Outlining the Clinical Profile of TCIRG1 14 Variants including 5 Novels with Overview of ARO Phenotype and Ethnic Impact in 20 Egyptian Families.

TCIRG1 gene mutations underlie osteopetrosis, a rare genetic disorder impacting osteoclast function with consequent brittle bones prone to fracture, in spite of being characterized by increased bone density. The disorder is known to exhibit marked genetic heterogeneity, has no treatment, and is lethal in most instances. There are reports of ethnic variations affecting bone mineral density and variants' expression as diverse phenotypes even within individuals descending from the same pedigree. We herein focus on one of osteopetrosis's three types: the autosomal recessive malignant form (MIM 259700) (ARO) that is almost always associated with severe clinical symptoms. We reviewed the results of about 1800 Egyptian exomes and we did not detect similar variants within our Egyptian dataset and secondary neurological deficit. We studied twenty Egyptian families: sixteen ARO patients, ten carrier parents with at least one ARO affected sib, and two fetuses. They were all subjected to thorough evaluation and TCIRG1 gene sequencing. Our results of twenty-eight individuals descending from twenty Egyptian pedigrees with at least one ARO patient, expand the phenotype as well as genotype spectrum of recessive mutations in the TCIRG1 gene by five novel pathogenic variants. Identifying TCIRG1 gene mutations in Egyptian patients with ARO allowed the provision of proper genetic counseling, carrier detection, and prenatal diagnosis starting with two families included herein. It also could pave the way to modern genomic therapeutic approaches.

Genetic and Molecular Evaluation: Reporting Three Novel Mutations and Creating Awareness of Pycnodysostosis Disease.

Pycnodysostosis is a rare autosomal recessive disorder with characteristic diagnostic manifestations. This study aims to phenotype and provide molecular characterization of Egyptian patients, with emphasis on identifying unusual phenotypes and raising awareness about pycnodysostosis with different presentations to avoid a mis- or under-diagnosis and consequent mismanagement. We report on 22 Egyptian pycnodysostosis patients, including 9 new participants, all descending from consanguineous families and their ages ranging from 6 to 15 years. In addition, prenatal diagnosis was performed in one family with affected siblings. They all presented with short stature, except for one patient who presented with pancytopenia as her primary complaint. Moreover, 41.2% of patients had sleep apnea, 14% presented with craniosynostosis, and 44.4% had failure of tooth development. Molecular analysis via direct exome sequencing of the cathepsin K gene revealed three novel mutations ((NM_000396.3) c.761_763delCCT, c.864_865delAA, and c.509G>T) as well as two previously reported mutations among nine new cases. The following is our conclusion: This study expands the molecular spectrum of pycnodysostosis by identifying three novel mutations and adds to the clinical and orodental aspects of the disease. The link between the CTSK gene mutations and the failure of tooth development has not been established, and further studies could help to improve our understanding of the molecular pathology.

Gene Mutations of the Three Ectodysplasin Pathway Key Players (EDA, EDAR, and EDARADD) Account for More than 60% of Egyptian Ectodermal Dysplasia: A Report of Seven Novel Mutations.

Ectodermal dysplasia (ED) is a diverse group of genetic disorders caused by congenital defects of two or more ectodermal-derived body structures, namely, hair, teeth, nails, and some glands, e.g., sweat glands. Molecular pathogenesis of ED involves mutations of genes encoding key proteins of major developmental pathways, including ectodysplasin (EDA) and wingless-type (WNT) pathways. The most common ED phenotype is hypohidrotic/anhidrotic ectodermal dysplasia (HED) featuring hypotrichosis, hypohidrosis/anhidrosis, and hypodontia. Molecular diagnosis is fundamental for disease management and emerging treatments. We used targeted next generation sequencing to study EDA, EDAR, EDARADD, and WNT10A genes in 45 Egyptian ED patients with or without hypohidrosis. We present genotype and phenotype data of 28 molecularly-characterized patients demonstrating genetic heterogeneity, variable expressivity, and intrafamilial phenotypic variability. Thirteen mutations were reported, including four novel EDA mutations, two novel EDARADD, and one novel EDAR mutations. Identified mutations congregated in exons encoding key functional domains. EDA is the most common gene contributing to 85% of the identified Egyptian ED genetic spectrum, followed by EDARADD (10%) and EDAR (5%). Our cohort represents the first and largest cohort from North Africa where more than 60% of ED patients were identified emphasizing the need for exome sequencing to explore unidentified cases.

Germline and Mosaic Variants in PRKACA and PRKACB Cause a Multiple Congenital Malformation Syndrome.

PRKACA and PRKACB code for two catalytic subunits (Cα and Cß) of cAMP-dependent protein kinase (PKA), a pleiotropic holoenzyme that regulates numerous fundamental biological processes such as metabolism, development, memory, and immune response. We report seven unrelated individuals presenting with a multiple congenital malformation syndrome in whom we identified heterozygous germline or mosaic missense variants in PRKACA or PRKACB. Three affected individuals were found with the same PRKACA variant, and the other four had different PRKACB mutations. In most cases, the mutations arose de novo, and two individuals had offspring with the same condition. Nearly all affected individuals and their affected offspring shared an atrioventricular septal defect or a common atrium along with postaxial polydactyly. Additional features included skeletal abnormalities and ectodermal defects of variable severity in five individuals, cognitive deficit in two individuals, and various unusual tumors in one individual. We investigated the structural and functional consequences of the variants identified in PRKACA and PRKACB through the use of several computational and experimental approaches, and we found that they lead to PKA holoenzymes which are more sensitive to activation by cAMP than are the wild-type proteins. Furthermore, expression of PRKACA or PRKACB variants detected in the affected individuals inhibited hedgehog signaling in NIH 3T3 fibroblasts, thereby providing an underlying mechanism for the developmental defects observed in these cases. Our findings highlight the importance of both Cα and Cß subunits of PKA during human development.

Lenz-Majewski syndrome in a patient from Egypt.

Lenz-Majewski syndrome (LMS) is an extremely rare type of cutis laxa caused by dominant mutations in PTDSS1 gene. We report an Egyptian patient who presented with cutis laxa, brachydactyly, and progeroid features. LMS syndrome was suspected and a previously reported de novo heterozygous missense mutation (c.284G > T, p.R95L) in PTDSS1 was identified. To the best of our knowledge, nine molecularly proven patients with LMS from different ethnicities have been reported. Our patient is the first report from the Middle East and the tenth molecularly proven patient reported to date. His clinical features were in accordance with LMS syndrome. In addition, his hands X-ray images showed hypoplastic or absent middle and proximal phalanges but sparing the thumbs. This hand patterning was similarly observed before. Further, he had relatively large and convex fingernails. Our report highlights this unique hand patterning and suggests these signs should be considered among the diagnostic criteria of LMS. Further reports of patients with PTDSS1 mutations are necessary to further elucidate the detailed clinical features of LMS syndrome.

Identification of a novel homozygous ALX4 mutation in two unrelated patients with frontonasal dysplasia type-2.

We report two unrelated boys with frontonasal dysplasias type-2 (FND-2) who shared an identical novel homozygous ALX4 mutation c.291delG (p.Q98Sfs*83). Both patients presented with a large skull defect but one had bilateral parietal meningocele-like cysts that lie along with the bony defect and increased in size with age. Scalp alopecia, hypertelorism, and clefted alae nasi were also detected in both of them. Furthermore, impalpable gonads were noted, being unilateral in one and bilateral in the other. Neuroimaging showed small dysplastic occipital lobes with dysgyria and midline subarachnoid cyst. Additional dysplastic corpus callosum and small cerebellar vermis were observed in one patient. Parietal foramina were noted in the parents of one patient. Our findings highlight the dosage effect of ALX4 and underscore the challenges of prenatal genetic counseling. Further, the indirect role of ALX4 in the development of the occipital lobe and posterior fossa is discussed.

Further delineation of the oculoauricular syndrome phenotype: A new family with a novel truncating HMX1 mutation.

Biallelic HMX1 mutations cause a very rare autosomal recessive genetic disorder termed as oculoauricular syndrome (OAS) because it is characterized only by the combination of eye and ear anomalies. We identified a new family bringing to three the total families reported with this disorder. Our proband presented with anteriorly protruded ears and malformed ear pinnae in association with microphthalmia, congenital cataract, microcornea, and iris and optic disc colobomata. Additionally, he had high and broad forehead with asymmetry giving a recognizable facial gestalt. Further, short left mandibular ramus and bifid cingulum in the boy and short right mandibular ramus in his father were observed. Mutation analysis revealed a novel homozygous nonsense mutation c.487G>T in the second exon of the HMX1 that predicted to introduce a premature stop codon at position 163 (p.E163*). Parents showed the heterozygous state of the detected mutation. Investigations in a process as complex as craniofacial development suggest that there are still additional, as yet unidentified, genes that play in orchestrate to determine the final phenotype.

Lipoid proteinosis: A clinical and molecular study in Egyptian patients.

Lipoid proteinosis (LP) is an autosomal recessive disorder caused by the loss of function of ECM1 gene. Clinical features include varying degrees of skin thickening, hoarseness of voice and less frequently neuropsychiatric abnormalities. Twelve patients from ten unrelated families with a clinical diagnosis of lipoid proteinosis were enrolled in this study. Extraction of DNA samples of the 12 patients and their parents from peripheral blood by standard methods was performed. Polymerase chain reaction (PCR) amplification of the ECM1 gene was conducted using eight pairs of primers spanning over the 10 exons and splice junctions. Patients exhibited a variety of clinical manifestations with skin affection and hoarseness of voice being the consistent feature. We identified five novel homozygous insertion, small deletion, missense, and splice site mutations as well as two homozygous previously published splice site mutation c.70+1G>C in intron 1 and c.1305-2A>G in intron 8. The specific mutations were: c.10_11insC in exon 1, c.690_691delAG in exon 6, c.734G>A in exon 7, c.1286_1287delAA in exon 8 and c.1393-1G>T in intron 9. The novel mutations c.1393-1G>T and c.10_11insC occurred in three (30%) and two (20%) unrelated patients of the studied families, respectively. Further studies may designate an increased frequency of these mutations among Egyptian LP patients. Identification of pathogenic ECM1 mutations is important for accurate diagnosis and proper genetic counseling.

Expanding the mutation and clinical spectrum of Roberts syndrome.

Roberts syndrome and SC phocomelia syndrome are rare autosomal recessive genetic disorders representing the extremes of the spectrum of severity of the same condition, caused by mutations in ESCO2 gene. We report three new patients with Roberts syndrome from three unrelated consanguineous Egyptian families. All patients presented with growth retardation, mesomelic shortening of the limbs more in the upper than in the lower limbs and microcephaly. Patients were subjected to clinical, cytogenetic and radiologic examinations. Cytogenetic analysis showed the characteristic premature separation of centromeres and puffing of heterochromatic regions. Further, sequencing of the ESCO2 gene identified a novel mutation c.244_245dupCT (p.T83Pfs*20) in one family besides two previously reported mutations c.760_761insA (p.T254Nfs*27) and c.764_765delTT (p.F255Cfs*25). All mutations were in homozygous state, in exon 3. The severity of the mesomelic shortening of the limbs and craniofacial anomalies showed variability among patients. Interestingly, patient 1 had abnormal skin hypopigmentation. Serial fetal ultrasound examinations and measurements of long bones diagnosed two affected fetuses in two of the studied families. A literature review and case comparison was performed. In conclusion, we report a novel ESCO2 mutation and expand the clinical spectrum of Roberts syndrome.