Mutational spectrum of BRCA1/2 genes in Moroccan patients with hereditary breast and/or ovarian cancer, and review of BRCA mutations in the MENA region.

PURPOSE: Breast cancer (BC) is the most common form of female cancer around the world. BC is mostly sporadic, and rarely hereditary. These hereditary forms are mostly BRCA1- and BRCA2-associated hereditary breast and ovarian cancer syndrome. BRCA1 and BRCA2 genes are large and had some recurrent mutations specific to some populations. Through this work we analyze the most recurrent mutations in Moroccan population and compared them to a large review of other BRCA1/2 spectrum mutations in the MENA region. METHODS: We report in this work a series of 163 unrelated patients (the largest series of Moroccan patients) with familial breast and/or ovarian cancer, selected among patients referred to our oncogenetic outpatient clinic, from 2006 to 2021. To identify genetic variants in these two genes, different genetic analysis strategies have been carried out, using Sanger Sequencing DNA or Target Panel Sequencing. RESULTS: Pathogenic variants were identified in 27.6% of patients. The most frequent mutation identified in our patients was the c.1310_1313delAAGA, BRCA2 (33%), and three other mutations seem more frequent in the Moroccan population (33%) of all reported patients: c.798_799delTT, BRCA1; and c.3279delC, BRCA1; and c.7234_7235insG in BRCA2 gene. CONCLUSION: Through this work, we emphasize the importance of screening for BRCA1 and BRCA2 recurrent mutations in Moroccan patients. Other MENA (MENA: English-language acronym referring to the Middle East and North Africa region) countries had also some recurrent BRCA mutations, which will allow a fast and unexpensive first line genetic analysis and a precise molecular diagnosis. This will allow an adapted follow-up of the patients and a pre-symptomatic diagnosis of their relatives.

Application of next generation sequencing in genetic counseling a case of a couple at risk of cystinosis.

BACKGROUND: In Morocco, consanguinity rate is very high; which lead to an increase in the birth prevalence of infants with autosomal recessive disorders. Previously, it was difficult to diagnose rare autosomal recessive diseases. Next Generation Sequencing (NGS) techniques have considerably improved clinical diagnostics. A genetic diagnosis showing biallelic causative mutations is the requirement for targeted carrier testing in parents, prenatal and preimplantation genetic diagnosis in further pregnancies, and also for targeted premarital testing in future couples at risk of producing affected children by a known autosomal recessive disease. METHODS: In this report, we present our strategy to advise a future couple of first cousins, whose descendants would risk cystinosis; an autosomal recessive lysosomal disease caused by mutations in the CTNS gene. Indeed, our future husband's sister is clinically and biochemically diagnosed with cystinosis in early childhood. First, we opted to identify the patient's CTNS gene abnormality by using (NGS), then we searched for heterozygosity in the couple's DNA, which allows us to predict the exact risk of this familial disease in the future couple's offspring. RESULTS: We have shown that the future husband, brother of the patient is heterozygous for the familial mutation. On the other hand, his future wife did not inherit the familial mutation. Therefore, genetic counseling was reassuring for the risk of familial cystinosis in this couple's offspring. CONCLUSIONS: We report in this study, one of the major applications of (NGS), an effective tool to improve clinical diagnosis and to provide the possibility of targeted premarital carrier testing in couples at risk.

Distribution of allelic and genotypic frequencies of NAT2 and CYP2E1 variants in Moroccan population.

BACKGROUND: Several pathogenesis and genetic factors influence predisposition to antituberculosis drug-induced hepatotoxicity (ATDH) especially for isoniazid (INH). However, the major susceptibility genes for ATDH are N-acetyltransferase 2 (NAT2) and cytochrome P450 2E1 (CYP2E1). NAT2 gene determines the individual's acetylator status (fast, intermediate or slow) to metabolize drugs and xenobiotics, while CYP2E1 c1/c1 genotype carriers had an increased risk of ATDH. Polymorphisms of the NAT2 and CYP2E1 genes vary remarkably among the populations of different ethnic origins. The aim of this study was to determine, for the first time, the frequency of slow acetylators in Moroccan population by genotyping of NAT2 gene variants and determining the genotype c1/c1 for CYP2E1 gene, in order to predict adverse effects of Tuberculosis treatment, particularly hepatotoxicity. RESULTS: The frequencies of specific NAT2 alleles were 53%, 25%, 2% and 4% for NAT2*5, NAT2*6, NAT2*7 and NAT2*14 respectively among 163 Moroccan studied group. Genotyping of CYP2E1 gene, by real-time polymerase chain reaction using TaqMan probes, revealed frequencies of 98.5% for c1/c1 and 1.5% for c1/c2 among 130 Moroccan studied group. CONCLUSION: The most prevalent genotypes of NAT2 gene in Moroccans are those which encode slow acetylation phenotype (72.39%), leading to a high risk of ATDH. Most Moroccans are homozygous for c1 allele of CYP2E1 gene which aggravates hepatotoxicity in slow acetylators. This genetic background should be taken into account in determining the minimum dose of INH needed to treat Moroccan TB patients, in order to decrease adverse effects.

Molecular diagnosis of dystrophinopathies in Morocco and report of six novel mutations.

Dystrophinopathies are the most common genetic neuromuscular disorders during childhood, with an X-linked recessive inheritance pattern. Because of clinical and genetic heterogeneity of dystrophinopathies, genetic testing of dystrophin gene at Xp21.2 is constantly evolving. Multiplex Polymerase Chain Reaction (MPCR) is used in the first line to detect common exon deletions of dystrophin gene (accounting for 65% of mutations), followed by the Multiplex Ligation-dependent Probe Amplification (MLPA) technique to reveal deletions of exons outside the usual hotspot and duplications in male and female carriers. (MLPA adds another 10-15% positive cases to MPCR). Recently, Next Generation Sequencing allows to screen for rare large and point mutations. We report here, molecular analysis results of dystrophin gene during 27 years in a large Moroccan cohort of 356 patients, using the multiplex polymerase chain reaction (MPCR) to screen for hot-spot exon deletions. First applications of whole dystrophin gene sequencing in our lab lead to the identification of six novel mutations.

Surprisingly good outcome in antenatal diagnosis of severe hydrocephalus related to CCDC88C deficiency.

Non-syndromic congenital hydrocephalus is aetiologically diverse and while a genetic cause is frequently suspected, it often cannot be confirmed. The most common genetic cause is L1CAM-related X-linked hydrocephalus and that explains only 5%-10% of all male cases. This underlines a current limitation in our understanding of the genetic burden of non-syndromic congenital hydrocephalus, especially for those cases with likely autosomal recessive inheritance. Additionally, the prognosis for most cases of severe congenital hydrocephalus is poor, with most of the surviving infants displaying significant intellectual impairment despite surgical intervention. It is for this reason that couples with an antenatal diagnosis of severe hydrocephalus are given the option, and may opt, for termination of the pregnancy. We present two families with CCDC88C-related recessive congenital hydrocephalus with children who had severe hydrocephalus. Those individuals who were shunted within the first few weeks of life, who did not require multiple surgical revisions, and who had a more distal truncating variant of the CCDC88C gene met their early childhood developmental milestones in some cases. This suggests that children with CCDC88C-related autosomal recessive hydrocephalus can have normal developmental outcomes under certain circumstances. We recommend CCDC88C analysis in cases of severe non-syndromic congenital hydrocephalus, especially when aqueduct stenosis with or without a medial diverticulum is seen, in order to aid prognosis discussion.

Identification of two novel SH3PXD2B gene mutations in Frank-Ter Haar syndrome by exome sequencing: Case report and review of the literature.

BACKGROUND: Frank-Ter Haar syndrome (FTHS) is an autosomal-recessive disorder characterized by skeletal, cardio-vascular, and eye abnormalities, such as increased intraocular pressure, prominent eyes, and hypertelorism. The most common underlying genetic defect in Frank-Ter Haar syndrome appears to be due to mutations in the SH3PXD2B gene on chromosome 5q35.1. Until now, only six mutations in SH3PXD2B gene have been identified. A genetic heterogeneity of FTHS was suggested in previous studies. DESIGN: FTHS was suspected clinically in a girl of 2years old, born from non-consanguineous Moroccan healthy parents. The patient had been referred to a medical genetics outpatient clinic for dysmorphic facial features. Whole Exome Sequencing (WES) was performed in the patient and her parents, in addition to Sanger sequencing that was carried out to confirm the results. RESULTS: We report the first description of a Moroccan FTHS patient with two novel compound heterozygous mutations c.806G>A; p.Trp269* (maternal allele) and c.892delC; p.Asp299Thrfs*44 (paternal allele) in the SH3PXD2B gene. Sanger sequencing confirmed this mutation in the affected girl and demonstrated that her parents carry this mutation in heterozygous state. CONCLUSION: Our results confirm the clinical diagnosis of FTHS in this reported family and contribute to expand the mutational spectrum of this rare disease. Our study shows also, that exome sequencing is a powerful and a cost-effective tool for the diagnosis of a supposed genetically heterogeneous disorder such FTHS.

Severe early onset retinitis pigmentosa in a Moroccan patient with Heimler syndrome due to novel homozygous mutation of PEX1 gene.

Heimler syndrome (HS) is a rare recessive disorder characterized by sensorineural hearing loss (SNHL), amelogenesis imperfecta, nail abnormalities, and occasional or late-onset retinal pigmentation. It is the mildest form known to date of peroxisome biogenesis disorder caused by hypomorphic mutations of PEX1 and PEX6 genes. We report on a second Moroccan family with Heimler syndrome with early onset, severe visual impairment and important phenotypic overlap with Usher syndrome. The patient carried a novel homozygous missense variant c.3140T > C (p.Leu1047Pro) of PEX1 gene. As standard biochemical screening of blood for evidence of a peroxisomal disorder did not provide a diagnosis in the individuals with HS, patients with SNHL and retinal pigmentation should have mutation analysis of PEX1 and PEX6 genes.

Hyaline fibromatosis syndrome with mutation c.1074delT of the CMG2 gene: a case report.

INTRODUCTION: Juvenile hyaline fibromatosis and infantile systemic hyalinosis are variants of the same autosomal recessive syndrome; hyaline fibromatosis syndrome, characterized by papulonodular skin lesions, gingival hypertrophy, flexion contractures of joints, osteolytic bone lesions and stunted growth. Infantile systemic hyalinosis is distinguished from juvenile hyaline fibromatosis by its more severe phenotype, which includes hyaline deposits in multiple organs, recurrent infections and death within the first two years of life.Hyaline fibromatosis syndrome is due to mutations of the gene-encoding capillary morphogenesis protein 2 (CMG2). Cases have been reported in different countries but to the best of our knowledge, this is the first reported Moroccan patient with hyaline fibromatosis syndrome and carrying the CMG2 mutation. CASE PRESENTATION: We report the case of an eight-year-old Moroccan male patient with typical features of hyaline fibromatosis syndrome: multiple recurring subcutaneous tumors, gingival hypertrophy, joint contractures and other anomalies carrying a homozygous mutation in the CMG2 gene. The identification of the mutation in our patient allowed us to do a presymptomatic diagnosis in our patient's sister, a two-day-old newborn, who is carrying the familial mutation in the heterozygous state. Early recognition of this condition is important for genetic counseling and early treatment. CONCLUSIONS: Hyaline fibromatosis syndrome might be underdiagnosed. Molecular diagnosis will help clinicians and geneticists, firstly to conduct genetic counseling, prenatal diagnosis and early treatment, and secondly to gain better understanding of the disease and genotype-phenotype correlations.

Low level of consanguinity in moroccan families at high risk of breast cancer.

BACKGROUND: Breast cancer is worldwide the most common cancer in women and is a major public health problem. Genes with high or low penetrance are now clearly implicated in the onset of breast cancer, mostly the BRCA genes. All women in families at high risk of breast cancer do not develop tumours, even when they carry the familial mutation, suggesting the existence of genetic and environmental protective factors. Several studies have shown that consanguinity is linked to a decreased or an increased risk of breast cancer, but to the best of our knowledge, there is no study concerning the association between consanguinity and the occurrence of tumours in women with high risk of breast cancer. The objective of this study was to examine whether parental consanguinity in families with genetic predisposition to breast cancer affect the risk of siblings for having this cancer. MATERIALS AND METHODS: Over a six-year period, 72 different patients with a histological diagnosis of breast or ovarian cancer from 42 families were recruited for genetic counselling to the Department of Medical Genetics, Rabat. Consanguinity rate was determined in cases and compared to the consanguinity rate in the Moroccan general population. RESULTS: Consanguinity rates were 9.72% in patients and 15.3% in controls, but the difference was statistically not significant (p>0.001) and the mean coefficient of consanguinity was lower in breast cancer patients (0.0034) than in controls (0.0065). CONCLUSIONS: Despite the relatively small sample size of the current study, our results suggest that parental consanguinity in Moroccan women might not be associated with an altered risk of breast cancer. Large scale studies should be carried out to confirm our results and to develop public health programs.

Cytogenetic analysis of 5572 patients referred for suspected chromosomal abnormalities in Morocco.

OBJECTIVES: The aim of this study was (1) to identify the profile of patients being referred for cytogenetic analysis in Morocco, (2) to determine the prevalence and type of chromosomal abnormalities in the different groups, (3) to compare the results with those of similar studies done in other countries. MATERIAL AND METHODS: 5572 patients ranging from newborns to 50 years of age were referred to the department of medical genetics, of the Moroccan National Institute of Health between 1993 and 2010, with a variety of clinical disorders such as mental retardation; multiple congenital malformations; clinical features of Down syndrome, Turner's syndrome, and Klinefelter syndrome; ambiguous sex; sterility; amenorrhea; recurrent miscarriage; and chromosome breakage syndromes. RESULTS: Of the 5572 cases studied, 4068 (73%) had a normal karyotype and 1504 (27%) had chromosomal abnormalities. Various types of chromosomal anomalies were found. The most common autosomal abnormalities were Down syndrome (1095 cases) and Turner's syndrome (122 cases) in abnormalities of sex chromosomes. CONCLUSION: This study compares the results of cytogenetic analysis of chromosomal abnormalities in the Moroccan population with other countries and research centers. This comparison will help Moroccan clinicians to determine the priority for requesting a cytogenetic analysis in individual cases.

Genetic testing and first presymptomatic diagnosis in Moroccan families at high risk for breast/ovarian cancer.

Germline mutations in the BRCA1 and BRCA2 genes highly predispose to breast and ovarian cancers and are responsible for a substantial proportion of familial breast and ovarian cancers. No female individuals from families from Morocco affected by breast cancer with mutations of these genes have previously been reported, and clinicians in Morocco are unaccustomed to dealing with healthy female individuals carrying mutations in the BRCA genes. This study aimed to report the initial experience of a group of Moroccan investigators carrying out predictive genetic testing to detect a known familial mutation in healthy Moroccan females with a high risk of developing breast cancer and to introduce supervision of these asymptomatic female carriers as a new approach in the prevention and early diagnosis of breast and ovarian cancers in Morocco. Presymptomatic diagnosis was carried out using DNA genetic testing in 5 healthy Moroccan female individuals from three families with an elevated risk of developing breast cancer. These are the first Moroccan families reported to be affected by breast cancers associated with BRCA mutations. Presymptomatic diagnosis was carried out for breast cancer in 5 female individuals from three Moroccan families with BRCA mutations. Two of the families are the first reported incidence of the founder mutation Ashkenazi BRCA1-185_186delAG in Moroccan patients. The third family carried the known BRCA2 mutation c.5073dupA/p.trp1692metfsX3. We tested the presence of these mutations in 5 asymptomatic healthy females from the three families. Two sisters from family 1 carried the BRCA1-185_186delAG mutation, whereas the third female individual from family 2 carried the c.5073dupA/p.trp1692metfsX3 mutation. However, one healthy female individual and her mother from family 3 did not carry the familial mutation of the BRCA1 gene. This study found BRCA mutations in three asymptomatic subjects, suggesting that this is the first step towards the development of persistent medical monitoring of females from families with a history of breast and ovarian cancers. Consequently, it is crucial for oncologists in Morocco to initiate the supervision of healthy female individuals with genetic defects which may lead to hereditary cancers.