The occurrence of a spontaneous nephropathy with intranuclear inclusions in laboratory mice has puzzled pathologists for over 4 decades, because its etiology remains elusive. The condition is more severe in immunodeficient animals, suggesting an infectious cause. Using metagenomics, we identify the causative agent as an atypical virus, termed "mouse kidney parvovirus" (MKPV), belonging to a divergent genus of Parvoviridae. MKPV was identified in animal facilities in Australia and North America, is transmitted via a fecal-oral or urinary-oral route, and is controlled by the adaptive immune system. Detailed analysis of the clinical course and histopathological features demonstrated a stepwise progression of pathology ranging from sporadic tubular inclusions to tubular degeneration and interstitial fibrosis and culminating in renal failure. In summary, we identify a widely distributed pathogen in laboratory mice and establish MKPV-induced nephropathy as a new tool for elucidating mechanisms of tubulointerstitial fibrosis that shares molecular features with chronic kidney disease in humans.

This review has provided population-based descriptive epidemiological data on clinically significant glomerulonephritis. This data provides important clues for further studies relating to the identification of risk factors for the various types of glomerulonephritis.

Action myoclonus-renal failure syndrome (AMRF) is an autosomal-recessive disorder with the remarkable combination of focal glomerulosclerosis, frequently with glomerular collapse, and progressive myoclonus epilepsy associated with storage material in the brain. Here, we employed a novel combination of molecular strategies to find the responsible gene and show its effects in an animal model. Utilizing only three unrelated affected individuals and their relatives, we used homozygosity mapping with single-nucleotide polymorphism chips to localize AMRF. We then used microarray-expression analysis to prioritize candidates prior to sequencing. The disorder was mapped to 4q13-21, and microarray-expression analysis identified SCARB2/Limp2, which encodes a lysosomal-membrane protein, as the likely candidate. Mutations in SCARB2/Limp2 were found in all three families used for mapping and subsequently confirmed in two other unrelated AMRF families. The mutations were associated with lack of SCARB2 protein. Reanalysis of an existing Limp2 knockout mouse showed intracellular inclusions in cerebral and cerebellar cortex, and the kidneys showed subtle glomerular changes. This study highlights that recessive genes can be identified with a very small number of subjects. The ancestral lysosomal-membrane protein SCARB2/LIMP-2 is responsible for AMRF. The heterogeneous pathology in the kidney and brain suggests that SCARB2/Limp2 has pleiotropic effects that may be relevant to understanding the pathogenesis of other forms of glomerulosclerosis or collapse and myoclonic epilepsies.

The BRAF(T1799A) mutation encodes BRAF(V600E) that leads to activation of the mitogen-activated protein kinase pathway. This study aimed to assess the clinico-pathological features of primary invasive melanomas containing the BRAF(T1799A) mutation. Patients (n=251) with invasive primary melanomas from Australia were interviewed and examined with respect to their melanoma characteristics and risk factors. Independent review of pathology, allele-specific PCR for the BRAF(T1799A) mutation, immunohistochemical staining with Ki67, and phospho-histone-H3 (PH3) were performed. The BRAF(T1799A) mutation was found in 112 (45%) of the primary melanomas. Associations with the BRAF(T1799A) mutation (P<0.05) were as follows: low tumor thickness (odds ratio (OR)=3.3); low mitotic rate (OR=2.0); low Ki67 score (OR=5.0); low PH3 score (OR=3.3); superficial spreading melanoma (OR=10.0); pigmented melanoma (OR=3.7); a lack of history of solar keratoses (OR=2.7); a location on the trunk (OR=3.4) or extremity (OR=2.0); a high level of self-reported childhood sun exposure (OR=2.0); < or =50 years of age (OR=2.5); and fewer freckles (OR=2.5). We conclude that the BRAF(T1799A) mutation has associations with host phenotype, tumor location, and pigmentation. Although implicated in the control of the cell cycle, the BRAF(T1799A) mutation is associated with a lower rate of tumor proliferation.

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Abstract-The loss of one allele for glial cell line-derived neurotrophic factor (GDNF) results in Ϸ30% fewer but normal sized glomeruli in young mice. Low nephron number, inherited or acquired, has been linked to increased risk of development of hypertension and renal failure. This study examines whether GDNF heterozygous mice, with an inherent reduction in nephron number, demonstrate a deterioration in renal structure and function and rise in arterial pressure in later life. Fourteen-month-old male GDNF heterozygous (nϭ7) and wild-type (nϭ6) mice were anesthetized and prepared for measurement of mean arterial pressure, glomerular filtration rate (GFR), and renal blood flow. Key Words: mice Ⅲ hypertension, genetic Ⅲ kidney Ⅲ blood flow Ⅲ arterial pressure I t has been hypothesized that low nephron numbers in the kidney may increase the risk of development of cardiovascular diseases such as hypertension and chronic renal failure and reduce the long-term success of renal allografts. 1-4 Thus, factors that affect nephrogenesis in the fetus may not only be critical in kidney development but also affect subsequent adult kidney function and underlie much subsequent renal pathology and abnormal physiology.Glial cell line-derived neurotrophic factor (GDNF) 5-7 has been shown to play a key role in kidney development through actions at the RET and GFR␣1 receptor and coreceptor. 8,9 Specifically, GDNF has been demonstrated to initiate budding of the ureteric duct from the Wolffian duct, branching of the ureteric epithelium within the metanephric mesenchyme, and the formation of new nephrons at the branch tips. [5][6][7] Increasing the levels of exogenous GDNF in metanephric culture medium leads to increases in both the number of ureteric branches and number of developing nephrons. 7 In the late 1990s, knockout studies demonstrated that homozygous null mutants for GDNF, 10 -13 as well as RET 14 and GFR␣1, 15,16 showed bilateral renal agenesis and died shortly after birth. In contrast, GDNF, RET, and GFR␣1 heterozygous mice were both fertile and viable. Whereas the RET and GFR␣1 heterozygotes demonstrated a normal renal phenotype, the GDNF heterozygotes showed an array of renal phenotypes, ranging from two smaller kidneys, many with abnormal shapes and cortical cysts, to unilateral renal agenesis. 10 -13 These results indicated that GDNF gene dosage influenced kidney development, with the loss of one allele being sufficient to cause a significant renal phenotype. Recently we found that the kidneys of these GDNF heterozygous mice at 30 days of age were Ϸ25% smaller than their wild-type littermates despite similar body weights. 17 Furthermore, stereologic estimates of nephron number identified a 30% decrease in nephron endowment in young heterozygous GDNF mice compared with wild-type mice. The GDNF heterozygous mouse thus provides a genetic model with which to test the hypothesis that an inherent reduction in nephron number contributes to the development of cardiovascular and renal disease that is uncomplicated by changes in...

Aims/hypothesis. Inflammation and fibrosis are pathological mechanisms that are partially regulated by cell signalling through the p38 mitogen-activated protein kinase (MAPK) pathway. Elements of the diabetic milieu such as high glucose and advanced glycation endproducts induce activation of this pathway in renal cells. Therefore, we examined whether p38 MAPK signalling is associated with the development of human and experimental diabetic nephropathy. Methods. Immunostaining identified phosphorylated (active) p38 MAPK in human biopsies with no abnormality (n=6) and with Type 2 diabetic nephropathy (n=12). Changes in kidney levels of phosphorylated p38 were assessed by immunostaining and western blotting in mice with streptozotocin-induced Type 1 diabetes that had been killed after 0.5, 2, 3, 4 and 8 months, and in Type 2 diabetic db/db mice at 2, 4, 6 and 8 months of age. Results. Phosphorylated p38 was detected in some intrinsic cells in normal human kidney, including podocytes, cortical tubules and occasional interstitial cells. Greater numbers of these phosphorylated p38+ cells were observed in diabetic patients, and phosphorylated p38 was identified in accumulating interstitial macrophages and myofibroblasts. A similar pattern of p38 activation was observed in both mouse models of diabetes. In mice, kidney levels of phosphorylated p38 increased (2-6 fold) following the onset of Type 1 and Type 2 diabetes. In both mouse models, interstitial phosphorylated p38+ cells were associated with hyperglycaemia, increased HbA 1 c levels and albuminuria. Further assessment of streptozotocin-induced diabetic nephropathy showed that interstitial phosphorylated p38+ cells correlated with interstitial fibrosis (myofibroblasts, collagen). Conclusions/interpretation. Increased p38 MAPK signalling is a feature of human and experimental diabetic nephropathy. Time course studies in mouse models suggest that phosphorylation of p38 plays a pathological role, particularly in the development of interstitial fibrosis.