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.     

Comparison of the pharmacokinetics of moxidectin and ivermectin after oral administration to beagle dogs

This study compares plasma disposition kinetics of ivermectin and moxidectin after oral administration to beagle dogs experimentally infected with the filarial parasite, Brugia pahangi. Sixteen dogs were selected and randomly allocated into two groups of eight dogs each. Animals in each group received either ivermectin or moxidectin by oral route at a dose of 250 microg/kg. Blood samples were collected from 0.5 h up to 56 days post-treatment and the plasma was analysed by high performance liquid chromatography (HPLC). The obtained data were analysed by compartmental and non-compartmental pharmacokinetic techniques. Peak plasma concentrations (C(max)) of 234.0 +/- 64.3 ng/ml (mean +/- SD) were obtained for moxidectin and 132.6 +/- 43.0 ng/ml for ivermectin. The terminal elimination half-life was significantly (p<0.01) longer in the moxidectin treated group (621.3 +/- 149.3 h) than for ivermectin treated group (80.3 +/- 29.8 h). A significantly (p< 0.01) larger V(ss)/F was obtained for moxidectin (19.21 +/- 3.61 l/kg) compared with ivermectin (5.35 +/- 1.29 l/kg). The mean estimates of CL/F of moxidectin and ivermectin were 0.0220 +/- 0.00381 and 0.0498 +/- 0.0179 l/h/kg, respectively. The comparative plasma disposition kinetics of ivermectin and moxidectin in dogs is reported for the first time.     

Jouberin localizes to collecting ducts and interacts with nephrocystin-1

Joubert syndrome and related disorders are autosomal recessive multisystem diseases characterized by cerebellar vermis aplasia/hypoplasia, retinal degeneration and cystic kidney disease. There are five known genes; mutations of which give rise to a spectrum of renal cystic diseases the most common of which is nephronophthisis, a disorder characterized by early loss of urinary concentrating ability, renal fibrosis, corticomedullary cyst formation and renal failure. Many of the proteins encoded by these genes interact with one another and are located at adherens junctions or the primary cilia and or basal bodies. Here we characterize Jouberin, a multi-domain protein encoded by the AHI1 gene. Immunohistochemistry with a novel antibody showed that endogenous Jouberin is expressed in brain, kidney and HEK293 cells. In the kidney, Jouberin co-localized with aquaporin-2 in the collecting ducts. We show that Jouberin interacts with nephrocystin-1 as determined by yeast-2-hybrid system and this was confirmed by exogenous and endogenous co-immunoprecipitation in HEK293 cells. Jouberin is expressed at cell-cell junctions, primary cilia and basal body of mIMCD3 cells while a Jouberin-GFP construct localized to centrosomes in subconfluent and dividing MDCK cells. Our results suggest that Jouberin is a protein whose expression pattern supports both the adherens junction and the ciliary hypotheses for abnormalities leading to nephronophthisis.     

The breast cancer resistance protein transporter ABCG2 is expressed in the human kidney proximal tubule apical membrane

The Breast Cancer Resistance Protein (BCRP/ABCG2) is a transporter restricting absorption and enhancing excretion of many compounds including anticancer drugs. This transporter is highly expressed in many tissues; however, in human kidney, only the mRNA was found in contrast to the mouse kidney, where the transporter is abundant. In bcrp/abcg2((-/-)) mice, the expression of two sterol transporter genes, abcg5 and abcg8, was strongly increased in the kidney, perhaps as a compensatory mechanism to upregulate efflux. We found using immunohistochemical analysis clear localization of BCRP/ABCG2 to the proximal tubule brush border membrane of the human kidney comparable to that of other ABC transporters such as P-glycoprotein/ABCB1, MRP2/ABCC2, and MRP4/ABCC4. Hoechst 33342 dye efflux from primary human proximal tubule cells was significantly reduced by the BCRP/ABCG2 inhibitors fumitremorgin C and nelfinavir. Our study shows that in addition to other apical ABC transporters, BCRP/ABCG2 may be important in renal drug excretion.     

HLA-B*27 typing by sequence specific amplification without DNA extraction.

HLA-B27 appears to play a direct role in the pathogenesis of ankylosing spondylitis and almost all patients with this disease have HLA-B27. Therefore, a diagnosis of ankylosing spondylitis can virtually be excluded in the absence of HLA-B27. Many techniques have been used for HLA-B*27 typing. Of these, molecular methods are the most sensitive and specific but require extracted DNA as the testing material. A technique where HLA-B*27 is amplified directly from whole blood using sequence specific primers has been developed. This technique uses small sample volumes, is not restricted by choice of anticoagulant or sample age up to at least six weeks, and can be applied to other clinical polymerase chain reaction based procedures.     

Cerebrospinal fluid drainage in the treatment of spontaneous spinal cord ischemia: a case report.

A patient with spontaneous acute spinal cord ischemia successfully treated with cerebrospinal fluid drainage is reported. There are no consensus guidelines on the management of spinal cord ischemia. Various preventive and rehabilitative measures have been suggested, but the best treatment remains unknown.     

Differential susceptibility to DL-alpha-difluoromethylornithine in clinical isolates of Trypanosoma brucei rhodesiense.

DL-alpha-Difluoromethylornithine is an enzyme-activated inhibitor of ornithine decarboxylase and an antagonist of polyamine metabolism that has been successful in clinical trials against West African sleeping sickness caused by Trypanosoma brucei gambiense. Its potential for use against the more virulent East African form of the disease, caused by T. brucei rhodesiense, is not certain. We examined 14 East African clinical isolates from the Kenya Trypanosomiasis Research Institute strain bank plus 2 established isolates for susceptibility to DL-alpha-difluoromethylornithine and to standard trypanocides. Seven of 16 strains were partially or totally refractory to DL-alpha-difluoromethylornithine in our test system. Four strains were also refractory to arsenical drugs, and five were refractory to diamidines. The results indicate that other novel agents or combinations of established agents may be needed for chemotherapy of East African disease.