We identified PNKP mutations in a Norwegian woman with AOA. This patient had the typical findings with cognitive dysfunction, peripheral neuropathy, cerebellar dysarthria, horizontal nystagmus, oculomotor apraxia, and severe truncal and appendicular ataxia. In addition, she had hypoalbuminemia and massive lower limb edema which showed some improvement with treatment. Exome sequencing identified two heterozygous mutations, one in exon 14 (c.1196T>C, p.Leu399Pro) and one in exon 16 (c.1393_1396del, p.Glu465*). This is the first non-Portuguese patient with AOA due to PNKP mutations and provides independent verification that PNKP mutations cause AOA.

The aim of this study was to evaluate if urinary sediment cells offered a robust alternative to muscle biopsy for the diagnosis of single mtDNA deletions.

Arachnoid cysts (AC) are filled with liquid very similar to cerebrospinal fluid (CSF). The mechanisms of fluid accumulation have remained unknown; previous studies have however indicated both fluid secretion and a one-way valve as a mechanism. If the filling was caused by fluid secretion, mechanisms similar to those underlying CSF production would be anticipated. We have investigated the expression levels of all genes known to be involved in mammalian CSF production in surgically removed AC. Based on mRNA microarray analysis of AC and normal arachnoid tissue, we extracted the RNA expression profiles of all genes known to code for proteins involved in CSF production. A selection of genes was further investigated with quantitative real-time polymerase chain reaction (qRT-PCR). For selected CSF production proteins, electron microscopic immunogold techniques (EM) and Western blots were performed. Seven genes were expressed in both cysts and controls. The gene encoding the Na(+)-K(+)-2Cl(-) cotransporter NKCC1 was significantly up-regulated in AC. Gene expression data were supported by Western blot. EM demonstrated NKCC1 expressed at the plasma membranes of the cyst-lining cells. This result points at secretion as the main mechanism of cyst filling, and NKCC1 as the key candidate of fluid transport. Based on these findings, we hypothesize that selective NKCC1 inhibitors could be used in preventing expansion of temporal AC.

Pathogenic germline variants in Breast cancer susceptibility gene 1 (BRCA1) predispose carriers to hereditary breast and ovarian cancer (HBOC). Through genetic testing of patients with suspected HBOC an increasing number of novel BRCA1 variants are discovered. This creates a growing need to determine the clinical significance of these variants through correct classification (class 1-5) according to established guidelines. Here we present a joint collection of all BRCA1 variants of class 2-5 detected in the four diagnostic genetic laboratories in Norway. The overall objective of the study was to generate an overview of all BRCA1 variants in Norway and unveil potential discrepancies in variant interpretation between the hospitals, serving as a quality control at the national level. For a subset of variants, we also assessed the change in classification over a ten-year period with increasing information available. In total, 463 unique BRCA1 variants were detected. Of the 126 variants found in more than one hospital, 70% were interpreted identically, while 30% were not. The differences in interpretation were mainly by one class (class 2/3 or 4/5), except for one larger discrepancy (class 3/5) which could affect the clinical management of patients. After a series of digital meetings between the participating laboratories to disclose the cause of disagreement for all conflicting variants, the discrepancy rate was reduced to 10%. This illustrates that variant interpretation needs to be updated regularly, and that data sharing and improved national inter-laboratory collaboration greatly improves the variant classification and hence increases the accuracy of cancer risk assessment.

Pathogenic mutations in the non-muscle single-headed myosin, myosin 1E (Myo1e), are a rare cause of pediatric focal segmental glomerulosclerosis (FSGS). These mutations are biallelic, to date only reported as homozygous variants in consanguineous families. Myo1e regulates the actin cytoskeleton dynamics and cell adhesion, which are especially important for podocyte functions.