The neuronal ceroid lipofuscinoses in human EPMR and mnd mutant mice are associated with mutations in CLN8.

The neuronal ceroid lipofuscinoses (NCLs) are a genetically heterogeneous group of progressive neurodegenerative disorders characterized by the accumulation of autofluorescent lipopigment in various tissues. Progressive epilepsy with mental retardation (EPMR, MIM 600143) was recently recognized as a new NCL subtype (CLN8). It is an autosomal recessive disorder characterized by onset of generalized seizures between 5 and 10 years, and subsequent progressive mental retardation. Here we report the positional cloning of a novel gene, CLN8, which is mutated in EPMR. It encodes a putative transmembrane protein. EPMR patients were homozygous for a missense mutation (70C-->G, R24G) that was not found in homozygosity in 433 controls. We also cloned the mouse Cln8 sequence. It displays 82% nucleotide identity with CLN8, conservation of the codon harbouring the human mutation and is localized to the same region as the motor neuron degeneration mouse, mnd, a naturally occurring mouse NCL (ref. 4). In mnd/mnd mice, we identified a homozygous 1-bp insertion (267-268insC, codon 90) predicting a frameshift and a truncated protein. Our data demonstrate that mutations in these orthologous genes underlie NCL phenotypes in human and mouse, and represent the first description of the molecular basis of a naturally occurring animal model for NCL.

Turkish variant late infantile neuronal ceroid lipofuscinosis (CLN7) may be allelic to CLN8.

One variant form of late infantile neuronal ceroid lipofuscinosis (LINCL) is found predominantly within the Turkish population (CLN7). Exclusion mapping showed that CLN7 was not an allelic variant of known NCL loci (CLN1, CLN2, CLN3, CLN5 or CLN6). Using the method of homozygosity mapping, a genome-wide search was undertaken and a total of 358 microsatellite markers were typed at an average distance of about 10 cM. A region of shared homozygosity was identified on chromosome 8p23. This telomeric region contained the recently identified CLN8 gene. A missense mutation in CLN8 causes progressive epilepsy with mental retardation (EPMR) or Northern epilepsy, which has so far been reported only from Finland and is now classified as an NCL. The mouse model mnd has been shown to carry a 1 bp insertion in the orthologous Cln8 gene. Statistically significant evidence for linkage was obtained in this region, with LOD scores > 3, assuming either homogeneity or heterogeneity. Flanking recombinants defined a critical region of 14 cM between D8S504 and D8S1458 which encompasses CLN8. This suggests that Turkish variant LINCL, despite having an earlier onset and more severe phenotype, may be an allelic variant of Northern epilepsy. However mutation analysis has not so far identified a disease causing mutation within the coding or non-coding exons of CLN8 in the families. The Turkish variant LINCL disease-causing mutation remains to be delineated.

[18 children with slight glomerular proteinuria demonstrated incidentally]. / Atten børn med lille tilfaeldigt påvist glomerulaer proteinuri.

Out of 61 children with idiopathic chronic glomerulonephritis confirmed by biopsy or minimal lesion diagnosed during the period 1964-1987, 18 were found in whom the first sign of renal disease was slight proteinuria demonstrated at routine examination of the urine. Five of these children were referred directly to a nephrological department with the object of further elucidation of the diagnosis. In six of the remaining 13 children, the first referral to hospital took place after an average of 5.9 years and after signs of renal disease were apparent for the first time. In ten of these 13 patients, an average period of 3.9 years elapsed before renal biopsy was carried out and the nature of the disease elucidated. 29 and 73% of these patients, respectively, had developed terminal uraemia five and ten years after establishing the diagnosis. It is recommended that children in whom persistent proteinuria is demonstrated, regardless of the magnitude, should be referred directly to a nephrological department or a paediatric department with special interests. Renal biopsy may be indicated. Life-long systematic follow-up control is indicated.

Acute renal failure caused by polymyxin B containing ointment.

A case is presented in which a 67-year-old man suffering from non-insulin-dependent diabetes mellitus, after being treated with polymyxin B containing ointment for leg ulcers, developed acute renal failure. After a period of 13 days during which the patient was treated with peritoneal dialysis 5 times, renal function returned. At discharge creatinine-clearance was 12 ml/min. Treating large ulcers with polymyxin B may be dangerous.

Benzodiazepine intoxication treated with flumazenil (Anexate, RO 15-1788).

The efficacy and safety of flumazenil were assessed in comparison to placebo in a double-blind randomised study of 31 adults intoxicated with benzodiazepines. The criteria of efficacy were the degree of sedation, and orientation in time and space. Patients who received flumazenil awoke within minutes but central depression returned partly one hour later, which reflects the short elimination half-life of the drug. Side effects were few and the results indicate that flumazenil is effective in the primary management of benzodiazepine overdose and in states where benzodiazepines have been taken with other drugs.

The neuronal ceroid lipofuscinosis CLN8 membrane protein is a resident of the endoplasmic reticulum.

Progressive epilepsy with mental retardation (EPMR) is a new member of the neuronal ceroid lipofuscinoses (NCLs). The CLN8 gene underlying EPMR was recently identified. It encodes a novel 286 amino acid transmembrane protein that contains an endoplasmic reticulum (ER)-retrieval signal (KKRP) in its C-terminus. A homozygous mutation in the orthologous mouse gene (Cln8) underlies the phenotype of a naturally occurring NCL model, the motor neuron degeneration mouse (mnd). To characterize the product of the CLN8 gene and to determine its intracellular localization, we expressed CLN8 cDNA in BHK, HeLa and CHO cell lines. In western blotting and pulse-chase analyses an approximately 33 kDa protein that does not undergo proteolytic processing steps was detected. Using CLN8 and cell organelle specific antibodies with confocal immunofluorescence microscopy the CLN8 protein was shown to localize in the ER. Partial localization to the ER-Golgi intermediate compartment (ERGIC) was also observed. The ER-ERGIC localization was not altered in the CLN8 protein representing the EPMR mutation. However, mnd mutant protein was only found in the ER. Mutations in the ER retrieval signal KKRP resulted in localization of CLN8 to the Golgi apparatus. Taken together, these data strongly suggest that CLN8 is an ER resident protein that recycles between ER and ERGIC.