Whole-exome screening for primary congenital glaucoma in Lebanon

PURPOSE

Mutations were previously identified in the CYP1B1 gene in six out of 18 Lebanese families (33%) with primary congenital glaucoma (PCG). The purpose of this study is to determine the frequency and type of pathogenic mutations in other genes and compare to other populations using whole-exome sequencing and perform genotype-phenotype correlations.

METHODS

Twelve PCG patients previously negative for CYP1B1/MYOC mutations were subjected to whole-exome sequencing. Targeted screening for glaucoma-associated genes was performed. Candidate variants were verified by Sanger sequencing and evaluated in family members for segregation analysis and in 100 normal controls. Clinical correlations were established as to severity of disease presentation, course, and visual outcomes.

RESULTS

Six mutations in known PCG-causing genes were identified in five patients: homozygous mutations in CYP1B1 (p.R368G), LTBP2 (p.E1013G), and TEK (p.T693I), and heterozygous mutations in FOXC1 (p.Q92*), TEK (c.3201-1 G>A), ANGPT1 (p.K186N), and CYP1B1 (p.R368G). Two patients, negative for CYP1B1 in the previous study, were revealed positive in the current study, due to different sets of primers and PCR conditions. Potentially damaging variants were noted in several candidate genes. Except for FOXC1 mutations, all genetic variants described here are novel. Intra-ocular pressure and final optic nerve cup-to-disc ratio were highest in the patient with three mutations in LTBP2/TEK/ANGPT1 genes.

CONCLUSION

This study provides new data on the spectrum of mutations of PCG in Lebanon. This highlights the genetic heterogeneity of the Lebanese population, noted for high rates of consanguinity in 50% in this cohort. This study emphasizes the importance of whole-exome sequencing in elucidating new candidate genes for PCG in the Lebanese.

Developmental Comparison of Ceramide in Wild-Type and Cln3 Δex7/8 Mouse Brains and Sera

CLN3 disease is a neurodevelopmental disease leading to early visual failure, motor decline, and death. CLN3 pathogenesis has been linked to dysregulation of ceramide, a key intracellular messenger impacting various biological functions. Ceramide is upregulated in brains of CLN3 patients and activates apoptosis. Ceramide levels over the lifespan of WT and Cln3^Δex7/8 mice were measured using the DGK assay. Ceramide subspecies were determined by LC-MS. Ceramide synthesis enzymes and pre- and post-synaptic mRNA expression was measured in Cln3^Δex7/8 and normal mouse brains. Neuronal cell death was established by PARP cleavage and Caspases 3/6/9 and cytochrome C mRNA expression in Cln3^Δex7/8 and normal mouse brains. In WT mouse, a ceramide peak was noted at 3 weeks of age. The absence of this peak in Cln3^Δex7/8 mice might be related to early disease pathogenesis. Increase of ceramide in Cln3^Δex7/8 mouse brain at 24 weeks of age precedes neuronal apoptosis. The correlation between serum and brain ceramide in WT mice, and dysregulation of ceramide in serum and brain of Cln3^Δex7/8 mice, and the significant increase in ceramide in Cln3^Δex7/8 mouse brains and sera argue for use of easily accessible serum ceramide levels to track response to novel therapies in human CLN3 disease.

RYR2, PTDSS1 and AREG genes are implicated in a Lebanese population-based study of copy number variation in autism

Autism Spectrum Disorders (ASDs) are a group of neurodevelopmental disorders characterized by ritualistic-repetitive behaviors and impaired verbal and non-verbal communication. Objectives were to determine the contribution of genetic variation to ASDs in the Lebanese. Affymetrix Cytogenetics Whole-Genome 2.7 M and CytoScan(™) HD Arrays were used to detect CNVs in 41 Lebanese autistic children and 35 non-autistic, developmentally delayed and intellectually disabled patients. 33 normal participants were used as controls. 16 de novo CNVs and 57 inherited CNVs, including recognized pathogenic 16p11.2 duplications and 2p16.3 deletions were identified. A duplication at 1q43 classified as likely pathogenic encompasses RYR2 as a potential ASD candidate gene. This previously identified CNV has been classified as both pathogenic, and, of uncertain significance. A duplication of unknown significance at 10q11.22, proposed as a modulator for phenotypic disease expression in Rett syndrome, was also identified. The novel potential autism susceptibility genes PTDSS1 and AREG were uncovered and warrant further genetic and functional analyses. Previously described and novel genetic targets in ASD were identified in Lebanese families with autism. These findings may lead to improved diagnosis of ASDs and informed genetic counseling, and may also lead to untapped therapeutic targets applicable to Lebanese and non-Lebanese patients.

Association between CLN3 (Neuronal Ceroid Lipofuscinosis, CLN3 Type) Gene Expression and Clinical Characteristics of Breast Cancer Patients

Breast cancer is the most common cancer in women worldwide. Elucidation of underlying biology and molecular pathways is necessary for improving therapeutic options and clinical outcomes. CLN3 protein (CLN3p), deficient in neurodegenerative CLN3 disease is anti-apoptotic, and defects in the CLN3 gene cause accelerated apoptosis of neurons in CLN3 disease and up-regulation of ceramide. Dysregulated apoptotic pathways are often implicated in the development of the oncogenic phenotype. Predictably, CLN3 mRNA expression and CLN3 protein were up-regulated in a number of human and murine breast cancer-cell lines. Here, we determine CLN3 expression in non-tumor vs. tumor samples from fresh and formalin-fixed/paraffin-embedded (FFPE) breast tissue and analyze the association between CLN3 overexpression and different clinicopathological characteristics of breast cancer patients. Additionally, gene expression of 28 enzymes involved in sphingolipid metabolism was determined. CLN3 mRNA is overexpressed in tumor vs. non-tumor breast tissue from FFPE and fresh samples, as well as in mouse MCF7 breast cancer compared to MCF10A normal cells. Of the clinicopathological characteristics of tumor grade, age, menopause status, estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2), only absence of HER2 expression correlated with CLN3 overexpression. Sphingolipid genes for ceramide synthases 2 and 6 (CerS2; CerS6), delta(4)-desaturase sphingolipid 2 (DEGS2), and acidic sphingomyelinase (SMPD1) displayed higher expression levels in breast cancer vs. control tissue, whereas ceramide galactosyltransferase (UGT8) was underexpressed in breast cancer samples. CLN3 may be a novel molecular target for cancer drug discovery with the goal of modulation of ceramide pathways.

Prediabetic changes in gene expression induced by aspartame and monosodium glutamate in Trans fat-fed C57Bl/6 J mice

BACKGROUND

The human diet has altered markedly during the past four decades, with the introduction of Trans hydrogenated fat, which extended the shelf-life of dietary oils and promoted a dramatic increase in elaidic acid (Trans-18.1) consumption. Food additives such as monosodium glutamate (MSG) and aspartame (ASP) were introduced to increase food palatability and reduce caloric intake. Nutrigenomics studies in small-animal models are an established platform for analyzing the interactions between various macro- and micronutrients. We therefore investigated the effects of changes in hepatic and adipose tissue gene expression induced by the food additives ASP, MSG or a combination of both additives in C57Bl/6 J mice fed a Trans fat-enriched diet.

METHODS

Hepatic and adipose tissue gene expression profiles, together with body characteristics, glucose parameters, serum hormone and lipid profiles were examined in C57Bl/6 J mice consuming one of the following four dietary regimens, commencing in utero via the mother's diet: [A] Trans fat (TFA) diet; [B] MSG + TFA diet; [C] ASP + TFA diet; [D] ASP + MSG + TFA diet.

RESULTS

Whilst dietary MSG significantly increased hepatic triglyceride and serum leptin levels in TFA-fed mice, the combination of ASP + MSG promoted the highest increase in visceral adipose tissue deposition, serum free fatty acids, fasting blood glucose, HOMA-IR, total cholesterol and TNFα levels. Microarray analysis of significant differentially expressed genes (DEGs) showed a reduction in hepatic and adipose tissue PPARGC1a expression concomitant with changes in PPARGC1a-related functional networks including PPARα, δ and γ. We identified 73 DEGs common to both adipose and liver which were upregulated by ASP + MSG in Trans fat-fed mice; and an additional 51 common DEGs which were downregulated.

CONCLUSION

The combination of ASP and MSG may significantly alter adiposity, glucose homeostasis, hepatic and adipose tissue gene expression in TFA-fed C57Bl/6 J mice.

Interactive effects of neonatal exposure to monosodium glutamate and aspartame on glucose homeostasis

BACKGROUND

Recent evidence suggests that the effects of certain food additives may be synergistic or additive. Aspartame (ASP) and Monosodium Glutamate (MSG) are ubiquitous food additives with a common moiety: both contain acidic amino acids which can act as neurotransmitters, interacting with NMDA receptors concentrated in areas of the Central Nervous System regulating energy expenditure and conservation. MSG has been shown to promote a neuroendocrine dysfunction when large quantities are administered to mammals during the neonatal period. ASP is a low-calorie dipeptide sweetener found in a wide variety of diet beverages and foods. However, recent reports suggest that ASP may promote weight gain and hyperglycemia in a zebrafish nutritional model.

METHODS

We investigated the effects of ASP, MSG or a combination of both on glucose and insulin homeostasis, weight change and adiposity, in C57BL/6 J mice chronically exposed to these food additives commencing in-utero, compared to an additive-free diet. Pearson correlation analysis was used to investigate the associations between body characteristics and variables in glucose and insulin homeostasis.

RESULTS

ASP alone (50 mg/Kgbw/day) caused an increase in fasting blood glucose of 1.6-fold, together with reduced insulin sensitivity during an Insulin Tolerance Test (ITT) P < 0.05. Conversely MSG alone decreased blood triglyceride and total cholesterol (T-CHOL) levels. The combination of MSG (120 mg/Kgbw/day) and ASP elevated body weight, and caused a further increase in fasting blood glucose of 2.3-fold compared to Controls (prediabetic levels); together with evidence of insulin resistance during the ITT (P < 0.05). T-CHOL levels were reduced in both ASP-containing diets in both genders. Further analysis showed a strong correlation between body weight at 6 weeks, and body weight and fasting blood glucose levels at 17 weeks, suggesting that early body weight may be a predictor of glucose homeostasis in later life.

CONCLUSIONS

Aspartame exposure may promote hyperglycemia and insulin intolerance. MSG may interact with aspartame to further impair glucose homeostasis. This is the first study to ascertain the hyperglycemic effects of chronic exposure to a combination of these commonly consumed food additives; however these observations are limited to a C57BL/6 J mouse model. Caution should be applied in extrapolating these findings to other species.

Gender dimorphism in aspartame-induced impairment of spatial cognition and insulin sensitivity

Previous studies have linked aspartame consumption to impaired retention of learned behavior in rodents. Prenatal exposure to aspartame has also been shown to impair odor-associative learning in guinea pigs; and recently, aspartame-fed hyperlipidemic zebrafish exhibited weight gain, hyperglycemia and acute swimming defects. We therefore investigated the effects of chronic lifetime exposure to aspartame, commencing in utero, on changes in blood glucose parameters, spatial learning and memory in C57BL/6J mice. Morris Water Maze (MWM) testing was used to assess learning and memory, and a random-fed insulin tolerance test was performed to assess glucose homeostasis. Pearson correlation analysis was used to investigate the associations between body characteristics and MWM performance outcome variables. At 17 weeks of age, male aspartame-fed mice exhibited weight gain, elevated fasting glucose levels and decreased insulin sensitivity compared to controls (P<0.05). Females were less affected, but had significantly raised fasting glucose levels. During spatial learning trials in the MWM (acquisition training), the escape latencies of male aspartame-fed mice were consistently higher than controls, indicative of learning impairment. Thigmotactic behavior and time spent floating directionless was increased in aspartame mice, who also spent less time searching in the target quadrant of the maze (P<0.05). Spatial learning of female aspartame-fed mice was not significantly different from controls. Reference memory during a probe test was affected in both genders, with the aspartame-fed mice spending significantly less time searching for the former location of the platform. Interestingly, the extent of visceral fat deposition correlated positively with non-spatial search strategies such as floating and thigmotaxis, and negatively with time spent in the target quadrant and swimming across the location of the escape platform. These data suggest that lifetime exposure to aspartame, commencing in utero, may affect spatial cognition and glucose homeostasis in C57BL/6J mice, particularly in males.

Nutrigenomics of hepatic steatosis in a feline model: effect of monosodium glutamate, fructose, and Trans-fat feeding

Nonalcoholic fatty liver disease begins with a relatively benign hepatic steatosis, often associated with increased adiposity, but may progress to a more severe nonalcoholic steatohepatitis with inflammation. A subset of these patients develops progressive fibrosis and ultimately cirrhosis. Various dietary components have been shown to contribute to the development of liver disease, including fat, sugars, and neonatal treatment with high doses of monosodium glutamate (MSG). However, rodent models of progressive disease have been disappointing, and alternative animal models of diet-induced liver disease would be desirable, particularly if they contribute to our knowledge of changes in gene expression as a result of dietary manipulation. The domestic cat has previously been shown to be an appropriate model for examining metabolic changes-associated human diseases such as diabetes. Our aim was therefore to compare changes in hepatic gene expression induced by dietary MSG, with that of a diet containing Trans-fat and high fructose corn syrup (HFCS), using a feline model. MSG treatment increased adiposity and promoted hepatic steatosis compared to control (P < 0.05). Exposure to Trans-fat and HFCS promoted hepatic fibrosis and markers of liver dysfunction. Affymetrix microarray analysis of hepatic gene expression showed that dietary MSG promoted the expression of genes involved in cholesterol and steroid metabolism. Conversely, Trans-fat and HFCS feeding promoted the expression of genes involved in lipolysis, glycolysis, liver damage/regeneration, and fibrosis. Our feline model examining gene-diet interactions (nutrigenomics) demonstrates how dietary MSG, Trans-fat, and HFCS may contribute to the development of hepatic steatosis.

Sex-dimorphism in cardiac nutrigenomics: effect of trans fat and/or monosodium glutamate consumption

BACKGROUND

A paucity of information on biological sex-specific differences in cardiac gene expression in response to diet has prompted this present nutrigenomics investigation. Sexual dimorphism exists in the physiological and transcriptional response to diet, particularly in response to high-fat feeding. Consumption of Trans-fatty acids (TFA) has been linked to substantially increased risk of heart disease, in which sexual dimorphism is apparent, with males suffering a higher disease rate. Impairment of the cardiovascular system has been noted in animals exposed to Monosodium Glutamate (MSG) during the neonatal period, and sexual dimorphism in the growth axis of MSG-treated animals has previously been noted. Processed foods may contain both TFA and MSG.

METHODS

We examined physiological differences and changes in gene expression in response to TFA and/or MSG consumption compared to a control diet, in male and female C57BL/6J mice.

RESULTS

Heart and % body weight increases were greater in TFA-fed mice, who also exhibited dyslipidemia (P < 0.05). Hearts from MSG-fed females weighed less than males (P < 0.05). 2-factor ANOVA indicated that the TFA diet induced over twice as many cardiac differentially expressed genes (DEGs) in males compared to females (P < 0.001); and 4 times as many male DEGs were downregulated including Gata4, Mef2d and Srebf2. Enrichment of functional Gene Ontology (GO) categories were related to transcription, phosphorylation and anatomic structure (P < 0.01). A number of genes were upregulated in males and downregulated in females, including pro-apoptotic histone deacetylase-2 (HDAC2). Sexual dimorphism was also observed in cardiac transcription from MSG-fed animals, with both sexes upregulating approximately 100 DEGs exhibiting sex-specific differences in GO categories. A comparison of cardiac gene expression between all diet combinations together identified a subset of 111 DEGs significant only in males, 64 DEGs significant in females only, and 74 transcripts identified as differentially expressed in response to dietary manipulation in both sexes.

CONCLUSION

Our model identified major changes in the cardiac transcriptional profile of TFA and/or MSG-fed mice compared to controls, which was reflected by significant differences in the physiological profile within the 4 diet groups. Identification of sexual dimorphism in cardiac transcription may provide the basis for sex-specific medicine in the future.

Effect of dietary monosodium glutamate on HFCS-induced hepatic steatosis: expression profiles in the liver and visceral fat

It has previously been shown that patients with nonalcoholic fatty liver disease (NAFLD) exhibit alterations in both hepatic and adipose tissue metabolism, and the dietary factors that contribute to the pathogenesis of NAFLD are likely to be multifactorial. Using C57BL/6J mice, we examined whether chronic exposure to low-dose dietary monosodium glutamate (MSG), high-fructose corn syrup (HFCS), or a combination of the two, vs. control would affect metabolism and hepatic and visceral fat gene expression in adult male progeny. A maternal diet containing 20% HFCS and/or dietary MSG (97.2 +/- 6.3 mg/kg body weight (bw), provided in the drinking water) was offered ad libitum from 3 weeks before mating, and continued throughout gestation and weaning until the progeny reached 32 weeks of age. Liver and abdominal fat gene expression was compared with control animals fed isocaloric standard chow under identical conditions. HFCS induced hepatic steatosis and increased the expression of genes involved in carbohydrate and lipid metabolism. Conversely, dietary MSG elevated serum free fatty acids (FFAs), triglycerides (TGs), high-density lipoprotein-cholesterol (HDL-C), and insulin, together with the expression of hepatic genes involved in lipid metabolism and bile synthesis. The HFCS+MSG combination elevated hepatic TGs, serum FFAs, and TG levels. In visceral white adipose tissue, both MSG and HFCS diets increased the expression of transcription factor Srebf2 and decreased expression of Ppargc1a, while downregulating the expression of mitochondrial respiratory chain components. MSG increased the expression of several genes implicated in adipocytes differentiation. We hypothesize that HFCS may promote hepatic steatosis, whereas dietary MSG induces dyslipidemia and markers of insulin resistance.

Diabetes of the liver: the link between nonalcoholic fatty liver disease and HFCS-55

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity and insulin resistance. It is also a predisposing factor for type 2 diabetes. Dietary factors are believed to contribute to all three diseases. NAFLD is characterized by increased intrahepatic fat and mitochondrial dysfunction, and its etiology may be attributed to excessive fructose intake. Consumption of high fructose corn syrup-55 (HFCS-55) stands at up to 15% of the average total daily energy intake in the United States, and is linked to weight gain and obesity. The aim of this study was to establish whether HFCS-55 could contribute to the pathogenesis of NAFLD, by examining the effects of HFCS-55 on hepatocyte lipogenesis, insulin signaling, and cellular function, in vitro and in vivo. Exposure of hepatocytes to HFCS-55 caused a significant increase in hepatocellular triglyceride (TG) and lipogenic proteins. Basal production of reactive oxygen metabolite (ROM) was increased, together with a decreased capacity to respond to an oxidative challenge. HFCS-55 induced a downregulation of the insulin signaling pathway, as indicated by attenuated (ser473)phosphorylation of AKT1. The c-Jun amino-terminal kinase (JNK), which is intimately linked to insulin resistance, was also activated; and this was accompanied by an increase in endoplasmic reticulum (ER) stress and intracellular free calcium perturbation. Hepatocytes exposed to HFCS-55 exhibited mitochondrial dysfunction and released cytochrome C (CytC) into the cytosol. Hepatic steatosis and mitochondrial disruption was induced in vivo by a diet enriched with 20% HFCS 55; accompanied by hypoadiponectinemia and elevated fasting serum insulin and retinol-binding protein-4 (RBP4) levels. Taken together our findings indicate a potential mechanism by which HFCS-55 may contribute to the pathogenesis of NAFLD.

Effect of dietary monosodium glutamate on trans fat-induced nonalcoholic fatty liver disease

The effects of dietary monosodium glutamate (MSG) on trans-fatty acid (TFA)-induced nonalcoholic fatty liver disease (NAFLD) are addressed in an animal model. We used Affymetrix microarray analysis to investigate hepatic gene expression and the contribution of visceral white adipose tissue (WAT) to diet-induced NAFLD. Trans-fat feeding increased serum leptin, FFA, HDL-cholesterol (HDL-C), and total cholesterol (T-CHOL) levels, while robustly elevating the expression of genes involved in hepatic lipogenesis, including the transcription factor sterol-regulatory element binding protein 1c. Histological examination revealed hepatic macrosteatosis in TFA-fed animals. Conversely, dietary MSG at doses similar to human average daily intake caused hepatic microsteatosis and the expression of beta-oxidative genes. Serum triglyceride, FFA, and insulin levels were elevated in MSG-treated animals. The abdominal cavities of TFA- or MSG-treated animals had increased WAT deposition compared with controls. Microarray analysis of WAT gene expression revealed increased lipid biosynthetic gene expression, together with a 50% decrease in the key transcription factor Ppargc1a. A combination of TFA+MSG resulted in the highest levels of serum HDL-C, T-CHOL, and leptin. Microarray analysis of TFA+MSG-treated livers showed elevated expression of markers of hepatic inflammation, lipid storage, cell damage, and cell cycle impairment. TFA+MSG mice also had a high degree of WAT deposition and lipogenic gene expression. Levels of Ppargc1a were further reduced to 25% by TFA+MSG treatment. MSG exacerbates TFA-induced NAFLD.

WFS1 mutations are frequent monogenic causes of juvenile-onset diabetes mellitus in Lebanon

Most cases of juvenile-onset diabetes (JOD) are diagnosed as type 1 diabetes (T1D), for which genetic studies conducted in outbred Caucasian populations support the concept of multifactorial inheritance. However, this view may be partly challenged in particular population settings. In view of the suggestive evidence for a high prevalence of Wolfram syndrome (WFS) in Lebanon, the phenotypic variability associated with WFS1 mutations, and the high consanguinity rate in Lebanon, we aimed to evaluate the contribution of WFS1 mutations as monogenic determinants to JOD in Lebanon. We performed a family-based genetic study, with linkage analysis followed by systematic mutation screening of WFS1 exons in all JOD probands. The study population consisted of an unbiased recruitment of all juvenile-onset insulin-dependent diabetic patients from a specialized diabetes pediatric clinic in Beirut, Lebanon. Homozygous or compound heterozygous WFS1 mutations were found in 22 of the 399 JOD probands (5.5%), resulting in WFS (17 probands) or in non-syndromic non-autoimmune diabetes mellitus (DM, five probands). These accounted for 12.1% (21/174) of probands in consanguineous families, compared with 0.4% (1/225) in non-consanguineous families. Of the 38 patients identified with homozygous or compound heterozygous WFS1 mutations, 11 (29%) had non-syndromic DM, all of whom carried a particular WFS1 mutation, WFS1(LIB), encoding a protein with an extended C-terminal domain. This mutation resulted in a delayed onset or absence of extrapancreatic features. These results underscore the major impact of population-specific factors, such as population-specific mutations and founder effects, and family structure in the genetic determinism of JOD.

Zidovudine and interferon-alpha treatment induces a high response rate and reduces HTLV-1 proviral load and VEGF plasma levels in patients with adult T-cell leukemia from North East Iran

Human T-cell lymphotropic virus type I (HTLV-I) associated adult T-cell leukemia/lymphoma (ATLL) is endemic in southern Japan, the Caribbean, intertropical Africa, and Brazil. Recently north east Iran, particularly the region of Mashhad, has been recognized as a new endemic region. ATLL is an aggressive T-cell lymphoproliferative disorder. Patients with ATLL have high plasma levels of VEGF that induce angiogenesis. Prognosis of ATLL remains poor because of immunosuppression and intrinsic resistance to chemotherapy. Important advances in the treatment of ATLL were reported with the combination of zidovudine (AZT) and interferon-alpha. We investigated the effect of AZT/IFN treatment on vascular endothelium growth factor (VEGF) plasma levels and HTLV-I proviral load in ATLL patients from the region of Mashhad. We confirmed that AZT/IFN treatment induces a high response rate and prolonged survival with minimal side effects. We also confirmed that VEGF plasma levels and HTLV-I proviral load are higher in ATLL patients than in asymptomatic carriers. We finally showed that AZT/IFN treatment reduced both HTLV-I proviral load and importantly VEGF plasma levels, suggesting a potential antiangiogenic effect of this therapy. These results provide further evidence for the efficacy and the mechanism of action of AZT/IFN therapy for ATLL in a developing country.

The consanguinity effect on QF-PCR diagnosis of autosomal anomalies

OBJECTIVES

Quantitative Fluorescent PCR (QF-PCR) is a simpler and faster method of detecting common chromosomal abnormalities when compared to cytogenetic analysis. The aim of our study is to investigate the applicability of this methodology in a population where consanguineous marriages are common and to estimate the heterozygous frequency of the PCR markers used.

METHODS

Four hundred and twenty-three DNA samples were extracted from uncultured amniocytes and amplified with 18 short tandem repeats (STR) markers specific to chromosomes 13, 18 and 21. Amplification products were analyzed using the GeneScan software.

RESULTS

QF-PCR correctly identified all the numerical abnormalities related to chromosomes 13, 18 and 21. A total of 24 autosomal trisomies (5.7%) were detected. The markers D21S1432 and D21S11 were the most consistent in providing unequivocal positive results for chromosome 21 and the heterozygosity percentages of the markers used were lower than the values reported in Western populations.

CONCLUSION

QF-PCR is reliable for the prenatal diagnosis of numerical anomalies of the chromosomes 13, 18 and 21 in our study population. The absence of STR heterozygosity data from Lebanon and surrounding countries makes our study very useful for the development of a reliable QF-PCR trisomy detection test.

Genetic Heterogeneity of Beta Thalassemia in Lebanon Reflects Historic and Recent Population Migration

Beta thalassemia is an autosomal recessive disorder characterized by reduced (beta(+)) or absent (beta(0)) beta-globin chain synthesis. In Lebanon it is the most predominant genetic defect. In this study we investigated the religious and geographic distribution of the beta-thalassemia mutations identified in Lebanon, and traced their precise origins. A total of 520 beta-globin chromosomes from patients of different religious and regional backgrounds was studied. Beta thalassemia mutations were identified using Amplification Refractory Mutation System (ARMS) PCR or direct gene sequencing. Six (IVS-I-110, IVS-I-1, IVS-I-6, IVS-II-1, cd 5 and the C > T substitution at cd 29) out of 20 beta-globin defects identified accounted for more than 86% of the total beta-thalassemia chromosomes. Sunni Muslims had the highest beta-thalassemia carrier rate and presented the greatest heterogeneity, with 16 different mutations. Shiite Muslims followed closely with 13 mutations, whereas Maronites represented 11.9% of all beta-thalassemic subjects and carried 7 different mutations. RFLP haplotype analysis showed that the observed genetic diversity originated from both new mutational events and gene flow from population migration. This study provides information about the types and distribution of beta-thalassemia mutations within each religious group and geographic region, which is essential for the implementation of screening and prevention programs.

Accurate and rapid prenatal diagnosis of the most frequent East Mediterranean beta-thalassemia mutations

Beta-thalassemia is the most common genetic disorder in the Lebanese population. Of the 200 different mutations in the beta-globin gene that leads to thalassemia, the IVSI-110 (29.87%), IVSI-6 (20.74%), IVSI-1 (14.07%), IVSII-1 (9.13%), Cd29 (9.13%), and Cd30 (3.95%) mutations are the most frequent among Lebanese thalassemic patients. These mutations are also present at high frequencies in the East Mediterranean region. Due to this high prevalence of certain beta-thalassemia mutations, a rapid technique for the prenatal diagnosis of these mutations was implemented. The technique used is based on Real-Time PCR quantification and melting curve analysis of the amplified fragment using the LightCycler. The DNA samples used for amplification were obtained from CVS or amniotic fluid. Six mutations were easily and efficiently detected using only 3 sets of probes. With this method, mutant genotypes can be easily distinguished from normal alleles. In prenatal diagnosis, the accuracy and the speed of testing are paramount. The method of prenatal beta-thalassemia mutations detection described here is efficient and fast, with the entire procedure including DNA preparation taking less than half a workday. It is safe, does not involve radioactivity, and is accurate showing 100% concordance with conventional DNA sequencing methods.