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The role of the prokineticin 2 pathway in human reproduction, olfactory bulb morphogenesis, and gonadotropin-releasing hormone secretion is well established. Recent studies have highlighted the implication of di/oligogenic inheritance in this disorder. In the present study, we aimed to identify the genetic mechanisms that could explain incomplete penetrance in hypogonadotropic hypogonadism (HH). This study involved two unrelated Tunisian patients with HH, which was triggered by identifying a homozygous p.(Pro290Ser) mutation in the PROKR2 gene in a girl (HH1) with Kallmann syndrome (KS). The functional effect of this variant has previously been well demonstrated. Unexpectedly, her unaffected father (HH1P) and brother (HH1F) also carried this genetic variation at a homozygous state. In the second family, we identified a heterozygous p.(Lys205del) mutation in PROKR2 , both in a male patient with normosmic idiopathic IHH (HH12) and his asymptomatic mother. Whole-exome sequencing in the three HH1 family members allowed the identification of additional variants in the prioritized genes. We then carried out digenic combination predictions using the oligogenic resource for variant analysis (ORVAL) software. For HH1, we found the highest number of disease-causing variant pairs. Notably, a CCDC141 variant (c.2803C > T) was involved in 18 pathogenic digenic combinations. The CCDC141 variant acts in an autosomal recessive inheritance mode, based on the digenic effect prediction data. For the second patient (HH12), prediction by ORVAL allowed the identification of an interesting pathogenic digenic combination between DUSP6 and SEMA7A genes, predicted as "dual molecular diagnosis." The SEMA7A variant p.(Glu436Lys) is novel and predicted as a VUS by Varsome. Sanger validation revealed the absence of this variant in the healthy mother. We hypothesize that disease expression in HH12 could be induced by the digenic transmission of the SEMA7A and DUSP6 variants or a monogenic inheritance involving only the SEMA7A VUS if further functional assays allow its reclassification into pathogenic. Our findings confirm that homozygous loss-of-function genetic variations are insufficient to cause KS, and that oligogenism is most likely the main transmission mode involved in Congenital Hypogonadotropic Hypogonadism., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Mkaouar, Abdallah, Naouali, Lahbib, Turki, Elouej, Bouyacoub, Somai, Mcelreavey, Bashamboo, Abdelhak and Messaoud.)

Background: Breast cancer is the world's most common cancer among women. It is becoming an increasingly urgent problem in low- and middle-income countries (LMICs) where a large fraction of women is diagnosed with advanced-stage disease and have no access to treatment or basic palliative care. About 5-10% of all breast cancers can be attributed to hereditary genetic components and up to 25% of familial cases are due to mutations in BRCA1 /2 genes. Since their discovery in 1994 and 1995, as few as 18 mutations have been identified in BRCA genes in the Tunisian population. The aim of this study is to identify additional BRCA mutations, to estimate their contribution to the hereditary breast and ovarian cancers in Tunisia and to investigate the clinicopathological signatures associated with BRCA mutations., Methods: A total of 354 patients diagnosed with breast and ovarian cancers, including 5 male breast cancer cases, have been investigated for BRCA1/2 mutations using traditional and/or next generation sequencing technologies. Clinicopathological signatures associated with BRCA mutations have also been investigated., Results: In the current study, 16 distinct mutations were detected: 10 in BRCA1 and 6 in BRCA2 , of which 11 are described for the first time in Tunisia including 3 variations that have not been reported previously in public databases namely BRCA1 _c.915T>A; BRCA2 _c.-227-?_7805+? and BRCA2 _c.249delG. Early age at onset, family history of ovarian cancer and high tumor grade were significantly associated with BRCA status. BRCA1 carriers were more likely to be triple negative breast cancer compared to BRCA2 carriers. A relatively high frequency of contralateral breast cancer and ovarian cancer occurrence was observed among BRCA carriers and was more frequent in patients carrying BRCA1 mutations., Conclusion: Our study provides new insights into breast and ovarian cancer genetic landscape in the under-represented North African populations. The prevalence assessment of novel and recurrent BRCA1/2 pathogenic mutations will enhance the use of personalized treatment and precise screening strategies by both affected and unaffected North African cancer cases., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Hamdi, Mighri, Boujemaa, Mejri, Ben Nasr, Ben Rekaya, Messaoud, Bouaziz, Berrazega, Rachdi, Jaidane, Daoud, Zribi, Ayari, El Benna, Labidi, Ben Hassouna, Haddaoui, Rahal, Benna, Mrad, Ben Ahmed, Boussen, Boubaker and Abdelhak.)

Populations in North Africa (NA) are characterized by a high rate of consanguinity. Consequently, the proportion of founder mutations might be higher than expected and could be a major cause for the high prevalence of recessive genetic disorders like Fanconi anemia (FA). We report clinical, cytogenetic, and molecular characterization of FANCA in 29 North African FA patients from Tunisia, Libya, and Algeria. Cytogenetic tests revealed high rates of spontaneous chromosome breakages for all patients except two of them. FANCA molecular analysis was performed using three different molecular approaches which allowed us to identify causal mutations as homozygous or compound heterozygous forms. It included a nonsense mutation (c.2749C > T; p.Arg917Ter), one reported missense mutation (c.1304G > A; p.Arg435His), a novel missense variant (c.1258G > A; p.Asp409Glu), and the FANCA most common reported mutation (c.3788_3790delTCT; p.Phe1263del). Furthermore, three founder mutations were identified in 86.7% of the 22 Tunisian patients: (1) a deletion of exon 15, in 36.4% patients (8/22); (2), a deletion of exons 4 and 5 in 23% (5/22) and (3) an intronic mutation c.2222 + 166G > A, in 27.3% (6/22). Despite the relatively small number of patients studied, our results depict the mutational landscape of FA among NA populations and it should be taken into consideration for appropriate genetic counseling., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Ben Haj Ali, Messaoud, Elouej, Talmoudi, Ayed, Mellouli, Ouederni, Hadiji, De Sandre-Giovannoli, Delague, Lévy, Bogliolo, Surrallés, Abdelhak and Amouri.)

Copy number variation (CNV) is considered as the most frequent type of structural variation in the human genome. Some CNVs can act on human phenotype diversity, encompassing rare Mendelian diseases and genomic disorders. The North African populations remain underrepresented in public genetic databases in terms of single-nucleotide variants as well as for larger genomic mutations. In this study, we present the first CNV map for a North African population using the Affymetrix Genome-Wide SNP (single-nucleotide polymorphism) array 6.0 array genotyping intensity data to call CNVs in 102 Tunisian healthy individuals. Two softwares, PennCNV and Birdsuite, were used to call CNVs in order to provide reliable data. Subsequent bioinformatic analyses were performed to explore their features and patterns. The CNV map of the Tunisian population includes 1083 CNVs spanning 61.443 Mb of the genome. The CNV length ranged from 1.017 kb to 2.074 Mb with an average of 56.734 kb. Deletions represent 57.43% of the identified CNVs, while duplications and the mixed loci are less represented. One hundred and three genes disrupted by CNVs are reported to cause 155 Mendelian diseases/phenotypes. Drug response genes were also reported to be affected by CNVs. Data on genes overlapped by deletions and duplications segments and the sequence properties in and around them also provided insights into the functional and health impacts of CNVs. These findings represent valuable clues to genetic diversity and personalized medicine in the Tunisian population as well as in the ethnically similar populations from North Africa.

Background: Typically, patients with Acid Sphingomyelinase Deficiency (ASMD) because of p.Arg610del mutation, have mild phenotype with normal linear growth., Observation: We reported the case of 2 Tunisian brothers who have been referred for splenomegaly, polyadenopathies, pubertal, and growth delay. Molecular testing of SMPD1 gene revealed the presence of a homozygous p.Arg610del mutation. Lysosphingomyelin and its isoform-509 were both increased confirming ASMD for both cases. Growth hormone deficiency was highly suspected but growth hormone response after stimulating tests was acceptable for both patients., Conclusions: There is no correlation between phenotype-genotype in case of p.Arg610del mutation that could be associated to a severe delay of growth.

In silico DNA sequence generation is a powerful technology to evaluate and validate bioinformatics tools, and accordingly more than 35 DNA sequence simulation tools have been developed. With such a diverse array of tools to choose from, an important question is: Which tool should be used for a desired outcome? This question is largely unanswered as documentation for many of these DNA simulation tools is sparse. To address this, we performed a review of DNA sequence simulation tools developed to date and evaluated 20 state-of-art DNA sequence simulation tools on their ability to produce accurate reads based on their implemented sequence error model. We provide a succinct description of each tool and suggest which tool is most appropriate for the given different scenarios. Given the multitude of similar yet non-identical tools, researchers can use this review as a guide to inform their choice of DNA sequence simulation tool. This paves the way towards assessing existing tools in a unified framework, as well as enabling different simulation scenario analysis within the same framework., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: Co-occurrence of two genetic diseases is challenging for accurate diagnosis and genetic counseling. The recent availability of whole exome sequencing (WES) has dramatically improved the molecular diagnosis of rare genetic diseases in particular in consanguineous populations., Methods: We report here on a consanguineous family from Southern Tunisia including three members affected with congenital ichthyosis. The index case had a hearing loss (HL) and ichthyosis and was primarily suspected as suffering from keratitis-ichthyosis-deafness (KID) syndrome. WES was performed for the index case, and all members of the nuclear family were sequenced (Sanger method)., Results: The WES approach allowed the identification of two strong candidate variants in two different genes; a missense mutation c.1334T>G (p.Leu445Trp) in exon 11 of SLC26A4 gene, associated with isolated HL and a novel missense mutation c.728G>T (p.Arg243Leu) in exon 8 of CYP4F22 gene likely responsible for ichthyosis. These two mutations were predicted to be pathogenic by three pathogenicity prediction softwares (Scale-Invariant Feature Transform [SIFT], Polymorphism Phenotyping [PolyPhen], Mutation Taster) to underlie the HL and ichthyosis, respectively., Conclusions: The present study raises awareness about the importance of familial history for accurate diagnosis of syndromic genetic diseases and differential diagnosis with co-occurrence of two distinct clinical entities. In addition, in countries with limited resources, WES sequencing for a single individual provides a cost effective tool for molecular diagnosis confirmation and genetic counseling., (© 2019 The International Society of Dermatology.)

Background: Several studies have shown a high rate of consanguinity and endogamy in North African populations. As a result, the frequency of autosomal recessive diseases is relatively high in the region with the co-occurrence of two or more diseases., Methods: We report here on a consanguineous Libyan family whose child was initially diagnosed as presenting Fanconi anemia (FA) with uncommon skeletal deformities. The chromosome breakage test has been performed using mitomycin C (MMC) while molecular analysis was performed by a combined approach of linkage analysis and whole exome sequencing., Results: Cytogenetic analyses showed that the karyotype of the female patient is 46,XY suggesting the diagnosis of a disorder of sex development (DSD). By looking at the genetic etiology of FA and DSD, we have identified p.[Arg798*];[Arg798*] mutation in FANCJ (OMIM #605882) gene responsible for FA and p.[Arg108*];[Arg1497Trp] in EFCAB6 (Gene #64800) gene responsible for DSD. In addition, we have incidentally discovered a novel mutation p.[Gly1372Arg];[Gly1372Arg] in the ERCC6 (CSB) (OMIM #609413) gene responsible for COFS that might explain the atypical severe skeletal deformities., Conclusion: The co-occurrence of clinical and overlapping genetic heterogeneous entities should be taken into consideration for better molecular and genetic counseling., (© 2019 The Authors. Molecular Genetics & Genomic Medicine published by Wiley Periodicals, Inc.)

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder due to a defect in the nucleotide excision repair (NER) DNA repair pathway, characterized by severe sunburn development of freckles, premature skin aging, and susceptibility to develop cancers at an average age of eight. XP is an example of accelerated photo-aging. It is a genetically and clinically heterogeneous disease. Eight complementation groups have been described worldwide. In Tunisia, five groups have been already identified. In this work, we investigated the genetic etiology in a family with an atypically mild XP phenotype. Two Tunisian siblings born from first-degree consanguineous parents underwent clinical examination in the dermatology department of the Charles Nicolle Hospital on the basis of acute sunburn reaction and mild neurological disorders. Blood samples were collected from two affected siblings after written informed consent. As all mutations reported in Tunisia have been excluded using Sanger sequencing, we carried out mutational analysis through a targeted panel of gene sequencing using the Agilent HaloPlex target enrichment system. Our clinical study shows, in both patients, the presence of achromic macula in sun exposed area with dermatological feature suggestive of Xeroderma pigmentosum disease. No developmental and neurological disorders were observed except mild intellectual disability. Genetic investigation shows that both patients were carriers of an homozygous T to C transition at the nucleotide position c.2333, causing the leucine to proline amino acid change at the position 778 (p.Leu778Pro) of the ERCC5 gene, and resulting in an XP-G phenotype. The same variation was previously reported at the heterozygous state in a patient cell line in Europe, for which no clinical data were available and was suggested to confer an XP/CS phenotype based on functional tests. This study contributes to further characterization of the mutation spectrum of XP in consanguineous Tunisian families and is potentially helpful for early diagnosis. It also indicates that the genotype-phenotype correlation is not always coherent for patients with mild clinical features. These data therefore suggest that targeted NGS is a highly informative diagnostic strategy, which can be used for XP molecular etiology determination.

Background: Breast cancer is the most common cancer in women worldwide. Around 50% of breast cancer familial risk has been so far explained by known susceptibility alleles with variable levels of risk and prevalence. The vast majority of these breast cancer associated variations reported to date are from populations of European ancestry. In spite of its heterogeneity and genetic wealth, North-African populations have not been studied by the HapMap and the 1000Genomes projects. Thus, very little is known about the genetic architecture of these populations., Methods: This study aimed to investigate a subset of common breast cancer loci in the general Tunisian population and to compare their genetic composition to those of other ethnic groups. We undertook a genome-wide haplotype study by genotyping 135 Tunisian subjects using the Affymetrix 6.0-Array. We compared Tunisian allele frequencies and linkage disequilibrium patterns to those of HapMap populations and we performed a comprehensive assessment of the functional effects of several selected variants., Results: Haplotype analyses showed that at risk haplotypes on 2p24, 4q21, 6q25, 9q31, 10q26, 11p15, 11q13 and 14q32 loci are considerably frequent in the Tunisian population (> 20%). Allele frequency comparison showed that the frequency of rs13329835 is significantly different between Tunisian and all other HapMap populations. LD-blocks and Principle Component Analysis revealed that the genetic characteristics of breast cancer variants in the Tunisian, and so probably the North-African populations, are more similar to those of Europeans than Africans. Using eQTl analysis, we characterized rs9911630 as the most strongly expression-associated SNP that seems to affect the expression levels of BRCA1 and two long non coding RNAs (NBR2 and LINC008854). Additional in-silico analysis also suggested a potential functional significance of this variant., Conclusions: We illustrated the utility of combining haplotype analysis in diverse ethnic groups with functional analysis to explore breast cancer genetic architecture in Tunisia. Results presented in this study provide the first report on a large number of common breast cancer genetic polymorphisms in the Tunisian population which may establish a baseline database to guide future association studies in North Africa.

H syndrome is a rare autosomal recessive disorder with characteristic dermatological findings consisting of hyperpigmentation and hypertrichosis patches mainly located on the inner thighs and multisystemic involvement including hepatosplenomegaly, hearing loss, heart abnormalities and hypogonadism. The aim of this study was to conduct a clinical and genetic investigation in five unrelated Tunisian patients with suspected H syndrome. Hence, genetic analysis of the SLC29A3 gene was performed for four patients with a clinical diagnosis of H syndrome. We identified a novel frame-shift mutation in the SLC29A3 gene in a female patient with a severe clinical presentation. Furthermore, we report two mutations previously described, the p.R363Q mutation in a male patient and the p.P324L mutation in two patients of different age and sex. This paper extends the mutation spectrum of H syndrome by reporting a novel frame-shift mutation, the p.S15Pfs*86 in exon 2 of SLC29A3 gene and emphasizes the relevance of genetic testing for its considerable implications in early diagnosis and clinical management., (© 2018 Japanese Dermatological Association.)

Background: A family history of breast cancer has long been thought to indicate the presence of inherited genetic events that predispose to this disease. In North Africa, many specific epidemio-genetic characteristics have been observed in breast cancer families when compared to Western populations. Despite these specificities, the majority of breast cancer genetics studies performed in North Africa remain restricted to the investigation of the BRCA1 and BRCA2 genes. Thus, comprehensive data at a whole exome or whole genome level from local patients are lacking., Methods: A whole exome sequencing (WES) of seven breast cancer Tunisian families have been performed using a family-based approach. We focused our analysis on BC-TN-F001 family that included two affected members that have been sequenced using WES. Relevant variants identified in BC-TN-F001 have been confirmed using Sanger sequencing. Then, we conducted an integrative analysis by combining our results with those from other WES studies in order to figure out the genetic transmission model of the newly identified genes. Biological network construction and protein-protein interactions analyses have been performed to decipher the molecular mechanisms likely accounting for the role of these genes in breast cancer risk., Results: Sequencing, filtering strategies, and validation analysis have been achieved. For BC-TN-F001, no deleterious mutations have been identified on known breast cancer genes. However, 373 heterozygous, exonic and rare variants have been identified on other candidate genes. After applying several filters, 12 relevant high-risk variants have been selected. Our results showed that these variants seem to be inherited in a family specific model. This hypothesis has been confirmed following a thorough analysis of the reported WES studies. Enriched biological process and protein-protein interaction networks resulted in the identification of four novel breast cancer candidate genes namely MMS19, DNAH3, POLK and KATB6., Conclusions: In this first WES application on Tunisian breast cancer patients, we highlighted the impact of next generation sequencing technologies in the identification of novel breast cancer candidate genes which may bring new insights into the biological mechanisms of breast carcinogenesis. Our findings showed that the breast cancer predisposition in non-BRCA families may be ethnic and/or family specific.

Background: Skin cancers (SC) are complex diseases that develop from complex combinations of genetic and environmental risk factors. One of the most severe and rare genetic diseases predisposing to SC is the Xeroderma pigmentosum (XP) syndrome., Objectives: First, to identify the genetic etiology of XP and to better classify affected patients. Second, to provide early molecular diagnosis for pre-symptomatic patient and finally to offer genetic counseling for related individuals., Methods: Whole Exome Sequencing (WES) and Run Of Homozygosity (ROH) were performed for two patients belonging to two different multiplex consanguineous families. The identified mutations were confirmed by Sanger sequencing and researched in ten Tunisian families including a total of 25 affected individuals previously suspected as having XP group V (XP-V) form. All patients had mild dermatological manifestations, absence of neurological abnormalities and late onset of skin tumors., Results: Screening for functional variations showed the presence of the ERCC2 p.Arg683Gln in XP14KA-2 patient and a novel mutation, DDB2 p. (Lys381Argfs*2), in XP51-MAH-1 patient. Sanger sequencing and familial segregation showed that the ERCC2 mutation is present at a homozygous state in 10 affected patients belonging to 3 families. The second mutation in DDB2, is present at a homozygous state in 5 affected cases belonging to the same family. These two mutations are absent in the remaining 10 affected patients. The ERCC2 c.2048G > A mutation is present in a medium ROH region (class B) suggesting that it mostly arises from ancient relatedness within individuals. However, the c.1138delG DDB2 mutation is present in a large ROH region (class C) suggesting that it arises from recent relatedness., Conclusion: To our knowledge, this is the first study that identifies XP-D and XP-E complementation groups in Tunisia. These two groups are very rare and under-diagnosed in the world and were not reported in North Africa., (Copyright © 2017 Japanese Society for Investigative Dermatology. Published by Elsevier B.V. All rights reserved.)

Competing Interests: CONFLICTS OF INTEREST: The authors have nothing to disclose.

Background: Epidemiological features and trends of cutaneous melanoma (CM) in North-African populations remain unclear. Those populations are of particular interest as they belong to a mosaic of various other origins (sub-Saharan, European Ancestry, and North-African Berbers). The aim of this study is to draw epidemiological profile and clinicopathological features of CM in the Tunisian population., Methods: Incidence analyses were based on data from regional cancer registries. Clinical data were collected from dermatological departments and xeroderma pigmentosum (XP) referral centers and provided CM clinicopathological characteristics and progression. Statistical analyses were achieved using R packages and SPSS 20.0., Results: The incidence of CM in Tunisia is relatively low (0.5-0.7 per 100,000 inhabitants per year). Gender differences were observed regarding anatomical distribution (P = 0.004). Acral lentiginous melanoma (ALM) was the most frequent histological subtype (32.3%); however, nodular melanoma (NM) was the most aggressive and responsible for 54.8% of deaths. CM in XP patients develops at a median age that is 42 years earlier than sporadic cases, with preferential localization on the head and neck (P < 0.001). Finally, male patients exhibited survival disadvantages compared with females (adjusted hazard ratio (HR) = 2.22, 95% CI: 1.05-4.68, P = 0.037)., Conclusions: Cutaneous melanoma features in Tunisia are closer to those of non-Caucasians, even though gender differences that are similar to those observed in Caucasians were uncovered. This study also emphasizes the aggressiveness of NM and its effect on melanoma patient deaths. Xeroderma pigmentosum stands as the major predisposing host factor., (© 2016 The International Society of Dermatology.)

Objectives: Consanguinity is common in Tunisia. However, little information exists on its impact on recessive disorders. In this study, we evaluate the impact of consanguineous marriages on the occurrence of some specific autosomal recessive disorders and consider how other factors, such as population substructure and mutation frequency, may be of equal importance in disease prevalence., Methods: Consanguinity profiles were retrospectively studied among 425 Tunisian patients suffering from autosomal recessive xeroderma pigmentosum, dystrophic epidermolysis bullosa, nonsyndromic retinitis pigmentosa, Gaucher disease, Fanconi anemia, glycogenosis type I, and ichthyosis, and compared to those of a healthy control sample., Results: Consanguinity was observed in 341 cases (64.94%). Consanguinity rates per disease were 75.63, 63.64, 60.64, 61.29, 57.89, 73.33, and 51.28%, respectively. First-cousin marriages were the most common form of consanguinity (48.94%) with the percentages of 55.46, 45.46, 47.87, 48.39, 45.61, 56.66, and 35.90%, respectively. A very high level of geographic endogamy was also observed (93.92%), with the values by disease ranging between 75.86 and 96.64%. We observed an overall excess risk associated to consanguinity of nearly sevenfold which was proportional to the number of affected siblings and the frequency of disease allele in the family. Consanguinity was significantly associated with the first five cited diseases (odds ratio = 24.41, 15.17, 7.5, 5.53, and 5.07, respectively). However, no meaningful effects were reported among the remaining diseases., Conclusions: This study reveals a variation in the excess risk linked to consanguinity according to the type of disorder, suggesting the potential of cryptic population substructure to contribute to disease incidence in populations with complex social structure like Tunisia. It also emphasizes the role of other health and demographic aspects such as mutation frequency and reproductive replacement in diseases etiology., (© 2015 Wiley Periodicals, Inc.)

Tunisian population is characterized by its heterogeneous ethnic background and high rate of consanguinity. In consequence, there is an increase in the frequency of recessive genetic disorders including Fanconi anemia (FA). The aim of this study was to confirm the existence of a founder haplotype among FA Tunisian patients and to identify the associated mutation in order to develop a simple tool for FA diagnosis. Seventy-four unrelated families with a total of 95 FA patients were investigated. All available family members were genotyped with four microsatellite markers flanking FANCA gene. Haplotype analysis and homozygosity mapping assigned 83 patients belonging to 62 families to the FA-A group. A common haplotype was shared by 42 patients from 26 families at a homozygous state while five patients from five families were heterozygous. Among them, 85% were from southern Tunisia suggesting a founder effect. Using multiplex ligation-dependent probe amplification (MLPA) technique, we have also demonstrated that this haplotype is associated with a total deletion of exon 15 in FANCA gene. Identification of a founder mutation allowed genetic counseling in relatives of these families, better bone marrow graft donor selection and prenatal diagnosis. This mutation should be investigated in priority for patients originating from North Africa and Middle East.

Located at the cross-road between Europe and Africa, Tunisia is a North African country of 11 million inhabitants. Throughout its history, it has been invaded by different ethnic groups. These historical events, and consanguinity, have impacted on the spectrum and frequency of genetic diseases in Tunisia. Investigations of Tunisian families have significantly contributed to elucidation of the genetic bases of rare disorders, providing an invaluable resource of cases due to particular familial structures (large family size, consanguinity and share of common ancestors). In the present study, we report on and review different aspects of consanguinity in the Tunisian population as a case study, representing several features common to neighboring or historically related countries in North Africa and the Middle East. Despite the educational, demographic and behavioral changes that have taken place during the last four decades, familial and geographical endogamy still exist at high frequencies, especially in rural areas. The health implications of consanguinity in Tunisian families include an increased risk of the expression of autosomal recessive diseases and particular phenotypic expressions. With new sequencing technologies, the investigation of consanguineous populations provides a unique opportunity to better evaluate the impact of consanguinity on the genome dynamic and on health, in addition to a better understanding of the genetic bases of diseases., (© 2014 S. Karger AG, Basel.)

Xeroderma pigmentosum (XP) is a rare autosomal recessive hereditary disease characterized by hyperphotosensitivity, DNA repair defects and a predisposition to skin cancers. The most frequently occurring type worldwide is the XP group A (XPA). There is a close relationship between the clinical features that ranged from severe to mild form and the mutational site in XPA gene. The aim of this study is to carry out the mutational analysis in Egyptian patients with XP-A. This study was carried out on four unrelated Egyptian XP-A families. Clinical features were examined and direct sequencing of the coding region of XPA gene was performed in patients and their parents. Direct sequencing of the whole coding region of the XPA gene revealed the identification of two homozygous nonsense mutations: (c.553C >T; p.(Gln185)) and (c.331G>T; p.(Glu111)), which create premature, stop codon and a homodeletion (c.374delC: p.Thr125Ilefs 15) that leads to frameshift and premature translation termination. We report the identification of one novel XPA gene mutation and two known mutations in four unrelated Egyptian families with Xermoderma pigmentosum. All explored patients presented severe neurological abnormalities and have mutations located in the DNA binding domain. This report gives insight on the mutation spectrum of XP-A in Egypt. This would provide a valuable tool for early diagnosis of this severe disease., (© 2013 Elsevier B.V. All rights reserved.)

Background/aims: The coexistence of triple A syndrome (AAAS) and congenital hypogonadotropic hypogonadism (CHH) has so far not been reported in the literature. This study aimed to characterize at the clinical and genetic level one patient presenting an association of AAAS and CHH in order to identify causal mutations., Methods: Clinical and endocrinal investigations were performed and followed by mutational screening of candidate genes., Results: At the age of 18, the patient presented sexual infantilism, a micropenis and gynecomastia. No mutation was revealed in GnRHR, TACR3/TAC3, PROK2/PROKR2 and PROP1 genes, except a homozygous intronic variation (c.244 + 128C>T; dbSNP: rs350129) in the KISS1R gene, which is likely nondeleterious. A homozygous splice-donor site mutation (IVS14 + 1G>A) was found in the AAAS gene. This mutation, responsible for AAAS, is a founder mutation in North Africa., Conclusion: This is the first report on a Tunisian patient with the coexistence of AAAS and CHH. The diagnosis of CHH should be taken in consideration in patients with Allgrove syndrome and who carry the IVS14 + 1G>A mutation as this might challenge appropriate genetic counseling., (2014 S. Karger AG, Basel)

Xeroderma pigmentosum Variant (XP-V) form is characterized by a late onset of skin symptoms. Our aim is the clinical and genetic investigations of XP-V Tunisian patients in order to develop a simple tool for early diagnosis. We investigated 16 suspected XP patients belonging to ten consanguineous families. Analysis of the POLH gene was performed by linkage analysis, long range PCR, and sequencing. Genetic analysis showed linkage to the POLH gene with a founder haplotype in all affected patients. Long range PCR of exon 9 to exon 11 showed a 3926 bp deletion compared to control individuals. Sequence analysis demonstrates that this deletion has occurred between two Alu-Sq2 repetitive sequences in the same orientation, respectively, in introns 9 and 10. We suggest that this mutation POLH NG&#95;009252.1: g.36847&#95;40771del3925 is caused by an equal crossover event that occurred between two homologous chromosomes at meiosis. These results allowed us to develop a simple test based on a simple PCR in order to screen suspected XP-V patients. In Tunisia, the prevalence of XP-V group seems to be underestimated and clinical diagnosis is usually later. Cascade screening of this founder mutation by PCR in regions with high frequency of XP provides a rapid and cost-effective tool for early diagnosis of XP-V in Tunisia and North Africa.

Tyrosinemia type II, also designated as oculocutaneous tyrosinemia or Richner-Hanhart syndrome (RHS), is a very rare autosomal recessive disorder. In the present study, we report clinical features and molecular genetic investigation of the tyrosine aminotransferase (TAT) gene in two young patients, both born to consanguineous unions between first-degree cousins. These two unrelated families originated from Northern and Southern Tunisia. The clinical diagnosis was based on the observation of several complications related to Richner-Hanhart syndrome: recurrent eye redness, tearing and burning pain, photophobia, bilateral pseudodendritic keratitis, an erythematous and painful focal palmo-plantar hyperkeratosis and a mild delay of mental development. The diagnosis was confirmed by biochemical analysis. Sequencing of the TAT gene revealed the presence of a previously reported missense mutation (c.452G>A, p.Cys151Tyr) in a Tunisian family, and a novel G duplication (c.869dupG, p.Trp291Leufs 6). Early diagnosis of RHS and protein-restricted diet are crucial to reduce the risk and the severity of long-term complications of hypertyrosinemia such as intellectual disability., (© 2013 Elsevier B.V. All rights reserved.)

Background: Primary hyperoxaluria type 1 (PH1) is an autosomal recessive inherited metabolic disease, characterized by progressive kidney failure due to renal deposition of calcium oxalate. Mutations in the AGXT gene, encoding the liver-specific enzyme alanine glyoxylate aminotransferase, are responsible for the disease. We aimed to determine the mutational spectrum causing PH1 and to provide an accurate tool for diagnosis as well as for prenatal diagnosis in the affected families., Methods: Direct sequencing was used to detect mutations in the AGXT gene in DNA samples from 13 patients belonging to 12 Tunisian families., Results: Molecular analysis revealed five mutations causing PH1 in Tunisia. The mutations were identified along exons 1, 2, 4, 5 and 7. The most predominant mutations were the Maghrebian "p.I244T" and the Arabic "p.G190R". Furthermore, three other mutations characteristic of different ethnic groups were found in our study population. These results confirm the mutational heterogeneity related to PH1 in Tunisian population. All the mutations are in a homozygous state, reflecting the high impact of endogamy in our population., Conclusion: Mutation analysis through DNA sequencing can provide a useful first line investigation for PH1. This identification could provide an accurate tool for prenatal diagnosis, genetic counseling and screen for potential presymptomatic individuals., (© 2013 Elsevier B.V. All rights reserved.)

Objectives: Mutations in GJB2 are found to be responsible for 50% of congenital autosomal recessive non-syndromic hearing loss, one of the most important mutations in this gene is the c.35delG, which is responsible for the majority of GJB2 related deafness in the Tunisian population. The aim of this study was to determine the molecular etiology of hearing loss in two Tunisian individuals., Methods: We screened two Tunisian individuals affected by congenital, bilateral, profound, sensorineural hearing loss for mutations in GJB2 gene using PCR and direct sequencing., Results: We identified a novel frameshift mutation in the GJB2 gene, the c.405delC resulting in a truncated protein (p.Tyr136Thrfs*32). It was found in compound heterozygosity with the c.35delG in two non-consanguineous unrelated families from Tunisia. One patient underwent a cochlear implant at 4 years. Initial evaluations post-implantation indicate a successful cochlear implant outcome since the patient began to acquire language abilities and auditory sensation., Conclusions: With this novel GJB2 mutation, the mutational spectrum of this gene continues to broaden in our population. The occurrence of biallelic GJB2 mutations for the other deaf girl, despite the neonatal pain and hypotension due to complicated delivery, led us to confirm the importance of GJB2 screening for cochlear implant candidates regardless of the etiology of deafness in populations with a relatively high frequency of GJB2 mutation carriers., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Xeroderma pigmentosum is a rare autosomal recessive disease characterized by hypersensitivity to UV light which is due to alterations of the nucleotide excision repair pathway. Eight genes (XPA to XPG and XPV) are responsible for the disease. Among them, the XPC gene is known to be the most mutated in Mediterranean patients. The aim of this study was to determine the frequency of the most common XPC mutation and describe the clinical features of Moroccan patients with xeroderma pigmentosum. Twenty four patients belonging to 21 unrelated Moroccan families and 58 healthy subjects were investigated. After clinical examination, the screening for the c.1643&#95;1644delTG (p.Val548AlafsX25) mutation in the XPC gene was performed by PCR and automated sequencing of exon 9 in all patients and controls. The molecular analysis showed that among the 24 patients, 17 were homozygous for the c.1643&#95;1644delTG mutation and all their tested parents were heterozygous, whereas the others (7 patients) did not carry the mutation. The frequency of this mutation was estimated to be 76.19 % (16/21 families). None of the 58 healthy individuals carried this mutation. In addition, clinical investigation showed that the majority of the patients bearing this mutation have the same clinical features. Our results revealed that the p.Val548AlafsX25 mutation is the major cause (76.19 %) of xeroderma pigmentosum in Moroccan families. This would have an important impact on improving management of patients and their relatives.

Xeroderma Pigmentosum (XP) is a rare recessive autosomal cancer prone disease, characterized by UV hypersensitivity and early appearance of cutaneous and ocular malignancies. We investigated four unrelated patients suspected to be XP-C. To confirm linkage to XPC gene, genotyping and direct sequencing of XPC gene were performed. Pathogenic effect of novel mutations was confirmed by reverse Transciptase PCR. Mutation screening revealed the presence of two novel mutations g.18246G>A and g.18810G>T in the XPC gene (NG&#95;011763.1). The first is present in one patient XP50NEF, but the second is present in three unrelated patients (XP16KEB, XP28SFA, and XP45GB). These 3 patients are from three different cities of Southern Tunisia and bear the same haplotype, suggesting a founder effect. Reverse Transciptase PCR revealed the absence of the XPC mRNA. In Tunisia, as observed in an other severe genodermatosis, the mutational spectrum of XP-C group seems to be homogeneous with some clusters of heterogeneity that should be taken into account to improve molecular diagnosis of this disease.

The occurrence of head and neck cancer (HNC) is associated with smoking and alcohol drinking. Tobacco smoking exposes smokers to a series of carcinogenic chemicals. Cytochrome P450 enzymes (CYP450s), such as CYP1A1, CYP1B1, and CYP2D6, usually metabolize carcinogens to their inactive derivatives, but they occasionally convert the chemicals to more potent carcinogens. In addition, via CYP450 (CYP2E1) oxidase, alcohol is metabolized to acetaldehyde, a highly toxic compound, which plays an important role in carcinogenesis. Furthermore, two N-acetyltransferase isozymes (NATs), NAT1 and NAT2, are polymorphic and catalyze both N-acetylation and O-acetylation of aromatic and heterocyclic amine carcinogens. Genetic polymorphisms are associated with a number of enzymes involved in the metabolism of carcinogens important in the induction of HNC. It has been suggested that such polymorphisms may be linked to cancer susceptibility. In this paper, we select four cytochrome P450 enzymes (CYP1A1, CYP1BA1, CYP2D6, and CYP2E1), and two N-acetyltransferase isozymes (NAT1 and NAT2) in order to summarize and analyze findings from the literature related to HNC risk by focusing on (i) the interaction between these genes and the environment, (ii) the impact of genetic defect on protein activity and/or expression, and (iii) the eventual involvement of race in such associations.

Background: Xeroderma Pigmentosum (XP) is a rare autosomal recessive disorder characterized by cutaneous and ocular alterations. Eight genes, Xeroderma Pigmentosum group A (XPA) to Xeroderma Pigmentosum group G (XPG) and Xeroderma Pigmentosum group V (XPV), are known to be responsible for the disease and products of these genes are involved in the repair of deoxyribonucleic acid (DNA) lesions generated by UV radiation. Several XP patients suffer from neurological defects, found in the XPA (the most common form), D and G groups. The aim of this study was to investigate the mutational spectrum of XPA in Tunisia, in order to propose a simple tool for molecular diagnosis., Methods: This study was carried out on six unrelated families with nine Tunisian XPA patients. Clinical features were recorded. As a previous study showed the presence of the R228X mutation in Tunisia, patients were first screened for this mutation by polymerase chain reaction-restriction fragment length polymorphism and then confirmed by direct sequencing., Results: The results showed that all patients carried the XPA R228X mutation. This mutation corresponds to a C to T transition, which creates a premature stop codon at position 228, thus causing a DNA repair defect., Conclusions: The XPA R228X mutation is common in Tunisian population. This mutation is associated with a relatively moderate phenotype of the XPA. As all explored patients presented the recurrent mutation XPA R228X, a potential founder effect was searched and confirmed by haplotype analysis. Taking into account similar genetic background, investigation of this mutation should allow a cost effective and rapid diagnosis of XPA in north-African populations.