Genetic insights into fetal kidney development: Variants in HNF1A and PKHD1 genes.

The orchestration of fetal kidney development involves the precise control of numerous genes, including HNF1A, HNF1B and PKHD1. Understanding the genetic factors influencing fetal kidney development is essential for unraveling the complexities of renal disorders. This study aimed to search for disease-causing variants in HNF1A, HNF1B, PKHD1 genes, among fetus and babies or via parental samples, using sanger sequencing, NGS technologie and MLPA. The study revealed an absence of gene deletions and disease-causing variants in the HNF1B gene. However, five previously SNPs in the HNF1A gene were identified in four patients (patients 1, 2, 3, and 4). These include c.51C > G (Exon1, p. Leu17=), c.79A > C (Exon1, p. Ile27Leu), c.1375C > T (Exon7, p. Leu459=), c.1460G > A (Exon7, p. Ser487Asn), and c.1501 + 7G > A (Intron7). Additionally, in addition to previously SNPs identified, a de novo heterozygous missense mutation (p.E508K) was detected in patient 4. Furthermore, a heterozygous mutation in exon 16 (p. Arg494*; c.1480C >T) was identified in both parents of patient 5, allowing predictions of fetal homozygosity. Bioinformatic analyses predicted the effects of the c.1522G > A mutation (p.E508K) on splicing processes, pre-mRNA structures, and protein instability and conformation. Similarly, the c.1480C > T mutation (p. Arg494*) was predicted to introduce a premature codon stop, leads to the production of a shorter protein with altered or impaired function. Identification of variants in the HNF1A and in PKHD1 genes provides valuable insights into the genetic landscape of renal abnormalities in affected patients. These findings underscore the heterogeneity of genetic variants contributing to renal disorders and emphasize the importance of genetic screening.

Strategies for diagnosis and management of CMMRD in low-resource countries: report of a Tunisian family.

Constitutional Mismatch Repair Deficiency (CMMRD) is a rare childhood cancer predisposition syndrome, caused by biallelic pathogenic germline variants in the mismatch repair genes. Diagnosis and management of this syndrome is challenging, especially in low-resource settings. This study describes a patient diagnosed with colorectal cancer and grade 3 astrocytoma at the age of 11 and 12 respectively. Immunohistochemistry analysis showed a loss of MSH2 and MSH6 protein expression in CRC tissues of the patient. We identified by Targeted Exome Sequencing a homozygous pathogenic germline variant in exon 9 of the MSH6 gene (c.3991 C > T; p.Ala1268Glyfs*6). Genetic investigation of the family showed that the father was heterozygous for the identified pathogenic variant while the brother was wild type for this variant. Our study highlights the importance of a correct and timely diagnosis of CMMRD which can have implications for treatment. It also underlines the imperative need to enhance awareness, diagnostic standards, and surveillance that are crucial for patients and their families.

An unusual familial Xp22.12 microduplication including EIF1AX: A novel candidate dosage-sensitive gene for premature ovarian insufficiency.

We report on the results of array-CGH and Whole exome sequencing (WES) studies carried out in a Tunisian family with 46,XX premature ovarian insufficiency (POI). This study has led to the identification of a familial Xp22.12 tandem duplication with a size of 559.4 kb, encompassing only three OMIM genes (RPS6KA3, SH3KBP1and EIF1AX), and a new heterozygous variant in SPIDR gene: NM_001080394.3:c.1845_1853delTATAATTGA (p.Ile616_Asp618del) segregating with POI. Increased mRNA expression levels were detected for SH3KBP1 and EIF1AX, while a normal transcript level for RPS6KA3 was detected in the three affected family members, explaining the absence of intellectual disability (ID). To the best of our knowledge, this is the first duplication involving the Xp22.12 region, reported in a family without ID, but rather with secondary amenorrhea (SA) and female infertility. As EIF1AX is a regulatory gene escaping X-inactivation, which has an extreme dosage sensitivity and highly expressed in the ovary, we suggest that this gene might be a candidate gene for ovarian function. Homozygous nonsense pathogenic variants of SPIDR gene have been reported in familial cases in POI. It has been suggested that chromosomal instability associated with SPIDR molecular defects supports the role of SPIDR protein in double-stranded DNA damage repair in vivo in humans and its causal role in POI. In this family, the variant (p.Ile616_Asp618del), present in a heterozygous state, is located in the domain that interacts with BLM and might disrupt the BLM binding ability of SPIDR protein. These findings strengthen the hypothesis that the additional effect of this variant could lead to POI in this family. Although the work represents the first evidence that EIF1AX duplication might be responsible for POI through its over-expression, further functional studies are needed to clarify and prove EIF1AX involvement in POI phenotype.

Update meta-analysis from biomedical literature about MTHFR'polymorphisms and the CML' risk.

BACKGROUND: The MTHFR gene polymorphisms are closely related to the chronic myeloid leukemia (CML). Case-control studies have associated the MTHFR polymorphisms and susceptibility to CML but the results were not conclusive. AIM: To assess this association through an update meta-analysis. METHODS: A descriptive and qualitative study was conducted among students in the 6th year of the faculty during the academic year 2020/2021. The data were collected through a questionnaire written in french evaluating the teaching methods. A focus group of ten persons was led to understand better student's opinions. RESULTS: Totally, 17 and 12 case-control studies including CML cases and controls were enrolled in the meta-analysis respectively for C677T and A1298C polymorphism and CML risk. A poor association between the C677T (T vs C ; OR= 1,28; IC95%= [1,01;1,63]; p=0,04) and the one not significant between the A1298C (C vs A ; OR= 1,52; IC95%= [0,92; 2,51]; p= 0,1) polymorphisms and the CML risk for overall population were found. CONCLUSION: The results of this meta-analysis suggested no significant association between C677T and A1298C polymorphisms and CML risk leading to consider other factors such us folic acid intake, gene-gene and gene- environment interactions.

Genetic diagnosis in Sudanese and Tunisian families with syndromic intellectual disability through exome sequencing.

BACKGROUND: Intellectual disability is a form of neurodevelopmental disorders that begin in childhood and is characterized by substantial intellectual difficulties as well as difficulties in conceptual, social, and practical areas of living. Several genetic and nongenetic factors contribute to its development; however, its most severe forms are generally attributed to single-gene defects. High-throughput technologies and data sharing contributed to the diagnosis of hundreds of single-gene intellectual disability subtypes. METHOD: We applied exome sequencing to identify potential variants causing syndromic intellectual disability in six Sudanese patients from four unrelated families. Data sharing through the Varsome portal corroborated the diagnosis of one of these patients and a Tunisian patient investigated through exome sequencing. Sanger sequencing validated the identified variants and their segregation with the phenotypes in the five studied families. RESULT: We identified three pathogenic/likely pathogenic variants in CCDC82, ADAT3, and HUWE1 and variants of uncertain significance in HERC2 and ATP2B3. The patients with the CCDC82 variants had microcephaly and spasticity, two signs absent in the two previously reported families with CCDC82-related intellectual disability. CONCLUSION: In conclusion, we report new patients with pathogenic mutations in the genes CCDC82, ADAT3, and HUWE1. We also highlight the possibility of extending the CCDC82-linked phenotype to include spastic paraplegia and microcephaly.

Annexin A1 and its receptor gene polymorphisms in systemic lupus erythematosus in the Tunisian population.

BACKGROUND: An association between ANXA1, FPR1 and FPR2 gene polymorphisms and the patho-physiology of many human diseases was suggested by numerous studies. OBJECTIVE: Our study aimed to evaluate association between common polymorphisms in the 9q21.13 and 19q13.41 and susceptibility to systemic lupus erythematosus (SLE) in the Tunisian population. MATERIALS: We performed a case-control study on 107 Tunisian SLE patients and 122 healthy controls to explore 9 polymorphisms of the three studied genes: rs2811226 and rs3739959 (ANXA1), rs5030880, rs1042229, rs1461765570, rs17849971, rs867228 (FPR1), rs17694990 and rs11666254 (FPR2). RESULTS: Four polymorphisms were found to be linked with SLE susceptibility: rs3739959-ANXA1 > G and GG (p = 0.021, OR = 1.73 and p = 0.014, OR = 2.06 respectively), rs867228-FPR1 > TT (p = 0.014, OR = 4.59), rs11666254-FPR2 > GG (p = 0.019, OR = 8.34) and rs17694990-FPR2 > T (p = 0.05, OR = 1.506). In homogenous groups of SLE patients depending on clinical manifestations and serological results, previous associations were confirmed with a panoply of manifestations of lupus including lupus nephritis, malar rash, mouth ulceration and hypocomplementia. CONCLUSION: Our study showed an association between ANXA1 > rs3739959, FPR1 > rs867228, FPR2 > rs11666254, FPR2 > rs17694990 and SLE susceptibility. Our results also showed a strong association between the two ANXA1 studied SNPs and LN which allowed us to suggest these two SNPs as biomarkers of LN development in SLE. Further research is needed to understand by which mechanism the gene variants affect susceptibility to SLE. Key Points • Lupus erythematosus is an autoimmune disease in which a panoply of factors are implicated • Annexin A1 interaction with its receptors are suggested as a target in therapy of a panoply of human disease in particular cancers • The present results highlighted the implication of Annexin A1 and its receptors gene polymorphisms in the physiopathology of lupus, in particular in the involvement of renal and cutaneous lesions.

Autosomal dominant polycystic kidney disease (ADPKD) in Tunisia: From molecular genetics to the development of prognostic tools.

A high prevalence of genetic kidney disease in Tunisia has been detected, and their study provides very important clinical and genetic information. Autosomal dominant polycystic kidney disease (ADPKD) is one of the main causes of morbidity and mortality associated with the kidneys in Tunisia. We present here clinical and genetic characteristics of a cohort of Tunisian patients with ADPKD. Nineteen Tunisian patients with ADPKD, among 4 familial cases and 11 sporadic cases, and 50 Healthy individuals were included in this cohort. Genetic studies of PKD1/2 were carried on using Sanger sequencing and MLPA. In our study, the mean age at diagnosis was 47 ± 18 years. In addition, 84.21% of cases present a family history of ADPKD. Overall, 57.89% of the affected individuals had HTA and 26.31% patients had hematuria. 15.78 % of the patient has extra-renal cysts i.e. one patient with splenic cysts and two patients had liver cysts. 57.89 % of patients were diagnosed with various extra-renal clinical presentations i.e. myopia, hernia, deafness, intracranial aneurysm, respiratory distress, hyperthyroidism, urinary tract infection and lower back pains. The PKD1 genotype showed earlier onset of ESRD compared to PKD2 genotype (43 vs. 55 years old). Six mutations have been detected in PKD1 gene. Among them, three were novels e.g. c.688 T>G, p.C230G and c.690C>G, p.C230W among exon 5 and c.8522A>G, p.N2841S among exon 23. In addition, thirteen single nucleotides polymorphisms have been reported in PKD1 gene. Among them, eleven previously reported in heterozygous state and two novel single nucleotides polymorphisms in heterozygous and homozygous state and predicted to be probable polymorphisms by computational tools: c.496C>T, p.L166= among the exon 4, and c.10165G>C and p.E3389Gln among the exon 31. Only three single nucleotides polymorphisms previously reported in ADPKD database have been identified in PKD2 gene. The description and analysis of our cohort can help in rapid and reliable diagnosis for early management of patients in Tunisia. Indeed, predictive genetic testing can facilitate donor evaluation and increase living related kidney transplantation.

MTHFR 677T-1298C haplotype in acute lymphoblastic leukemia: Impact on methotrexate therapy.

INTRODUCTION: Functional variants of the Methylenetetrahydrofolate reductase (MTHFR) gene, the C677T and A1298C, have largely investigated in pharmacogenomics of Methotrexate (MTX) in acute lymphoblastic leukemia (ALL), yet the conclusions are inconsistent. In addition; most of these studies do not analyze haplotypes. Here, we investigate the MTHFR 677/1298 genotypes and the 677-1298 haplotype and characterize the MTX response in Northern African ALL patients. METHODS: Genomic DNA was extracted from whole venous from a total of 28 patients with ALL. Genotyping were carried out with restriction fragment length polymorphism (RFLP). A toxicity score (TS) is calculated for each patient and correlate to the haplotype. RESULTS: The allelic frequency of MTHFR 677T-1298C haplotype was 10.7% in ALL patients. According to the toxicity's score (TS) there was no significant differences between haplotype groups (p = 0.79): TS was higher with wild type of MTHFR (TS = 3.43; SEM ± 0.85) followed by combined genotype (677T-1298C) (TS = 2.67; SEM ± 0.88) and isolated variant (C677T or A1298C) (TS = 2.64; SEM ± 0.92). CONCLUSION: Despite the limitation of this study; our results suggest that the MTHFR 677T-1298C haplotype is common in ALL and may be a promising HD-MTX chemotherapy-related adverse effects biomarker.

Assessment of molecular response to tyrosine kinase inhibitors in Tunisian Patients with Chronic Myeloid Leukemia.

AIM: This study was carried out to assess the minimal residual disease in Tunisian patients with chronic myeloid leukemia (CML) treated with tyrosine kinase inhibitors in routine clinical practice, to recognize potentially eligible carrier for treatment discontinuation, based on a molecular response (MR). PATIENTS AND METHODS: A retrospective study was carried out in the Hospital University of Sfax, south of Tunisia from January 2016 to October 2020, including all CML patients in the chronic phase at diagnosis, treated with TKI (tyrosine kinase inhibitors) for a minimum duration of 6 months. Quantitative assessment of the BCR-ABL transcript was performed using the Cepheid Xpert BCR-ABL ultra-assay. Molecular response and outcome were evaluated, according to the European Leukemia Net guidelines. RESULTS: A total of 162 CML patients were carried out. The median age was 50 years, the sex ratio M/F was 1.62. The rate of cumulative EMR; MMR and DMR was 80.8%; 73.8% and 55.9% respectively. According to the ELN criteria, 141 CML patients were evaluable. Optimal, suboptimal response and failure were noted in 81 (57.4%), 33(23.4%), and 27(19.1%) patients, respectively. Overall survival (OS) and progression-free survival (PFS) were 96.3% and 85%. Risk factors for an event (death/progression) were lack of EMR, MMR, and DMR (P < 0.05). Among 149 patients with sustained DMR; 14 (8.6%) CML patients have discontinued TKI therapy. CONCLUSION: Despite the limit of our study (duration and size), the available real-life molecular responses with TKI therapy should be considered to identify potentially CML patients eligible for discontinuation of TKI therapy.

Further insights into the spectrum phenotype of TRAPPC9 and CDK5RAP2 genes, segregating independently in a large Tunisian family with intellectual disability and microcephaly.

Intellectual disability (ID) often co-occurs with other neurologic phenotypes making molecular diagnosis more challenging particularly in consanguineous populations with the co-segregation of more than one ID-related gene in some cases. In this study, we investigated the phenotype of three patients from a large Tunisian family with significant ID phenotypic variability and microcephaly and performed a clinical exome sequencing in two cases. We identified, within the first branch, a homozygous variant in the TRAPPC9 gene (p.Arg472Ter) in two cases presenting severe ID, absent speech, congenital/secondary microcephaly in addition to autistic features, supporting the implication of TRAPPC9 in the "secondary" autism spectrum disorders and congenital microcephaly. In the second branch, we identified a homozygous variant (p.Lys189ArgfsTer15) in the CDK5RAP2 gene associated with an heterozygous TRAPPC9 variant (p.Arg472Ter) in one case harbouring primary hereditary microcephaly (MCPH) associated with an inter-hypothalamic adhesion, mixed hearing loss, selective thinning in the retinal nerve fiber layer and parafoveal ganglion cell complex, and short stature. Our findings expand the spectrum of the recently reported neurosensorial abnormalities and revealed the variable phenotype expressivity of CDK5RAP2 defect. Our study highlights the complexity of the genetic background of microcephaly/ID and the efficiency of the exome sequencing to provide an accurate diagnosis and to improve the management and follow-up of such patients.

8q21.11 microdeletion syndrome: Delineation of HEY1 as a candidate gene in neurodevelopmental and cardiac defects.

BACKGROUND: 8q21.11 microdeletion syndrome is a rare chromosomal disorder characterized by recurrent dysmorphic features, a variable degree of intellectual disability and ocular, cardiac and hand/feet abnormalities. To date, ZFHX4 is the only candidate gene implicated in the ocular findings. In this study, we evaluated a patient with a de novo 8q21.13-21.3 deletion to define a new small region of overlap (SRO) for this entity. METHODS: We conducted a clinical evaluation and comparative genomic hybridization (CGH) 4x44K microarrays in a patient with de novo unbalanced translocation t(8;16)(q21; q11.2). RESULTS: The case, a 6-year-old boy, presented dysmorphic features including an elongated face, brachycephaly with a high forehead, an underdeveloped ala, thin upper lip, micrognathia, low-set ears, hypotonia, mild intellectual disability, cortical atrophy with thin corpus callosum defect, and an atrial septal defect. No ocular abnormalities were found. Microarray analysis revealed a 9.6 Mb interstitial 8q21.11-21.3 deletion, not including the ZFHX4 gene. This microdeletion was confirmed in our patient through qPCR analysis, and both parents had a normal profile. Alignment analysis of our case defined a new SRO encompassing five genes. Among them, the HEY1 gene is involved in the embryonic development of the heart, central nervous system, and vascular system. Hrt1/Hey1 null mice show perinatal lethality due to congenital malformations of the aortic arch and its branch arteries. HEY1 has also been linked to the maintenance of neural stem cells, inhibition of oligodendrocyte differentiation, and myelin gene expression. CONCLUSION: HEY1 is a candidate gene for both neurological and cardiac features of the 8q21.11 microdeletion syndrome and might, therefore, explain specific components of its pathophysiology.

Novel pathogenic mutations and further evidence for clinical relevance of genes and variants causing hearing impairment in Tunisian population.

Introduction: Hearing impairment (HI) is characterized by complex genetic heterogeneity. The evolution of next generation sequencing, including targeted enrichment panels, has revolutionized HI diagnosis. Objectives: In this study, we investigated genetic causes in 22 individuals with non-GJB2 HI. Methods: We customized a HaloplexHS kit to include 30 genes known to be associated with autosomal recessive nonsyndromic HI (ARNSHI) and Usher syndrome in North Africa. Results: In accordance with the ACMG/AMP guidelines, we report 11 pathogenic variants; as follows; five novel variants including three missense (ESRRB-Tyr295Cys, MYO15A-Phe2089Leu and MYO7A-Tyr560Cys) and two nonsense (USH1C-Gln122Ter and CIB2-Arg104Ter) mutations; two previously reported mutations (OTOF-Glu57Ter and PNPT1-Glu475Gly), but first time identified among Tunisian families; and four other identified mutations namely WHRN-Gly808AspfsX11, SLC22A4-Cys113Tyr and two MYO7A compound heterozygous splice site variants that were previously described in Tunisia. Pathogenic variants in WHRN and CIB2 genes, in patients with convincing phenotype ruling out retinitis pigmentosa, provide strong evidence supporting their association with ARNSHI. Moreover, we shed lights on the pathogenic implication of mutations in PNPT1 gene in auditory function providing new evidence for its association with ARNSHI. Lack of segregation of a previously identified causal mutation OTOA-Val603Phe further supports its classification as variant of unknown significance. Our study reports absence of otoacoustic emission in subjects using bilateral hearing aids for several years indicating the importance of screening genetic alteration in OTOF gene for proper management of those patients. Conclusion: In conclusion, our findings do not only expand the spectrum of HI mutations in Tunisian patients, but also improve our knowledge about clinical relevance of HI causing genes and variants.

Next-generation sequencing in patients with familial FSGS: first report of collagen gene mutations in Tunisian patients.

Focal segmental glomerulosclerosis (FSGS) is a histological lesion with many causes, including inherited genetic defects, with significant proteinuria being the predominant clinical finding at presentation. FSGS is considered as a podocyte disease due to the fact that in the majority of patients with FSGS, the lesion results from defects in the podocyte structure. However, FSGS does not result exclusively from podocyte-associated genes. In this study, we used a genetic approach based on targeted next-generation sequencing (NGS) of 242 genes to identify the genetic cause of FSGS in seven Tunisian families. The sequencing results revealed the presence of eight distinct mutations including seven newly discovered ones: the c.538G>A (p.V180M) in NPHS2, c.5186G>A (p.R1729Q) in PLCE1 and c.232A>C (p.I78L) in PAX2 and five novel mutations in COL4A3 and COL4A4 genes. Four mutations (c.209G>A (p.G70D), c.725G>A (p.G242E), c.2225G>A (p.G742E), and c. 1681_1698del) were detected in COL4A3 gene and one mutation (c.1424G>A (p.G475D)) was found in COL4A4. In summary, NGS of a targeted gene panel is an ideal approach for the genetic testing of FSGS with multiple possible underlying etiologies. We have demonstrated that not only podocyte genes but also COL4A3/4 mutations should be considered in patients with FSGS.

Co-existence of BCR-ABL and JAK2V617F mutation in resistant chronic myeloid leukemia in the imatinib era: Is there a correlation?

INTRODUCTION: Diagnoses of myeloproliferative disorder is based on molecular marker. Chronic Myeloid Leukemia and Myeloproliferative neoplasms were considered mutually exclusive and co-existence of BCR/ABL1 and JAK2 mutation is a rare phenomenon. CASE REPORT: Here, we present two cases of co-existence of BCR-ABL and JAK2V617F positivity. We characterize the course of the disease, mainly the minimal residual disease.Management and outcome: The two cases was initially managed as Chronic Myeloid Leukemia and treated by TKI inhibitors. The first one was diagnosed in 2010. He started the first line of TKI, and then switched to second line without obtaining a major molecular response. Hence he was tested for JAK2V617F mutation and positivity was diagnosed. The second patient showed Chronic Myeloid Leukemia phenotype with coexistence of BCR/ABL1 and JAK2 mutation at diagnosis. Molecular monitoring reveals a high BCR-ABL1 transcript level (20%) at the last follow-up (12 months). DISCUSSION: Ours results highlight that JAK2V617F/BCR-ABL double positivity may be a potential marker of resistance in Chronic Myeloid Leukemia and clonal molecular analysis is mandatory to elucidate the mechanism. Moreover, the combination of JAK and TKI inhibitors might be effective and potentially be guided by molecular monitoring of minimal residual disease.

SRD5A3-CDG: 3D structure modeling, clinical spectrum, and computer-based dysmorphic facial recognition.

Pathogenic variants in Steroid 5 alpha reductase type 3 (SRD5A3) cause rare inherited congenital disorder of glycosylation known as SRD5A3-CDG (MIM# 612379). To date, 43 affected individuals have been reported. Despite the development of various dysmorphic features in significant number of patients, facial recognition entity has not yet been established for SRD5A3-CDG. Herein, we reported a novel SRD5A3 missense pathogenic variant c.460 T > C p.(Ser154Pro). The 3D structural modeling of the SRD5A3 protein revealed additional transmembrane α-helices and predicted that the p.(Ser154Pro) variant is located in a potential active site and is capable of reducing its catalytic efficiency. Based on phenotypes of our patients and all published SRD5A3-CDG cases, we identified the most common clinical features as well as some recurrent dysmorphic features such as arched eyebrows, wide eyes, shallow nasal bridge, short nose, and large mouth. Based on facial digital 2D images, we successfully designed and validated a SRD5A3-CDG computer based dysmorphic facial analysis, which achieved 92.5% accuracy. The current work integrates genotypic, 3D structural modeling and phenotypic characteristics of CDG-SRD5A3 cases with the successful development of computer tool for accurate facial recognition of CDG-SRD5A3 complex cases to assist in the diagnosis of this particular disorder globally.

Copy-number variation of the NPHP1 gene in patients with juvenile Nephronophthisis.

Objective: Juvenile nephronophthisis (NPHP) is an autosomal recessive cystic disease of the kidney. It represents the most frequent genetic cause of chronic renal failure in children. Methods: we investigated clinical and molecular features in two children with Juvenile nephronophthisis using firstly Multiplex ligation-dependent probe amplification (MLPA) and secondly multiplex PCR. Results: we report a homozygous NPHP1 deletion in two children. Conclusion: NPHP1 deletion analysis using diagnostic methods (e.g. MLPA, Multiplex PCR) should always be considered in patients with nephronophthisis, especially from consanguineous families. Our results provide insights into genotype-phenotype correlations in juvenile nephronophthisis that can be utilized in genetic counseling.

Involvement of C677T MTHFR variant but not A1298C in methotrexate-induced toxicity in acute lymphoblastic leukemia.

BACKGROUND: Methotrexate (MTX) is a key drug in acute lymphoblastic leukemia (ALL) treatment; it inhibits DNA replication by blocking the conversion of 5, 10 Methylenetetrahydrofolate to 5-methylene tetrahydrofolate by methylenetetrahydrofolate reductase (MTHFR). Variants of the Methylenetetrahydrofolate reductase (MTHFR) and MTX related toxicities were largely investigated in several populations, nevertheless, the results are conflicting. OBJECTIVE: This study aimed to assess the prevalence of MTHFR SNVs: C677>T and A1298>C in Tunisian patients with ALL and the relation to the frequency of drug-induced complications. METHODS: 28 ALL patients were included in the study. They were treated according to EORTOC, in which a high dose of MTX (HDMTX) was prescribed. A toxicity score (ST) is calculated for each patient, summing the grades of toxicities. Genotyping of MTHFR variants was done with a PCR-based restriction fragment length polymorphism assay. RESULTS: The toxicity's score (TS) was higher with C677T variant compared to wild genotype (C677C) (TS = 4; IC95% [-2.65-13.32] versus TS = 2.5; IC95% [1.65-4.55], respectively; p = 0.2); but lower with the A1298C mutation compared to those with the wild genotype (A1298A) (TS = 2.5; IC95% [0.48-4.77], versus TS =3; IC95% [1.9-5.69], p = 0.4). HDMTX-related toxicity is associated with the 677CT genotype in ALL patients (RR = 1.41, p = 0.2); not for the A1298C [OR = 0.46, [0.08-2.61], p = 0.18]. CONCLUSION: Our preliminary findings highlight the impact of the C677T variant of MTHFR, but not the A1289C; in HD-MTX chemotherapy-related adverse effects in younger Tunisian ALL.

Detection of a novel mutation in a Tunisian child with polycystic kidney disease.

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common monogenic disease that has an adverse impact on the patients' health and quality of life. ADPKD is usually known as "adult-type disease," but rare cases have been reported in pediatric patients. We present here a 2-year-old Tunisian girl with renal cyst formation and her mother with adult onset ADPKD. Disease-causing mutation has been searched in PKD1 and PKD2 using Long-Range and PCR followed by sequencing. Molecular sequencing displayed us to identify a novel likely pathogenic mutation (c.696 T > G; p.C232W, exon 5) in PKD1. The identified PKD1 mutation is inherited and unreported variant, which can alter the formation of intramolecular disulfide bonds essential for polycystin-1 function. We report here the first mutational study in pediatric patient with ADPKD in Tunisia.

A novel disease-causing mutation in the Renin gene in a Tunisian family with autosomal dominant tubulointerstitial kidney disease.

Autosomal dominant tubulointerstitial kidney disease (ADTKD) is a rare group of disease that affect the tubules of the kidney. There are 4 known subtypes of ADTKD classified based on causative genes and clinical features. In our study, we aimed to identify the causative subtypes of ADTKD in a Tunisian ADTKD family (3 affected members), in whom standard nephrological diagnosis did not provide clear subtype of ADTKD, until genetic testing was performed. Sanger sequencing was performed for UMOD, HNF1ß and REN genes. Mutational analysis allowed us to detect a heterozygous mutation in the REN gene: c.1172C > G, (p.T391R) in exon 10. In silico analyses predicted that the novel likely pathogenic mutation affect protein stability and 3D structure. Our study highlights the importance of establishing a genetic diagnosis to identify the subtype of ADTKD for better patient care. To the best of our knowledge, we report here a first Tunisian ADTKD-REN family.

A novel de novo splicing mutation c.1444-2A>T in the TSC2 gene causes exon skipping and premature termination in a patient with tuberous sclerosis syndrome.

Tuberous sclerosis complex (TSC) syndrome is a neurocutaneous syndrome that affects the brain, skin, and kidneys that has an adverse impact on the patient's health and quality of life. There have been several recent advances that elucidate the genetic complex of this disorder that will help understand the basic neurobiology of this disorder. We report a Tunisian patient with clinical manifestations of TSC syndrome. We investigated the causative molecular defect in this patient using PCR followed by direct sequencing. Subsequently, in silico studies and mRNA analysis were performed to study the pathogenicity of the new variation found in the TSC2. Bioinformatics tools predicted that the novel mutation c.1444-2A>T have pathogenic effects on splicing machinery. RT-PCR followed by sequencing revealed that the mutation c.1444-2A>T generates two aberrant transcripts. The first, with exon 15 skipping, is responsible for the loss of 52 amino acids, which causes the production of an aberrant protein isoform. The second, with the inclusion of 122 nucleotides of intron 14, is responsible for the creation of new premature termination codons (TGA), which causes the production of a truncated TSC2 protein. This study highlighted the clinical features of a Tunisian patient with TSC syndrome and revealed a splicing mutation c.1444-2A>T within intron 14 of TSC2 gene, which is present for the first time using Sanger sequencing approach, as a disease-causing mutation in a Tunisian patient with TSC syndrome.