Hypomorphic mutations in meckelin (MKS3/TMEM67) cause nephronophthisis with liver fibrosis (NPHP11).

BACKGROUND: Nephronophthisis (NPHP), a rare recessive cystic kidney disease, is the most frequent genetic cause of chronic renal failure in children and young adults. Mutations in nine genes (NPHP1-9) have been identified. NPHP can be associated with retinal degeneration (Senior-Løken syndrome), brainstem and cerebellar anomalies (Joubert syndrome), or liver fibrosis. METHODS: To identify a causative gene for the subset of patients with associated liver fibrosis, the authors performed a genome wide linkage search in a consanguineous family with three affected patients using 50K SNP microarrays and homozygosity mapping. RESULTS: The authors obtained a significant maximum parametric LOD (logarithm of odds) score of Z(max) = 3.72 on chromosome 8q22 and identified a homozygous missense mutation in the gene MKS3/TMEM67. When examining a worldwide cohort of 62 independent patients with NPHP and associated liver fibrosis we identified altogether four novel mutations (p.W290L, p.C615R, p.G821S, and p.G821R) in five of them. Mutations of MKS3/TMEM67, found recently in Meckel-Gruber syndrome (MKS) type 3 and Joubert syndrome (JBTS) type 6, are predominantly truncating mutations. In contrast, the mutations detected here in patients with NPHP and associated liver fibrosis are exclusively missense mutations. This suggests that they may represent hypomorphic alleles, leading to a milder phenotype compared with the more severe MKS or JBTS phenotype. Additionally, mutation analysis for MKS3/TMEM67 in 120 patients with JBTS yielded seven different (four novel) mutations in five patients, four of whom also presented with congenital liver fibrosis. CONCLUSIONS: Hypomorphic MKS3/TMEM67 mutations cause NPHP with liver fibrosis (NPHP11). This is the first report of MKS3 mutations in patients with no vermian agenesis and without neurological signs. Thus NPHP, JBTS, and MKS represent allelic disorders.

Mutational analysis of the RPGRIP1L gene in patients with Joubert syndrome and nephronophthisis.

Joubert syndrome (JS) is an autosomal recessive disorder, consisting of mental retardation, cerebellar vermis aplasia, an irregular breathing pattern, and retinal degeneration. Nephronophthisis (NPHP) is found in 17-27% of these patients, which was designated JS type B. Mutations in four separate genes (AHI1, NPHP1, CEP290/NPHP6, and MKS3) are linked to JS. However, missense mutations in a new ciliary gene (RPGRIP1L) were found in type B patients. We analyzed a cohort of 56 patients with JS type B who were negative for mutations in three (AHI1, NPHP1, and CEP290/NPHP6) of the four genes previously linked to the syndrome. The 26 exons encoding RPGRIP1L were analyzed by means of PCR amplification, CEL I endonuclease digestion, and subsequent sequencing. Using this approach, four different mutations in the RPGRIP1L gene in five different families were identified and three were found to be novel mutations. Additionally, we verified that missense mutations are responsible for JS type B and cluster in exon 15 of the RPGRIP1L gene. Our studies confirm that a T615P mutation represents the most common mutation in the RPGRIP1L gene causing disease in about 8-10% of JS type B patients negative for NPHP1, NPHP6, or AHI1 mutations.

The Uromodulin C744G mutation causes MCKD2 and FJHN in children and adults and may be due to a possible founder effect.

Autosomal dominant medullary cystic kidney disease type 2 (MCKD2) is a tubulo-in terstitial nephropathy that causes renal salt wasting, hyperuricemia, gout, and end-stage renal failure in the fifth decade of life. This disorder was described to have an age of onset between the age of 20-30 years or even later. Mutations in the Uromodulin (UMOD) gene were published in patients with familial juvenile hyperuricemic nephropathy (FJHN) and MCKD2. Clinical data and blood samples of 16 affected individuals from 11 different kindreds were collected. Mutational analysis of the UMOD gene was performed by exon polymerase chain reaction (PCR) and direct sequencing. We found the heterozygous C744G (Cys248Trp) mutation, which was originally published by our group, in an additional four kindreds from Europe and Turkey. Age of onset ranged from 3 years to 39 years. The phenotype showed a variety of symptoms such as urinary concentration defect, vesicoureteral reflux, urinary tract infections, hyperuricemia, hypertension, proteinuria, and renal hypoplasia. Haplotype analysis showed cosegragation with the phenotype in all eight affected individuals indicating that the C744G mutation may be due to a founder effect. Moreover, we describe a novel T229G (Cys77Gly) mutation in two affecteds of one kindred. Three of the affected individuals were younger than 10 years at the onset of MCKD2/FJHN. Symptoms include recurrent urinary tract infections compatible with the published phenotype of the Umod knockout mouse model. This emphasizes that MCKD2 is not just a disease of the young adult but is also relevant for children.

A new missense mutation of the vasopressin-neurophysin II gene in a family with neurohypophyseal diabetes insipidus.

OBJECTIVE: Autosomal dominant familial neurohypophyseal diabetes insipidus is a rare disorder characterized by polydipsia and polyuria. We present the results of the molecular analysis of the AVP-NPII gene of a German kindred. METHODS: All three exons of the gene were amplified by polymerase chain reaction and sequenced. RESULTS: In 7 affected individuals a new missense mutation (1770G > T) in exon 2 was found predicting a cysteine to phenylalanine substitution at codon 58 in the neurophysin II domain (NPII). CONCLUSION: As a result of this mutation a cysteine residue is exchanged, which is involved in a disulfide bond with cysteine 44 of the NPII moiety, hypothesizing that the resulting misfolded protein may lead to chronic neurotoxicity by accumulation of these products in the endoplasmatic reticulum.

Ten novel mutations found in Aniridia.

Aniridia (AN) is a sight-threatening congenital ocular disorder characterized by iris hypoplasia, corneal pannus, foveal and optic nerve hypoplasia, cataract formation, and glaucoma. In two-thirds of the patients, AN is inherited in an autosomal dominant fashion with almost complete penetrance but variable expression. The remaining cases are sporadic. Aniridia has been shown to be associated with mutations in the PAX6 gene, located on chromosome 11p13, telomeric to the Wilms' tumor predisposition gene (WT1). This paper describes 14 mutations in the PAX6 gene in patients with AN. Among these 14 mutations, 10 have been unpublished until now. They result most probably in haploinsufficiency and consequently in a reduced protein level of functional PAX6 protein. The mutations reported here are scattered all over the gene, including the paired-box, the glycine-rich region, the homeobox, and the proline-serine-threonine (PST)-rich region.

An anesthetic for the adult patient with congenital tracheoesophageal fistula: a case report.

A 20-year-old male with a history of recurrent pneumonia was diagnosed as having an N-type tracheoesophageal fistula. A general anesthetic was planned to facilitate the repair of the tracheoesophageal fistula using a left anterior cervical approach. Intraoperatively, the surgeons were unable to identify the defect after surgical exposure. To facilitate location of the tracheoesophageal fistula, a flexible pediatric fiberoptic bronchoscope was passed through an elbow adapter connected to the endotracheal tube. The scope was then visually passed via the trachea through the defect into the esophagus. The surgeons were able to palpate the fistula with the bronchoscope passed through the defect. Ease of identification allowed the tracheoesophageal fistula to be quickly repaired. At the completion of the surgery, the patient was extubated, and recovery was uneventful. The patient was discharged 48 hours postoperatively.

Multidose vial contamination in anesthesia.

The intent of this research was to address the following question: Will an alteration in the drug aspiration technique cause a significant difference in the incidence of multidose vial contamination? The control group consisted of multidose vials collected at the end of each day from staff anesthetists. The use of these vials reflected the practice technique of a single needle and syringe for each vial. The vial, as well as needle and syringe, were used on all cases managed for the day. The experimental group consisted of multidose vials collected at the end of each day from the four investigators. The vials and syringes were utilized in the same manner as the control group with the exception that a new needle was used each time a vial was reentered. Upon completion of the collection period, guaiac testing, using Hemoccult slides and developer, was performed on a 0.1 cc sample from each vial. A multidose vial was considered positive for blood contamination if traces of blue appeared on the Hemoccult slide in a 15-minute period. A chi-square statistic was applied to the cumulative data. The control group consisted of 492 multidose vials. Of the 492 multidose vials tested, 11 were guaiac positive, 2.24%. The experimental group consisted of 369 multidose vials. Of the 369 multidose vials, one tested guaiac positive, 0.27%. A chi-square test on the cumulative data demonstrated a significant (p less than .05) difference between the two groups. The research demonstrated that occult blood may be contained within the used multidose vials suggesting that contaminated drug may then be injected into another patient.(ABSTRACT TRUNCATED AT 250 WORDS)