Clinical Exome Sequencing Reveals Novel Mutations in SPTB Gene Associated with Hereditary Spherocytosis in Patients with Suspected Congenital Hemolytic Anemia.

Congenital hemolytic anemia (CHA) is defined as the premature destruction of red blood cells (RBC) due to congenital or acquired defects. The hereditary form of hemolytic anemia can be divided into hemoglobinopathies, membranopathies, and enzymopathies. Hereditary spherocytosis (HS) is the most common inherited RBC membranopathy leading to congenital hemolytic anemia. To date; five genes have been associated with HS coding for cytoskeleton and transmembrane proteins, those genes are SPTB, SLC4A1, EPB42, ANK1, and SPTA1. Due to genetic heterogeneity, clinical exome sequencing (CES) was performed on four unrelated Moroccan patients referred for CHA investigation. Sanger sequencing and qPCR were performed to confirm CES results and to study the de novo character of identified variants. The molecular analysis revealed 3 novel mutations and one previously reported pathogenic variant of the SPTB gene confirming the diagnosis of HS in the four patients. Hereditary spherocytosis anemia is a genetically heterogenous disease which could be misdiagnosed clinically. The introduction of novel sequencing technologies can facilitate accurate genetic diagnosis, allowing an adapted care of the patient and his family.

Next generation sequencing identifies a pathogenic mutation of WFS1 gene in a Moroccan family with Wolfram syndrome: a case report.

BACKGROUND: Wolfram syndrome is a rare autosomal recessive neurodegenerative disorder that affects 1/200,000 to 1/1,000,000 children. It is characterized by juvenile onset diabetes, optic nerve atrophy and other systemic manifestations. Symptoms of the disease arise mostly in early childhood with a high mortality rate due to severe neurological complications. Two causative genes have been identifed in this syndrome; the classical form is caused by autosomal recessive mutations of the WFS1 gene, and a smaller portion of patients has mutations in the CIDS2 gene, which are responsible for autosomal recessive Wolfram syndrome 2. CASE PRESENTATION: We report the case of a 28-year-old Moroccan boy born from consanguineous parents referred to the department of medical genetics at the National Institute of Health in Rabat. The diagnosis of Wolfram syndrome was made based on insulin-dependent diabetes, optic nerve atrophy, sensorineural deafness, urological abnormalities and psychiatric illness. To establish the diagnosis at a molecular level, we performed next-generation sequencing in the index patient, which revealed compound heterozygous WFS1 mutations: c.1113G > A (p.Trp371Ter) and c.1223_1224insGGAACCACCTGGAGCCCTATGCCCATTT (p.Phe408fs). This second variant has never been described in patients with Wolfram syndrome. CONCLUSION: The identification of the genetic substrate in our patient confirmed the clinical diagnosis of Wolfram syndrome and allowed us to provide him an appropriate management and genetic counseling to his family.

Novel mutation in the TGFBI gene in a Moroccan family with atypical corneal dystrophy: a case report.

BACKGROUND: Corneal dystrophies (CDs) are a heterogeneous group of bilateral, genetically determined, noninflammatory bilateral corneal diseases that are usually limited to the cornea. CD is characterized by a large variability in the age of onset, evolution and visual impact and the accumulation of insoluble deposits at different depths in the cornea. Clinical symptoms revealed bilateral multiple superficial, epithelial, and stromal anterior granular opacities in different stages of severity among three patients of this family. A total of 99 genes are involved in CDs. The aim of this study was to identify pathogenic variants causing atypical corneal dystrophy in a large Moroccan family and to describe the clinical phenotype with severely different stages of evolution. CASE PRESENTATION: In this study, we report a large Moroccan family with CD. Whole-exome sequencing (WES) was performed in the three affected members who shared a phenotype of corneal dystrophy in different stages of severity. Variant validation and familial segregation were performed by Sanger sequencing in affected sisters and mothers and in two unaffected brothers. Whole-exome sequencing showed a novel heterozygous mutation (c.1772C > A; p.Ser591Tyr) in the TGFBI gene. Clinical examinations demonstrated bilaterally multiple superficial, epithelial and stromal anterior granular opacities in different stages of severity among three patients in this family. CONCLUSIONS: This report describes a novel mutation in the TGFBI gene found in three family members affected by different phenotypic aspects. This mutation is associated with Thiel-Behnke corneal dystrophy; therefore, it could be considered a novel phenotype genotype correlation, which will help in genetic counselling for this family.

A novel non sense mutation in WDR62 causes autosomal recessive primary microcephaly: a case report.

BACKGROUND: Autosomal recessive primary microcephaly (MCPH) is a rare genetically heterogeneous disorder of neurogenic brain development characterized by a reduced head circumference at birth with no remarkable anomalies of brain architecture and variable degrees of intellectual impairment. Clinical and genetic heterogeneity in genetic disorders represent a major diagnostic challenge. CASE PRESENTATION: Two patients, 11 and 9 years old, born from consanguineous parents, were referred to the department of medical genetics at the National Institute of Health in Rabat. The diagnosis of MCPH was made, based on reduced head circumference without brain architecture abnormalities. The two patients were subject to the whole-exome sequencing, which allowed to diagnose a novel homozygous mutation c.1027C > T; p.Gln343* in exon 8 of WDR62, a gene already known to be related to MCPH. Sanger sequencing confirmed the segregation of the mutation in the family. CONCLUSION: Our data expends the spectrum of mutations in WDR62 gene, proves the efficiency and cost-effectiveness of whole exome sequencing for the molecular diagnosis of genetically heterogeneous disorders such MCPH. Exome sequencing led to the rapid and cost-effective identification of a novel homozygous mutation in WDR62 gene, thereby facilitating genetic counseling.

Marfanoid habitus is a nonspecific feature of Perrault syndrome.

The objective of this study was to report the clinical and biological characteristics of two Perrault syndrome cases in a Moroccan family with homozygous variant c.1565C>A in the LARS2 gene and to establish genotype-phenotype correlation of patients with the same mutation by review of the literature. Whole-exome sequencing was performed. Data analysis was carried out and confirmed by Sanger sequencing and segregation. The affected siblings were diagnosed as having Perrault syndrome with sensorineural hearing loss at low frequencies; the female proband had primary amenorrhea and ovarian dysgenesis. Both affected individuals had a marfanoid habitus and no neurological features. Both patients carried the homozygous variant c.1565C>A; p.Thr522Asn in exon 13 of the LARS2 gene. This variant has already been reported as a homozygous variant in three other Perrault syndrome families. Both affected siblings of a Moroccan consanguineous family with LARS2 variants had low-frequency sensorineural hearing loss, marfanoid habitus, and primary ovarian insufficiency in the affected girl. According to the literature, this variant, c.1565C>A; p.Thr522Asn, can be correlated with low-frequency hearing loss. However, marfanoid habitus was been considered a nonspecific feature in Perrault syndrome, but we believe that it may be more specific than considered previously. This diagnosis allowed us to provide appropriate management to the patients and to provide more accurate genetic counseling to this family.

Novel splice site mutation in CNNM4 gene in a family with Jalili syndrome.

Jalili syndrome is a rare autosomal recessive genetic disease characterized by the association of amelogenesis imperfecta and cone-rod retinal dystrophy. This syndrome is caused by mutations in the CNNM4 gene. Different types of CNNM4 mutations have been reported; missense, nonsense, large deletions, single base insertion, and duplication. We used Sanger sequencing to analyze a large consanguineous family with three siblings affected with Jalili syndrome, suspected clinically after dental and ophthalmological examination. These patients are carrying a novel homozygous mutation in the splice site acceptor of intron 3 (c.1682-1G > C) in the CNNM4 gene. We compare the findings of the present family to those from literature, in order to further delineate Jalili syndrome.

Non lethal Raine syndrome and differential diagnosis.

Raine syndrome is a rare autosomal recessive bone dysplasia characterized by characteristic facial features with exophthalmos and generalized osteosclerosis. Amelogenesis imperfecta, hearing loss, seizures, and intracerebral calcification are apparent in some affected individuals. Originally, Raine syndrome was originally reported as a lethal syndrome. However, recently a milder phenotype, compatible with life, has been described. Biallelic variants inFAM20C, encoding aGolgi casein kinase involved in biomineralisation, have been identified in affected individuals. We report here a consanguineous Moroccan family with two affected siblingsa girl aged 18 and a boy of 15years. Clinical features, including learning disability, seizures and amelogenesis imperfecta, initially suggested a diagnosis of Kohlschutter-Tonz syndrome. However,a novel homozygous FAM20Cvariantc.676T > A, p.(Trp226Arg) was identified in the affected siblings. Our report reinforces that Raine syndrome is compatible with life, and that mild hypophosphatemia and amelogenesis imperfecta are key features of the attenuated form.

Novel Mutation and Structural RNA Analysis of the Noncoding RNase MRP Gene in Cartilage-Hair Hypoplasia.

Cartilage-hair hypoplasia (CHH) is an autosomal recessive disorder which is characterized by bone metaphysis anomalies with manifestations that include short stature, defective cellular immunity, and predisposition to several cancers. It is caused by mutations in RMRP, which is transcribed as an RNA component of the mitochondrial RNA-processing ribonuclease. We report the clinical and molecular data of a Moroccan patient with CHH. Sequencing of RMRP identified 2 mutations in the patient: the known mutation g.97G>A and the variation g.27G>C, which has not been reported previously. Given the high mutational heterogeneity, the high frequency of variations in the region, and the fact that RMRP is a non-coding gene, assigning the pathogenicity to RMRP mutations remains a difficult task. Therefore, we compared the characteristics of the primary and secondary structures of mutated RMRP sequences. The location of our mutations within the secondary structure of the RMRP molecule revealed that the novel g.27G>C mutation causes a disruption in the Watson-Crick base pairing, which results in an impairment of a highly conserved P3 domain. Our work prompts considering the consequences of novel RMRP nucleotide variations on conserved RNA structures to gain insights into the pathogenicity of mutations.

Further evidence for causal FAM20A mutations and first case of amelogenesis imperfecta and gingival hyperplasia syndrome in Morocco: a case report.

BACKGROUND: Amelogenesis imperfecta represents a group of developmental conditions, clinically and genetically heterogeneous, that affect the structure and clinical appearance of enamel. Amelogenesis imperfecta occurred as an isolated trait or as part of a genetic syndrome. Recently, disease-causing mutations in the FAM20A gene were identified, in families with an autosomal recessive syndrome associating amelogenesis imperfecta and gingival fibromatosis. CASE PRESENTATION: We report, the first description of a Moroccan patient with amelogenesis imperfecta and gingival fibromatosis, in whom we performed Sanger sequencing of the entire coding sequence of FAM20A and identified a homozygous mutation in the FAM20A gene (c.34_35delCT), already reported in a family with this syndrome. CONCLUSION: Our finding confirms that the mutations of FAM20A gene are causative for amelogenesis imperfecta and gingival fibromatosis and underlines the recurrent character of the c.34_35delCT in two different ethnic groups.