Weiyue Gu

Gitelman syndrome (GS) is an autosomal recessive disorder and mild variant of classic Bartter syndrome. The latter is caused by defects in the genes CLCNKB and/or CLCNKA (chloride voltage-gated channel Ka and Kb). Patients with GS usually have loss-of-function mutations in SLC12A3. No patient has been reported with compound heterozygous mutations in these genes. We report a girl with GS with a paternally inherited heterozygous mutation in SLC12A3, and maternally inherited heterozygous variants in both CLCNKB and CLCNKA. In this report, we reported a female patient (8 y and 10 mo) who had growth retardation (111.8 cm, − 1.62 standard deviation height for age) and normal blood pressure, with persistent hypokalemia, hypomagnesemia, hypocalciuria, hypochloremic alkalosis, and elevated levels of plasma renin and aldosterone. Her younger brother, father, and paternal grandmother all had histories of mild low levels of plasma potassium (3.0–3.5 mmol/L), which were rectified by potassium-rich foods. The genomic DNA of the patient, younger brother, parents, and grandparents were screened for gene variations and pedigree analysis using trio whole exome sequencing (WES). The candidate variants were validated by Sanger sequencing. Protein-protein interaction analysis utilized the following databases: Biogrid, MINT, HPRD, STRING, IntAct, iRefIndex, and ppiTrim. The trio WES screening showed that the patient has paternally inherited SLC12A3 p.N359K, and maternally inherited CLCNKB p.L94I. The paternal grandmother and younger brother are both carriers of SLC12A3 p.N359K. According to the STRING database, SLC12A3 and CLCNKB proteins may interact or coexpress with proteins associated with GS. Based on clinical phenotypes, genetic evidence of the pedigree, and previous reported studies, this case of GS indicates a digenetic inheritance of SLC12A3 and CLCNKB that resulted in renal tubular dysfunction perhaps, due to a genetic double-hit mechanism. The putative pathogenicity of the CLCNKB p.L94I variant requires confirmation.

Tandem mass spectrometry (MS MS) and simple fluorometric assays are currently used in newborn screening programs to detect inborn errors of metabolism (IEM). The aim of the study was to evaluate the clinical utility of exome sequencing as a second tier screening method to assist clinical diagnosis of the newborn. A novel PCR-exome amplification and re-sequencing (PEARS) assay was designed and used to detect mutations in 122 genes associated with 101 IEM. Newborn bloodspots positive by biochemical testing were analysed by PEARS assay to detect pathogenic mutations relevant to the IEM. In initial validation studies of genomic DNA samples, PEARS assay correctly detected 25 known mutations associated with 17 different IEM. Retrospective gene analysis of newborns with clinical phenylketonuria (PKU), identified compound heterozygote phenylalanine hydroxylase (PAH) gene mutations in eight of nine samples (89%). Prospective analysis of 211 bloodspots correctly identified the two true PKU samples, yielding positive and negative predictive values of 100%. Testing of 8 true positive MS MS samples correctly identified potentially pathogenic compound heterozygote genotypes in 2 cases of citrullinemia type 1 and one case each of methylmalonic acidemia, isobutyryl-CoA dehydrogenase deficiency, short chain acyl-CoA dehydrogenase deficiency and glutaric acid type II and heterozygous genotypes in 2 cases of autosomal dominant methioninemia. Analysis of 11 of 12 false positive MS MS samples for other IEM identified heterozygous carriers in 8 cases for the relevant genes associated with the suspected IEM. In the remaining 3 cases, the test revealed compound heterozygote mutations in other metabolic genes not associated with the suspected IEM, indicating a misinterpretation of the original MS MS data. The PEARS assay has clinical utility as a rapid and cost effective second-tier test to assist the clinician to accurately diagnose newborns with a suspected IEM.

We ought to explore the acquired somatic alterations, shedding light on genetic basis of somatic alterations in NB patients with chemotherapy. Marrow blood samples from NB patients were collected before treatment, after the 2nd and 4th chemotherapy for baseline research and continuous monitoring by whole exome sequencing. Plasma cell free DNA (cfDNA) was prepared for baseline research. Finger nail cells were extracted as self control. The clinical data was analyzed. From December 2014 to February 2016, 27 cases of children with stage IV NB were diagnosed. The follow up time ranged from 5 to 25 months, with a median follow up time of 17 months, 20 patients were stable, one patient died of pulmonary embolism during surgery, six patients died of disease progression. Marrow blood whole exome sequencing demonstrated that several novel somatic mutations were identified in all three trios comply or against the trendy of tumor size variation. Of note, six recurrent mutations in bromodomain PHD finger transcription factor (BPTF) were identified in nine NB patients under the continuous monitoring. The mutation rates variation was positively correlated to tumor size (CC = 0.428, P = 0.021), and patients with BPTF mutation may have a worse prognosis compared with wild type. Meanwhile, CGREF1, CUX2, GP1BA, SLC45A1 and TRA2A were mutated with the trendy oppose as therapeutic effects. The baseline research in three NB patients demonstrated that mutation rate of BPTF, TMCO3, GPRIN2 and C20orf96 in plasma cfDNA were in positive correlation with bone marrow genomic DNA (P = 0.001). Our study showed that BPTF along with other mutations may function as a biomarker for evaluating to effects of chemotherapy to this refractory tumor, and patients with BPTF mutation might have a worse prognosis.