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DRG1 is a highly conserved member of a class of GTPases implicated in ribosome biogenesis and translation. The expression of mammalian DRG1 is elevated in the central nervous system during development, and its function has been implicated in fundamental cellular processes including protein synthesis and cellular proliferation. Using exome sequencing, we identified rare and likely pathogenic germline DRG1 variants including three stop-gained p.Gly54*, p.Arg140*, p.Lys263* and a p.Asn248Phe missense variant. These alleles segregate recessively in four affected individuals from three unrelated families and cause a neurodevelopmental disorder with global developmental delay, microcephaly, short stature and craniofacial anomalies. Using functional assays, we show that these loss-of-function variants: 1) severely disrupt DRG1 mRNA/protein stability in patient-derived fibroblasts, 2) impair it’s GTPase activity in vitro and 3) compromise it’s binding to partner protein ZC3H15. Consistent with the importance of DRG1 in humans, targeted inactivation of Drg1 in mice resulted in pre-weaning lethality. Our work highlights the importance of DRG1 GTPase activity for normal development and underscores the significance of translation factor GTPases in human physiology and homeostasis.

ObjectiveTo test the utility and diagnostic yield of a medical-exome gene panel for identifying pathogenic variants in Mendelian disorders.MethodsNext-generation sequencing was performed with the TruSight One gene panel (targeting 4813 genes) followed by MiSeq sequencing on 216 patients who presented with suspected genetic disorders as assessed by their attending physicians.ResultsThere were 56 pathogenic and 36 likely pathogenic variants across 57 genes identified in 87 patients. Causal mutations were more likely to be truncating and from patients with a prior clinical diagnosis. Another 18 promising variants need further evaluation for more evidence to meet the requirement for potential upgrade to pathogenic. Forty-five of the 92 clinically significant variants were novel.ConclusionThe 40.3% positive yield compares favourably with similar studies using either this panel or whole exome sequencing, demonstrating that large gene panels could be a good alternative to whole exome sequencing for quick genetic confirmation of Mendelian disorders.

ObjectiveUse next-generation sequencing (NGS) technology to improve our diagnostic yield in patients with suspected genetic disorders in the Asian setting.DesignA diagnostic study conducted between 2014 and 2019 (and ongoing) under the Singapore Undiagnosed Disease Program. Date of last analysis was 1 July 2019.SettingInpatient and outpatient genetics service at two large academic centres in Singapore.PatientsInclusion criteria: patients suspected of genetic disorders, based on abnormal antenatal ultrasound, multiple congenital anomalies and developmental delay. Exclusion criteria: patients with known genetic disorders, either after clinical assessment or investigations (such as karyotype or chromosomal microarray).InterventionsUse of NGS technology—whole exome sequencing (WES) or whole genome sequencing (WGS).Main outcome measures(1) Diagnostic yield by sequencing type, (2) diagnostic yield by phenotypical categories, (3) reduction in time to diagnosis and (4) change in clinical outcomes and management.ResultsWe demonstrate a 37.8% diagnostic yield for WES (n=172) and a 33.3% yield for WGS (n=24). The yield was higher when sequencing was conducted on trios (40.2%), as well as for certain phenotypes (neuromuscular, 54%, and skeletal dysplasia, 50%). In addition to aiding genetic counselling in 100% of the families, a positive result led to a change in treatment in 27% of patients.ConclusionGenomic sequencing is an effective method for diagnosing rare disease or previous ‘undiagnosed’ disease. The clinical utility of WES/WGS is seen in the shortened time to diagnosis and the discovery of novel variants. Additionally, reaching a diagnosis significantly impacts families and leads to alteration in management of these patients.

Neurofibromatosis type 1 (NF1) is one of the most common inherited disorders. It is caused by mutations in the neurofibromin-1 gene (NF1) and affects the formation and growth of nerve tissues. More than 3,600 pathogenic variants in the NF1 gene have been identified from patients with most of the germline variants are from the Western populations. We found 16 patients (15 Chinese and 1 Asian Indian) who had heterozygous variants in NF1 through targeted next-generation sequencing. There were 15 different variants: 4 frameshift, 4 nonsense, 5 missense, and 2 splice variants. One nonsense variant and three frameshift variants had never been reported in any population or patient database. Twelve of the 16 patients met the NF1 diagnostic criteria, and each was found to have a pathogenic or likely pathogenic variant. Three different missense variants of unknown significance were discovered in the other four patients who did not meet NF1 diagnostic criteria. Our findings add four novel variants to the list of genetic mutations linked to NF1's various clinical manifestations.

Published 2019. This article is a U.S. Government work and is in the public domain in the USA. This study explored patients' experiences and perceptions of living with thalassemia (an inherited hematologic disorder), perceptions of social stigma, and impact on disclosure decision-making. Semistructured, in-person interviews were conducted in Singapore with 30 individuals: 16 thalassemia major patients and 14 parents of children with thalassemia. Findings were indicative of felt or enacted stigma that may have influenced disclosure decisions. Although affected individuals commonly disclosed their thalassemia diagnosis to family members, they either downplayed the condition with or avoided disclosure to unrelated individuals. Disclosure outside the family occurred only in response to triggers, such as questions about absences due to medical care. Health professionals should provide anticipatory guidance about disclosure strategies when managing individuals with thalassemia.

Objective: Use rapid next-generation sequencing (NGS) to improve our diagnostic yield in critically ill paediatric patients with suspected genetic disorders in the Asian setting.Design: A diagnostic study conducted between April 2018 and January 2019.Methods: Next-generation sequencing was performed with the TruSight One gene panel (targeting 4813 genes) followed by MiSeq sequencing on 10 patients who presented with suspected genetic disorders as assessed by their attending physicians. Results: In 4 of the 10 cases (40%), a genetic diagnosis was achieved, with one further case diagnosed on re-analysis of data 2 years later. The median turn-around time (TAT) for results was 9.5 working days (range 5-19 days). Challenges faced during implementation included sample availability, managing parental and primary physician expectations, cost of testing, and bioinformatic resources.Conclusion: RapidSeq is an effective method for diagnosing patients with rare diseases, which aids in shortening the diagnostic odyssey, while allowing clinicians to appropriately tailor management for the underlying disorder, and provide accurate genetic counselling for families. However, challenges such as cost and insurance implications still remain a barrier to more widespread use of genomic testing in the local setting, and continued efforts will be required to optimise RapidSeq for use in paediatric patients in the ICU.

ARGONAUTE-2 and associated miRNAs form the RNA-induced silencing complex (RISC), which targets mRNAs for translational silencing and degradation as part of the RNA interference pathway. Despite the essential nature of this process for cellular function, there is little information on the role of RISC components in human development and organ function. We identify 13 heterozygous mutations in AGO2 in 21 patients affected by disturbances in neurological development. Each of the identified single amino acid mutations result in impaired shRNA-mediated silencing. We observe either impaired RISC formation or increased binding of AGO2 to mRNA targets as mutation specific functional consequences. The latter is supported by decreased phosphorylation of a C-terminal serine cluster involved in mRNA target release, increased formation of dendritic P-bodies in neurons and global transcriptome alterations in patient-derived primary fibroblasts. Our data emphasize the importance of gene expression regulation through the dynamic AGO2-RNA association for human neuronal development., AGO2 binds to miRNAs to repress expression of cognate target mRNAs. Here the authors report that heterozygous AGO2 mutations result in defects in neurological development and impair RNA interference.

Down syndrome is the most common cause of cognitive impairment and presents clinically with universally recognizable signs and symptoms. In this study, we focus on exam findings and digital facial analysis technology in individuals with Down syndrome in diverse populations. Photos and clinical information were collected on 65 individuals from 13 countries, 56.9% were male and the average age was 6.6 years (range 1 month to 26 years; SD = 6.6 years). Subjective findings showed that clinical features were different across ethnicities (Africans, Asians, and Latin Americans), including brachycephaly, ear anomalies, clinodactyly, sandal gap, and abundant neck skin, which were all significantly less frequent in Africans (P

Background Pathogenic variants of the ARID1B gene are recognized as the most common cause of Coffin-Siris syndrome (CSS) and also one of the most common causes for intellectual disability (ID). Reported ARID1B variants in association with CSS are mostly from patients of European ancestry. Methods We performed next-generation sequencing to identify pathogenic variants in patients with congenital disorders from the Genetics clinics. The identified variants were validated by Sanger sequencing. Parental samples were tested by Sanger sequencing to determine inheritance status. Results Truncating variants in ARID1B were identified in five unrelated Asian patients (one Malay, two Chinese and two Indian) with features of CSS. One was a nonsense mutation which had been documented in three other reports while the other four were novel variants, including two nonsense substitutions and two small deletions resulting in premature termination of translation. Similar to previous reports, all patients have developmental and speech delay, with additional presentations such as ectodermal/facial abnormalities commonly observed in CSS patients. Conclusions Our results unveil ARID1B variants in association with CSS in multiple Southeast Asian ethnic groups, and confirm that variants associated with this disorder tend to be of the truncating type. This finding may provide additional insight into the function of the protein and the disease mechanism.

Left ventricular non-compaction (LVNC) is reported to affect 0.14 % of the pediatric population. The etiology is heterogeneous and includes a wide number of genetic causes. As an illustration, we report two patients with LVNC who were diagnosed with a genetic syndrome. We then review the literature and suggest a diagnostic algorithm to evaluate individuals with LVNC. Case 1 is a 15-month-old girl who presented with hypotonia, global developmental delay, congenital heart defect (including LVNC) and facial dysmorphism. Case 2 is a 7-month-old girl with hypotonia, seizures, laryngomalacia and LVNC. We performed chromosomal microarray for both our patients and detected chromosome 1p36 microdeletion. We reviewed the literature for other genetic causes of LVNC and formulated a diagnostic algorithm, which includes assessment for syndromic disorders, inborn error of metabolism, copy number variants and non-syndromic monogenic disorder associated with LVNC. LVNC is a relatively newly recognized entity, with heterogeneity in underlying etiology. For a systematic approach of evaluating the underlying cause to improve clinical care of these patients, a diagnostic algorithm for genetic evaluation of patients with LVNC is proposed.

The Professional Society of Genetic Counselors in Asia (PSGCA) was recently established as a special interest group of the Asia Pacific Society of Human Genetics. Fostering partnerships across the globe, the PSGCA’s vision is to be the lead organization that advances and mainstreams the genetic counseling profession in Asia and ensures individuals have access to genetic counseling services. Its mission is to promote quality genetic counseling services in the region by enhancing practice and curricular standards, research and continuing education. The PSGCA was formally launched during the Genetic Counseling Pre-Conference Workshop held at the 11th Asia-Pacific Conference on Human Genetics in Hanoi, Viet Nam, September 16, 2015. The pre-conference workshop provided an opportunity for medical geneticists and genetic counselors from across 10 Asia Pacific countries to learn about the varied genetic counseling practices and strategies for genetic counseling training. This paper provides an overview of the current status and challenges in these countries, and proposed course of unified actions for the future of the genetic counseling profession.

International audience; Cellular homeostasis is maintained by the highly organized cooperation of intracellular trafficking systems, including COPI, COPII, and clathrin complexes. COPI is a coatomer protein complex responsible for intracellular protein transport between the endoplasmic reticulum and the Golgi apparatus. The importance of such intracellular transport mechanisms is underscored by the various disorders, including skeletal disorders such as cranio-lenticulo-sutural dysplasia and osteogenesis imperfect, caused by mutations in the COPII coatomer complex. In this article, we report a clinically recognizable craniofacial disorder characterized by facial dysmorphisms, severe micrognathia, rhizomelic shortening, microcephalic dwarfism, and mild developmental delay due to loss-of-function heterozygous mutations in ARCN1, which encodes the coatomer subunit delta of COPI. ARCN1 mutant cell lines were revealed to have endoplasmic reticulum stress, suggesting the involvement of ER stress response in the pathogenesis of this disorder. Given that ARCN1 deficiency causes defective type I collagen transport, reduction of collagen secretion represents the likely mechanism underlying the skeletal phenotype that characterizes this condition. Our findings demonstrate the importance of COPI-mediated transport in human development, including skeletogenesis and brain growth.

Chinese hamster ovary (CHO) cells are one of the most important cell lines in biological research, and are the most widely used host for industrial production of recombinant therapeutic proteins. Despite their extensive applications, little sequence information is available for molecular based research. To facilitate gene discovery and genetic engineering, two cDNA libraries were constructed from three CHO cell lines grown under various conditions. The average insert size for both libraries is approximately 800-850 bp, and each library has comparable redundancy levels of 36%-38% for the sequences isolated. Random sequencing of 4,608 ESTs yielded 2,602 unique assemblies, 76% of which were annotated as orthologs of sequences in the GenBank database. A high abundance of mitochondrial genome transcripts facilitated the assembly of the complete mitochondrial genome by PCR walking. Comparative analysis of sequences from both mitochondrial and nuclear genomes with orthologous genes from other species shows that CHO sequences are generally most similar to mouse; however, examples with highest similarity to rat or human are common. A cDNA microarray, including all 4,608 ESTs, was constructed. The microarray results reveal a high level of consistency between transcript abundance in the libraries and fluorescence intensities. Inclusion of redundant clones in the microarray, additionally, allows small changes in abundant mRNAs to be discerned with a high degree of confidence. The information and tools generated provide access to genomic technology for this important cell line.