Asian Continental Ancestry Group ; Bartter Syndrome ; genetics ; Child ; Chloride Channels ; genetics ; Humans ; Male ; Mutation

OBJECTIVETo investigate the mutation of related genes and prenatal diagnosis of a family with Bartter syndrome (BS).

METHODSThe high-throughput capture sequencing technique and PCR-Sanger sequencing were used to detect pathogenic genes in the proband of this family and analyze the whole family at the genomic level. After the genetic cause was clarified, the amniotic fluid was collected from the proband's mother who was pregnant for 5 months for prenatal diagnosis.

RESULTSThe proband carried compound heterozygous mutations of c.88C>T(p.Arg30*) and c.968+2T>A in the CLCNKB gene; c.88C>T(p.Arg30*) had been reported as a pathogenic mutation, and c.968+2T>A was a new mutation. Pedigree analysis showed that the two mutations were inherited from the mother and father, respectively. Prenatal diagnosis showed that the fetus did not inherit the mutations from parents and had no mutations at the two loci. The follow-up visit confirmed that the infant was in a healthy state, which proved the accuracy of genetic diagnosis and prenatal diagnosis.

CONCLUSIONSThe compound heterozygous mutations c.88C>T(p.Arg30*) and c.968+2T>A in the CLCNKB gene are the cause of BS in the proband, and prenatal diagnosis can prevent the risk of recurrence of BS in this family.

Bartter syndrome is an inherited metabolic disorder characterized by hypokalemic alkalosis and high rennin-angiotensin-aldosteronism which can occur at all ages but mainly in childhood. Classical Bartter syndrome is caused by loss-of-function variants in the gene encoding basolateral chloride channel ClC-Kb (CLCNKB), which is a common type of Bartter syndrome characterized with diverse clinical manifestations ranging from severe to very mild. This article reviews the function and mechanism of CLCNKB variants in Chinese population and the genotype-phenotype correlation of CLCNKB variants in classical Bartter syndrome.
Asian Continental Ancestry Group ; Bartter Syndrome ; genetics ; pathology ; Chloride Channels ; genetics ; Genetic Association Studies ; Humans ; Research ; trends

OBJECTIVE: To explore the genetic basis for a pedigree affected with Bartter's syndrome (BS). METHODS: Panel-based next-generation sequencing (NGS) was carried out to detect mutation in BS-related genes SLC12A1, KCNJ1, BSND and CLCNKB. Sanger sequencing of MAGED2 gene and chromosomal microarray analysis (CMA) were also performed on the patient. Suspected mutation was validated in her family members. RESULTS: No pathogenic mutation was detected by NGS, while a 0.152 Mb microdeletion at Xp11.21 (54 834 585-54 986 301) was found in the male fetus, which removed the entire coding region of the MAGED2 gene. His mother was a heterozygous carrier of the deletion. His father and sister did not carry the same deletion. CONCLUSION The loss of the MAGED2 gene may underlie the BS in this pedigree.
Adaptor Proteins, Signal Transducing ; genetics ; Antigens, Neoplasm ; genetics ; Bartter Syndrome ; genetics ; Female ; Genetic Testing ; Heterozygote ; Humans ; Male ; Mutation ; Pedigree ; Sequence Deletion

Cystic fibrosis (CF) is a fatal autosomal-recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. CF is characterized by recurrent pulmonary infection with obstructive pulmonary disease. CF is common in the Caucasian population but is rare in the Chinese population. The symptoms of early-stage CF are often untypical and may sometimes manifest as Bartter syndrome (BS)-like hypokalemic alkalosis. Therefore, the ability of doctors to differentiate CF from BS-like hypokalemic alkalosis in Chinese infants is a great challenge in the timely and accurate diagnosis of CF. In China, sporadic CF has not been diagnosed in children younger than three years of age to date. Three infants, who were initially admitted to our hospital over the period of June 2013 to September 2014 with BS-like hypokalemic alkalosis, were diagnosed with CF through exome sequencing and sweat chloride measurement. The compound heterozygous mutations of the CFTR gene were detected in two infants, and a homozygous missense mutation was found in one infant. Among the six identified mutations, two are novel point mutations (c.1526G > C and c.3062C > T) that are possibly pathogenic. The three infants are the youngest Chinese patients to have been diagnosed with sporadic CF at a very early stage. Follow-up examination showed that all of the cases remained symptom-free after early intervention, indicating the potential benefit of very early diagnosis and timely intervention in children with CF. Our results demonstrate the necessity of distinguishing CF from BS in Chinese infants with hypokalemic alkalosis and the significant diagnostic value of powerful exome sequencing for rare genetic diseases. Furthermore, our findings expand the CFTR mutation spectrum associated with CF.
Alkalosis ; complications ; Bartter Syndrome ; China ; Cystic Fibrosis ; diagnosis ; genetics ; Cystic Fibrosis Transmembrane Conductance Regulator ; genetics ; Diagnosis, Differential ; Exome ; Female ; Humans ; Hypokalemia ; complications ; Infant ; Male ; Mutation

OBJECTIVES: To study the clinical features and gene mutation sites of children with cystic fibrosis (CF), in order to improve the understanding of CF to reduce misdiagnosis and missed diagnosis. METHODS: A retrospective analysis was performed on the medical records of 8 children with CF who were diagnosed in Hebei Children's Hospital from 2018 to 2021. RESULTS: Among the 8 children with CF, there were 5 boys and 3 girls, with an age of 3-48 months (median 8 months) at diagnosis, and the age of onset ranged from 0 to 24 months (median 2.5 months). Clinical manifestations included recurrent respiratory infection in 7 children, sinusitis in 3 children, bronchiectasis in 4 children, diarrhea in 8 children, fatty diarrhea in 3 children, suspected pancreatic insufficiency in 6 children, pancreatic cystic fibrosis in 1 child, malnutrition in 5 children, and pseudo-Bartter syndrome in 4 children. The most common respiratory pathogens were Pseudomonas aeruginosa (4 children). A total of 16 mutation sites were identified by high-throughput sequencing, multiplex ligation-dependent probe amplification, and Sanger sequencing, including 5 frameshift mutations, 4 nonsense mutations, 4 missense mutations, 2 exon deletions, and 1 splice mutation. CFTR mutations were found in all 8 children. p.G970D was the most common mutation (3 children), and F508del mutation was observed in one child. Four novel mutations were noted: deletion exon15, c.3796_3797dupGA(p.I1267Kfs*12), c.2328dupA(p.V777Sfs*2), and c.2950G>A(p.D984N). CONCLUSIONS p.G970D is the most common mutation type in children with CF. CF should be considered for children who have recurrent respiratory infection or test positive for Pseudomonas aeruginosa, with or without digestive manifestations or pseudo-Bartter syndrome.
Bartter Syndrome ; Child, Preschool ; Cystic Fibrosis/genetics* ; Cystic Fibrosis Transmembrane Conductance Regulator/genetics* ; Diarrhea ; Female ; Humans ; Infant ; Infant, Newborn ; Male ; Mutation ; Respiratory Tract Infections ; Retrospective Studies

Objective: To clarify the molecular basis of patients with Bartter syndrome type I and explore the therapeutic effect of trafficking-defective variations by chemical chaperone 4-Phenylbutyric acid(4-PBA). Methods: The clinical characteristics, laboratory findings and genetic data of 3 patients diagnosed with Bartter syndrome type I who were admitted to Department of Nephrology, Children's Hospital of Nanjing Medical University from 2017 to 2018 were retrospectively analyzed. Wild type and variant SLC12A1 gene constructs were transiently overexpressed in HEK293 cells. Western blotting was used to detect the expression levels of Na⁺-K⁺-2Cl^-cotransporter(NKCC2) protein. Immunofluorescent staining was applied to investigate the subcellular localization of NKCC2 protein. In addition, the effect of the chemical chaperone 4-PBA on the expression and localization of the SLC12A1 gene variants was investigated. Unpaired t test was used for statistical analysis of 4-PBA treatment. Results: All the 3 patients (2 males and 1 female), aged 3.0, 4.0 and 1.2 years, respectively. All patients had antenatal onset with polyhydramnios and were born prematurely. After birth, all patients presented with hypochlorine alkalosis accompanied by hypokalemia and hyponatremia. Sequencing analysis revealed that the 3 patients were homozygotes or compound heterozygotes for variants in the SLC12A1 gene. In HEK293 cells, the surface expression of NKCC2 in 3 variants (p.L463S, p.L479V, p.507-510del) are all lower than in wild type (0.718±0.039, 0.287±0.081, 0.025±0.156 vs. 1.001±0.028, t=5.92, 8.35, 30.49, all P<0.01). Moreover, the total protein expression of p.L479V and p.507-510del group were all lower than that in wild type group (0.630±0.032, 0.043±0.003 vs. 1.000±0.111, t=3.21, 8.65, all P<0.05). 4-PBA treatment increased the mature protein expression level of the p.L463S and p. L479V group in 4-PBA treatment group are all higher than the untreated group (0.459±0.018 vs. 1.123±0.024, 0.053±0.012 vs. 1.256±0.037, t=2.75, 18.35, all P<0.05). Cytoplasmic retention of the L479V and 507-510del variants were observed by immunofluorescent staining. 4-PBA treatment could rescue a number of NKCC2 L479V variants to the membrane. Conclusions: The 3 SLC12A1 variants cause expression or subcellular localization defects of the protein. The findings that plasma membrane expression and activity can be rescued by 4PBA might help to develop novel therapeutic strategy for Bartter syndrome type Ⅰ.
Bartter Syndrome/genetics* ; Child, Preschool ; Female ; HEK293 Cells ; Homozygote ; Humans ; Infant ; Male ; Pregnancy ; Retrospective Studies ; Solute Carrier Family 12, Member 1/genetics*

Gitelman's syndrome (GS) is caused by loss-of-function mutations in SLC12A3 and characterized by hypokalemic metabolic alkalosis, hypocalciuria, and hypomagnesemia. Long-term prognosis and the role of gene diagnosis in GS are still unclear. To investigate genotype-phenotype correlation in GS and Gitelman-like syndrome, we enrolled 34 patients who showed hypokalemic metabolic alkalosis without secondary causes. Mutation analysis of SLC12A3 and CLCNKB was performed. Thirty-one patients had mutations in SLC12A3, 5 patients in CLCNKB, and 2 patients in both genes. There was no significant difference between male and female in clinical manifestations at the time of presentation, except for early onset of symptoms in males and more profound hypokalemia in females. We identified 10 novel mutations in SLC12A3 and 4 in CLCNKB. Compared with those with CLCNKB mutations, patients with SLC12A3 mutations were characterized by more consistent hypocalciuria and hypomagnesemia. Patients with 2 mutant SLC12A3 alleles, compared with those with 1 mutant allele, did not have more severe clinical and laboratory findings except for lower plasma magnesium concentrations. Male and female patients did not differ in their requirement for electrolyte replacements. Two patients with concomitant SLC12A3 and CLCNKB mutations had early-onset severe symptoms and showed different response to treatment. Hypocalciuria and hypomagnesemia are useful markers in differentiation of GS and classical Bartter's syndrome. Gender, genotypes or the number of SLC12A3 mutant alleles cannot predict the severity of disease or response to treatment.
Adolescent ; Adult ; Alleles ; Bartter Syndrome/genetics/pathology ; Chloride Channels/*genetics ; DNA Mutational Analysis ; Female ; Genetic Association Studies ; Genotype ; Gitelman Syndrome/*genetics/pathology ; Humans ; Hypokalemia/etiology ; Male ; Middle Aged ; Phenotype ; Polymorphism, Genetic ; Solute Carrier Family 12, Member 3/genetics ; Young Adult

Bartter syndrome (BS) is classified into 5 genotypes according to underlying mutant genes and BS III is caused by loss-of-function mutations in the CLCNKB gene encoding for basolateral ClC-Kb. BS III is the most common genotype in Korean patients with BS and W610X is the most common CLCNKB mutation in Korean BS III. In this study, we tested the hypothesis that the CLCNKB W610X mutation can be rescued in vitro using aminoglycoside antibiotics, which are known to induce translational read-through of a nonsense mutation. The CLCNKB cDNA was cloned into a eukaryotic expression vector and the W610X nonsense mutation was generated by site-directed mutagenesis. Cultured polarized MDCK cells were transfected with the vectors, and the read-through was induced using an aminoglycoside derivative, G418. Cellular expression of the target protein was monitored via immunohistochemistry. While cells transfected with the mutant CLCNKB failed to express ClC-Kb, G418 treatment of the cells induced the full-length protein expression, which was localized to the basolateral plasma membranes. It is demonstrated that the W610X mutation in CLCNKB can be a good candidate for trial of translational read-through induction as a therapeutic modality.
Animals ; Bartter Syndrome/genetics/*pathology ; Chloride Channels/analysis/genetics/*metabolism ; Cloning, Molecular ; Codon, Nonsense ; Dogs ; Humans ; Immunohistochemistry ; Madin Darby Canine Kidney Cells ; Microscopy, Confocal ; Mutagenesis, Site-Directed ; Recombinant Fusion Proteins/analysis/biosynthesis/genetics ; Transfection

Channelopathies are a heterogeneous group of disorders resulting from the dysfunction of ion channels located in the membranes of all cells and many cellular organelles. These include diseases of the nervous system (e.g., generalized epilepsy with febrile seizures plus, familial hemiplegic migraine, episodic ataxia, and hyperkalemic and hypokalemic periodic paralysis), the cardiovascular system (e.g., long QT syndrome, short QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia), the respiratory system (e.g., cystic fibrosis), the endocrine system (e.g., neonatal diabetes mellitus, familial hyperinsulinemic hypoglycemia, thyrotoxic hypokalemic periodic paralysis, and familial hyperaldosteronism), the urinary system (e.g., Bartter syndrome, nephrogenic diabetes insipidus, autosomal-dominant polycystic kidney disease, and hypomagnesemia with secondary hypocalcemia), and the immune system (e.g., myasthenia gravis, neuromyelitis optica, Isaac syndrome, and anti-NMDA [N-methyl-D-aspartate] receptor encephalitis). The field of channelopathies is expanding rapidly, as is the utility of molecular-genetic and electrophysiological studies. This review provides a brief overview and update of channelopathies, with a focus on recent advances in the pathophysiological mechanisms that may help clinicians better understand, diagnose, and develop treatments for these diseases.
Ataxia ; Bartter Syndrome ; Brugada Syndrome ; Cardiovascular System ; Channelopathies* ; Diabetes Insipidus, Nephrogenic ; Diabetes Mellitus ; Endocrine System ; Epilepsy, Generalized ; Genetics ; Hypoglycemia ; Hypokalemic Periodic Paralysis ; Immune System ; Ion Channels ; Isaacs Syndrome ; Long QT Syndrome ; Membranes ; Migraine with Aura ; Myasthenia Gravis ; Nervous System ; Neuromyelitis Optica ; Organelles ; Polycystic Kidney Diseases ; Respiratory System ; Seizures, Febrile