The unc-13 homolog B (UNC13B) gene encodes a presynaptic protein, mammalian uncoordinated 13–2 (Munc13-2), that is highly expressed in the brain—predominantly in the cerebral cortex—and plays an essential role in synaptic vesicle priming and fusion, potentially affecting neuronal excitability. However, the functional significance of UNC13B mutation in human disease is not known. In this study we screened for novel genetic variants in a cohort of 446 unrelated cases (families) with partial epilepsy without acquired causes by trio-based whole-exome sequencing. UNC13B variants were identified in 12 individuals affected by partial epilepsy and/or febrile seizures from eight unrelated families. The eight probands all had focal seizures and focal discharges in EEG recordings, including two patients who experienced frequent daily seizures and one who showed abnormalities in the hippocampus by brain MRI; however, all of the patients showed favorable outcome without intellectual or developmental abnormalities. The identified UNC13B variants included one nonsense variant, two variants at or around a splice site, one compound heterozygous missense variant, and four missense variants that cosegregated in the families. The frequency of UNC13B variants identified in the present study was significantly higher than that in a control cohort of Han Chinese and controls of the East Asian and all populations in the Genome Aggregation Database. Computational modeling, including hydrogen bond and docking analyses, suggested that the variants lead to functional impairment. In Drosophila, seizure rate and duration were increased by Unc13b knockdown compared to wild-type flies, but these effects were less pronounced than in sodium voltage-gated channel alpha subunit 1 (Scn1a) knockdown Drosophila. Electrophysiologic recordings showed that excitatory neurons in Unc13b-deficient flies exhibited increased excitability. These results suggest that UNC13B is potentially associated with epilepsy. The frequent daily seizures and hippocampal abnormalities but ultimately favorable outcome under antiepileptic therapy in our patients indicate that partial epilepsy caused by UNC13B variant is a clinically manageable condition.

Hereditary spherocytosis (HS), the most common cause of congenital hemolytic anemia, is caused by deficiency of the erythrocyte membrane proteins. Five causative genes (ANK1, SPTB, SPTA1, SLC4A1, and EPB42) have been identified. To date, molecular genetic studies have been performed in different populations, including the American, European, Brazilian, Japanese and Korean populations, whereas only a few studies have been described in the Chinese population. Here, by reanalysis of the exome data, we revealed causative mutations and established a definitive diagnosis of HS in all 38 Chinese families. We found 34 novel mutations and four reported mutations in three known HS-causing genes-17 in ANK1, 17 in SPTB and four in SLC4A1, suggesting that ANK1 and SPTB are the major genes in Chinese patients with HS. All of the ANK1 or SPTB mutations, scattered throughout the entire genes, are non-recurrent; and most of them are null mutations, which might cause HS via a haploinsufficiency mechanism. De novo mutations in ANK1 or SPTB often occur with an unexpected high frequency (87.5% and 64.2%, respectively). Our study updates our knowledge about the genetic profile of HS in Chinese and shows that family-based, especially parent-offspring trio, sequencing analysis can help to increase the diagnostic power and improve diagnostic efficiency.

Neurodevelopmental delay accompanied unexplained dyspnea is a highly lethal disease in clinic. This study is to investigate the performance characteristics of trio whole exome sequencing (Trio-WES) in a pediatric setting by presenting our patient cohort and displaying the diagnostic yield. A total of 31 pediatric patients showing neurodevelopmental delay accompanied unexplained dyspnea were admitted to our hospital and referred for molecular genetic testing using Trio-WES. Eight genes namely MMACHC, G6PC, G6PT, ETFDH, OTC, NDUFAF5, SLC22A5, and MAGEL2 were suspected to be responsible for the onset of the clinical symptoms and 6 variants were novel. Standard interpretation according to ACMG guideline showed that the variants were pathogenic. Finally, diagnosis of methylmalonic aciduria and homocystinuria, glycogen storage disease, ornithine transcarbamylase deficiency, glutaric acidemia II, mitochondrial complex 1 deficiency, carnitine deficiency, and Schaaf-Yang syndrome was made in 12 out of the 31 patients. Trio-WES is an effective means for molecular diagnosis of infantile neurodevelopmental delay accompanied unexplained dyspnea. As for molecular etiology identification, when routine potential monogenetic inheritance patterns including de novo, autosomal recessive, autosomal dominant, and X-linked recessive inheritance analysis is negative, physicians should take into account imprinted genes.

Hereditary hemorrhagic telangiectasia (HHT) can be clinically diagnosed, but children often lack characteristic features. We report a family with homozygous growth differentiation factor 2 (GDF2)–related HHT diagnosed by genetic testing. A boy aged 5 years and 2 months presented with isolated hypoxemia. He was the product of a consanguineous marriage; his parents were second cousins. Physical examination revealed cyanosis of nail beds and clubbed fingers. Pulse oxygen saturation was 84% to 89%. Lung function, contrast-enhanced lung computed tomography, and noncontrast echocardiography were normal. A pulmonary perfusion scan revealed radioactivity in the brain and bilateral kidney, suggesting the existence of a intrapulmonary shunt. Whole-exome sequencing revealed a homozygous variant [c.1060_1062delinsAG (p.Tyr354ArgfsTer15)] in GDF2, which was found to be inherited from his heterozygous parents. At the age of 8 years, he developed epistaxis, and an angiogram revealed diffuse pulmonary arteriovenous malformations. At the age of 9 years, he was treated with sirolimus, and his condition improved significantly. However, his now 7-year-old sister with the same homozygous variant currently has no symptoms. Physical examinations revealed 1 pinpoint-sized telangiectasia on the chest of his mother and a vascular lesion on the forehead of his sister. Additionally, the patient’s father and great-uncle had a history of mild to moderate epistaxis. Mutation in GDF2 is a rare cause of HHT. Ours is the first report of homozygous GDF2-related HHT; in addition, this variant has not been reported previously. In our report, we also confirm variable expressivity, even with the same pathogenic variant in GDF2-related HHT.

The genetic effect of more pathogenic variants in various DKD susceptibility genes, especially variants in the gene, partially explained the more severe kidney phenotype in probands with kidney biopsy-proven DKD.