Ebtesam M. Abdalla

Mutations in RIPK4 Cause the Autosomal-Recessive Form of Popliteal Pterygium Syndrome

The autosomal-recessive form of popliteal pterygium syndrome, also known as Bartsocas-Papas syndrome, is a rare, but frequently lethal disorder characterized by marked popliteal pterygium associated with multiple congenital malformations. Using Affymetrix 250K SNP array genotyping and homozygosity mapping, we mapped this malformation syndrome to chromosomal region 21q22.3. Direct sequencing of RIPK4 (receptor-interacting serine/threonine kinase protein 4) showed a homozygous transversion (c.362T>A) that causes substitution of a conserved isoleucine with asparagine at amino acid position 121 (p.Ile121Asn) in the serine/threonine kinase domain of the protein. Additional pathogenic mutations-a homozygous transition (c.551C>T) that leads to a missense substitution (p.Thr184Ile) at a conserved position and a homozygous one base-pair insertion mutation (c.777_778insA) predicted to lead to a premature stop codon (p.Arg260ThrfsX14) within the kinase domain-were observed in two families. Molecular modeling of the kinase domain showed that both the Ile121 and Thr184 positions are critical for the proteins stability and kinase activity. Luciferase reporter assays also demonstrated that these mutations are critical for the catalytic activity of RIPK4. RIPK4 mediates activation of the nuclear factor-κB (NF-κB) signaling pathway and is required for keratinocyte differentiation and craniofacial and limb development. The phenotype of Ripk4(-/-) mice is consistent with the human phenotype presented herein. Additionally, the spectrum of malformations observed in the presented families is similar, but less severe than the conserved helix-loop-helix ubiquitous kinase (CHUK)-deficient human fetus phenotype; known as Cocoon syndrome; this similarity indicates that RIPK4 and CHUK might function via closely related pathways to promote keratinocyte differentiation and epithelial growth.

Diagnostic exome sequencing to elucidate the genetic basis of likely recessive disorders in consanguineous families.

Rare, atypical, and undiagnosed autosomal‐recessive disorders frequently occur in the offspring of consanguineous couples. Current routine diagnostic genetic tests fail to establish a diagnosis in many cases. We employed exome sequencing to identify the underlying molecular defects in patients with unresolved but putatively autosomal‐recessive disorders in consanguineous families and postulated that the pathogenic variants would reside within homozygous regions. Fifty consanguineous families participated in the study, with a wide spectrum of clinical phenotypes suggestive of autosomal‐recessive inheritance, but with no definitive molecular diagnosis. DNA samples from the patient(s), unaffected sibling(s), and the parents were genotyped with a 720K SNP array. Exome sequencing and array CGH (comparative genomic hybridization) were then performed on one affected individual per family. High‐confidence pathogenic variants were found in homozygosity in known disease‐causing genes in 18 families (36%) (one by array CGH and 17 by exome sequencing), accounting for the clinical phenotype in whole or in part. In the remainder of the families, no causative variant in a known pathogenic gene was identified. Our study shows that exome sequencing, in addition to being a powerful diagnostic tool, promises to rapidly expand our knowledge of rare genetic Mendelian disorders and can be used to establish more detailed causative links between mutant genotypes and clinical phenotypes.

A novel WNT10A mutation causes non-syndromic hypodontia in an Egyptian family

OBJECTIVE Tooth agenesis is the most common dental anomaly, whose aetiology still remains to be fully elucidated. The aim of this study was to investigate the genetic cause of non-syndromic hypodontia with clinical variability in an Egyptian family. DESIGN The entire coding regions including exon-intron boundaries of the MSX1, PAX9 and WNT10A genes were investigated by direct sequencing in all affected family members. RESULTS Novel heterozygous mutation inherited in an autosomal dominant manner was identified in the WNT10A gene. This 21-bp deletion combined with 1-bp insertion, c.-14_7delinsC, eliminates the translation initiation codon leading to either no protein production or translation of alternative open reading frames. None of the control subjects (400 chromosomes) were carriers of this novel WNT10A mutation. No pathogenic mutations were found in the MSX1 and PAX9 genes. CONCLUSIONS The novel c.-14_7delinsC mutation might be the etiological variant of the WNT10A gene responsible for the permanent tooth agenesis in the Egyptian family. WNT10A is a major candidate gene for non-syndromic hypodontia.

Novel PITX2 gene mutations in patients with Axenfeld‐Rieger syndrome

Mutations in the bicoid‐like transcription factor PITX2 gene often result in Axenfeld‐Rieger syndrome (ARS), an autosomal‐dominant inherited disorder. We report here the discovery and characterization of novel PITX2 deletions in a small kindred with ARS.

Kyphoscoliotic type of Ehlers-Danlos Syndrome (EDS VIA) in six Egyptian patients presenting with a homogeneous clinical phenotype

AbstractThe kyphoscoliotic type of the Ehlers-Danlos syndrome (EDS VIA) is a rare recessively inherited connective tissue disorder characterized by bruisable, hyperextensible skin, generalized joint laxity, severe muscular hypotonia at birth and progressive congenital scoliosis or kyphosis. Deficiency of the enzyme lysyl hydroxylase 1 (LH1) due to mutations in PLOD1 results in underhydroxylation of collagen lysyl residues and, hence, in the abnormal formation of collagen cross-links. Here, we report on the clinical, biochemical, and molecular findings in six Egyptian patients from four unrelated families severely affected with EDS VIA. In addition to the frequently reported p.Glu326_Lys585dup, we identified two novel sequence variants p.Gln208* and p.Tyr675*, which lead either to loss of function of LH1 or to its deficiency. All affected children presented with similar clinical features of the disorder, and in addition, several dysmorphic craniofacial features, not yet described in EDS VIA. These were specific for the affected individuals of each family, but absent in their parents and their unaffected siblings. Conclusion: Our description of six patients presenting with a homogeneous clinical phenotype and dysmorphic craniofacial features will help pediatricians in the diagnosis of this rare disorder.

Recurrent hydatidiform mole: detection of two novel mutations in the NLRP7 gene in two Egyptian families

OBJECTIVES Hydatidiform mole is an aberrant pregnancy with hyperproliferative vesicular trophoblast and defective fetal development. In 2006, mutations in NLRP7 were found to be responsible for recurrent hydatidiform moles (RHM), but genetic heterogeneity has been demonstrated and mutations of C6orf221 were later reported in several families. Here we report a new Egyptian family in which two sisters had eleven and four molar pregnancies, respectively. The objective was to present the results of the mutation analysis of NLRP7 and C6orf221 genes in Egyptian women with RHM. STUDY DESIGN Three women from two unrelated Egyptian families; two sisters and a previously described sporadic case, all presenting with RHM, were enrolled. The cases were subjected to detailed history taking, karyotyping and screening for mutations in NLRP7 and C6orf221. RESULTS Two NLRP7 mutations have been detected, one in each family. In the first family, sequencing identified a homozygous 2 bp deletion in the seventh coding exon of NLRP7, while a homozygous G-to-A substitution in the third coding exon of NLRP7 was detected in the second family. Both of them result in a truncated protein. The two mutations have not been previously described in the literature. No mutations in C6orf221 were found in any of the samples. CONCLUSION The detection of an NLRP7 mutation in both the familial and the apparently isolated case of RHM provides further evidence for the previously established role of NLRP7 mutations in the pathophysiology of RHM and increases the diversity of mutations described in the Egyptian population. Our results also expand further the spectrum of reproductive wastage associated with NLRP7 mutations to patients with recurrent spontaneous abortion.

Neuroimaging findings in Mowat-Wilson syndrome: a study of 54 patients

Purpose:Mowat–Wilson syndrome (MWS) is a genetic disease characterized by distinctive facial features, moderate to severe intellectual disability, and congenital malformations, including Hirschsprung disease, genital and eye anomalies, and congenital heart defects, caused by haploinsufficiency of the ZEB2 gene. To date, no characteristic pattern of brain dysmorphology in MWS has been defined.Methods:Through brain magnetic resonance imaging (MRI) analysis, we delineated a neuroimaging phenotype in 54 MWS patients with a proven ZEB2 defect, compared it with the features identified in a thorough review of published cases, and evaluated genotype–phenotype correlations.Results:Ninety-six percent of patients had abnormal MRI results. The most common features were anomalies of corpus callosum (79.6% of cases), hippocampal abnormalities (77.8%), enlargement of cerebral ventricles (68.5%), and white matter abnormalities (reduction of thickness 40.7%, localized signal alterations 22.2%). Other consistent findings were large basal ganglia, cortical, and cerebellar malformations. Most features were underrepresented in the literature. We also found ZEB2 variations leading to synthesis of a defective protein to be favorable for psychomotor development and some epilepsy features but also associated with corpus callosum agenesis.Conclusion:This study delineated the spectrum of brain anomalies in MWS and provided new insights into the role of ZEB2 in neurodevelopment.Genet Med advance online publication 10 November 2016

A cohort of 17 patients with kyphoscoliotic Ehlers-Danlos syndrome caused by biallelic mutations in FKBP14: expansion of the clinical and mutational spectrum and description of the natural history.

PurposeIn 2012 we reported in six individuals a clinical condition almost indistinguishable from PLOD1-kyphoscoliotic Ehlers–Danlos syndrome (PLOD1-kEDS), caused by biallelic mutations in FKBP14, and characterized by progressive kyphoscoliosis, myopathy, and hearing loss in addition to connective tissue abnormalities such as joint hypermobility and hyperelastic skin. FKBP14 is an ER-resident protein belonging to the family of FK506-binding peptidyl-prolyl cis–trans isomerases (PPIases); it catalyzes the folding of type III collagen and interacts with type III, type VI, and type X collagens. Only nine affected individuals have been reported to date.MethodsWe report on a cohort of 17 individuals with FKBP14-kEDS and the follow-up of three previously reported patients, and provide an extensive overview of the disorder and its natural history based on clinical, biochemical, and molecular genetics data.ResultsBased on the frequency of the clinical features of 23 patients from the present and previous cohorts, we define major and minor features of FKBP14-kEDS. We show that myopathy is confirmed by histology and muscle imaging only in some patients, and that hearing impairment is predominantly sensorineural and may not be present in all individuals.ConclusionOur data further support the extensive clinical overlap with PLOD1-kEDS and show that vascular complications are rare manifestations of FKBP14-kEDS.

Lethal multiple pterygium syndrome: A severe phenotype associated with a novel mutation in the nebulin gene

Fetal akinesia deformation sequence is a clinically and genetically heterogeneous disorder characterized by a variable combination of fetal akinesia, intrauterine growth restriction, developmental abnormalities such as cystic hygroma, hydrops fetalis, pulmonary hypoplasia, occasional arthrogryposis, and pterygia. The pathogenetic mechanisms of fetal akinesia deformation sequence include neuropathy, muscular disorders, neuromuscular junction disorders, maternal myasthenia gravis, restrictive dermopathy and others. We here report an Egyptian family presenting with recurrent lethal multiple pterygium syndrome. The diagnosis was based on antenatal sonographic demonstration of complete fetal akinesia and a large cystic hygroma with severe limb contractures evident on postmortem examination. Next generation sequencing performed on the second affected fetus identified a novel homozygous essential splice-site variant in the nebulin gene. In conclusion, our report adds further evidence for the involvement of the nebulin gene in the etiology of fetal akinesia deformation sequence/lethal multiple pterygium syndrome.

Homozygosity for a Robertsonian Translocation (13q;14q) in an Otherwise Healthy 44, XY Man With a History of Repeated Fetal Losses

We report a unique karyotype of 44,XY,der(13;14)(q10;q10)×2 detected in a phenotypically normal man married to a consanguineous healthy woman. The couple had a history of 3 second-trimester intrauterine fetal deaths (IUFDs) that involved multiple congenital anomalies. Together with a few previous observations in living patients who were homozygous for 13;14 and 14;21 translocations, this case supports the idea that subjects with 44 chromosomes can be healthy and lacking in dysmorphic features. Reproductive options for carriers of these translocations are discussed herein. With an incidence of approximately 1:1000, Robertsonian translocations are considered the most common structural chromosomal anomalies in humans.1 These translocations may arise de novo or be inherited. Among the Robertsonian translocations, 13;14 and 14;21 are the most common.2 Although the vast majority of carriers of Robertsonian translocations are phenotypically normal, the abnormality contributes to genetic imbalances in the offspring, causing early spontaneous abortions, fetal losses, mental retardation, multiple congenital anomalies, uniparental disomy, and infertility.3,4 An increased frequency of Robertsonian translocations has been reported among men with severe oligozoospermia and azoospermia.5 Balanced translocations interfere with normal chromosome pairing and segregation at meiosis phase I, thus creating the potential for the formation of unbalanced gametes and subsequent unbalanced phenotypically abnormal offspring.6 Despite the relative high incidence of Robertsonian translocations, reports of homozygosity for these chromosomal abnormalities are extremely rare. In a review of the literature, very few cases were found to have 2 translocations involving the same acrocentric chromosomes.7–13 Herein, we report a homozygous (13;14) Robertsonian translocation detected in the male partner of a couple with repeated fetal losses. ### Case Presentation The probands are a phenotypically normal consanguineous couple who attended our clinic seeking genetic counseling because of their history of 3 consecutive intrauterine fetal deaths (IUFDs) involving multiple congenital anomalies. The husband was 26 years old …