Mainzer-Saldino syndrome (MSS) is a rare disorder characterized by phalangeal cone-shaped epiphyses, chronic renal failure, and early-onset, severe retinal dystrophy. Through a combination of ciliome ...resequencing and Sanger sequencing, we identified IFT140 mutations in six MSS families and in a family with the clinically overlapping Jeune syndrome. IFT140 is one of the six currently known components of the intraflagellar transport complex A (IFT-A) that regulates retrograde protein transport in ciliated cells. Ciliary abundance and localization of anterograde IFTs were altered in fibroblasts of affected individuals, a result that supports the pivotal role of IFT140 in proper development and function of ciliated cells.
To investigate the utility of autozygome analysis and exome sequencing in a cohort of patients with suspected or confirmed mitochondrial encephalomyopathy.
Autozygome was used to highlight candidate ...genes for direct sequencing in 10 probands, all born to consanguineous parents. Autozygome was also used to filter the variants from exome sequencing of four probands.
In addition to revealing mutations in known mitochondrial genes, the analysis revealed the identification of two novel candidate disease genes: MFF and FARS2, encoding the mitochondrial fission factor and phenylalanyl-tRNA synthetase, respectively.
These findings expand the repertoire of genes that are mutated in patients with mitochondrial disorders and highlight the value of integrating genomic approaches in the evaluation of these patients.
Mutations in several known or putative glycosyltransferases cause glycosylation defects in α-dystroglycan (α-DG), an integral component of the dystrophin glycoprotein complex. The hypoglycosylation ...reduces the ability of α-DG to bind laminin and other extracellular matrix ligands and is responsible for the pathogenesis of an inherited subset of muscular dystrophies known as the dystroglycanopathies. By exome and Sanger sequencing we identified two individuals affected by a dystroglycanopathy with mutations in β-1,3-N-acetylgalactosaminyltransferase 2 (B3GALNT2). B3GALNT2 transfers N-acetyl galactosamine (GalNAc) in a β-1,3 linkage to N-acetyl glucosamine (GlcNAc). A subsequent study of a separate cohort of individuals identified recessive mutations in four additional cases that were all affected by dystroglycanopathy with structural brain involvement. We show that functional dystroglycan glycosylation was reduced in the fibroblasts and muscle (when available) of these individuals via flow cytometry, immunoblotting, and immunocytochemistry. B3GALNT2 localized to the endoplasmic reticulum, and this localization was perturbed by some of the missense mutations identified. Moreover, knockdown of b3galnt2 in zebrafish recapitulated the human congenital muscular dystrophy phenotype with reduced motility, brain abnormalities, and disordered muscle fibers with evidence of damage to both the myosepta and the sarcolemma. Functional dystroglycan glycosylation was also reduced in the b3galnt2 knockdown zebrafish embryos. Together these results demonstrate a role for B3GALNT2 in the glycosylation of α-DG and show that B3GALNT2 mutations can cause dystroglycanopathy with muscle and brain involvement.
The current study characterizes a cohort of limb-girdle muscular dystrophy (LGMD) in the United States using whole-exome sequencing. Fifty-five families affected by LGMD were recruited using an ...institutionally approved protocol. Exome sequencing was performed on probands and selected parental samples. Pathogenic mutations and cosegregation patterns were confirmed by Sanger sequencing. Twenty-two families (40%) had novel and previously reported pathogenic mutations, primarily in LGMD genes, and also in genes for Duchenne muscular dystrophy, facioscapulohumeral muscular dystrophy, congenital myopathy, myofibrillar myopathy, inclusion body myopathy and Pompe disease. One family was diagnosed via clinical testing. Dominant mutations were identified in COL6A1, COL6A3, FLNC, LMNA, RYR1, SMCHD1 and VCP, recessive mutations in ANO5, CAPN3, GAA, LAMA2, SGCA and SGCG, and X-linked mutations in DMD. A previously reported variant in DMD was confirmed to be benign. Exome sequencing is a powerful diagnostic tool for LGMD. Despite careful phenotypic screening, pathogenic mutations were found in other muscle disease genes, largely accounting for the increased sensitivity of exome sequencing. Our experience suggests that broad sequencing panels are useful for these analyses because of the phenotypic overlap of many neuromuscular conditions. The confirmation of a benign DMD variant illustrates the potential of exome sequencing to help determine pathogenicity.
Whole-exome sequencing and autozygosity mapping studies, independently performed in subjects with defective combined mitochondrial OXPHOS-enzyme deficiencies, identified a total of nine ...disease-segregating FBXL4 mutations in seven unrelated mitochondrial disease families, composed of six singletons and three siblings. All subjects manifested early-onset lactic acidemia, hypotonia, and developmental delay caused by severe encephalomyopathy consistently associated with progressive cerebral atrophy and variable involvement of the white matter, deep gray nuclei, and brainstem structures. A wide range of other multisystem features were variably seen, including dysmorphism, skeletal abnormalities, poor growth, gastrointestinal dysmotility, renal tubular acidosis, seizures, and episodic metabolic failure. Mitochondrial respiratory chain deficiency was present in muscle or fibroblasts of all tested individuals, together with markedly reduced oxygen consumption rate and hyperfragmentation of the mitochondrial network in cultured cells. In muscle and fibroblasts from several subjects, substantially decreased mtDNA content was observed. FBXL4 is a member of the F-box family of proteins, some of which are involved in phosphorylation-dependent ubiquitination and/or G protein receptor coupling. We also demonstrate that FBXL4 is targeted to mitochondria and localizes in the intermembrane space, where it participates in an approximately 400 kDa protein complex. These data strongly support a role for FBXL4 in controlling bioenergetic homeostasis and mtDNA maintenance. FBXL4 mutations are a recurrent cause of mitochondrial encephalomyopathy onset in early infancy.
Primary microcephaly (PM) is a developmental disorder of early neuroprogenitors that results in reduction of the brain mass, particularly the cortex. To gain fresh insight into the pathogenesis of ...PM, we describe a consanguineous family with a novel genetic variant responsible for the disease. We performed autozygosity mapping followed by exome sequencing to detect the causal genetic variant. Several functional assays in cells expressing the wild-type or mutant gene were performed to understand the pathogenesis of the identified mutation. We identify a novel mutation in PHC1, a human orthologue of the Drosophila polyhomeotic member of polycomb group (PcG), which significantly decreases PHC1 protein expression, increases Geminin protein level and markedly abolishes the capacity to ubiquitinate histone H2A in patient cells. PHC1 depletion in control cells similarly enhances Geminin expression and decreases histone H2A ubiquitination. The ubiquitination defect and accumulation of Geminin with consequent defect in cell cycle are rescued by over-expression of PHC1 in patient cells. Although patients with the PHC1 mutation exhibit PM with no overt progression of the disease, patient cells also show aberrant DNA damage repair, which is rescued by PHC1 overexpression. These findings reveal several cellular defects in cells carrying the PHC1 mutation and highlight the role of chromatin remodeling in the pathogenesis of PM.
Environmental pollution has been an emerging global public health problem worldwide. This study aimed to investigate the impact of air pollutants particulate matter PM2.5, PM10, Carbon Monoxide (CO), ...Nitrogen Dioxide (NO2), Sulfur Dioxide (SO2), and Ozone (O3) on lung functions.
In this matched case-control, cross-sectional study, two schools were selected located in two different areas, school # 1 was located near a traffic-polluted area, and school # 2 was in an area away from the traffic-polluted area. Of a total of 300 students, 150 (75 boys and 75 girls) students from school # 1 and 150 students (75 boys and 75 girls) were from school # 2 located away from a traffic-polluted area. The mean age of students was 13.53 ± 1.20 years. The students in both schools were enrolled in the study on their voluntary involvement, and health status, matched by age, height, weight, gender, nationality, regional, socioeconomic, and cultural background, and the admission criteria of their schools. The environmental pollutants particulate matter “PM2.5, PM10, CO, NO2, SO2, and O3” were recorded. The level of air pollutants in school # 1 was 35.00 ± 0.65, significantly higher compared to school # 2 (29.95 ± 0.32). The pulmonary function test (PFT) parameters were performed on an electronic Spirometer. The parameters included “Forced Vital Capacity (FVC); Forced Expiratory Volume in the first second (FEV1); Forced Expiratory Ratio (FEV1/FVC %); Forced Expiratory Flow 25 % (FEF 25 %); Forced Expiratory Flow 50 % (FEF 50 %); Forced Expiratory Flow 75 % (FEF 75 %) and Peak Expiratory Flow Rate (PEFR) were recorded”.
The results revealed that the mean values for FEF-50 % (3.31 ± 1.18); FEF-75 % (1.66 ± 0.80) and PEFR (5.02 ± 1.79) were significantly decreased among students studying in school situated in a motor vehicle polluted area compared to those studying in school positioned away from the motor vehicle polluted area FEF-50 % (5.85 ± 6.21) (p = 0.001); and FEF-75 % (4.49 ± 6.87) (p = 0.001), and PEFR (8.14 ± 15.08) (p = 0.012). However, the groups had no significant difference between FVC, FEV1, FEV1/FVC Ratio (%), and FEF-25 %. The findings further demonstrated that the pattern of lung function impairment was peripheral airway lung involvement amongst the students in schools placed in environmentally contaminated areas.
Environmental pollution significantly impaired lung function parameters FEF-50%, FEF-75% and PEFR, with peripheral airway lung involvement among students who studied in a school situated in motor vehicle-polluted areas. The results highlight the importance of the implementation of effective mitigation strategies and promoting sustainable and environmentally friendly transportation options to combat environmental pollution.
Emery-Dreifuss muscular dystrophy (EDMD) is a rare disorder characterized by early joint contractures, muscular dystrophy, and cardiac involvement with conduction defects and arrhythmias. So far, ...only 35% of EDMD cases are genetically elucidated and associated with
EMD or
LMNA gene mutations, suggesting the existence of additional major genes. By whole-genome scan, we identified linkage to the Xq26.3 locus containing the
FHL1 gene in three informative families belonging to our
EMD- and
LMNA-negative cohort. Analysis of the
FHL1 gene identified seven mutations, in the distal exons of
FHL1 in these families, three additional families, and one isolated case, which differently affect the three FHL1 protein isoforms: two missense mutations affecting highly conserved cysteines, one abolishing the termination codon, and four out-of-frame insertions or deletions. The predominant phenotype was characterized by myopathy with scapulo-peroneal and/or axial distribution, as well as joint contractures, and associated with a peculiar cardiac disease characterized by conduction defects, arrhythmias, and hypertrophic cardiomyopathy in all index cases of the seven families. Heterozygous female carriers were either asymptomatic or had cardiac disease and/or mild myopathy. Interestingly, four of the
FHL1-mutated male relatives had isolated cardiac disease, and an overt hypertrophic cardiomyopathy was present in two. Expression and functional studies demonstrated that the FHL1 proteins were severely reduced in all tested patients and that this was associated with a severe delay in myotube formation in the two patients for whom myoblasts were available. In conclusion,
FHL1 should be considered as a gene associated with the X-linked EDMD phenotype, as well as with hypertrophic cardiomyopathy.
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