Affinity kinetics of leptin-reactive immunoglobulins are associated with plasma leptin and markers of obesity and diabetes.

Obese subjects display elevated plasma levels of leptin reflecting the phenomenon of leptin resistance. Here, we aimed to determine whether leptin-reactive immunoglobulins (Ig) are present in obese and type 2 diabetes (T2D) patients and whether their plasma levels and affinity kinetics may correlate with obesity and diabetes markers. We show that leptin levels are increased in obese patients with and without T2D. Although mean plasma levels of leptin-reactive IgG were similar between study groups, IgG in obese non-diabetic patients had increased dissociation rate and lower affinity (increased dissociation equilibrium constant value; KD). In controls and diabetic patients, the association rates of leptin IgG correlated negatively with obesity and diabetes markers, respectively. In contrast, KD values correlated positively with plasma leptin levels and obesity traits in our cohort, and with diabetes markers in both the total cohort and in the obese T2D group. Taken together, our data reveal that leptin-reactive IgG are present in healthy subjects, obese, and diabetic patients but display altered affinity kinetics in obesity. Increased IgG binding to leptin in healthy subjects associated with lower body mass index (BMI) suggests an enhancing role of IgG in leptin signaling. Accordingly, a decreased affinity of IgG for leptin, found in obese patients, can be relevant to leptin resistance.

Potential role of liver enzyme levels as predictive markers of glucose metabolism disorders in a Tunisian population.

The relationship between liver enzymes and T2D risk is inconclusive. We aimed to evaluate the association between liver markers and risk of carbohydrate metabolism disorders, as well as their discriminatory power, for T2D prediction. This cross-sectional study enrolled 216 participants classified as normoglycemic, prediabetic, newly diagnosed diabetics, and diagnosed diabetics. All participants underwent anthropometric and biochemical measurements. The relationship between hepatic enzymes and glucose metabolism markers was evaluated by analyses of covariance. The associations between liver enzymes and incident carbohydrate metabolism disorders were analyzed through logistic regression and their discriminatory capacity to predict T2D by ROC analysis. High AP, ALT, γGT, and AST levels were independently related to decreased insulin sensitivity. Interestingly, a higher AP level was significantly associated with an increased risk of prediabetes (p = 0.017), newly diagnosed diabetes (p = 0.004), and T2D (p = 0.007). An elevated γGT level was an independent risk factor for T2D (p = 0.032) and undiagnosed T2D (p = 0.010) in prediabetic and normoglycemic subjects, respectively. In ROC analysis, AP was a powerful predictor of incident diabetes and significantly improved T2D prediction. Liver enzymes within the normal range, specifically AP levels, are associated with increased risk of carbohydrate metabolism disorders and significantly improved T2D prediction.

Down-expression of P2RX2, KCNQ5, ERBB3 and SOCS3 through DNA hypermethylation in elderly women with presbycusis.

CONTEXT: Presbycusis, an age-related hearing impairment (ARHI), represents the most common sensory disability in adults. Today, the molecular mechanisms underlying presbycusis remain unclear. This is in particular due to the fact that ARHI is a multifactorial complex disorder resulting from several genomic factors interacting with lifelong cumulative effects of: disease, diet, and environment. OBJECTIVE: Identification of novel biomarkers for presbycusis. MATERIALS AND METHODS: We selectively ascertained 18 elderly unrelated women lacking environmental and metabolic risk factors. Subsequently, we screened for methylation map changes in blood samples of women with presbycusis as compared to controls, using reduced representation bisulfite sequencing. We focused on hypermethylated cytosine bases located in gene promoters and the first two exons. To elucidate the related gene expression changes, we performed transcriptomic study using gene expression microarray. RESULTS: Twenty-seven genes, known to be expressed in adult human cochlea, were found in the blood cells to be differentially hypermethylated with significant (p < 0.01) methylation differences (>30%) and down-expressed with fold change >1.2 (FDR <0.05). Functional annotation and qRT-PCR further identified P2RX2, KCNQ5, ERBB3 and SOCS3 to be associated with the progression of ARHI. DISCUSSION AND CONCLUSION: Down-expressed genes associated with DNA hypermethylation could be used as biomarkers for understanding complex pathogenic mechanisms underlying presbycusis.

Potential Predictive Role of Lipid Peroxidation Markers for Type 2 Diabetes in the Adult Tunisian Population.

OBJECTIVES: We evaluated the potential clinical relevance of malondialdehyde (MDA) and autoantibodies to copper oxidized low-density lipoprotein (CuOx-LDL) in type 2 diabetes occurrence. METHODS: This cross-sectional study enrolled 69 normoglycemic subjects, 18 prediabetic patients and 108 type 2 diabetes patients. MDA concentration was assessed spectrophotometrically. Plasma IgG, IgA and IgM levels to CuOx-LDL were determined by ELISA. RESULTS: Plasma MDA levels were considerably higher in obese, prediabetic and type 2 diabetes subjects compared to controls. In multiple linear regression analysis, both MDA and IgA to CuOx-LDL were significantly associated with glucose metabolism markers (p<0.05). Multiple logistic regression analyses showed that high plasma MDA and IgA to CuOx-LDL were independent risk factors for type 2 diabetes (OR 1.196, 95% CI: 1.058 to 1.353; p=0.004; OR 1.626, 95% CI: 1.066 to 2.481; p=0.024; respectively). Importantly, elevated IgA to CuOx-LDL predicted incident diabetes in patients with prediabetes (OR 2.321, 95% CI:1.063 to 5.066; p=0.035). From stratified analyses by body mass index (BMI), both MDA and IgA to CuOx-LDL remained independent predictors of type 2 diabetes occurrence in non-obese subjects (p<0.05). More interesting, elevated IgA to CuOx-LDL levels could be predictors of type 2 diabetes in obese prediabetic subjects (p=0.044). Conversely, neither IgG nor IgM to CuOx-LDL was associated with glucose metabolism markers, obesity or type 2 diabetes. CONCLUSIONS: Plasma MDA and IgA to CuOx-LDL were significantly associated with blood markers of glucose metabolism. High levels of MDA and IgA to CuOx-LDL could independently predict type 2 diabetes development in normoglycemia and prediabetic subjects.

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.

Segregation of S292F TPO gene mutation in three large Tunisian families with thyroid dyshormonogenesis: evidence of a founder effect.

UNLABELLED: We aimed to identify causal mutation(s) in 13 patients with thyroid dyshormonogenesis (TD) from three consanguineous Tunisian families. A 12-year clinical follow-up showed phenotypic variability ranging from the presence to the absence of goiter, sensorineural deafness, and mental retardation. Genetic analysis using microsatellite markers within two candidate genes (TPO and PDS) gave evidence of linkage with the TPO gene. Sequencing of its 17 exons and their flanking intron-exon junctions revealed the previously described c.875C>T (p.S292F) mutation in homozygous state. No additional mutations were found in either a 900 bp of the TPO gene promoter or PDS gene. In silico analysis showed that p.S292F mutation might reduce the catalytic cavity of the TPO which would restrict access of a potential substrate to the catalytic pocket. Using 4SNPs and one microsatellite marker in the TPO gene, an associated haplotype: G-C-G-G-214 was found, giving evidence of a founder mutation. CONCLUSION: This is the first description of a TD causing mutation in Tunisia and thus may help to develop a genetic screening protocol for congenital hypothyroidism in the studied region. Although structural modeling suggested a pathogenic effect of this mutation, functional studies are needed. Additional causing and/or modifier genes, together with late diagnosis could explain the clinical variability observed in our patients.

Analysis of two Arab families reveals additional support for a DFNB2 nonsyndromic phenotype of MYO7A.

Variants in the head and tail domains of the MYO7A gene, encoding myosin VIIA, cause Usher syndrome type 1B (USH1B) and nonsyndromic deafness (DFNB2, DFNA11). In order to identify the genetic defect(s) underling profound deafness in two consanguineous Arab families living in UAE, we have sequenced a panel of 19 genes involved in Usher syndrome and nonsyndromic deafness in the index cases of the two families. This analysis revealed a novel homozygous insertion of AG (c.1952_1953insAG/p.C652fsX11) in exon 17 of the MYO7A gene in an Iraqi family, and a homozygous point mutation (c.5660C>T/p.P1887L) in exon 41 affecting the same gene in a large Palestinian family. Moreover, some individuals from the Palestinian family also harbored a novel heterozygous truncating variant (c.1267C>T/p.R423X) in the DFNB31 gene, which is involved in autosomal recessive nonsyndromic deafness type DFNB31 and Usher syndrome type II. Assuming an autosomal recessive mode of inheritance in the two inbred families, we conclude that the homozygous variants in the MYO7A gene are the disease-causing mutations in these families. Furthermore, given the absence of retinal disease in all affected patients examined, particularly a 28 year old patient, suggests that at least one family may segregate a DFNB2 presentation rather than USH1B. This finding further supports the premise that the MYO7A gene is responsible for two distinct diseases and gives evidence that the p.P1887L mutation in a homozygous state may be responsible for nonsyndromic hearing loss.

A 20 year history of clinical and genetic study of thyroid autoimmunity in a Tunisian multigenerational family: Evidence for gene interaction.

Autoimmune thyroid diseases (AITD), which include Hashimoto thyroiditis (HT), Graves' disease (GD) and primary idiopathic myxoedema (PIM), are recognized by their clinical and genetic heterogeneity. In this study, we have carried on a global approach gathering 20 year genetic and clinical data on a Tunisian multigenerational family (Akr). Our purpose was search for a combined genotype involved in AITD susceptibility using 33 gene polymorphisms. The Akr pedigree is composed of more than 400 members distributed on 10 generations. Clinical follow-up was performed by appreciation of the thyroid gland and measurement of both thyroid hormone and auto antibody levels. We used FBAT software to test for association between gene polymorphisms and AITDs. Clinical follow-up has showed that the number of AITD patients has increased from 25 to 78 subjects subdivided on 51 cases of GD, 22 PIM and 5 HT. Concerning genetic analysis, our study has revealed new gene association when compared with our previous analysis (considering single genes). Thus, PTPN22, TG and VDR gene polymorphisms have became associated with p-values ranging from 4.6  10(- 2) to 4  10(- 3) when considered with other genes on the same chromosome; giving evidence for gene interaction. The most significant association was found with the MHC region (p = 7.15 10(- 4)). Moreover, and among gene polymorphisms explored, our analysis has identified some of them as AITD biomarkers. Indeed, PDS gene polymorphisms were associated with either exophthalmia or goiter (p-values from 10(- 2) to 10(- 3)). In conclusion, our study gives evidence for gene interaction in AITD development confirming genetic complexity of these diseases.

Posterior microphthalmia and nanophthalmia in Tunisia caused by a founder c.1059_1066insC mutation of the PRSS56 gene.

Congenital microphthalmia (CMIC) is a common developmental ocular disorder characterized by a small, and sometimes malformed, eye. Posterior microphthalmia (PM) and nanophthalmia are two rare subtypes of isolated CMIC characterized by extreme hyperopia due to short axial length and elevated lens/eye volume ratio. While nanophthalmia is associated with a reduced size in both anterior and posterior segments, PM involves a normal-size anterior chamber but a small posterior segment. Several genes encoding transcription and non-transcription regulators have been identified in different forms of CMIC. MFRP gene mutations have, for instance, been associated with nanophthalmia, and mutations in the recently identified PRSS56 gene have been linked to PM. So far, these two forms of CMIC have been associated with 9 mutations in PRSS56. Of particular interest, a c.1059_1066insC mutation has recently been reported in four Tunisian families with isolated PM and one Tunisian family with nanophthalmia. Here, we performed a genome-wide scan using a high density single nucleotide polymorphism (SNP) array 50 K in a large consanguineous Tunisian family (PM7) affected with PM and identified the same causative disease mutation. A total of 24 polymorphic markers spanning the PRSS56 gene in 6 families originating from different regions of Tunisia were analyzed to investigate the origin of the c.1059_1066insC mutation and to determine whether it arose in a common ancestor. A highly significant disease-associated haplotype, spanning across the 146 kb of the 2q37.1 chromosome, was conserved in those families, suggesting that c.1059_1066insC arose from a common founder. The age of the mutation in this haplotype was estimated to be around 1,850 years. The identification of such 'founder effects' may greatly simplify diagnostic genetic screening and lead to better prognostic counseling.

Association of intronic repetition of SLC26A4 gene with Hashimoto thyroiditis disease.

Intronic microsatellites repeats were implicated in the pathogenic mechanisms of several diseases. SLC26A4 gene, involved in the genetic susceptibility of autoimmune thyroid disease (AITD), harbours large non-coding introns. Using the tandem repeat finder (TRF) Software, two new polymorphic microsatellite markers, rs59736472 and rs57250751, located at introns 10 and 20, respectively, were identified. A case-control design including 308 patients affected with AITD (146 GD, 90 HT and 72 PIM) and 212 unmatched healthy controls were performed for each marker (rs59736472, D7S2459 and rs57250751). Furthermore, we used PHASE 2.0 version to reconstruct haplotypes, Kolmogorov-Smirnov (KS) and the Clump analysis program for multivariate analysis. The fluorescent genotyping revealed three alleles (106,112 and 115 bp) for rs57250751 and 12 alleles for both D7S2459 and rs59736472 ranging from 134 to 156 bp and from 144 to 168 bp, respectively. The case-control analysis confirmed the positive association of D7S2459 with Hashimoto thyroiditis (HT) disease previously reported. Moreover, a significant association was found only with rs59736472 and HT disease. Haplotype-specific analysis showed that the 140-148-115 haplotype may increase the risk of HT (χ2=9.8, 1 df, P=0.0017, OR=2.07, IC [1.27-3.36]). Consequently, considering the number of repetitions of both D7S2459 and rs59736472, we found 15 alleles ranging from 45 to 59 repetitions. The case-control analysis showed a significant association of the 55 repetition with HT disease (χ2=6.32, 1 df, p c=0.012, OR=1.74, IC [1.1-2.76]). In conclusion, we suggest the association of longer alleles of intron 10 of SLC26A4 gene with HT disease.

IL-1ß and TSH disturb thyroid epithelium integrity in autoimmune thyroid diseases.

Pro-inflammatory cytokines such as IL-1ß and TNFα are known to affect thyroid function. They stimulate IL-6 secretion and modify epithelium integrity by altering junction proteins. To study the role of cytokines on thyroid epithelia tightness in autoimmune thyroid diseases (AITD), we analyzed the expression profiles of junction proteins (ZO-1, Claudin, JAM-A) and cytokines in human thyroid slices and also investigated the effect of IL-1ß on the epithelium integrity in primary cultures of human thyrocytes. Junction proteins expression (ZO-1, Claudin, JAM-A) has been analyzed by immunohistochemistry on thyroid slices and by Western blot on membrane proteins extracted from thyrocytes of patients suffering from Graves and Hashimoto diseases. The high expression of junction proteins we found on Graves' disease thyroid slices as well as in cell membrane extracts acknowledges the tightness of thyroid follicular cells in this AITD. In contrast, the reduced expression of JAM and ZO-1 in thyroid cells from patients suffering from Hashimoto thyroiditis is in agreement with the loss of thyroid follicular cell integrity that occurs in this pathology. Concerning the effects on epithelium integrity of TSH and of the pro-inflammatory cytokine IL-1ß in primary cultures of human thyroid cells, TSH appeared able to modify JAM-A localization but without any change in the expression levels of JAM-A, Claudin and ZO-1. Inversely, IL-1ß provoked a decrease in the expression of- and a redistribution of both, Claudin and ZO-1 without modifying the expression and sub-cellular distribution patterns of JAM-A in thyroid cells. These results demonstrate (i) that Hashimoto's- and Graves' diseases display different junction proteins expression patterns with a loss of epithelium integrity in the former and (ii) that IL-1ß modifies thyroid epithelial tightness of human thyrocytes by altering the expression and localization of junction proteins. Therefore, IL-1ß could play a role in the pathogenesis of thyroid autoimmunity.

DNA repair gene polymorphisms at XRCC1 (Arg194Trp, Arg280His, and Arg399Gln) in a healthy Tunisian population: interethnic variation and functional prediction.

The genetic polymorphisms in DNA repair genes might affect the repair activities of the enzymes, predisposing individuals to cancer risk. Due to these genetic variants, interethnic differences in DNA repair capacity were observed in various populations. Hence, our study aimed to determine the prevalence of three nonsynonymous single-nucleotide polymorphisms (SNPs) in an X-ray repair cross-complementation group 1 gene (XRCC1) (Arg194Trp, Arg280His, and Arg399Gln) in a healthy Tunisian population (TUN) and to compare that with HapMap ( www.hapmap.org ) populations. Also, we predicted their eventual functional effect based on the protein conservation analysis by Sorting Intolerant From Tolerant (SIFT; http://sift.jcvi.org/www/SIFT_dbSNP.html ) software. The genotypes of 154 healthy individuals were determined by the polymerase chain reaction-restriction fragment length polymorphism. Tunisians showed a relative relatedness with Caucasians (European ancestry) for Arg194Trp and Arg399Gln that may be explained by the strategic geographic location of Tunisia in the Mediterranean, allowing exchanges with European countries. However, a characteristic pattern was observed in Arg280His polymorphism, which could be explained by the high inbreeding rate in TUN. The analysis of protein conservation showed that the three amino acid substitutions were predicted as damaged. The results presented here provide the first report on XRCC1 polymorphisms about Tunisians and may establish baseline database for our future clinical and genetic studies.

IL-1ß a potential factor for discriminating between thyroid carcinoma and atrophic thyroiditis.

Interactions between cytokines and others soluble factors (hormones, antibodies...) can play an important role in the development of thyroid pathogenesis. The purpose of the present study was to examine the possible correlation between serum cytokine concentrations, thyroid hormones (FT4 and TSH) and auto-antibodies (Tg and TPO), and their usefulness in discriminating between different thyroid conditions. In this study, we investigated serum from 115 patients affected with a variety of thyroid conditions (44 Graves' disease, 17 Hashimoto's thyroiditis, 11 atrophic thyroiditis, 28 thyroid nodular goitre and 15 papillary thyroid cancer), and 30 controls. Levels of 17 cytokines in serum samples were measured simultaneously using a multiplexed human cytokine assay. Thyroid hormones and auto-antibodies were measured using ELISA. Our study showed that IL-1ß serum concentrations allow the discrimination between atrophic thyroiditis and papillary thyroid cancer groups (p = 0.027).

An interethnic variability and a functional prediction of DNA repair gene polymorphisms: the example of XRCC3 (p.Thr241>Met) and XPD (p.Lys751>Gln) in a healthy Tunisian population.

Genetic polymorphisms in DNA repair genes might influence the repair activities of the enzymes predisposing individuals to cancer risk. Owing to the presence of these genetic variants, interethnic differences in DNA repair capacity have been observed in various populations. The present study was undertaken to determine the allele and genotype frequencies of two common non-synonymous SNPs, XRCC3 p.Thr241>Met (C > T, rs861539) and XPD p.Lys751>Gln (T > G, rs13181) in a healthy Tunisian population and to compare them with HapMap ( http://www.hapmap.org/ ) populations. Also, we predicted their eventual functional effect based on bioinformatics tools. The genotypes of 154 healthy and unrelated individuals were determined by PCR-RFLP procedure. Our findings showed a close relatedness with Caucasians from European ancestry which might be explained by the strategic geographic location of Tunisia in the Mediterranean, thus allowing exchanges with Europeans countries. The in silico predictions showed that p.Thr241>Met substitution in XRCC3 protein was predicted as possibly damaging, indicating that it is likely to have functional consequences as well. To the best of our knowledge, this is the first study in this regard in Tunisia. So, these data could provide baseline database and help us to explore the relationship of XRCC3 and XPD polymorphisms with both cancer risk and DNA repair variability in our population.

Segregation of a new mutation in SLC26A4 and p.E47X mutation in GJB2 within a consanguineous Tunisian family affected with Pendred syndrome.

OBJECTIVE: Recessive mutations of the SLC26A4 (PDS) gene on chromosome 7q31 can cause sensorineural hearing loss with goiter (Pendred syndrome) or non-syndromic autosomal recessive hearing loss (DFNB4). Furthermore, mutations in the GJB2 gene results in autosomal recessive (DFNB1) and dominant (DFNA3) non-syndromic hearing loss. The aim of the present study was to characterize a family with Pendred syndrome affected by severe to profound HL and presenting goiter. METHODS: Affected members underwent detailed audiologic examination and characterization. DNA samples from family members were genotyped with polymorphic microsatellite markers and sequencing of the SLC26A4 and GJB2 genes was performed. A total of 25 families with non-syndromic hearing loss were screened for the common p.E47X mutation in the GJB2 gene by direct dideoxy sequencing. RESULTS: Genetic microsatellite analysis showed linkage to the 7q22-q31 chromosomal region and mutation analysis revealed a novel frameshift mutation (c.451delG) in the SLC26A4 gene. Screening of the GJB2 gene in one patient, displayed a homozygous p.E47X mutation, together with a heterozygous c.451delG mutation. Screening of 25 families with HL showed frequent segregation of the p.E47X mutation, which was homozygous in five of these families. Haplotype analysis using microsatellite markers and single nucleotide polymorphisms (SNPs) closely flanking the GJB2 gene, revealed the presence of two disease-associated-haplotypes suggesting the presence of at least, two founder effects carrying the p.E47X non-sense mutation in the Tunisian population. CONCLUSIONS: The segregation of both SLC26A4 and GJB2 mutations in the family illustrates once again the unexpected intra-familial genetic heterogeneity in consanguineous families and highlights the difficulty of genetic counselling in such families. In addition, our results disclose the existence of founder effects in the Tunisian population.

A novel missense mutation in the ESRRB gene causes DFNB35 hearing loss in a Tunisian family.

Autosomal recessive non-syndromic hearing loss (ARNSHL) is a genetically heterogenous disorder with 41 genes so far identified. Among these genes, ESRRB whose mutations are responsible for DFNB35 hearing loss in Pakistani and Turkish families. This gene encodes the estrogen-related receptor beta. In this study, we report a novel mutation (p.Y305H) in the ESRRB gene in a Tunisian family with ARNSHL. This mutation was not detected in 100 healthy individuals. Molecular modeling showed that the p.Y305H mutation is likely to alter the conformation of the ligand binding-site by destabilizing the coactivator binding pocket. Interestingly, this ligand-binding domain of the ESRRB protein has been affected in 5 out of 6 mutations causing DFNB35 hearing loss. Using linkage and DHPLC analysis, no more mutations were detected in the ESRRB gene in other 127 Tunisian families with ARNSHL indicating that DFNB35 is most likely to be a rare type of ARNSHL in the Tunisian population.

DFNB66 and DFNB67 loci are non allelic and rarely contribute to autosomal recessive nonsyndromic hearing loss.

We previously mapped the DFNB66 locus to an interval overlapping the DFNB67 region. Mutations in the LHFPL5 gene were identified as a cause of DFNB67 hearing loss (HL). However, screening of the coding exons of LHFPL5 did not reveal any mutation in the DFNB66 family. The objective of this study was to check whether DFNB66 and DFNB67 are distinctive loci and determining their contribution to HL. In the DFNB66 family, sequencing showed absence of mutations in the untranslated regions and the predicted promoter sequence of LHFPL5. Analysis of five microsatellites in the 6p21.31-22.3 region and screening of the LHFPL5 gene by DNA heteroduplex analysis in DHPLC revealed a novel mutation (c.89dup) in one out of 129 unrelated Tunisian families with autosomal recessive nonsyndromic (ARNS) HL. Our findings suggest that two distinct genes are responsible for DFNB66 and DFNB67 HL. These loci are likely to be a rare cause of ARNSHL.

Genotyping of Tunisian azoospermic men with Sertoli cell-only and maturation arrest.

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