Recurrent URAT1 gene mutations and prevalence of renal hypouricemia in Japanese

Recent identification of the urate transporter in the kidney (URAT1, encoded by SLC22A12) led to the molecular elucidation of idiopathic renal hypouricemia, which is a predisposition toward exercise-induce acute renal failure. One Japanese patient with renal hypouricemia demonstrated compound heterozygous mutations of the URAT1 gene (Q297X and IVS2+1G>A). It was suggested that these two mutations are recurrent mutations of the URAT1 gene in a Japanese population. In addition, we expect the prevalence of renal hypouricemia, 0.23%, from the analysis of serum urate levels in 1,730 Japanese children.     

Interactions of urate transporter URAT1 in human kidney with uricosuric drugs

Aim: Hyperuricaemia is a significant factor in a variety of diseases, including gout and cardiovascular diseases. The kidney plays a dominant role in maintaining plasma urate levels through the excretion process. Human renal urate transporter URAT1 is thought to be an essential molecule that mediates the reabsorption of urate on the apical side of the proximal tubule. In this study the pharmacological characteristics and clinical implications of URAT1 were elucidated. Methods: Madin–Darby canine kidney (MDCK) cells stably expressing URAT1 (MDCK‐URAT1) were established and examined the interactions of URAT1 with various drugs such as benzbromarone and its metabolites including 6‐hydroxybenzbromarone, angiotensin‐converting enzyme inhibitors, non‐steroidal anti‐inflammatory drugs and urate transport inhibitors including E3040 and probenecid. Results: MDCK‐URAT1 cells exhibited a time‐ and dose‐dependent increase in urate uptake, with a Km value of 570.7 µmol/L. When an URAT1‐green fluorescent protein fusion protein construct was expressed in MDCK cells, the protein was sorted mainly to the apical side of the membrane. The drugs except for captoril dose‐dependently inhibited urate uptake mediated by URAT1, with half maximal inhibitory concentration (IC₅₀) values ranging 0.05–716 µmol/L. Conclusion: Comparing these IC₅₀ values with intratubular concentrations of unbound drugs in humans, it is thought that URAT1 is a target molecule of uricosuric drugs, including 6‐hydroxybenzbromarone, probenecid, indomethacin and salicylate, to inhibit urate reabsorption in vivo. In addition, a cell line that stably expressing URAT1 could be a useful tool for the development of uricosuric drugs.     

The W258X mutation in SLC22A12 is the predominant cause of Japanese renal hypouricemia

Recently, a urate transporter, hURAT1 (human uric acid transporter 1) encoded by SLC22A12, was isolated from the human kidney. hURAT1 is presumed to play the central role in reabsorption of urate from glomerular filtrate. In the present study, we analyzed SLC22A12 in seven unrelated Japanese patients with renal hypouricemia whose serum level of urate was less than 1.0 mg/dl, and their family members. We performed direct DNA sequencing of the exon and exon-intron boundaries of SLC22A12 using genomic DNA. Six of the seven patients (86%) possess mutations in SLC22A12. In five patients, a homozygous G to A transition at nucleotide 774 within exon 4 of SLC22A12, which forms a stop codon (TGA) at codon 258 (TGG), was identified (W258X). In one patient, the C to T transition within exon 3, which changes threonine at codon 217 to methionine (T217 M), and the W258X mutation were found (compound heterozygote). Thus, among 12 mutational alleles in six patients, 11 were the W258X mutation (92%). Family members with the heterozygous W258X mutation (carriers) show relatively low levels of serum urate. The present study demonstrates that homozygous W258X mutation is the predominant genetic cause of idiopathic renal hypouricemia in Japanese patients.     

Roles of organic anion transporters (OATs) and a urate transporter (URAT1) in the pathophysiology of human disease

Renal proximal and distal tubules are highly polarized epithelial cells that carry out the specialized directional transport of various solutes. This renal function, which is essential for homeostasis in the body, is achieved through the close pairing of apical and basolateral carriers expressed in the renal epithelial cells. The family of organic anion transporters (OATs), which belong to the major facilitator superfamily (SLC22A), are expressed in the renal epithelial cells to regulate the excretion and reabsorption of endogenous and exogenous organic anions. We now understand that these OATs are crucial components in the renal handling of drugs and their metabolites, and they are implicated in various clinically important drug interactions, and their adverse reactions. In recent years, the molecular entities of these transporters have been identified, and their function and regulatory mechanisms have been partially clarified. Workers in this field have identified URAT1 (urate transporter 1), a novel member of the OAT family that displays unique and selective substrate specificity compared with other multispecific OATs. In the OAT family, URAT1 is the main transporster responsible for human genetic diseases. In this review, we introduce and discuss some novel aspects of OATs, with special emphasis on URAT1, in the context of their biological significance, functional regulation, and roles in human disease.     

Analysis of mutations in the urate transporter 1 (URAT1) gene of Japanese patients with hypouricemia in northern Japan and review of the literature

BACKGROUND: Renal hypouricemia is an autosomal recessive disorder resulting from inactivating mutations in the urate transporter 1 (URAT1) encoded by SLC22A12. To date, 10 mutations have been identified and W258X in the URAT1 gene is the predominant cause in middle to southwestern Japan. However, it is still unclear whether there is a regional specific distribution of mutations in northern Japan. In this study, we analyzed mutations in the URAT1 gene of five Japanese patients with renal hypouricemia in northern Japan. METHODS: Peripheral blood mononuclear cells were isolated from patients with hypouricemia and healthy control subjects. A mutation analysis of the URAT1 gene was performed completely by direct automated sequencing of polymerase chain reaction-amplified DNA products. RESULTS: We identified two mutations. These mutations [c.269G>A (R90H) and c.774G>A (W258X)] have been reported in Japanese patients. Two of five patients were homozygotes (W258X), two carried single heterozygous mutations (W258X), and the remaining one was a compound heterozygote (R90H and W258X). CONCLUSIONS: Our study suggests that there is no regional different distribution of the URAT1 genetic mutations in Japanese with renal hypouricemia.     

PCR—SSCP法检测大肠肿瘤APC基因MCR区段基因突变

目的：检测ＡＰＣ（ａｄｅｎｏｍａｔｏｕｓ ｐｏｌｙｐｏｓｉｓ ｃｏｌｉ）基因在国人大肠肿瘤中的突变情况，探讨ＡＰＣ基因突变与大肠肿瘤病理学特征的关系。同时探讨单链ＤＮＡ碱基构成与最适ＳＳＣＰ电泳温度的关系。方法：应用聚合酶链反应－单链构象多态（ＰＣＲ－ＳＳＣＰ）技术对６６例散发性大肠癌、１７例大肠腺瘤性息肉、４例家族性腺瘤性息肉病（ｆａｍｉｌｉａｌ ａｄｅｎｏｍａｔｏｕｓ ｐｏｌｙｐｏｓｉｓ，ＦＡＰ）ＡＰＣ基因第１５外显子ＭＣＲ区段的突变进行检测。结果：散发性大肠癌和尕瘤性息肉ＡＰＣ基因突变率分别为２１．２％（１４／６６）和２３．５％（４／１７），两者差异无显著性。散发性大肠癌ＡＰＣ基因突变与肿瘤的位置、浸润深度、组织类型、分化程度、分期以及淋巴结转移无关。ＭＣＲ区段中以密码子１３３７～１４５３区域突变率最高。     

Mutations in PLCE1 are a major cause of isolated diffuse mesangial sclerosis (IDMS)

Background and objectives. Diffuse mesangial sclerosis (DMS)is a histologically distinct variant of nephrotic syndrome (NS)that is characterized by early onset and by progression to end-stagekidney disease (ESKD). Besides syndromic DMS, isolated (non-syndromic)DMS (IDMS) has been described. The etiology and pathogenesisof DMS is not understood. We recently identified by positionalcloning recessive mutations in the gene PLCE1/NPHS3 as a novelcause of IDMS. We demonstrated a role of PLCE1 in glomerulogenesis.Mutations in two other genes WT1 and LAMB2 may also cause IDMS.We therefore determine in this study the relative frequencyof mutations in PLCE1, WT1 or LAMB2 as the cause of IDMS ina worldwide cohort. Methods. We identified 40 children from 35 families with IDMSfrom a worldwide cohort of 1368 children with NS. All the subjectswere analyzed for mutations in all exons of PLCE1 by multiplexcapillary heteroduplex analysis and direct sequencing, by directsequencing of exons 8 and 9 of WT1, and all the exons of LAMB2. Results. The median (range) age at onset of NS was 11 (1–72)months. We detected truncating mutations in PLCE1 in 10/35 (28.6%)families and WT1 mutations in 3/35 (8.5%) families. We foundno mutations in LAMB2. Conclusions. PLCE1 mutation is the most common cause of IDMSin this cohort. We previously reported that one child with truncatingmutation in PLCE1 responded to cyclosporine therapy. If thisobservation is confirmed in a larger study, mutations in PLCE1may serve as a biomarker for selecting patients with IDMS whomay benefit from treatment.     

Preoperative Systemic Treatment in BRCA-Positive Breast Cancer Patients: Case Report and Review of the Literature

BACKGROUND: In vitro and in vivo analyses have shown differences in chemosensitivity between breast cancers associated with BRCA1/2 mutations compared to sporadic variants. In the preoperative setting, the tumor response can be directly measured. Therefore, preoperative systemic treatment (PST) offers the opportunity to assess the chemosensitivity in vivo. However, there have been neither clear guidelines for mutation carriers in terms of choice of chemotherapy regimen nor recommendations how to proceed in case of an inadequate response to PST. CASE REPORT: Herein, we present the history of a 39-year-old woman with bilateral breast cancer who was tested positive for germ-line BRCA1 mutation while under PST. We performed a comprehensive literature review covering the MEDLINE database from 1992 to 2010 on published data regarding PST options for BRCA mutation carriers. CONCLUSIONS: If results of genetic testing are obtained during PST, individual therapy adaptations can be discussed with respect to mainly retrospective data of response to specific drugs. However, larger studies with longer follow-up are eagerly needed to draw firm conclusions before any specific treatment recommendations can be given for BRCA mutation carriers. PST is an ideal setting to evaluate such treatment options and to describe predictive markers that can help define subgroups that benefit most.     

Macrofollicular Variant of Follicular Thyroid Carcinoma (MV-FTC) with a Somatic DICER1 Gene Mutation: Case Report and Review of the Literature

Benign thyroid lesions such as multinodular goiter and adenomatoid nodules are well-circumscribed lesions displaying a macrofollicular growth pattern and lack of nuclear atypia. The highly unusual macrofollicular variant of follicular thyroid carcinoma (MV-FTC) mirrors these attributes and is thereby misclassified by cytological examination of fine-needle aspiration biopsies. The MV-FTC diagnosis is instead suggested following histological investigation, in which malignant attributes, most commonly capsular invasion, are noted. The bulk of MV-FTCs described in the literature arise in younger female patients and carry an excellent prognosis. A recent coupling to mutations in the DICER1 tumor suppressor gene has been proposed, possibly indicating aberrancies in micro-RNA (miRNA) patterns as responsible of the tumorigenic process. We describe the cytological, histological and molecular phenotype of a 35 mm large MV-FTC arising in the right thyroid lobe of a 33-year-old female with a family history of multinodular goiter. The tumor was encapsulated and strikingly inconspicuous in terms of cellularity and atypia, but nevertheless displayed multiple foci with capsular invasion. A next-generation molecular screening of tumor DNA revealed missense variants in DICER1 (p. D1709N) and MET (p. T1010I), but no established fusion gene events. After sequencing of germline DNA, the DICER1 mutation was confirmed as somatic, while the MET variant was constitutional. The patient is alive and well, currently awaiting radioiodine treatment. This MV-FTC mirrors previous publications, suggesting that these tumors carry a favorable prognosis and predominantly arise in younger females. Moreover, DICER1 mutations should be considered a common driver event in the development of MV-FTCs.     

Impact of KIT and PDGFRA Gene Mutations on Prognosis of Patients with Gastrointestinal Stromal Tumors After Complete Primary Tumor Resection

Introduction  To investigate the impact of KIT and PDGFRA gene mutations on the prognosis of gastrointestinal stromal tumors (GIST). Material and Methods  Tumor tissue from 184 patients with primary GIST was submitted to mutational analysis of exons 9, 11, 13, and 17 of the KIT gene and exons 12 and 18 of the PDGFRA gene. Clinical and pathological parameters were analyzed and correlated to the risk of recurrence and disease-free survival (DFS). Results and Discussion  The authors found that somatic mutations were detected in 162 tumors (88.0%). Age, clinical stage, mitotic count, and tumor size were of prognostic relevance on both univariate and multivariate analysis. Five-year DFS was 41.9%. While the presence of a KIT or PDGFRA mutation per se was not associated with tumor recurrence and/or disease-free survival, exon 11 deletion and hemizygous mutation status were both independent factors highly predictive for poor survival. Conclusion  The authors conclude that KIT exon 11 deletions and somatic loss of the wild-type KIT identified patients with poor prognosis. Age, clinical stage, tumor size, and mitotic count were standard clinicopathologic features that significantly influenced the prognosis. Mutation type of the mitogen receptor c-kit has a potential for predicting the course of the disease and might contribute to management individualization of GIST patients. Ying-Yong Hou and Florian Grabellus contributed equally to this work.     

Additional Primary Malignancies in Patients with Gastrointestinal Stromal Tumor (GIST): A Clinicopathologic Study of 260 Patients with Molecular Analysis and Review of the Literature

Annals of Surgical Oncology - The incidence of other primary neoplasms in gastrointestinal stromal tumor (GIST) patients is relatively high. Our aim was to better characterize the clinicopathologic...     

Polymerase Chain Reaction Analysis of the Y Chromosome Long Arm in Azoospermic Patients: Lack of the Y Chromosome Recognition Motif (YRRM1) Gene

We analyzed DNA from a patient with azoospermia whose Y chromosome was cytogenetically normal. A total of 16 loci on the Y chromosome long arm were examined: 15 loci between DYS7E and DYZ1, and the Y chromosome RNA recognition motif (YRRM1) locus, a candidate gene for the azoospermic factor AZF. We did not detect the YRRM1 gene in this patient. This finding supports the theory that YRRM1 is an essential gene for spermatogenesis.     

A Complete World Literature Review of Quality of Life (QOL) in Patients with Kidney Stone Disease (KSD)

Purpose of Review

The purpose of this study was to review the current evidence for quality of life (QOL) in patients with kidney stone disease (KSD).

Recent Findings

A review of literature from inception to May 2016 for all prospective English language articles on QOL in patients with KSD was done. QOL studies post urological procedures or ureteric stents were excluded. Nine studies (1570 patients) were included of which most (n?=?6) used the SF-36 QOL tool. Overall, seven of the nine studies demonstrated a lower QOL in patients with KSD. Bodily pain and general health were significantly lower in patients with KSD compared to their control groups.

Summary

Patients with KSD have an overall lower QOL with most impact on bodily pain and general health domains. Compared to the scale of patients suffering from KSD, more work needs to be done in measuring QOL both in terms of ‘Stone specific’ QOL measuring tools and the quality/number of studies in this field.

     

Subject Review: Pancreatic Ductal Adenocarcinoma in the Setting of Mutations in the Cystic Fibrosis Transmembrane Conductance Regulator Gene: Case Report and Review of the Literature

Background  

Cystic fibrosis (CF) is the most commonly inherited lethal autosomal recessive genetic disease amongst Caucasians. CF results from mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Patients with homozygous or compound heterozygous CFTR mutations have a risk of pancreatitis, but typically do not live long enough to develop pancreatic ductal adenocarcinoma (PDA), a disease that has an average age at diagnosis of 65 years. Little is known about the risk of the development of PDA in people who are heterozygous for mutations in the CFTR gene.     

Association between ABCB1 (MDR1) Gene 3435 C>T Polymorphism and Colchicine Unresponsiveness of FMF Patients

The multidrug resistance gene-1 (MDR1, adenosine triphosphate-binding cassette transporter: ABCB1, P-glycoprotein) encodes membrane proteins that play a crucial role in protecting cells from xenobiotics, chemicals, and drugs. The TT genotype of 3435 codon in exon 26 of MDR1 gene causes overexpression of gene activity and effluxes many chemically diverse compounds across the plasma membrane. We studied the association between C3435T polymorphisms (single nucleotide polymorphism) of MDR1 gene and colchicine-resistant familial Mediterranean fever (FMF) patients. Total genomic DNA samples from 52 FMF patients of colchicine unresponsiveness were used for FMF (MEFV) and MDR1 genes profile analyses. Target genes were genotyped by multiplex PCR-based reverse-hybridization Strip Assay method. The preliminary current results showed increased T allele frequency (0.596) in colchicine unresponsiveness of FMF patients. The distributions of the CC, CT, and TT genotypes in colchicine nonresponder FMF patients were 17%, 46%, and 37%, respectively. Our results indicate that C3435T polymorphism in exon 26 of MDR1 gene is associated with colchicine resistance in nonresponder FMF patients during the common therapy protocol.     

肾平滑肌肉瘤1例报告并文献复习

目的：探讨肾平滑肌肉瘤（LMSK）的临床特点和诊治方法.方法：回顾性分析1例LMSK患者的临床资料,并结合文献复习讨论LMSK的临床表现、病理特点、诊治方法和预后.患者为女性,主要表现为腰部阵发性疼痛8天,B超和CT提示左肾占位性病变.行根治性肾切除术.结果：病理检查肿瘤直径6 cm,光镜下见肿瘤细胞主要为平行束状或交织束状排列的嗜酸性梭形细胞,胞核钝圆,胞浆嗜酸性.免疫组织化学染色α-平滑肌肌动蛋白（α-SMA）和结蛋白（Des）阳性,细胞角蛋白（CK）和黑色素瘤抗体（HMB-45）阴性.TNM分期为T2b N0M0,分级为G2.患者术后5个月死于局部肿瘤复发和肺转移.结论：LMSK临床少见,恶性程度高,预后差.临床表现和影像学检查无特异性表现,通常为术后病理检查确诊.手术为主要治疗手段,辅助化疗和放疗效果尚有争议.