GAPVD1 and ANKFY1 Mutations Implicate RAB5 Regulation in Nephrotic Syndrome.

BACKGROUND: Steroid-resistant nephrotic syndrome (SRNS) is a frequent cause of CKD. The discovery of monogenic causes of SRNS has revealed specific pathogenetic pathways, but these monogenic causes do not explain all cases of SRNS. METHODS: To identify novel monogenic causes of SRNS, we screened 665 patients by whole-exome sequencing. We then evaluated the in vitro functional significance of two genes and the mutations therein that we discovered through this sequencing and conducted complementary studies in podocyte-like Drosophila nephrocytes. RESULTS: We identified conserved, homozygous missense mutations of GAPVD1 in two families with early-onset NS and a homozygous missense mutation of ANKFY1 in two siblings with SRNS. GAPVD1 and ANKFY1 interact with the endosomal regulator RAB5. Coimmunoprecipitation assays indicated interaction between GAPVD1 and ANKFY1 proteins, which also colocalized when expressed in HEK293T cells. Silencing either protein diminished the podocyte migration rate. Compared with wild-type GAPVD1 and ANKFY1, the mutated proteins produced upon ectopic expression of GAPVD1 or ANKFY1 bearing the patient-derived mutations exhibited altered binding affinity for active RAB5 and reduced ability to rescue the knockout-induced defect in podocyte migration. Coimmunoprecipitation assays further demonstrated a physical interaction between nephrin and GAPVD1, and immunofluorescence revealed partial colocalization of these proteins in rat glomeruli. The patient-derived GAPVD1 mutations reduced nephrin-GAPVD1 binding affinity. In Drosophila, silencing Gapvd1 impaired endocytosis and caused mistrafficking of the nephrin ortholog. CONCLUSIONS: Mutations in GAPVD1 and probably in ANKFY1 are novel monogenic causes of NS. The discovery of these genes implicates RAB5 regulation in the pathogenesis of human NS.

Ultrastructural Features of Alkhumra Hemorrhagic Fever Virus Infection of Cells Under In Vivo and In Vitro Conditions.

Alkhumra hemorrhagic fever virus (AHFV) is an emerging novel flavivirus that was discovered in Saudi Arabia in 1995. The virus has since caused several outbreaks in the country that resulted in case fatality rates ranging from 1% to 25%. Meager information has been published on the ultrastructural features of the virus on cells under in vitro or in vivo conditions. The present electron microscopic study examined and compared the intracellular growth of the AHFV on the LLC-MK2 cells and brain cells of new born Wistar rats, inoculated intracerebrally. The cytopathological changes in both cell systems were noted, and localization of the virus particles in different cellular components was observed. Both apoptotic and lytic cell interactions were seen in the electron micrographs of both the LLC-MK2 and the rat brain cells. The results were discussed in relation to similar situations reported for other virus members of the genus Flavivirus.

Electron Microscopy of Alkhumra Hemorrhagic Fever Virus.

Alkhumra hemorrhagic fever virus (AHFV) is a newly described zoonotic flavivirus that was first isolated during 1994-1995 from the Alkhumra district south of Jeddah, Saudi Arabia. Subsequently, the virus was also isolated from Makkah city (2001-2003) and Najran (2008-2009), Saudi Arabia. The virus causes acute febrile illness with hepatitis, hemorrhagic manifestations, and encephalitis. A case fatality rate of 25% was reported among hospitalized patients. Although several biological and molecular characteristics of the virus have been published, no data are available on electron microscopic features of the virus. In this article, we describe the morphological features and metrics of the AHFV particles under electron microscopy, and localization of the virus particles in brain cells of newborn Wistar rats and in Rhesus monkey (Macaca mulatta) kidney epithelial cells (LLC-MK2). Virus particles in both the LLC-MK2 cells and the rat brain cells showed dark hexagonal core (capsid) and a translucent envelope. The mean diameter of the enveloped virus particle was 40.59 ± 1.29 nm in the rat brain cells (n = 154) and 40.97 ± 1.40 nm in the LLC-MK2 cells (n = 105; p > 0.05). The virus particles, both in vitro and in vivo, were enclosed into cytoplasmic vesicles. In conclusion, the shape, size, and diameter of the AHFV particle lie within the framework of the genus Flavivirus, family Flaviviridae.

A clinicopathological study of C1q nephropathy at King Abdulaziz University.

INTRODUCTION: C1q nephropathy is a relatively rare idiopathic glomerulopathy characterized by mesangial immunoglobulin and complement deposits with dominance or co-dominance of C1q, with no evidence of systemic lupus erythematosus. We describe the incidence, clinical manifestation, histopathological features, and follow-up of patients with C1q nephropathy at our institute. MATERIALS AND METHODS: Of 750 kidney biopsy specimens obtained in the period of January 2000 to December 2011, all the cases that meet the criteria for the diagnosis of C1q nephropathy were retrieved.  The histological slides were examined and the clinical charts were reviewed by 2renal pathologists. RESULTS: We had 11 patients, all children, that met the criteria for the diagnosis of C1q nephropathy accounting for an incidence of 1.5%.  The mean age at the time of presentation was 3.7 years and all the patients were presented with nephrotic syndrome. Two patients had microhematuria and 2 had hypertension. Histological examination of these cases showed variable degrees of mesangial cells hypercellularity and matrix expansion with focal segmental glomerulosclerosis observed in 2 cases. Nine patients were steroid resistant (82%) and 2 were steroid dependent. Six patients required immunosuppressive therapy and 1 patient developed end-stage renal disease. CONCLUSIONS: In our series, C1q nephropathy affected predominantly young children. Mesangioproliferative pattern was the most frequent histopathological finding in these patients. Clinically, despite steroid resistance, the patients had a relatively good outcome; the worst prognostic outcome was associated with collapsing glomerulopathy.

Severe acute post-streptococcal glomerulonephritis in an infant.

Acute post-streptococcal glomerulonephritis (APSGN) is very rare below the age of two years. We report a 14-month-old girl who presented with frank hematuria and nephrotic syndrome following group A streptococcal pharyngitis (GAS), which was confirmed by laboratory investigations. The patient underwent a renal biopsy to confirm the diagnosis and was treated with prednisolone. The proteinuria and hematuria resolved completely in eight weeks. Our case demonstrates that APSGN should be considered in evaluating hematuria and nephrotic syndrome in infants and children below two years of age.

Simultaneous onset of steroid resistant nephrotic syndrome and IDDM in two young children.

The cases are reported of two young children who developed insulin-dependent diabetes mellitus (IDDM) within 2 weeks of receiving a diagnosis of nephrotic syndrome. Neither patient responded to 8 weeks of daily prednisolone. The first patient presented at 2 years and 9 months of age. Her renal biopsy showed mesangial proliferation. The second child presented with steroid resistant nephrotic syndrome at 18 months of age and developed IDDM 2 weeks later. He achieved partial remission with cyclosporine therapy. His initial renal biopsy at 3 years of age showed minimal change disease and follow-up renal biopsy at 5 years of age showed early diabetic glomerulosclerosis. Tests for NPHS2 and WT1 genetic mutations were negative in both patients. To our knowledge this is the first report of steroid resistant nephrotic syndrome with almost simultaneous onset of IDDM in young children.

IgG glomerulonephritis: a morphologic study of a rare entity.

Mesangial IgG glomerulonephritis (MesIgGN) is recently recognized as a distinct type of glomerulonephritis. In our renal biopsy series, two patients with MesIgGN were identified. The morphologic criteria detected in these patients included mesangial dense deposits by ultrastructural studies, which were predominantly positive for IgG by immunofluorescence. Both patients were young boys, one presented with hematuria and the other with the nephrotic syndrome. Similar cases have been reported in other studies from around the world; however, this is the first report of MesIgGN from Saudi Arabia.

Pattern of steroid resistant nephrotic syndrome in children living in the kingdom of Saudi Arabia: a single center study.

Steroid resistant nephrotic syndrome (SRNS) remains a challenge facing pediatric nephrologists. The underlying histopathology usually affects the course of the disease and the response to treatment. We studied the pattern of histopathology in children with SRNS who presented to the King Abdul Aziz University Hospital (KAUH), Jeddah, Saudi Arabia. The records of all children with primary SRNS, who were seen between 2002 and 2007 were reviewed. Only patients who had undergone a renal biopsy were included in the study. The histopathology slides were reviewed by two renal pathologists independently. Patients with congenital nephrotic syndrome, lupus or sickle cell disease, were excluded from the study. Thirty-six children fulfilled the inclusion criteria, and included 25 girls and 11 boys with female to male ratio of 2.3:1. Fifty percent of the children (n=18) were Saudi and the remaining 50% were from various other racial backgrounds (9 Asians, 4 Arabs, 2 Africans and 3 from the Far East). Their mean age at presentation was 4.3 +/- 3.0 years (range 1-12 years). The mean serum albumin at presentation was 15.6 +/- 7.1 g/L and all of them had 4+ proteinuria on urinalysis. Five children had elevated serum creatinine at presentation while the mean serum creatinine was 50.4 +/- 45.6 micromol/L. Three children had low serum complement levels at presentation and none were positive for hepatitis B surface antigen or antinuclear antibody (ANA). The renal histopathology was compatible with focal and segmental glomerulosclerosis (FSGS) in 39% (n=14), IgM nephro-pathy in 28% (n=10), mesengioproliferative glomerulonephritis (MesPGN) in 17% (n=6), mini-mal change disease (MCD) and C1q nephropathy (C1qNP) in 8% each (n=3 + 3) and IgA nephro-pathy in 3% (n=1). Our retrospective review shows that FSGS was the commonest underlying histopathology in children who presented with SRNS followed by IgM nephropathy and other variants of MCD such as MesPGN. C1qNP was the underlying cause in some children.

Childhood primary glomerular diseases in the western region of Saudi Arabia.

We report our institute experience on primary glomerular disease in children in the western region of Saudi Arabia over the last 18 years (1988 to 2006). A total of 169 cases were identified as primary glomerular diseases in children and adolescent with age range from first year of life till 18 years. Minimal change disease and focal segmental glomerulosclerosis were the commonly encountered primary glomerular diseases (20.1%and 19.5% respectively), mesangioproliferative glomerulonephritis IgM nephropathy (14.8%), IgA nephropathy (10.7%), postinfectious glomerulonephritis (9.5%), membranous glomerulonephritis (7.1%), membranoproliferative glomerulonephritis (5.9%) and mesangioproliferative glomerulonephritis with negative immunofluorescence (5.9%). The less frequently encountered primary glomerular diseases were congenital nephritic syndrome Finnish type (2.4%), Alport syndrome (2.4%), dense deposit disease (1.2%), and mesangio-proliferative glomerulonephritis with IgG positive (0.6%). We concluded that minimal change disease and focal segmental glomerulosclerosis are the most common primary glomerular disorder en-countered in children in our series and with similar age distribution.

Patterns of primary glomerular diseases among adults in the western region of Saudi Arabia.

The frequency of primary glomerular diseases is variable from one part of the world to the other. Data published from Saudi Arabia has shown wide range of variation in the different regions of the country. This study reports the frequency of primary glomerulonephritis (GN) in adults in the Western region of Saudi Arabia. The study is based on retrospective evalua-tion of archived renal biopsy in the period of 18 years (1989-2007). The 296 selected cases of primary GN were studied by light, immunofluorescence, and electron microscopy. The patients age range between 17-76 years. Results show that the most frequent primary GN is membranous GN (MGN) constituting 25.7%, followed by focal segmental glomerulosclerosis (FSGSC) at 21.3%. Less frequent GN are immunoglobulins A nephropathy (IgAN) representing 17.6%, membrano-proliferative GN (MPGN) 11.5%, immunoglobulin M nephropathy (IgMN) 7.8%, minimal change disease (MCD) 5.4% and mesangioprolifertive GN (MesPGN) 4.7%. Other GN which are rarely encountered in this study are fibrillary GN (FGN) (3%), postinfectious GN (PIGN) (2%), Alport syndrome (AS) (0.7%) and membranoproliferative GN type II or dense deposit disease (DDD) (0.3%). In conclusion this study demonstrates that MGN is the most common primary GN encountered in the studied cases, the second more frequent is FSGSC. This result is in contrast to previous reports from Saudi Arabia where MGN is reported with low frequency and FSGSC is reported the most common primary GN.

Electron microscopic study of the myelinated nerve fibres and the perineurial cell basement membrane in the diabetic human peripheral nerves.

OBJECTIVE: To study the quantitative and ultrastructural changes in myelinated nerve fibers and the basement membranes of the perineurial cells in diabetic nerves. METHODS: The study was performed at the Department of Anatomy, Faculty of Medicine, King Abdul-Aziz University, Jeddah, Saudi Arabia from 2003 to 2005. Human sural nerves were obtained from 15 lower limbs and 5 diabetic nerve biopsies. The total mean and density of myelinated nerve fibers per fascicle were calculated, with density of microtubules and mitochondria in the axoplasm. The number of the perineurial cell basement membrane layers was counted, and thickness of the basement membrane was measured. RESULTS: Among the 15 diabetic and 5 normal human sural nerves, the average diameters, number and surface area of myelinated nerve fibers and axonal microtubules density were found to be less in diabetic nerves. Mitochondrial density was higher in diabetic axons. Thickness of the perineurial cell basement membrane had a greater mean, but the number of perineurial cell layers was less than that of the diabetic group. The inner cellular layer of the perineurium of the diabetic nerves contained large vacuoles containing electron-dense degenerated myelin. A few specimens showed degenerated myelinated nerve fibers, while others showed recovering ones. Retracted axoplasms were encountered with albumin extravasation. CONCLUSION: Diabetes caused an increase in perineurial permeability. The diabetic sural nerve showed marked decrease in the myelinated nerve fibres, increase degenerated mitochondria, and decreased microtubules.

Non-diabetic renal disease in diabetic patients.

The occurrence of non-diabetic renal diseases (NDRD) in diabetic patient is well recognized. Different frequencies for NDRD have been reported from different parts of the world. This is a retrospective study of 16 renal biopsies from diabetic patients. The biopsy samples were all examined by light, immunofluoresence and electron microscopy. Non-diabetic renal diseases were encountered in eight cases (50%). Membranous glomerulonephritis (MGN) was the most common NDRD seen in three of the eight cases (37.5%). Immunoglobulin A nephropathy (IgAN), membranoproliferative glomerulonephritis type I (MPGN) and postinfectious glomerulonephritis (PIGN) were seen in one case each (12.5%). Interstitial nephritis was seen in two cases representing 25% of NDRD. In conclusion, the current study demonstrates the occurrence of NDRD in diabetic patients and the most frequently encountered lesion was MGN. Thus, renal biopsy in diabetic patients may prove to be helpful in identifying an underlying NDRD for better management.

C1q nephropathy in two young sisters.

C1q nephropathy (C1qNP) is a controversial and uncommon form of glomerulonephritis, characterized by mesangial immunoglobulin and complement deposits, predominantly C1q, with no evidence of systemic lupus erythematosus. Clinically, it may present as nephrotic syndrome and non-nephrotic proteinuria per se or associated with microhematuria, hypertension, or renal insufficiency. We describe two sisters with C1qNP, who presented with steroid-resistant nephrotic syndrome. Both sisters presented before the age of 2 years, and they showed a poor response to other immunosuppressive therapy. Both girls had normal serum complement levels, negative antinuclear antibodies (ANAs) and negative hepatitis B antigen. Renal biopsy in both patients showed histological features of mesangioproliferative glomerulonephritis, with diffuse "full-house" positive immunofluorescence reaction in the mesangial area. The immunofluorescence reaction for C1q was most intense and co-dominant with IgG in both patients. Correspondingly, electron microscopy demonstrated dense deposits mainly in the mesangial areas too. We report on two young sisters with the characteristic features of C1qNP presented in early childhood. To the best of our knowledge, this is the first report of C1qNP in siblings.

Ultrastructural changes of compressed lumbar ventral nerve roots following decompression.

OBJECTIVE: To study whether there will be a permanent lumbar nerve root scarring or degeneration secondary to continuous compression followed by decompression on the nerve roots, which can account for postlaminectomy leg weakness or back pain. METHODS: The study was performed at the Department of Anatomy, Faculty of Medicine, King Abdul-Aziz University, Jeddah, Kingdom of Saudi Arabia during 2003-2005. Twenty-six adult male New Zealand rabbits were used in the present study. The ventral roots of the left fourth lumbar nerve were clamped for 2 weeks then decompression was allowed by removal of the clips. The left ventral roots of the fourth lumbar nerve were excised for electron microscopic study. RESULTS: One week after nerve root decompression, the ventral root peripheral to the site of compression showed signs of Wallerian degeneration together with signs of regeneration. Schwann cells and myelinated nerve fibers showed severe degenerative changes. Two weeks after decompression, the endoneurium of the ventral root showed extensive edema with an increase in the regenerating myelinated and unmyelinated nerve fibers, and fibroblasts proliferation. Three weeks after decompression, the endoneurium showed an increase in the regenerating myelinated and unmyelinated nerve fibers with diminution of the endoneurial edema, and number of macrophages and an increase in collagen fibrils. Five and 6 weeks after decompression, the endoneurium showed marked diminution of the edema, macrophages, mast cells and fibroblasts. The endoneurium was filled of myelinated and unmyelinated nerve fibers and collagen fibrils. CONCLUSION: Decompression of the compressed roots of a spinal nerve is followed by regeneration of the nerve fibers and nerve recovery without endoneurial scarring.

Glomerular changes in microscopic haematuria, studied by quantitative immunoelectron microscopy and in situ zymography.

BACKGROUND: Haematuria of glomerular origin, even if mild, implies the development of defects in the glomerular basement membrane (GBM). In diseases where there is no infiltration of leukocytes into the glomerulus-such as thin basement membrane disease (TBMD) and histologically mild cases of IgA nephropathy (IgAN)-the mechanism by which such defects form is unclear. METHODS: Frozen renal tissue from 18 cases of TBMD, 18 of mild IgAN and 18 cases with no detectable abnormality were studied: (i) by quantitative in situ zymography, to estimate the activity of glomerular collagenases; and (ii) by quantitative immunoelectron microscopy to estimate the amount of major basement membrane proteins per unit length and per unit area of glomerular basement membrane. RESULTS: Cases of IgAN showed considerably more glomerular collagenase activity than normal (P=0.001). Thin basement membrane disease showed no difference in collagenase activity. A count of LCA-positive cells in glomeruli confirmed that the IgAN cases did not show glomerular leukocyte infiltration. Conversely, cases of IgAN showed no difference in GBM composition from normal, nor was any difference in GBM thickness detected in this group. However, cases of TBMD showed considerably less laminin (P=0.0008), fibronectin (P=0.002) and type VI collagen (P=0.0005) per unit length of basement membrane. Collagen IV showed a smaller reduction per unit length (P=0.01), but unlike the other protein studies it appeared to be present in higher concentration per unit area (P=0.03), suggesting that it is more 'compact' in TBMD disease. CONCLUSIONS: Two distinct mechanisms of haematuria seem to be involved in these two conditions. In IgAN there is increased activity of enzymes that can degrade GBM, probably reflecting mesangial cell activation. In TBMD an abnormal composition of the thinned GBM is confirmed. When considered with published reports of genetic abnormalities in TBMD, these results raise the possibility of an abnormal interaction between collagen IV and laminin.