive or unstable gene product. Furthermore, we found an unusual case of a 17 years old female homozygous for the p.R392H mutation with no clinical symptoms. Our results illustrate a heterogeneous mutation spectrum and clinical presentation in the relatively small UAE population.

Identification of mutations underlying 20 inborn errors of metabolism in the United Arab Emirates population.

Inborn errors of metabolism (IEM) are frequently encountered by physicians in the United Arab Emirates (UAE). However, the mutations underlying a large number of these disorders have not yet been determined. Therefore, the objective of this study was to identify the mutations underlying a number of IEM disorders among UAE residents from both national and expatriate families. A case series of patients from 34 families attending the metabolic clinic at Tawam Hospital were clinically evaluated, and molecular testing was carried out to determine their causative mutations. The mutation analysis was carried out at molecular genetics diagnostic laboratories. Thirty-eight mutations have been identified as responsible for twenty IEM disorders, including in the metabolism of amino acids, lipids, steroids, metal transport and mitochondrial energy metabolism, and lysosomal storage disorders. Nine of the identified mutations are novel, including two missense mutations, three premature stop codons and four splice site mutations. Mutation analysis of IEM disorders in the UAE population has an important impact on molecular diagnosis and genetic counseling for families affected by these disorders.

Endoplasmic reticulum quality control is involved in the mechanism of endoglin-mediated hereditary haemorrhagic telangiectasia.

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant genetic condition affecting the vascular system and is characterised by epistaxis, arteriovenous malformations and mucocutaneous and gastrointestinal telangiectases. This disorder affects approximately 1 in 8,000 people worldwide. Significant morbidity is associated with this condition in affected individuals, and anaemia can be a consequence of repeated haemorrhages from telangiectasia in the gut and nose. In the majority of the cases reported, the condition is caused by mutations in either ACVRL1 or endoglin genes, which encode components of the TGF-beta signalling pathway. Numerous missense mutations in endoglin have been reported as causative defects for HHT but the exact underlying cellular mechanisms caused by these mutations have not been fully established despite data supporting a role for the endoplasmic reticulum (ER) quality control machinery. For this reason, we examined the subcellular trafficking of twenty-five endoglin disease-causing missense mutations. The mutant proteins were expressed in HeLa and HEK293 cell lines, and their subcellular localizations were established by confocal fluorescence microscopy alongside the analysis of their N-glycosylation profiles. ER quality control was found to be responsible in eight (L32R, V49F, C53R, V125D, A160D, P165L, I271N and A308D) out of eleven mutants located on the orphan extracellular domain in addition to two (C363Y and C382W) out of thirteen mutants in the Zona Pellucida (ZP) domain. In addition, a single intracellular domain missense mutant was examined and found to traffic predominantly to the plasma membrane. These findings support the notion of the involvement of the ER's quality control in the mechanism of a significant number, but not all, missense endoglin mutants found in HHT type 1 patients. Other mechanisms including loss of interactions with signalling partners as well as adverse effects on functional residues are likely to be the cause of the mutant proteins' loss of function.

Reinforcement of a minor alternative splicing event in MYO7A due to a missense mutation results in a mild form of retinopathy and deafness.

PURPOSE: Recessive mutations of the myosin VIIA (MYO7A) gene are reported to be responsible for both a deaf-blindness syndrome (Usher type 1B [USH1B] and atypical Usher syndrome) and nonsyndromic hearing loss (HL; Deafness, Neurosensory, Autosomal Recessive 2 [DFNB2]). The existence of DFNB2 is controversial, and often there is no relationship between the type and location of the MYO7A mutations corresponding to the USH1B and DFNB2 phenotype. We investigated the molecular determinant of a mild form of retinopathy in association with a subtle splicing modulation of MYO7A mRNA. METHODS: Affected members underwent detailed audiologic and ocular characterization. DNA samples from family members were genotyped with polymorphic microsatellite markers. Sequencing of MYO7A was performed. Endogenous lymphoid RNA analysis and a splicing minigene assay were used to study the effect of the c.1935G>A mutation. RESULTS: Funduscopy showed mild retinitis pigmentosa in adults with HL. Microsatellite analysis showed linkage to markers in the region on chromosome 11q13.5. Sequencing of MYO7A revealed a mutation in the last nucleotide of exon 16 (c.1935G>A), which corresponds to a substitution of a methionine to an isoleucine residue at amino acid 645 of the myosin VIIA. However, structural prediction of the molecular model of myosin VIIA shows that this amino acid replacement induces only minor structural changes in the immediate environment of the mutation and thus does not alter the overall native structure. We found that, although predominantly included in mature mRNA, exon 16 is in fact alternatively spliced in control cells and that the mutation at the very last position is associated with a switch toward a predominant exclusion of that exon. This observation was further supported using a splicing minigene transfection assay; the c.1935G>A mutation was found to trigger a partial impairment of the adjacent donor splice site, suggesting that the unique change at the last position of the exon is responsible for the enhanced exon exclusion in this family. CONCLUSIONS: This study shows how an exonic mutation that weakens the 5' splice site enhances a minor alternative splicing without abolishing a complete exclusion of the exon and therefore causes a less severe retinitis pigmentosa than the USH1B-associated alleles. It would be interesting to examine a possible correlation between intrafamilial phenotypic variability and the subtle variation in exon 16 inclusion, probably related to genetic background specificities.

Mutation in gap and tight junctions in patients with non-syndromic hearing loss.

Biallelic mutations in the GJB2, GJB3, GJB6 and CLDN14 genes have been implicated in autosomal recessive non-syndromic hearing impairment (ARNSHI). Moreover, a large number of GJB2 heterozygous patients was reported. The phenotype was in partly justified by the occurrence of two deletions including GJB6. We analysed GJB2, GJB6, GJB3 and CLDN14 in 102 Tunisian patients with ARNSHI. The deletions del(GJB6-D13S1830) and del(GJB6-D13S1854) were also screened. The c.35delG in GJB2 was the most frequent mutation (21.57%). It was detected at heterozygous state in 2 patients. The del(GJB6-D13S1830) was identified in one case at heterozygous state. No other mutation in studied gap junction genes was detected in heterozygous patients. Several polymorphisms were identified in GJB3, GJB6 and CLDN14. Our study confirms the importance of GJB2 screening in ARNSHI and suggests that in consanguineous populations, a single DFNB1 mutant allele in individuals with HI is likely due to a coincidental carrier state.

Identification of candidate regions for a novel Usher syndrome type II locus.

PURPOSE: Chronic diseases affecting the inner ear and the retina cause severe impairments to our communication systems. In more than half of the cases, Usher syndrome (USH) is the origin of these double defects. Patients with USH type II (USH2) have retinitis pigmentosa (RP) that develops during puberty, moderate to severe hearing impairment with downsloping pure-tone audiogram, and normal vestibular function. Four loci and three genes are known for USH2. In this study, we proposed to localize the gene responsible for USH2 in a consanguineous family of Tunisian origin. METHODS: Affected members underwent detailed ocular and audiologic characterization. One Tunisian family with USH2 and 45 healthy controls unrelated to the family were recruited. Two affected and six unaffected family members attended our study. DNA samples of eight family members were genotyped with polymorphic markers. Two-point and multipoint LOD scores were calculated using Genehunter software v2.1. Sequencing was used to investigate candidate genes. RESULTS: Haplotype analysis showed no significant linkage to any known USH gene or locus. A genome-wide screen, using microsatellite markers, was performed, allowing the identification of three homozygous regions in chromosomes 2, 4, and 15. We further confirmed and refined these three regions using microsatellite and single-nucleotide polymorphisms. With recessive mode of inheritance, the highest multipoint LOD score of 1.765 was identified for the candidate regions on chromosomes 4 and 15. The chromosome 15 locus is large (55 Mb), underscoring the limited number of meioses in the consanguineous pedigree. Moreover, the linked, homozygous chromosome 15q alleles, unlike those of the chromosome 2 and 4 loci, are infrequent in the local population. Thus, the data strongly suggest that the novel locus for USH2 is likely to reside on 15q. CONCLUSIONS: Our data provide a basis for the localization and the identification of a novel gene implicated in USH2, most likely localized on 15q.