Phenotypic and genotypic characterization of families with complex intellectual disability identified pathogenic genetic variations in known and novel disease genes.

Intellectual disability (ID), which presents itself during childhood, belongs to a group of neurodevelopmental disorders (NDDs) that are clinically widely heterogeneous and highly heritable, often being caused by single gene defects. Indeed, NDDs can be attributed to mutations at over 1000 loci, and all type of mutations, ranging from single nucleotide variations (SNVs) to large, complex copy number variations (CNVs), have been reported in patients with ID and other related NDDs. In this study, we recruited seven different recessive NDD families with comorbidities to perform a detailed clinical characterization and a complete genomic analysis that consisted of a combination of high throughput SNP-based genotyping and whole-genome sequencing (WGS). Different disease-associated loci and pathogenic gene mutations were identified in each family, including known (n = 4) and novel (n = 2) mutations in known genes (NAGLU, SLC5A2, POLR3B, VPS13A, SYN1, SPG11), and the identification of a novel disease gene (n = 1; NSL1). Functional analyses were additionally performed in a gene associated with autism-like symptoms and epileptic seizures for further proof of pathogenicity. Lastly, detailed genotype-phenotype correlations were carried out to assist with the diagnosis of prospective families and to determine genomic variation with clinical relevance. We concluded that the combination of linkage analyses and WGS to search for disease genes still remains a fruitful strategy for complex diseases with a variety of mutated genes and heterogeneous phenotypic manifestations, allowing for the identification of novel mutations, genes, and phenotypes, and leading to improvements in both diagnostic strategies and functional characterization of disease mechanisms.

Expression analysis and genotyping of DGKZ: a GWAS-derived risk gene for schizophrenia.

Schizophrenia (SCZ) is a disabling and severe mental illness characterized by abnormal social behavior and disrupted emotions. Similar to other neuropsychological disorders, both genetics and environmental factors interplay so as to develop SCZ. It is acknowledged that genes such as DGKZ are involved in lipid signaling pathways that are the basis of neural activities, memory, and learning and are considered as candidate loci for SCZ. The aim of the present study was to evaluate the expression level and genotypes of DGKZ in patients with SCZ and controls. We used q-PCR to measure the relative expression of DGKZ in blood. To determine DGKZ-rs7951870 genotypes, tetra-ARMS PCR was used. Our results showed a significant difference in DGKZ mRNA ratio between SCZ patients and healthy controls (P = 2 × 10-4). Also, we showed that rs7951870-TT genotype was strongly associated with increased DGKZ expression level (P = 0.038). In conclusion, our findings revealed dysregulation of DGKZ in SCZ patients and a significant correction between the gene expression and DGKZ variant rs7951870.

Molecular characterization of PRKN structural variations identified through whole-genome sequencing.

BACKGROUND: Early-onset Parkinson's disease (PD) is the most common inherited form of parkinsonism, with the PRKN gene being the most frequently identified mutated. Exon rearrangements, identified in about 43.2% of the reported PD patients and with higher frequency in specific ethnicities, are the most prevalent PRKN mutations reported to date in PD patients. METHODS: In this study, three consanguineous families with early-onset PD were subjected to whole-genome sequencing (WGS) analyses that were followed by Sanger sequencing and droplet digital PCR to validate and confirm the disease segregation of the identified genomic variations and to determine their parental origin. RESULTS: Five different PRKN structural variations (SVs) were identified. Because the genomic sequences surrounding the break points of the identified SVs might hold important information about their genesis, these were also characterized for the presence of homology and repeated sequences. CONCLUSION: We concluded that all identified PRKN SVs might originate through retrotransposition events.

A novel mutation in SMOC1 and variable phenotypic expression in two patients with Waardenburg anophthalmia syndrome.

Waardenburg anophthalmia syndrome (WAS) is a rare disorder that mostly affects the eyes and distal limbs. In the current study we reported two Iranian patients with WAS. The first case was a 26-year-old girl with unilateral anophthalmia, bilateral camptodactyly and clinodactyly in her hands, oligodactly in her left foot and syndactyly of the second to fifth toes in her right foot. She also had severe hearing loss in both ears. The second case was a 12-year-old boy with bilateral anophthalmia, camptodactyly in his right hand, oligodactyly in his foot, clubfoot, and cryptorchidism. Both patients were mentally normal. To detect the causative mutation all exons and exon-intron boundaries of SMOC1 gene were sequenced in patients and other normal family members. We found a homozygous missense mutation (NM_001034852.2(SMOC1):c.367T > C) in exon 3 of SMOC1 gene in both patients. As the mutation segregated with the disease in the family, it should be the causative mutation. Our study extended the mutation spectrum of SMOC1 gene related to WAS.

Novel Mutations in TACSTD2 Gene in Families with Gelatinous Drop-like Corneal Dystrophy (GDLD).

In the current study, we conducted a mutation screening of tumor-associated calcium signal transducer 2 (TACSTD2) gene in six consanguineous Iranian families with gelatinous drop-like corneal dystrophy (GDLD), in order to find the causative mutations. Detailed eye examination was performed by ophthalmologist to confirm GDLD in patients. To detect the possible mutations, direct Sanger sequencing was performed for the only exon of TACSTD2 gene, and its boundary regions in all patients. In the patients with GDLD, the corneal surface showed lesions with different shapes from mild to severe forms depending on the progress of the disease. The patients showed grayish corneal deposits as a typical mulberry form, corneal dystrophy along with corneal lipid deposition, and vascularization. Targeted Sanger sequencing in TACSTD2 gene revealed the causative mutations in this gene in all studied families. Our study expanded the mutational spectrum of TACSTD2 which along with the related symptoms could help with the diagnosis, and management of the disease.