Mutation analysis and phenotypic investigation in patients with primary distal renal tubular acidosis / 中华肾脏病杂志

Objective:To analyze the gene variants in patients with primary distal renal tubular acidosis (dRTA), and explore the correlation between the genotype and phenotype.Methods:The Sanger direct sequencing or whole-exome sequencing was used to identify causal variants and the variation pathogenicity was evaluated according to 2015 American College of Medical Genetics and Genomics (ACMG) standards and guidelines in 44 dRTA patients (37 families) diagnosed in the Affiliated Qingdao Municipal Hospital of Qingdao University and the Affiliated Hospital of Qingdao University from April 2010 to September 2020. The clinical features of the patients were summarized, and the correlation between the genotype and phenotype was investigated.Results:Seven variants of SLC4A1 gene, 17 variants of ATP6V0A4 gene, and 15 variants of ATP6V1B1 gene were identified in 44 patients with dRTA, and of which 11 variants were new ones. According to ACMG guidelines, the pathogenic, likely pathogenic, benign variants among the 39 variants were 22, 16 and 1, respectively. Nine patients were autosomal dominant hereditary dRTA caused by SLC4A1 gene mutation, 4 patients with autosomal recessive hereditary dRTA complicated with Southeast Asian ovalocytosis and anemia were caused by SLC4A1 gene mutation, and 14 patients caused by ATP6V0A4 gene mutation and 8 patients caused by ATP6V1B1 gene mutation were autosomal recessive hereditary dRTA; Two children with dRTA were found to carry one monoallelic defect in ATP6V1B1, and no causal gene mutation was identified in 7 patients. One patient showed incomplete dRTA, and the other 43 patients showed complete dRTA. The prevalence of sensory neural hearing loss caused by ATP6V0A4 and ATP6V1B1 mutation were 2/14 and 6/10 respectively. The frequency of chronic kidney disease in adults, children and infants were 4/4, 2/4, and 1/36, separately. After the drug treatment based on potassium citrate and sodium citrate, the growth and development (28/40) and electrolyte disturbance (41/44) of most patients were significantly improved. Conclusions:The present study has identified 39 variants of SLC4A1, ATP6V0A4 and ATP6V1B1 genes in 44 patients with dRTA, including 11 novel ones. There is a close relationship between genotype and phenotype in dRTA patients and most patients' conditions were improved after proper treatment. This study enriches the human gene mutation database and provides valuable references for diagnosis, treatment and genetic counseling in patients with dRTA.

Mutation analysis of 5 children with primary distal renal tubular acidosis / 中华肾脏病杂志

Objective To analyze the mutations of causal genes in 5 children with primary distal renal tubular acidosis (dRTA),and explore their association of genotype and phenotype,so as to raise the awareness of the disease.Methods The whole exome sequencing was used to identify mutations in these 5 children from 5 families.Results A total of 4 different mutations of ATP6V0A4 gene were found in 2 dRTA children,including a novel heterozygous intron mutation (c.639 + 1G＞ A),a reported heterozygous nonsense variant (c.580C ＞T,p.Arg194*) and 2 novel heterozygous duplications (c.1504dupT,p.Tyr502Leufs*22;c.2351dupT,p.Phe785Ilefs*28).Two novel heterozygous missense mutations of ATP6V 1B 1 gene (c.409C ＞ T,p.Pro 137Ser;c.904C ＞ T,p.Arg302Trp) were identified in the third child,and a heterozygous missense mutation of SLC4A1 gene (c.1765C ＞ A,p.Arg589Ser) previously reported was found in the fourth child.No mutation of the dRTA-related causal genes was found in the fifth child.Furthermore,the mutations of causal genes in each of the first three children were compound heterozygous,which were consistent with the autosomal recessive inheritance pattern,and the variant from the fourth child was de novo.Conclusions The present study has found 7 mutations,including 5 novel variants,which enriches the human gene mutation database (HGMD) and contributes to a better understanding of the disease mechanisms.

Two Korean Cases of Hereditary Spherocytosis Caused by Mutations in SLC4A1

Hereditary spherocytosis (HS) is caused by mutations in the SPTA1, SPTB, ANK1, SLC4A1, and EPB42 genes, all of which encode erythrocyte membrane proteins. Mutations in SLC4A1, which encodes band 3 protein, have rarely been reported as the causative factor among Korean patients with HS. Here, we report two Korean patients with HS carrying mutations in SLC4A1. Patient 1 was a 3-year-old girl with unremarkable past and family histories and was evaluated for anemia that was detected after a complete blood count. She was suspected of having HS considering the spherocytosis of her peripheral blood smear, increased osmotic fragility, hemolytic features in blood chemistry tests, and splenomegaly. Sequence analysis revealed that the patient harbored a single heterozygous missense mutation, c.2278C>T (p.Arg760Trp) in exon 17 of SLC4A1. Patient 2 was a 23-year-old man who had a prior history of intermittent jaundice. Although the patient did not have anemia, a genetic test for HS was performed due to evidence of hemolytic features in the blood chemistry test, splenomegaly, and a family history of HS. The test confirmed a single heterozygous missense mutation, c.2423G>T (p.Arg808Leu) in exon 18 of SLC4A1.

Primary Autosomal Recessive Distal Renal Tubular Acidosis Caused by a Common Homozygous SLC4A1 Mutation in Two Lao Families

Primary distal renal tubular acidosis (dRTA) caused by mutations of the SLC4A1 gene, which encodes for erythroid and kidney isoforms of anion exchanger, shows marked difference in inheritance patterns and clinical features in different parts of the world. While the disease shows autosomal dominant inheritance without any red cell morphological abnormalities in the temperate countries, it is almost invariably recessive, and often accompanies red cell morphological abnormalities or hemolytic anemia in the tropics, especially in Southeast Asia. Here, we report three patients with autosomal recessive (AR) dRTA, presenting with typical findings of failure to thrive and rickets, from two unrelated Lao families. The mutational analyses revealed that all three patients harbored the same homozygous SLC4A1 mutation, p.Gly701Asp. Adequate supplementation of alkali and potassium resulted in remarkable improvement of growth retardation and skeletal deformities of the patients. This is the first case report of Lao patients with AR dRTA caused by SLC4A1 mutations.

Analysis of the SLC4A1 gene in three Mexican patients with hereditary spherocytosis: report of a novel mutation

We analyzed the SLC4A1 gene in three Mexican patients with Hereditary Spherocytosis (HS). The promoter and all 20 exons were investigated through heteroduplex analysis and DNA sequencing. No DNA changes were detected in one of the three patients. Two well-known polymorphisms, Memphis I and the Diego-a blood group, were detected in another one. In the third, the HS phenotype could be explained by the novel 1885_1888dupCCGG mutation found in heterozygosis. This frameshift mutation is predicted to result in a truncated and unstable protein lacking normal functions.

Andálisis de los polimorfismos G199A, NcoI del gen ANK1 y Memphis I del gen SLC4A1 en individuos sanos y pacientes mexicanos con esferocitosis hereditaria / Polymorphism analysis of G199A, Ncol in ANK1 and Memphis I in SLC4A1 genes in Mexican healthy individuals and subjects affected with hereditary spherocytosis

Antecedentes. En México la esferocitosis hereditaria (EH) es la causa principal de anemia hemolítica hereditaria y se debe a mutaciones en uno o más genes implicados en la membrana eritrocitaria, lo que dificulta la identificación del gen primario. Objetivo. Con el fin de valorar la utilización de los polimorfismos G199A y NcoI del gen ANK1, y Memphis I del gen SLC4A1 como marcadores genéticos para identificar esta enfermedad, estimamos sus frecuencias alélicas y genotípicas en 45 muestras de ADN de pacientes con EH y 28 de individuos sanos, las cuales fueron similares en uno y otro grupos para los polimorfismos G199A y Memphis I, con baja frecuencia de heterocigotos, lo que limita su utilidad como marcador genético. Resultados. El polimorfismo NcoI no mostró diferencias alélicas y genotípicas en los grupos de estudio, pero sí mayor frecuencia de heterocigotos (0.49 y 0.43 en enfermos y sanos respectivamente), característica que le confiere ventajas para ser utilizado como marcador genético en familias con EH. Conclusiones. Finalmente, debido a que existen otros genes implicados en la patología molecular de la EH, consideramos que es necesario analizar otros polimorfismos de genes que codifican para las proteínas involucradas en las deficiencias que conducen a esferocitosis hereditaria en la población mexicana.

BACKGROUND: In Mexico, Hereditary Spherocytosis (HS) is the main cause of hereditary hemolytic anemia, due to mutations of one or more genes involved in the erythrocyte membrane, making it difficult to identify the primary gene. OBJECTIVE: With the purpose of estimating the use of the polymorphisms G199A and NcoI of ANK1 gene, and Memphis I of SLC4A1 gene, as genetic markers to screen this disease, we searched the allelic and genotypic frequencies in 45 DNA samples of HS patients and 28 from healthy individuals. RESULTS: Allelic and genotypic frequencies were similar in both studied groups for the G199A and Memphis I polymorphisms, with low frequency of heterozygosis showing its limited use as a genetic marker. The allelic and genotypic frequencies of the NcoI polymorphism were also similar in both groups, however a higher heterozygote frequency was observed (0.49 and 0.43 in patients and healthy individuals), a feature that may turn it into a useful genetic marker. CONCLUSIONS: Since there are other genes implicated in the molecular pathology of the HS, we consider it necessary to continue analyzing other polymorphisms of the genes involved in Hereditary Spherocytosis among the Mexican population.