Mutational analysis in 119 families with nephronophthisis

Nephronophthisis (NPHP) is the most common genetic cause of end-stage renal disease (ESRD) in the first three decades of life. Six genes, NPHP1-6, have been reported, which when mutated result in NPHP. Our aim was to examine 119 families with NPHP and absence of homozygous NPHP1 deletions for mutations in NPHP2-6 and the two candidate genes BCL2 and CYS1. The 119 individuals affected with NPHP were selected from unrelated families, in which homozygous NPHP1 deletions were excluded. A combination of CEL-1 endonuclease digestion and direct sequencing was used for focused mutational analysis in this cohort. All individuals were examined for homozygous deletions in NPHP1 and directly sequenced for BCL2 and CYS1. As selected by appropriate phenotype, 9%, 38%, 97%, 20% and 20% of individuals were examined for mutations in NPHP2, 3, 4, 5, and 6 respectively. No mutations in known NPHP genes or in the candidate genes, BCL2 and CYS1, were found sufficient to explain NPHP in affected individuals. These findings demonstrate the need to evaluate additional candidate genes as the cause of NPHP.     

Mutational analysis of the BMP-1 gene in patients with gastroschisis

BACKGROUND: Gastroschisis is a rare abdominal wall defect. Although the pathogenesis of gastroschisis is unknown, there is some evidence of the genetic etiology of gastroschisis. Recently, a functionally null deletion of the mouse bone morphogenic protein-1 (BMP-1) gene resulted in a phenotype that resembled a human neonate with gastroschisis. BMP-1 thus became the first potential candidate gene for gastroschisis. METHODS: To explore this possibility the authors collected blood samples from 11 patients who had gastroschisis. Mutational analysis of exons 2 to 15 of the human BMP-1 gene was performed using genomic polymerase chain reaction, single-strand conformation polymorphism analysis and direct sequencing methods. RESULTS: No mutation of the human BMP-1 gene was observed in any of these patients. CONCLUSION: Although heterogeneous etiologies might be proposed for gastroschisis, our results provide further evidence of a nongenetic etiology for gastroschisis. J Pediatr Surg 36:885-887.     

Lack of large, homozygous deletions of the nephronophthisis 1 region in Joubert syndrome type B

Joubert syndrome type B (JSB) is a developmental disorder of the nephronophthisis (NPH) complex with multiple organ involvement, including NPH, coloboma of the eye, aplasia of the cerebellar vermis, and the facultative symptoms of psychomotor retardation, polydactyly, and neonatal tachypnea. In isolated autosomal recessive NPH type 1 (NPH1), homozygous deletions have been described as causative in more than 80% of patients. Since different combinations of the extrarenal symptoms with NPH occur in JSB, a contiguous gene deletion syndrome in the NPH1 genetic region would seem a highly likely cause for JSB. We therefore examined 11 families with JSB for the presence of extended deletions at the NPH1 locus. Genomic DNA was examined using four consecutive polymerase chain reaction (PCR) markers that are deleted in NPH1 and three PCR makers flanking the NPH1 deletion. In all seven markers examined, there was no homozygous deletion detected in any of the 11 JSB families studied. Since these markers saturate the NPH1 deletion region at high density, this finding excludes the presence of large homozygous deletions of the NPH1 region in these JSB families, making it unlikely that deletions of the NPH1 region are a primary cause for JSB. Received February 18, 1997; received in revised form and accepted June 26, 1997     

High NPHP1 and NPHP6 mutation rate in patients with Joubert syndrome and nephronophthisis: potential epistatic effect of NPHP6 and AHI1 mutations in patients with NPHP1 mutations

Joubert syndrome (JS) is an autosomal recessive disorder that is described in patients with cerebellar ataxia, mental retardation, hypotonia, and neonatal respiratory dysregulation. Kidney involvement (nephronophthisis or cystic renal dysplasia) is associated with JS in one fourth of known cases. Mutations in three genes--AHI1, NPHP1, and NPHP6--have been identified in patients with JS. However, because NPHP1 mutations usually cause isolated nephronophthisis, the factors that predispose to the development of neurologic involvement are poorly understood. In an attempt to identify such genetic determinants, a cohort of 28 families with nephronophthisis and at least one JS-related neurologic symptom were screened for mutations in AHI1, NPHP1, and NPHP6 genes. NPHP1 and NPHP6 homozygous or compound heterozygous mutations were found in 13 (46%) and six (21%) unrelated patients, respectively. Two of the 13 patients with NPHP1 mutations carried either a heterozygous truncating mutation in NPHP6 or a heterozygous missense mutation in AHI1. Furthermore, five patients with NPHP1 mutations carried the AHI1 variant R830W, which was predicted to be "possibly damaging" and was found with significantly higher frequency than in healthy control subjects and in patients with NPHP1 mutations without neurologic symptoms (five of 26 versus four of 276 and three of 152 alleles; P < 0.001 and P < 0.002, respectively). In contrast to the variable neurologic and milder retinal phenotype of patients with NPHP1 mutations, patients with NPHP6 mutations presented with a more severe neurologic and retinal phenotype. In conclusion, NPHP1 and NPHP6 are major genes of nephronophthisis associated with JS. Epistatic effects that are provided by heterozygous NPHP6 and AHI1 mutations and variants may contribute to the appearance of extrarenal symptoms in patients with NPHP1 mutations.     

Identification of the first AHI1 gene mutations in nephronophthisis-associated Joubert syndrome

Joubert syndrome (JBTS) is an autosomal recessive multisystem disease characterized by cerebellar vermis aplasia, mental retardation, muscular hypotonia, an irregular breathing pattern in the neonatal period and abnormal eye movements. Some individuals have progressive renal failure characterized by nephronophthisis (NPHP) and/or retinal dystrophy. Homozygous deletions of NPHP1 on chromosome 2q13 have been identified in individuals with NPHP-associated JBTS. Recently, mutations in AHI1 on chromosome 6q23.3 were found in JBTS patients without NPHP. Here, by direct sequencing, we identify novel truncating mutations within AHI1 in affected patients from two families. One patient had the association of JBTS and NPHP with chronic renal failure. This is the first report of AHI1 mutations causing JBTS associated with NPHP, confirming the clinical and genetic heterogeneity of NPHP.Boris Utsch and John A. Sayer contributed equally to this work     

Mutational analysis of HOXA10 gene in Chinese patients with cryptorchidism

Cryptorchidism is one of the most common congenital anomalies and affects 2–4% of full‐term new born boys. Its aetiology is poorly understood at present. HOXA10 plays a pivotal role in regulation of testicular descent. Male mice mutant for Hoxa10 exhibit unilateral or bilateral cryptorchidism as a result of impaired development of the gubernaculums. In this study, we performed mutation analysis of HOXA10 gene in a cohort of 98 cryptorchid patients. And we found a mutation (N27K) in a boy with unilateral cryptorchidism. The mutation was not detected in 106 healthy controls. Both in silico analyses and functional studies showed that the mutation affected the function of HOXA10. The results demonstrated that mutation in HOXA10 gene contributes to the pathogenesis of cryptorchidism, but may not be a common cause.     

Mutational analysis of Aurora kinase C gene in Egyptian patients with macrozoospermia

Macrozoospermia is a rare syndrome. The key marker of the disease is a high percentage of spermatozoa with abnormal phenotypes namely enlarged head and multiple tails. The presence of at least 70% of spermatozoa with a large head is usually associated with Aurora kinase C gene (AURKC) mutations. We sought to assess AURKC as a potential genetic actor of macrozoospermia in a sample of infertile Egyptian men. We recruited 30 patients and conducted a clinical examination, semen analysis, and DNA sequencing and RFLP for AURKC. We diagnosed 17 patients with characteristic macrozoospermia and classified them into eight severe and nine mild cases. We detected genetic variants of AURKC in five patients (29.4%): Three patients with severe macrozoospermia had c.144delC mutations in exon 3 (37.5% of the severe), and two mild cases had c.1157G>A polymorphism in the 3′ UTR (22.2% of the mild). A successful intracytoplasmic sperm injection (ICSI) was achieved only with a severe macrozoospermia patient without apparent AURKC mutation. The present study is the first report to link macrozoospermia and AURKC mutations in Egypt. The study recommends macrozoospermia patients to perform AURKC gene analysis and attempt ICSI, even those with a high percentage of large head spermatozoa.     

中国南方汉族散发性激素耐药型肾病综合征儿童NPHS1基因突变分析

目的 研究我国南方汉族散发性激素耐药型肾病综合征(SRNS)儿童NPHS1基 因突变情况.方法 对象为40例南方汉族散发性SRNS儿童,50例尿检正常的汉族健康成年人作为对照.取受检者外周静脉血3ml,10％枸橼酸钠抗凝,提取基因组DNA.应用PCR方法扩增NPHS1基因全部29个外显子及其周围的部分内含子,对PCR产物直接进行DNA序列测定及突变分析.结果 6例存在NPHS1基因突变-928G ＞A (D310N)、2677A ＞G( T893A)、2869G＞C( V957L)、IVS8+30C＞T、IVS21+ 14G＞A、IVS25-23C ＞T和*142T＞C,突变检出率为15％.在50例健康对照人群中未检测出这7个变异,其中2677A ＞G、IVS8 +30C ＞T、IVS21+ 14G＞A、IVS25-23C＞T和*142T＞C为新发现NPHS1基因突变.此外,还确定了13个已报道的NPHS1基因多态性-294C ＞T、349G ＞A、IVS3+ 15C ＞T、IVS3 +61A ＞G、803G ＞A、IVS8+68A ＞G、1339G ＞A、1802G ＞C、2223C ＞T、2289C ＞T、IVS24 +36C ＞T、3315G＞A和IVS27 +45C ＞T.结论 在40例南方汉族散发性SRNS患儿中,NPHS1基因突变检出率为15％,提示南方汉族散发性SRNS患儿存在NPHS1基因突变,对这类患儿需进行NPHS1基因突变分析.     

中国汉族人3个家族性激素耐药型肾病综合征家系WT1和PLCE1基因突变分析

目的 分析中国汉族人家族性激素耐药型肾病综合征（SRNS）家系WT1和PLCE1基因突变及其特点。 方法 研究对象为A、B、C 3个汉族人SRNS家系的先证者（已除外NPHS2基因突变）及其父母,A、B 2个家系先证者的姐姐,50例尿检正常的汉族成年人作为对照人群。取所有研究对象外周静脉血3 ml,提取基因组DNA,PCR扩增WT1基因全部10个外显子和PLCE1基因全部31个编码外显子及其周围的部分内含子,应用直接DNA序列测定法和限制性片段长度多态性PCR（RFLP-PCR）分析法检测WT1和PLCE1基因变异。 结果 未发现WT1和PLCE1基因的致病突变。但是,在3个SRNS家系的先证者检测到3个WT1基因多态性：126C>T（P42P）、IVS5－64A>G和903A>G（R300R）,其中IVS5－64A>G为新发现的WT1基因多态性,126C>T和903A>G已见文献报道;还检测到13个PLCE1基因多态性 －134A>G、810T>C（C270C）、960G>A（E320E）、IVS11－28C>G、IVS15+26A>C、4724G>C（R1575P）、IVS20+40C>T、IVS21+64G>A、IVS22－26T>A、5320C>T（T1777I）、5780A>G（H1927R）、IVS27+24A>G和IVS31+48_49insT,其中IVS22－26T>A为新发现的PLCE1基因多态性,其余12个PLCE1基因多态性已见公布。 结论 WT1和PLCE1基因突变不是本研究3个中国汉族人家族性SRNS家系的主要致病原因。     

Mutational analysis of COL4A5 gene in Korean Alport syndrome

Mutational analysis of the COL4A5 gene in X-linked Alport syndrome (AS) requires an expensive and time-consuming procedure with a detection rate of 50%, at best. There have been three multicenter collaborative studies of mutation analysis in the COL4A5 gene using systematic screening of entire coding regions of the gene. This is a similar study executed in a single center in Korea. Twenty-five unrelated Korean patients with AS in whom the diagnosis was confirmed pathologically were included in the study. By systematic screening of all 51 exons of the gene using polymerase chain reaction/single-strand conformation polymorphism analysis, ten mutations were detected in 10 unrelated patients. These included one medium-sized deletion involving exon 49–51, one single base pair deletion, one nonsense point mutation, one splice site mutation, and six missense point mutations. Of the six missense mutations, four involved a glycine residue and disrupted the Gly-X-Y repeats in the collagenous domain. The overall detection rate of mutations was 40%. Although DNA analysis in AS is currently not applicable to routine clinical diagnosis due to several practical and technical problems, it is likely to replace morphological diagnosis in the near future. Received: 22 March 1999 / Revised: 21 May 1999 / Accepted: 21 May 1999     

一例NPHP1纯合缺失所致的Joubert综合征

患儿,男,因"6月龄竖头欠稳"于浙江大学医学院附属儿童医院康复科就诊。查体发现双眼追视欠灵活,竖头欠稳,不会翻身,双手握拳,双下肢负重差,四肢肌张力低。磁共振结果显示小脑蚓部小,中脑呈"磨牙状"改变,诊断为Joubert综合征。全外显子组测序及Sanger测序发现患儿存在AHI1基因的杂合移码突变(c.533_534delAA),该突变位点遗传自母亲;而针对已知致病基因的拷贝数变异分析提示NPHP1基因可能存在纯合型缺失。经多重连接探针扩增(multiplex ligation-dependent probe amplification,MLPA)方法进行验证,结果表明患儿的NPHP1基因确实存在纯合型缺失,且父母均为NPHP1杂合缺失的携带者。这是国内首次报道的由NPHP1纯合缺失所导致的Joubert综合征病例。由于NPHP1基因突变与肾脏损害相关性较高,应注意对此类突变患儿的密切随访。     

Anaesthetic management of children with Joubert syndrome

We report the anaesthetic management of two children with Joubert syndrome. Children with this syndrome have abnormalities of respiratory control due to changes in the brainstem and cerebellum. They are extremely sensitive to the respiratory depressant effects of anaesthetic agents, including nitrous oxide. Anaesthesia using inhalational induction, controlled ventilation, avoidance of opioids, and close postoperative monitoring is recommended.     

Mutational survey of the PHEX gene in patients with X-linked hypophosphatemic rickets

X-linked hypophosphatemic rickets (XLH) is a dominantly inherited disorder characterized by renal phosphate wasting, aberrant vitamin D metabolism, and abnormal bone mineralization. XLH is caused by inactivating mutations in PHEX (phosphate-regulating gene with homologies to endopeptidases on the X chromosome). In this study, we sequenced the PHEX gene in subjects from 26 kindreds who were clinically diagnosed with XLH. Sequencing revealed 18 different mutations, of which thirteen have not been reported previously. In addition to deletions, splice site mutations, and missense and nonsense mutations, a rare point mutation in the 3'-untranslated region (3'-UTR) was identified as a novel cause of XLH. In summary, we identified a wide spectrum of mutations in the PHEX gene. Our data, in accord with those of others, indicate that there is no single predominant PHEX mutation responsible for XLH.     

Identification of a gene locus for Senior-L?ken syndrome in the region of the nephronophthisis type 3 gene.

Senior-L?ken syndrome is an autosomal recessive disease with the main features of nephronophthisis (NPH) and Leber congenital amaurosis. The gene for adolescent nephronophthisis (NPHP3) was recently localized to chromosome 3q21-q22. The hypothesis was tested that Senior-L?ken syndrome (SLS) might localize to the same region by studying a kindred of German ancestry with extended consanguinity and typical findings of SLS. Twenty highly polymorphic markers located in the vicinity of the NPHP3 genetic region were tested. Haplotype analysis revealed homozygosity by descent in affected individuals, and linkage analysis yielded a parametric maximum multipoint logarithm of likelihood of odds (LOD) score of 3.14, thus identifying the first locus for SLS. The SLS1 locus is flanked by D3S1587 and D3S621 and contains a 14-cM interval that contains the whole critical NPHP3 region. Three additional families with SLS were studied, and evidence for genetic heterogeneity in one of them was found. Localization of a SLS locus to the region of NPHP3 opens the possibilities of both diseases arising by mutations within the same pleiotropic gene or two adjacent genes.