Genetic polymorphisms of 17 X-STR loci in two Tunisian populations from Sousse and Makthar.

BACKGROUND: Tunisia has a complex demographic history of migrations from within Africa, Europe, and the Middle East. However, only one population study based on X-STR markers has been reported so far. AIM: To investigate the genetic polymorphisms of 17 X-STRs in two Tunisian populations from the cities of Sousse and Makthar, and to reveal the genetic relationships with other reference populations. SUBJECTS AND METHODS: A total of 194 unrelated healthy individuals were analysed for 17 X-STR markers. RESULTS: Our results indicate that DXS6809 is the most polymorphic locus, whereas DXS6807 is the least informative marker in the populations of Sousse and Makthar. In addition, forensic statistical parameters, such as the power of discrimination in males and females, as well as the mean of exclusion in duos and trios, reveal that the panel of 17 X-STRs is highly informative and useful in different forensic applications. Overall, pairwise genetic distances (Fst) and non-metric MDS plots demonstrate clustering of different populations according to their geographic locations and their historical relationships. CONCLUSION: Overall, the study of X-STR markers of the Tunisian populations can help to promote the establishment of a forensic DNA reference database in Tunisia and provide reference for future anthropological research.

Deep analysis of the LRTOMTc.242G>A variant in non-syndromic hearing loss North African patients and the Berber population: Implications for genetic diagnosis and genealogical studies.

Autosomal recessive non-syndromic hearing loss (ARNSHL) is the most common inherited sensory impairment. It is particularly frequent in North African populations who have a high rate of consanguineous marriage. The c.242G>A homozygous variant in LRTOMT gene was previously established as pathogenic and is associated with NSHL in both humans and mice. The aim of this study is to determine the carrier frequency for the LRTOMT c.242G>A variant and also to estimate its age in addition to evaluating its diagnostic potential as a deafness biomarker among various populations and ethnicities in Northern African countries. A total of 179 Tunisian and 34 Libyan unrelated deafness patients were screened for this variant. The homozygous c.242G>A variant was found in 5.02% and 2.94% in Tunisian and Libyan families, respectively. Subsequent screening for this variant in 263 healthy controls of various ethnicities (136 Tunisian Berbers, 32 Andalusian and 95 Tunisian from undefined ethnic origin) revealed higher frequency for the heterozygous state among Tunisians of Berber origin only (19.11%). Genotyping 7 microsatellite markers nearby the variant location in ARNSHL patients who had the homozygous variant revealed the same haplotype suggesting a common founder origin for this variant. The age of this variant was estimated to be between 2025 and 3425 years (this corresponds to 3400 years when the variant rate was set at 10-3 or 2600 years when the variant rate is set at 10-2 ), spreading along with the Berber population who migrated to North Africa. In conclusion, the LRTOMT c.242G>A homozygous variant could be used as a useful deafness biomarker for North African ARNSHL patients meanwhile the heterozygous variant could be utilized in genealogical studies for tracing those of the Berber ethnic group.

Insights into the Middle Eastern paternal genetic pool in Tunisia: high prevalence of T-M70 haplogroup in an Arab population.

To obtain refreshed insights into the paternal lineages of Tunisian populations, Y-chromosome diversity was assessed in two populations belonging to an Arab genealogical lineage, Kairouan and Wesletia, as well as in four Tunisian Andalusian populations, Testour, Slouguia, Qalaat-El-Andalous and El Alia. The Arabs from Kairouan revealed 73.47% of E-M81 and close affinities with Berber groups, indicating they are likely arabized Berbers, clearly differentiated from the Arabs from Wesletia, who harbored the highest frequency (71.8%) of the Middle Eastern component ever observed in North Africa. In the Tunisian Andalusians, the North African component largely prevailed, followed by the Middle Eastern contribution. Global comparative analysis highlighted the heterogeneity of Tunisian populations, among which, as a whole, dominated a set of lineages ascribed to be of autochthonous Berber origin (71.67%), beside a component of essentially Middle Eastern extraction (18.35%), and signatures of Sub-Saharan (5.2%), European (3.45%) and Asiatic (1.33%) contributions. The remarkable frequency of T-M70 in Wesletia (17.4%) prompted to refine its phylogeographic analysis, allowing to confirm its Middle Eastern origin, though signs of local evolution in Northern Africa were also detected. Evidence was clear on the ancient introduction of T lineages into the region, probably since Neolithic times associated to spread of agriculture.

PTEN Loss and Cyclin A2 Upregulation Define a PI3K/AKT Pathway Activation in Helicobacter pylori-induced MALT and DLBCL Gastric Lymphoma With Features of MALT.

Helicobacter pylori infection is strongly associated with primary gastric diseases, such as extranodal mucosa-associated lymphoid tissue (MALT) lymphoma, diffuse large B-cell lymphoma (DLBCL) with histologic evidence of MALT origin, and gastric carcinoma. The cytotoxin-associated gene A (CagA) protein behaves as a bacterial oncoprotein, promoting tumorigenesis via dysregulation of the phosphatidylinositol 3-kinase/AKT pathway (PI3K/AKT). We investigated the molecular mechanisms of PI3K/AKT pathway dysregulation in H. pylori-induced MALT and DLBCL gastric lymphoma. Immunohistochemical assays for CagA, phospho(p)-S473-AKT, PTEN, SHIP, and cyclin A2 proteins were performed on samples from 23 patients with H. pylori-positive MALT lymphoma and 16 patients with H. pylori-positive gastric DLBCL. We showed that CagA localization is correlated with the activation of the AKT pathway in both MALT and DLBCL lymphoma cells. Interestingly, we found a close association between the loss of PTEN, the overexpression of cyclin A2, and the phosphorylation of AKT in gastric MALT and DLBCL tumor cells.

Genetic analysis of sixteen autosomal STR loci in three Tunisian populations from Makthar, Nabeul and Sousse.

BACKGROUND: Due to its strategic location, Tunisia witnessed the succession and influence of many civilisations throughout history. However, the majority of studies carried out on Tunisia are focussed on Barbarian ethnicity. AIM: To estimate genetic diversity and genetic structure of three Tunisian populations using autosomal STRs. SUBJECTS AND METHODS: 278 individuals were analysed for sixteen STRs. Allele frequencies and statistical parameters were determined. RESULTS: The studied populations showed genetic affinity with geographically close populations. AMOVA showed no genetic difference between the Tunisian populations. Nevertheless, the variance between the populations of the same group was significant, reflecting their heterogeneity even though they came from the same geographical area, and had the same ethnicity and complex demographic history. CONCLUSION: Our results strongly supported the application of autosomal genetic markers in anthropological and forensic studies. The analyses conducted at the 15-loci level provide the resolution to assess the phylogenetic relationships among the populations examined and other geographically targeted worldwide populations, while the results resulting from the 10-loci studies provide an understanding of the relationships and origins of the North African populations. Furthermore, the current report demonstrates that the battery of autosomal STRs reported are useful, providing the power of discrimination for forensic and paternity analyses.

A Distinctive Pattern of Diversity for the TAS2R38 Gene in North Africa.

The TAS2R38 gene is involved in bitter taste perception. This study documents the distinctive diversity patterns in northern Africa of functional single-nucleotide polymorphisms (SNPs) rs713598 and rs1726866 at the TAS2R38 locus and places those patterns in the context of global TAS2R38 diversity. Data previously genotyped with TaqMan assay were analyzed for rs713598 and rs1726866 for 375 unrelated subjects (305 Tunisians from seven locations: Mahdia, Sousse, Kesra, Nebeur, Kairouan, Smar, and Kerkennah; plus 70 Libyans). Data were analyzed to present haplotypes and genotypes before comparison with data from worldwide populations. This study provides information about TAS2R38 diversity in a part of the world that is relatively understudied. Considering the two SNPs rs713598 and rs1726866, the CA nucleotide haplotype leading to the PV amino acid haplotype is extremely rare almost everywhere, but it is relatively frequent (between 6% and 15%) in northern Africa, where it coexists with the globally common amino acid haplotypes PA, AA, and AV. Given its higher frequency in North Africa, the authors propose the CA nucleotide haplotype as a biogeographic marker for forensic purposes.

MICA-129 Met/Val polymorphism could be a genetic biomarker for Familial Breast Cancer in the Tunisian population.

Identification of candidate genes associated with susceptibility of breast cancer can have a significant impact at a cancer management national healthcare systems level, making genetic testing more affordable and cost-effective. We have previously shown that the major histocompatibility complex class I-related chain A (MICA) was related to breast cancer and plays an important role in modulating immune response mechanisms through NKG2D receptor activation. Compared to our previous study, in this work, we recruited a new cohort composed of 354 unrelated Tunisian women affected by breast cancer and 380 age-matched women as controls, all genotyped for MICA-129 Met/Val (rs 1051792). Subsequently, we exanimated the distribution of this polymorphism in ten families. As a result, an association was found between the Val allele and Val/Val genotype and the risk of breast cancer (p = 2.5 × 10-15 ; OR = 2.40; p = 6.5 × 10-13 ; OR = 3.03, respectively). Stratified analysis with age and family history of cancer revealed an association between the Val/Val genotype and younger patients <40 years (p = .003; OR = 2.03). Among those patients having a family history of cancer, 68% had a Val/Val genotype (p = .02; OR = 1.82). In the family study, an analyse of pedigrees revealed that the majority of families showed the development of breast cancer at a young age. Moreover, all patients diagnosed with early-onset breast cancer had a Val/Val genotype. Our results lead us to propose that this polymorphism may be an inherited genetic biomarker contributing to an increased breast cancer risk in Tunisian women.

Expression and polymorphism of micro-RNA according to body mass index and breast cancer presentation in Tunisian patients.

Micro-RNAs (miRs) constitute a class of small noncoding RNAs implicated in the regulation of gene expression by binding to target mRNAs. A miR can target several mRNAs, being involved in different biologic processes and pathologies. This pleiotropic function might explain the link between diseases co-occurrence. Epigenetic origin of the link between obesity and breast cancer (BC) is investigated in a cohort of Tunisian patients, focusing on polymorphism at germline level (miR-146a) and on expression in mammary tumors (miR-21, miR-146a, and miR-34a), according to body mass index (BMI) and clinico-pathologic features. The measure of miR expression in 60 mammary tumors was realized using quantitative RT-PCR. Study of rs 2910164 in miR-146a was performed by PCR and direct sequencing using blood DNA of 83 affected women and 50 unrelated subjects from Great Tunis. MiR-21, miR-146a, and miR-34a have been quantified in breast tumor according to BMI. MiR-21 is significantly more expressed in tumors of obese women comparatively to nonobese patients. On the contrary, miR-34a is decreased in tumors of obese women. Moreover, in obese BC patients, a significant increase in both miR-21 and miR-146a expression is revealed in cases with lymph node metastasis. The polymorphism at rs 2910164 (miR-146a) locus was not shown as a risk factor for BC. However the mutant CC genotype was revealed to be associated with a risk for bad outcome of the disease. Chronic inflammation in obese women would be linked to aggressive breast tumors via induction of oncomiRs overexpression and decrease of tumor suppressor miRs.

A genome wide SNP genotyping study in the Tunisian population: specific reporting on a subset of common breast cancer risk loci.

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.

Targeting Tumor Metabolism: A New Challenge to Improve Immunotherapy.

Currently, a marked number of clinical trials on cancer treatment have revealed the success of immunomodulatory therapies based on immune checkpoint inhibitors that activate tumor-specific T cells. However, the therapeutic efficacy of cancer immunotherapies is only restricted to a small fraction of patients. A deeper understanding of key mechanisms generating an immunosuppressive tumor microenvironment (TME) remains a major challenge for more effective antitumor immunity. There is a growing evidence that the TME supports inappropriate metabolic reprogramming that dampens T cell function, and therefore impacts the antitumor immune response and tumor progression. Notably, the immunosuppressive TME is characterized by a lack of crucial carbon sources critical for T cell function and increased inhibitory signals. Here, we summarize the basics of intrinsic and extrinsic metabolic remodeling and metabolic checkpoints underlying the competition between cancer and infiltrating immune cells for nutrients and metabolites. Intriguingly, the upregulation of tumor programmed death-L1 and cytotoxic T lymphocyte-associated antigen 4 alters the metabolic programme of T cells and drives their exhaustion. In this context, targeting both tumor and T cell metabolism can beneficially enhance or temper immunity in an inhospitable microenvironment and markedly improve the success of immunotherapies.

Ancient and recent Middle Eastern maternal genetic contribution to North Africa as viewed by mtDNA diversity in Tunisian Arab populations.

OBJECTIVES: Through previous mitochondrial DNA studies, the Middle Eastern maternal genetic contribution to Tunisian populations appears limited. In fact, most of the studied communities were cosmopolitan, or of Berber or Andalusian origin. To provide genetic evidence for the actual contribution of Middle Eastern mtDNA lineages to Tunisia, we focused on two Arab speaking populations from Kairouan and Wesletia known to belong to an Arab genealogical lineage. MATERIALS AND METHODS: A total of 114 samples were sequenced for the mtDNA HVS-I and HVS-II regions. Using these data, we evaluated the distribution of Middle Eastern haplogroups in the study populations, constructed interpolation maps, and established phylogenetic networks allowing estimation of the coalescence time for three specific Middle Eastern subclades (R0a, J1b, and T1). RESULTS: Both studied populations displayed North African genetic structure and Middle Eastern lineages with a frequency of 12% and 28.12% in Kairouan and Wesletia, respectively. TMRCA estimates for haplogroups T1a, R0a, and J1b in Tunisian Arabian samples were around 15 000 YBP, 9000 to 5000 YBP, and 960 to 600 YBP, respectively. CONCLUSIONS: The Middle Eastern maternal genetic contribution to Tunisian populations, as to other North African populations, occurred mostly in deep prehistory. They were brought in different migration waves during the Upper Paleolithic, probably with the expansion of Iberomaurusian culture, and during Epipaleolithic and Early Neolithic periods, which are concomitant with the Capsian civilization. Middle Eastern lineages also came to Tunisia during the recent Islamic expansion of the 7th CE and the subsequent massive Bedouin migration during the 11th CE.

The Orientalisation of North Africa: New hints from the study of autosomal STRs in an Arab population.

BACKGROUND: Recent genomic analyses suggest that the current North African gene pool was mainly influenced by population flow coming from the East that altered the genetic structure of autochthonous Berber populations. Such genetic flow has not been extensively addressed yet using North African populations of Middle-eastern origin as reference. AIM: To discern the Middle-eastern component in the genetic background of Tunisian Arabs and evaluate the extent of gene flow from the Middle East into North African autochthonous Berber populations. SUBJECTS AND METHODS: This study has examined 113 Tunisians of well-known Arabian origin from Kairouan region, using 15 autosomal Short Tandem Repeats (STRs) loci. RESULTS: No deviations from Hardy-Weinberg equilibrium were observed and all loci presented high levels of heterozygosity. Principal coordinate and STRUCTURE analyses were consistent in clustering together North African and Middle Eastern populations, likely reflecting the recent gene flow from the East dating back to the Arab conquest period. This demographic migration and the Arabisation process that submerged the original Berber language and customs seems to have be accompanied by substantial gene flow and genetic admixture. CONCLUSION: This study represents an additional step to obtain a comprehensive understanding of the complex demographic history of North African populations.

Involvement of genetic factors and lifestyle on the occurrence of colorectal and gastric cancer.

Gastrointestinal cancers are diseases due to genetic and environmental factors. In this present work we are interested in the influence of environmental factors on the occurrence of gastrointestinal cancers in Tunisian population. We found that the MTHFR C677T polymorphism was associated with colorectal cancer (P<0.04) but not with gastric cancer. In addition, we have shown that alcohol is associated with an increased risk of colorectal cancer, but the consumption of cheese is protective. Furthermore, we studied tymidylate synthase gene involved in folate metabolism. Indeed, we observed that the 5'UTR repeat polymorphism, is associated with risk of colorectal cancer, and the LL genotype (3R/3R) was significantly frequent in patients with colorectal cancer compared to controls (p=0.002; OR=2.7, 95% CI=1.4-5.2). While we found that SL genotype (2R/3R) was associated with risk of gastric cancer (p=0.015; OR=4.46, 95% CI=1.08-19-64). This polymorphism was also shown to be a predictor of response to chemotherapy based 5'-fluorouracil. However, we are interested in studying the GPX -1 gene involved in phase I metabolism of xenobiotics. We therefore evaluated the risk of TT genotype in GPX-1 C599T polymorphism with the onset of gastric cancer (P=0.0001; OR=5.41, 95% CI 1.98 to 15.58) and colorectal cancer (P=0.00008; OR=4.40, 95% CI 1.93 to 10.27). To clarify the possible relationship between environmental factors and the occurrence of the disease, we studied the additive effect of risk genotype and behavior in order to highlight the interaction of gene-environment factors.

Computer-Assisted Classification Patterns in Autoimmune Diagnostics: The AIDA Project.

Antinuclear antibodies (ANAs) are significant biomarkers in the diagnosis of autoimmune diseases in humans, done by mean of Indirect ImmunoFluorescence (IIF) method, and performed by analyzing patterns and fluorescence intensity. This paper introduces the AIDA Project (autoimmunity: diagnosis assisted by computer) developed in the framework of an Italy-Tunisia cross-border cooperation and its preliminary results. A database of interpreted IIF images is being collected through the exchange of images and double reporting and a Gold Standard database, containing around 1000 double reported images, has been settled. The Gold Standard database is used for optimization of a CAD (Computer Aided Detection) solution and for the assessment of its added value, in order to be applied along with an Immunologist as a second Reader in detection of autoantibodies. This CAD system is able to identify on IIF images the fluorescence intensity and the fluorescence pattern. Preliminary results show that CAD, used as second Reader, appeared to perform better than Junior Immunologists and hence may significantly improve their efficacy; compared with two Junior Immunologists, the CAD system showed higher Intensity Accuracy (85,5% versus 66,0% and 66,0%), higher Patterns Accuracy (79,3% versus 48,0% and 66,2%), and higher Mean Class Accuracy (79,4% versus 56,7% and 64.2%).

Involvement of IL17A, IL17F and IL23R Polymorphisms in Colorectal Cancer Therapy.

IL23/IL17 pathway plays an important role in the development of inflammatory bowel diseases (IBD). In general, the genes encoding the cytokines are genetically polymorphic and polymorphisms in genes IL23R and IL17 have been proved to be associated with its susceptibility to inflammatory diseases as well as cancer including colorectal cancer. Moreover, it has been shown that these interleukins are involved in anti-tumor or pro-tumor effects of various cancers. Previously, we showed that there is a significant association between IL17A, IL17F and IL23R polymorphisms as well as the occurrence of colorectal cancer and the clinical features of the disease. The purpose of the present work is to investigate an association between IL17A, IL17F and IL23R polymorphisms in 102 Tunisian patients with colorectal cancer treatment. The association was analyzed by statistical tools. We found that patients with mutated genotypes of IL17A G197A SNP could be a risk factor for the inefficiency of chemotherapy and radiotherapy. Unlike IL17F variant, patients with wild type genotypes require surgery and adjuvant chemotherapy. On the one hand, we found no evidence that supports a significant association between IL23R polymorphism and the combined genotypes of these three genes and the colorectal cancer treatment. On the other hand, we showed that there is an important interaction between IL17A/IL17F polymorphisms and the stage of the disease as well as its treatment. Finally, patients with IL17F wild type genotype highlighted that there is a valid longer OS without all treatments and with radiotherapy and a neoadjuvant chemotherapy. In contrast, we observed that there are no relationships between IL17A, IL23R and the survival of these patients neither with nor without the treatment. Our results suggest that polymorphisms in IL17A and IL17F genes may be a predictive source of colorectal cancer therapy type. Therefore, IL17F may serve as an independent prognostic factor for overall survival in patients with colorectal cancer.

The immune microenvironment of the colorectal tumor: Involvement of immunity genes and microRNAs belonging to the TH17 pathway.

Colorectal cancer is a complex and multifactorial disease. Various factors such as genetic, immunological, epigenetic and environmental constitute minor risk factors with their additive effects contributing to the advent of colorectal cancer. In order to evaluate the role of innate and adaptive immunity in the susceptibility, the presentation and the development of colorectal cancer, we considered an immunogenetic approach on polymorphisms in the TLR4 gene and NOD2/CARD15 gene (receptors of innate immunity) as well as in cytokine genes of the TH17 pathway IL17A, IL17F and cytokine receptor IL23R. Then, we evaluated the expression of microRNAs regulated by TLR4 and NOD2/CARD15 or targeting TLR4, IL17 and proinflammatory cytokines (IL-6, TNF) induced by IL17. Through a case-control study, we showed that the polymorphism of IL17A is associated with its susceptibility to colorectal cancer. Considering the tumor location, we found that the mutated alleles of IL17A, IL17F and IL23R are rather associated with colon cancer and not with rectum cancer. This result confirms that the colon and rectum are two different physiological entities. This study shows that TLR4, IL17A/F and IL23R polymorphisms are involved in the presentation of the disease with regard to tumor architecture, histology, and differentiation, advanced stage of the disease and lymph node and metastasis. Overall, these polymorphisms are associated with a poor prognosis of the disease. Furthermore, in order to evaluate the involvement of epigenetic mechanisms in the occurrence of colorectal cancer, we aimed at analyzing the tumor compared to a normal adjacent tissue and the expression of miRNAs (miR21, miR146a, miR135a, miR147b and miR155) that regulate immunity genes especially the cytokines of the TH17 pathway. This research has shown that microRNAs 21, 135a and 146a are associated with colorectal cancer. Indeed, these three miRs are overexpressed in cancer tissue compared to healthy tissue. These results clearly confirm the involvement of epigenetics in colorectal cancer. In other words, this study reveals the importance of immunity and specifically the TH17 pathway in the development and presentation of colorectal cancer. These results suggest that TLR4, IL17A, IL17F and IL23R polymorphisms as well as the expression of microRNAs that regulate inflammation and the TH17 pathway are associated with the evolution and progression of the colorectal tumor that could be considered as biomarkers in colorectal cancer.

Mutation spectrum of RB1 gene in unilateral retinoblastoma cases from Tunisia and correlations with clinical features.

Retinoblastoma, an embryonic neoplasm of retinal origin, is the most common primary intraocular malignancy in children. Somatic inactivation of both alleles of the RB1 tumor suppressor gene in a retinal progenitor cell through diverse mechanisms including genetic and epigenetic modifications, is the crucial event in initiation of tumorigenesis in most cases of isolated unilateral retinoblastoma. We analyzed DNA from tumor tissue and from peripheral blood to determine the RB1 mutation status and seek correlations with clinical features of 37 unrelated cases of Tunisian origin with sporadic retinoblastoma. All cases were unilateral except one who presented with bilateral disease, in whom no germline coding sequence alteration was identified. A multi-step mutation scanning protocol identified bi-allelic inactivation of RB1 gene in 30 (81%) of the samples tested. A total of 7 novel mutations were identified. There were three tumors without any detectable mutation while a subset contained multiple mutations in RB1 gene. The latter group included tumors collected after treatment with chemotherapy. There were seven individuals with germline mutations and all presented with advanced stage of tumor. There was no difference in age of onset of RB based on the germline mutation status. Thus 20% of the individuals with sporadic unilateral RB in this series carried germline mutations and indicate the importance of genetic testing all children with sporadic retinoblastoma. These findings help to characterize the spectrum of mutations present in the Tunisian population and can improve genetic diagnosis of retinoblastoma.

Sousse: extreme genetic heterogeneity in North Africa.

The male genetic landscape of the territory currently known as Tunisia is hampered by the scarcity of data, especially from cosmopolitan areas such as the coastal city of Sousse. In order to alleviate this lacuna, 220 males from Sousse were examined, for the first time, for more than 50 Y-chromosome single-nucleotide polymorphisms (Y-SNPs) markers and compared with 3099 individuals from key geographically targeted locations in North Africa, Europe and the Near East. The paternal lineages observed belong to a common set of Y haplogroups previously described in North Africa. In addition to the prominent autochthonous North African E-M81 haplogroup which is exclusively represented by its subclade E-M183 (44.55% of Y-chromosomes), a number of Near Eastern Neolithic lineages including E-M78, J-M267 and J-M172 account for 39% of the Y-chromosomes detected. Principal component analysis based on haplogroup frequencies, multidimensional scaling based on Rst genetic distances and analyses of molecular variance using both Y-chromosome short tandem repeat haplotypes and Y-SNP haplogroup data revealed that the Tunisian and North African groups, as a whole, are intra- and inter-specific diverse with Sousse being highly heterogeneous.

Genetic testing in Tunisian families with heritable retinoblastoma using a low cost approach permits accurate risk prediction in relatives and reveals incomplete penetrance in adults.

Heritable retinoblastoma is caused by oncogenic mutations in the RB1 tumor suppressor gene. Identification of these mutations in patients is important for genetic counseling and clinical management of relatives at risk. In order to lower analytical efforts, we designed a stepwise mutation detection strategy that was adapted to the spectrum of oncogenic RB1 gene mutations. We applied this strategy on 20 unrelated patients with familial and/or de novo bilateral retinoblastoma from Tunisia. In 19 (95%) patients, we detected oncogenic mutations including base substitutions, small length mutations, and large deletions. Further analyses on the origin of the mutations showed mutational mosaicism in one unilaterally affected father of a bilateral proband and incomplete penetrance in two mothers. In a large family with several retinoblastoma patients, the mutation identified in the index patient was also detected in several non-penetrant relatives. RNA analyses showed that this mutation results in an in-frame loss of exon 9. In summary, our strategy can serve as a model for RB1 mutation identification with high analytical sensitivity. Our results point out that genetic testing is needed to reveal or exclude incomplete penetrance specifically in parents of patients with sporadic disease.

MicroRNAs 146a and 147b biomarkers for colorectal tumor's localization.

The recently identified class of microRNAs (miRs) provided a new insight into cancer research, since abnormalities of members of microRNAs family have been found in various types of cancer. However, the relationship between five miRNAs (miR146a, miR155, miR21, miR135a, and miR147b) and colorectal cancer remains unclear. In the present study, we examined expression of these miRNAs in 25 pair-matched colon cancer tissues and normal colon mucosa. The expression levels of miR146a, miR155, miR21, miR135a, and miR147b were quantified by real-time PCR. We found that miR21, miR146a, and miR135a were all expressed at higher levels in colon tumors. On the other hand, miR146a and miR147b expressions are significantly higher in left colon compared to right colon. These two miRs, especially miR146a, seemed to be markers for the left colon tumors. Moreover, significant proportional and inverse correlations were found between miR expressions in tumor and healthy tissue, and the correlations profiles were different depending on cancer localization. Taken together, these results lead us to suggest the presence of different mechanisms regulating miRs expression and consequently their target genes in left and right colon. So the pathway of colorectal carcinogenesis would be different according to the site of the tumor.