A deletion of the paracellin-1 gene is responsible for renal tubular dysplasia in cattle

Various hereditary diseases analogous to particular human heritable diseases have been identified in cattle. Investigation of these cattle diseases will provide useful information regarding the pathogenesis of the corresponding human diseases. Renal tubular dysplasia is an autosomal recessive disease of Japanese black cattle characterized by renal failure and growth retardation. We have previously mapped the locus responsible for the disease within a region on bovine chromosome 1. In the present study, we further typed additional markers in this region and found that a genomic segment of bovine chromosome 1 including the microsatellite marker BMS4009 was deleted in the affected animals. Construction of a physical map covering this region with BAC clones and comparison of the nucleotide sequences of this region between normal and affected animals revealed that a region of 37 kb including exons 1 to 4 of the bovine paracellin-1 gene was deleted in the affected animals. The paracellin-1 gene, which is the causative gene for human renal hypomagnesemia with hypercaciuria and nephrocalcinosis, encodes a tight junction protein of renal epithelial cells. Therefore, we concluded that deletion of the paracellin-1 gene is responsible for renal tubular dysplasia of cattle, and the cattle disease could be a good model for the human disease.

A recessive contiguous gene deletion causing infantile hyperinsulinism, enteropathy and deafness identifies the Usher type 1C gene

Usher syndrome type 1 describes the association of profound, congenital sensorineural deafness, vestibular hypofunction and childhood onset retinitis pigmentosa. It is an autosomal recessive condition and is subdivided on the basis of linkage analysis into types 1A through 1E. Usher type 1C maps to the region containing the genes ABCC8 and KCNJ11 (encoding components of ATP-sensitive K + (KATP) channels), which may be mutated in patients with hyperinsulinism. We identified three individuals from two consanguineous families with severe hyperinsulinism, profound congenital sensorineural deafness, enteropathy and renal tubular dysfunction. The molecular basis of the disorder is a homozygous 122-kb deletion of 11p14-15, which includes part of ABCC8 and overlaps with the locus for Usher syndrome type 1C and DFNB18. The centromeric boundary of this deletion includes part of a gene shown to be mutated in families with type 1C Usher syndrome, and is hence assigned the name USH1C. The pattern of expression of the USH1C protein is consistent with the clinical features exhibited by individuals with the contiguous gene deletion and with isolated Usher type 1C.

Homozygosity mapping of the locus responsible for renal tubular dysplasia of cattle on bovine chromosome 1

Renal tubular dysplasia is a hereditary disease of Japanese black cattle showing renal failure and growth retardation with an autosomal recessive trait. In the present study, we mapped the locus responsible for the disease (RTD) by linkage analysis with an inbred paternal half-sib pedigree obtained from commercial herds. By analyzing segregation of microsatellite markers in the half-sibs, significant linkage was observed between the RTD locus and markers on bovine Chromosome (Chr) 1 with the highest lod score of 11.4. Homozygosity mapping with the inbred pedigree further defined the localization of the RTD locus in a 4-cM region between microsatellite markers BMS4003 and INRA119. Mapping of the RTD locus on bovine Chr 1 will facilitate cloning and characterization of the gene responsible for this disease.

The malformed kidney: disruption of glomerular and tubular development

Renal malformations are the major cause of renal failure during early childhood. They are found in approximately 100 genetic syndromes. We review the embryologic development of the kidney and its molecular control. Important new information has been derived from mutational analysis in humans and mice. We describe how mutations in nine transcription factors, 12 signaling molecules and nine gene products involved in a variety of other cellular functions disrupt renal morphogenesis. The information presented provides a template for integrating new discoveries on the molecular basis of renal development, for classifying renal malformations observed in the clinical setting, and for identifying defective genes in affected patients.

Abnormal urinary acidification in infants with hydronephrosis

Distal renal tubular abnormalities have been observed in patients with dilated urinary tract disorders. The present study was undertaken to look for patterns in urinary acidification in infants with varying degrees of hydronephrosis due to either reflux or obstruction and occurring as unilateral or bilateral disease. Three groups of infants (mean age 3.7+/-3.8 months) were studied prospectively. Groups IA and IB included patients with hydronephrosis who were acidotic and non-acidotic, respectively. Group II served as controls and consisted of patients with diarrhea and secondary metabolic acidosis with no known renal disease. Serum electrolytes, creatinine, and urine pH were measured in all patients. Urinary titratable acidity, ammonium (NH4), and net acid excretion (NAE) were measured by the titrimetric method. Infants with hydronephrosis demonstrated lower urinary buffering capacity, reflected in low NAE in the face of acidosis. Deficiencies were noted in both titratable acid and NH4 excretion compared with control infants. Acidosis was as common in unilateral as in bilateral disease, regardless of severity score. These data confirm a defect in distal urinary acidification in infants with hydronephrosis, whether unilateral or bilateral. Immaturity and endogenous acid load may play a significant role in the manifestation of metabolic acidosis with unilateral disease.

Renal tubular dysgenesis, absent nipples, and multiple malformations in three brothers: a new, lethal syndrome

We report on three brothers with renal tubular dysgenesis and absent nipples, each also had other malformations including pre-auricular pits and a preauricular tag, branchial clefts, choanal atresia, pulmonary lobation anomaly, ventricular septal defect, type IIB interrupted aortic arch, absent gallbladder, absent thymus, parathyroid gland, accessory spleen, imperforate anus, clinodactyly, and broad digits and small nails. All three infants died neonatally. This pattern of clinical malformations appears to be a previously unreported syndrome.

[Renal tubular dysgenesis in upper and western Galilee]

Renal tubular dysgenesis (RTD) is a very rare malformation. 48 cases have been described, mostly in North America, Europe and Israel. Histopathological examination plays a key role in its diagnosis of RTD. We present the results of a retrospective study documenting the frequency, clinical manifestations and pathological findings in RTD in the Upper and Eastern Galilee. In 343 perinatal autopsies performed in Safed and Nahariya Hospitals between 1974 and 1997, there were 5 cases with RTD. All were men, 3 were Druze and 2 were Jews. The parents of the Druze patients were first cousins; 2 cases were twins of whom 1 had RTD; intrauterine growth retardation was documented in 2 and oligohydramnios in 3 cases. Life span of 4 newborns ranged from 1.1 to 49 hours and was complicated by severe respiratory failure and anuria. Ultrasound and postmortem examinations revealed no pathology of the kidney and urinary tracts. Absence of the proximal tubules was supported by immunohistochemistry for epithelial membrane antigen. Our previous assumption about the importance of lysozyme immunostaining for diagnosis of RTD was confirmed by this larger series of cases and by statistical analysis. Because RTD is considered an autosomal recessive phenotype with a recurrence rate of 25%, there should be genetic counseling of the family in every case of RTD.

Renal tubular dysgenesis in twins

In a fetal autopsy series, we have explored the occurrence of renal tubular dysgenesis in twins. Renal tubular dysgenesis was found exclusively among those monozygotic twins with evidence of twin transfusion syndrome, particularly in those donor twins with oligohydramnios and growth restriction. We infer that hypotension in the donor twin of the twin transfusion syndrome pair is responsible for the failure of proximal convoluted tubule differentiation, and the disturbance of renal function is manifested as oligohydramnios prenatally, and either oliguria or tubular dysfunction postnatally.

Cerebral defects and nephrogenic diabetes insipidus with the ARC syndrome: additional findings or a new syndrome (ARCC-NDI)?

We report on 4 children from 2 unrelated families who appear to have the lethal ARC syndrome (arthrogryposis, renal tubular dysfunction, and cholestasis) together with the additional findings of nephrogenic diabetes insipidus and cerebral anomalies, including deafness. With increased survival time in our patients, paucity of the intrahepatic bile ductules and cholestasis progressed to cirrhosis, growth was severely impaired, and severe mental retardation became apparent. No evidence was found for peroxisomal, chromosomal, or mitochondrial disorders. We propose to amend the ARC mnemonic to ARCC-NDI (A-Arthrogryposis, R-renal Fanconi, C-cerebral, C-cholestasis, NDI-nephrogenic diabetes insipidus) to name the major manifestations of this syndrome, several of which have not been appreciated.

Renal tubular dysgenesis with microcephaly

Renal tubular dysgenesis, a rare, lethal, autosomal recessive disorder, is characterized by short and poorly differentiated proximal convoluted tubules associated with oligohydramnios, Potter sequence, and neonatal death due to respiratory failure. Abnormalities of the skull may occur in some cases. We report an infant born of a consanguineous union who also had microcephaly, among other features. A history of oligohydramnios with or without skull abnormalities and a lethal outcome without obvious explanation should occasion renal histological study aimed at precise diagnosis and genetic counselling.

Congenital renal tubular dysplasia and skull ossification defects similar to teratogenic effects of angiotensin converting enzyme (ACE) inhibitors

An apparently autosomal recessive syndrome of congenital renal tubular dysplasia and skull ossification defects is described in five infants from two separate, consanguineous, Pakistani Muslim kindreds. The clinical, pathological, and radiological features are similar to the phenotype associated with fetal exposure to angiotensin converting enzyme (ACE) inhibitors: intrauterine growth retardation, skull ossification defects, and fetal/ neonatal anuric renal failure associated with renal tubular dysplasia. There was no fetal exposure to ACE inhibitors in the affected infants. Phenotypic similarities between these familial cases and those associated with ACE inhibition suggest an abnormality of the "renin-angiotensin-aldosterone" system (RAS). It is postulated that the molecular pathology in this uncommon autosomal recessive proximal renal tubular dysgenesis could be related to mutations of the gene systems governing the RAS.

Glomerular number and size following chronic angiotensin II blockade in the postnatal rat

Chronic angiotensin-converting enzyme (ACE) inhibition with enalapril or angiotensin II (Ang II) receptor antagonism with either losartan (specific for Ang II type-1 receptor, AT1) or PD 123319 (specific for the Ang II type-2 receptor, AT2) were effected between postnatal days 3 and 21 in the rat. Following quantitative analysis of the kidneys using recently developed unbiased stereological techniques we found that none of the treatments resulted in changes in glomerular number or size. This implies that inhibition of Ang II activity had no effect on postnatal nephron induction or glomerular development. However, following both chronic ACE inhibition and AT1 antagonism, abnormalities of tubules and their associated vessels were evident throughout the kidney and were accompanied by an increased proportion of interstitium. The structural abnormalities were most prominent in the outer medulla and were consistent with interruption of descent of the loops of Henle and vasa rectae. In contrast, no renal morphological abnormalities were observed following chronic AT2 antagonism.

Renal tubular abnormalities in hydrops fetalis: a histological and immunohistochemical study

An immunohistochemical study of renal tubule cell differentiation in hydrops fetalis was performed using antibodies against lysozyme, CD15, keratin, epithelial membrane antigen and Leu-7, and formalin-fixed, paraffin-embedded sections of tissue that was obtained at autopsy. In 3 cases among 17 cases of hydrops fetalis (17.6%) there was a marked decrease in the number of cells stained positively for lysozyme, suggesting abnormal differentiation of the cells of the proximal convoluted tubules. This is the first report concerning the abnormalities of the renal tubular epithelium in hydrops fetalis.

Renal tubular dysgenesis: a report of two cases

Renal tubular dysgenesis, a congenital disorder of renal tubular development, was diagnosed in two newborns with oligohydramnios and Potter phenotype. Renal tubular dysgenesis (RTD) is a recently recognized congenital disorder of renal tubular development associated with oligohydramnios, Potter phenotype, and neonatal respiratory and renal failure. We report two newborn siblings with typical clinical and anatomic features of RTD. The diagnosis was proven by autopsy in one child. The pediatrician should consider the diagnosis of RTD in a child with congenital anuria and structurally normal kidneys on ultrasound, especially if a maternal history of late trimester oligohydramnios is present.

Familial renal tubular dysgenesis: a disorder not isolated to proximal convoluted tubules

The autopsy findings of a newborn with renal tubular dysgenesis, born to first cousins of Moslim Arab descent, are described. Hypocalvaria and hyperflexible joints were noted in addition to the renal lesion. A microdissection study demonstrated marked shortening of all the nephron segments from the glomeruli to the collecting tubules, rather than an isolated abnormality of the proximal convoluted tubules.

Renal tubular dysgenesis: evidence of abnormality in the renin-angiotensin system

Renal tubular dysgenesis is an autosomal recessive condition characterized by short, abnormally developed cortical tubules that lack proximal differentiation. Despite the lack of normal proximal tubules, the major site of water resorption in the kidney, the principal clinical manifestations are caused by fetal and neonatal oliguria. The kidneys in three cases of neonatal renal tubular dysgenesis were found to contain large amounts of immunohistochemically reactive renin in preglomerular arterioles, glomerular hilums, and glomerular mesangial areas, far exceeding the intensity of staining and the numbers of sites stained in control kidneys. The increased accumulation of renin may reflect strong local vasoconstriction, which is responsible for reduced glomerular perfusion. This accumulation suggests faulty feedback control of renin secretion, the basis of which is still to be identified.

Renal tubular dysgenesis present in a newborn with meconium ileus

The combination of renal tubular dysgenesis (RTD) and meconium ileus in a native Israeli is presented for the first time. The clinical diagnosis was oligohydramnios and abruptio placentae, respiratory failure, and anuria refractory to treatment. The autopsy revealed meconium ileus and meconium peritonitis. RTD was established by the detection of a monomorphous undifferentiated population of tubules, absence of proximal tubules, and dense epithelial membrane antigen immunoreactivity of all tubules. The lack of alpha 1-antitrypsin- and lysozyme-immunoreactive tubules was first revealed in the kidney with RTD. These findings extend the possibilities of RTD detection.

Renal and biliary abnormalities in a new murine model of autosomal recessive polycystic kidney disease

Current models of autosomal recessive polycystic kidney disease (ARPKD) fail to demonstrate biliary abnormalities in association with renal cysts. We therefore studied a new murine model of ARPKD in which dual renal tubular and biliary epithelial abnormalities are present. Affected homozygous animals typically die 1 month postnatally in renal failure with progressively enlarged kidneys. Renal cysts shift in site from inner cortical proximal tubules at birth to collecting tubules 20 days later, as determined by segment-specific lectin binding. Increased numbers of mitosis were demonstrated in proximal and collecting tubular cysts. In addition, epithelial hyperplasia was demonstrated morphometrically in the intra- and extrahepatic biliary tract of affected animals. The number of intrahepatic biliary epithelial cells was increased by 50% on postnatal day 5 and by 100% on postnatal day 25 (P < 0.01). Despite an increased frequency of "chaotic" portal areas in mice with renal cysts, no intrahepatic cysts or shape abnormalities of the biliary lumen were detected using biliary casts and morphometry. Additionally there was nonobstructive hyperplastic dilatation of the extrahepatic biliary tract which was linked in all animals to the presence of renal cysts. The hyperplastic abnormalities in both renal and biliary epithelium make this new mouse strain a good model for the study of the dual organ cellular pathophysiology of ARPKD.

Renal tubular dysgenesis: a description of early renal maldevelopment in siblings

A family is described in which three siblings, born after pregnancies complicated by oligohydramnios, developed renal abnormalities. In the first infant, of 38 weeks gestation, histologic changes were nearly identical to those found in renal tubular dysgenesis (RTD), a recently identified disorder characterized by the absence of recognizable renal proximal tubules. Additional findings include bilateral renal vein thrombosis and marked calvarial bone hypoplasia. The other two gestations were 20 and 22 weeks long. Renal histology in these cases showed nonspecific abnormalities with focal tubular dilatation, decreased tubule formation, and increased interstitial connective tissue. Clearly recognizable proximal tubules were present, though decreased in number. The latter two gestations described herein are the earliest examined in a family with RTD and the renal abnormalities may represent early changes seen in this disorder.

Effect of ACE inhibition on the fetal kidney: decreased renal blood flow

The kidneys of nine fetuses whose mothers were chronically hypertensive were examined microscopically. Three of these mothers used antihypertensive agents throughout pregnancy including one who used an angiotensin-converting enzyme (ACE) inhibitor. The tubular defects found in these kidneys were compared to the kidneys of 20 normal controls, 13 fetuses with various multiple malformation syndromes and six cases of the twin to twin transfusion syndrome. Evidence from these cases as well as the literature suggest that the primary mechanism by which ACE inhibitors affect development of the fetal kidney is through decreased renal blood flow.