Wehave shown previously that the 5' ends of the genes for the ca5(IV) and ca6(IV) collagen chains lie head-to-head on Xq22 and are deleted in patients with Alport syndrome (AS)-associated diffuse leiomyomatosis. In this study, we raised a rabbit anti-human ca6(IV) chain antibody, demonstrated its specificity by the analysis of recombinant NC1 domains of all six type IV chains, and studied the distribution of the a6(IV) chain in relation to the a1(IV) and a5(IV) chains in human adult and fetal tissues involved in AS and diffuse leiomyomatosis. The a6(IV) chain colocalizes with the ca5(IV) chain in basement membranes (BMs) of many tissues, but not in glomerular BM. These data exclude the a6(IV) chain as a site for AS mutations. The head-to-head genomic pairing of the a5 (IV) and a6(IV) genes implies coordinate transcription of the two genes. Differential localization of the a5(IV) and ci6(IV) chains shows that the two chains are not always coordinately regulated. The a6(IV) chain, together with the a3(IV) a5(IV) chains, was absent from all renal BMs in eight patients with X-linked AS while the ctl(IV) and a2(IV) chains were increased. The data support the existence of two independent collagen networks, one for the ca3 (IV) a6 (IV) chains and one for the al (IV) and a2(IV) chains. (J. Clin. Invest. 1995. 96:1948-1957.)

Background: Autosomal recessive hereditary nephropathy (ARHN) was diagnosed in 2 English Springer Spaniels (ESS), a breed not previously reported to be affected by hereditary nephropathy (HN).Objective: To identify and characterize the genetic cause of ARHN in ESS.Animals: Sixty-three ESS (2 with ARHN, 2 obligate carriers, and 59 others), 2 mixed-breed dogs with X-linked HN, and 2 English Cocker Spaniels (ECS) with ARHN were included.Methods: ARHN was diagnosed based on transmission electron microscopy and immunostaining of kidney. DNA from affected dogs was screened for the mutation known to cause ARHN in ECS. Quantities of COL4A3, COL4A4, and COL4A5 mRNA transcripts in renal cortex were determined using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for ARHN-affected dogs and 7 other dogs. The coding regions of COL4A3 and COL4A4 were sequenced for the 2 ARHN-affected ESS and an unaffected dog. Exon 30 of COL4A4 was sequenced for all 63 ESS.Results: qRT-PCR indicated a significant reduction in transcript levels of both COL4A3 and COL4A4 mRNA in the kidney of ARHN-affected ESS. Sequencing identified a single nucleotide substitution in COL4A4 at base 2806 resulting in a premature stop codon. Thirteen of 25 related dogs were identified as carriers.Conclusions and Clinical Importance: A mutation highly likely to cause ARHN in ESS has been identified.

X linked Alport syndrome (ATS, OMIM 301050) is a hereditary glomerulonephritis resulting from either point mutations or intragenic deletions of the COL4A5 gene encoding the α5 chain of type IV collagen.1–3 Contiguous gene syndromes are phenotypically complex disorders associated with the deletion of multiple adjacent genes. There are several examples of such syndromes on the X chromosome.4, 5 Until recently, the only known contiguous gene syndrome involving the COL4A5 gene was Alport syndrome and diffuse leiomyomatosis (ATS-DL, OMIM 308940),6–9 in which the deletion extends towards the centromere to include the first two exons of the adjacent COL4A6 gene. In 1998, we described a new Xq22.3 contiguous gene syndrome which we named AMME (OMIM 300194) because of the distinctive features observed in affected males: Alport syndrome (A), mental retardation (M), midface hypoplasia (M), and elliptocytosis (E).10 After the original publication, clinical re-evaluation of the family showed alterations of cardiac rhythm and morphology on echocardiography.11 To elucidate the molecular basis of this complex syndrome, we cloned three genes from the deleted region: FACL4 ,12 AMMECR1 ,13 and KCNE1L ,11 recently renamed KCNE5 .14 Now we report the characterisation of the deletion, which extends for about 2 Mb, and the identification of a second family which bears a smaller deletion of about 1 Mb. Comparison with two other deletions extending beyond COL4A5 in the telomeric direction and generating only ATS allowed us to define the critical region for mental retardation (MR), which contains four candidate genes. We now propose renaming this condition ATS-MR, so that consistent terminology is used to describe the known ATS contiguous gene syndromes. FISH (fluorescence in situ hybridisation) analysis was performed essentially as described by Lichter et al 15 with minor modifications. Somatic hybrid construction from a lymphoblastoid …

Humar, Abhinav1; Arrazola, Luis1; Durand, Brenda1; Gillingham, Kristen1; Mauer, Michael2; Kashtan, Clifford2; Nevins, Thomas2; Chavers, Blanche2; Matas, Arthur1 Author Information

Alport syndrome is a primary genetic disease of basement membranes, manifested clinically as a progressive nephropathy variably associated with sensorineural deafness and a plethora of ocular abnormalities. The long-recognized phenotypic heterogeneity of Alport syndrome may be considered on several levels, including basement membrane biochemistry, basement membrane ultrastructure, the natural history of the nephropathy, and the occurrence of extrarenal abnormalities. This review discusses the possible molecular bases for the heterogeneity. The discussion draws upon recent insights into the molecular genetics of Alport syndrome, and the biochemistry of normal and Alport syndrome basement membranes, in order to provide a framework for understanding the variable renal and extrarenal manifestations of the disease.

This review focuses on recent insights into the genetics and pathogenesis of several inherited glomerular diseases. Investigation of these disorders has resulted in the identification of proteins that play important roles in glomerular development, structure, and function.

We describe four patients aged 14 to 21 years who developed acute aortic dissection. In three of the four patients, the course was fatal, despite aggressive medical and surgical intervention. All four patients had sustained systemic hypertension related to chronic renal insufficiency. The patients had no other identifiable risk factors for aortic dissection, including congenital cardiovascular disease, advanced atherosclerosis, vasculitis, trauma, pregnancy, or family history of aortic dissection. Although aortic dissection is rare in individuals younger than 40 years of age, young patients with sustained systemic hypertension are at increased risk for this serious and often fatal condition. Physicians must be aware of this rare complication of hypertension and consider aortic dissection in the differential diagnosis of unusual chest, abdominal, and back pain in hypertensive children, adolescents, and young adults.

Eight children with autosomal recessive polycystic kidney disease (ARPKD) and recurrent bacteremia with enteric pathogens are described. Typical clinical features of bacterial cholangitis were absent, although in five patients histological and/or microbiological data indicated that the bacteremic episodes originated in the biliary tree. Bacteremia with enteric pathogens or recurrent culture-negative febrile illness in a child with ARPKD should raise suspicion of cholangitis, even in the absence of typical clinical findings.

We describe a family with four members, a mother, two sons, and a daughter, who show clinical features consistent with X linked Alport syndrome. The two males presented with additional features including mental retardation, dysmorphic facies with marked midface hypoplasia, and elliptocytosis. The elliptocytosis was not associated with any detectable abnormalities in red cell membrane proteins; red cell membrane stability and rigidity was normal on ektacytometry. Molecular characterisation suggests a submicroscopic X chromosome deletion encompassing the entire COL4A5 gene. We propose that the additional abnormalities found in the affected males of this family are attributable to deletion or disruption of X linked recessive genes adjacent to the COL4A5 gene and that this constellation of findings may represent a new X linked contiguous gene deletion syndrome.

The goals of this brief review are to provide current information on the pathogenesis of important genetic renal diseases that present in childhood and to discuss the impact of these fresh insights on the diagnosis of these conditions. Space limitations preclude detailed consideration of each disorder.

Children with methylmalonic acidemia frequently develop chronic renal insufficiency, for reasons unknown. We administered MMA chronicaally to rats to test the hypothesis that MMA is nephrotoxic. Methods: 3-wk-old Sprague-Dawley rats received MMA (pH 7.2-7.4), 20mg/100g BW daily by SQ injection X 6 wks (N=6), then in drinking water (40mg/100g BW/day) for 6 more wks. Two rats received MMA in drinking water from the outset (20mg/100g BW/day X 4 wks, 40mg/100g BW/day X 8 wks). Five rats received saline injections twice daily X 6 wks. Urine and blood were collected every 2 wks. Renal biopsy was performed at 6 wks and necropsy at 12 wks. Urinary MMA was measured by stable isotope dilution gas chromatography- mass spectometry. Results: MMA-treated rats and controls were similar in food and water intake, weight gain, serum creatinine and BUN. SQ or oral MMA produced high urinary MMA levels (e.g., 1646 μM/mM creatinine at 6 wks (mean), vs. 8.26 in controls). Six of 8 MMA-treated rats had proteinuria, that was first detected at 2 wks and thereafter increased (Table). After 12 wks of MMA, glomeruli appeared normal but tubules of proteinuric rats were variably dilated (especially in the renal medulla) with proteinaceous casts and flattened epithelium. By EM, tubular epithelium showed variable mitochondrial swelling and disorganization of cristae, dilated smooth endoplasmic reticulum, dilatation of basolateral intercellular spaces, and more secondary lysosomes than controls. Conclusions: Chronic administration of MMA rats causes renal injury, which histologically appears to predominantly affect tubular epithelial cells. These findings suggest that chronic renal insufficiency associated with methylmalonic acidemia results from nephrotoxicity of MMA.