Autosomal dominant polycystic kidney disease with anticipation and Caroli's disease associated with a PKD1 mutation. Rapid communication

Pathogenesis of Choledochal Cyst: Insights from Genomics and Transcriptomics

Choledochal cysts (CC) is characterized by extra- and/or intra-hepatic b\ile duct dilations. There are two main theories, “pancreaticobiliary maljunction” and “congenital stenosis of bile ducts” proposed for the pathogenesis of CC. Although family cases or CC associated with other anomalies have been reported, the molecular pathogenesis of CC is still poorly understood. Recent advances in transcriptomics and genomics analysis platforms have unveiled key expression signatures/genes/signaling pathways in the pathogenesis of human diseases including CC. This review summarizes insights from genomics and transcriptomics studies into the pathogenesis of CC, with the aim to improve (i) our understanding of its underlying complex pathomechanisms, and (ii) clinical management of different subtypes of CC, in particular their associated hepatic fibrotic change and their risk of malignancy transformation.

Giant choledochal cyst and infantile polycystic kidneys as prenatal sonographic features of Caroli syndrome

Caroli syndrome is a developmental disorder caused by complete or partial arrest of ductal plate remodeling, leading to dilated bile ducts along with fibrosis surrounding the portal tracts. It is most commonly associated with autosomal recessive polycystic kidney (ARPKD). We report a unique case of Caroli syndrome, diagnosed prenatally at 24 weeks of gestation in a 29-year-old Thai woman. Ultrasound findings revealed the association of a fetal giant choledochal cyst with ARPKD. Autopsy findings showed ductal plate malformation, typical of Caroli syndrome, associated with giant choledocal cyst and ARPKD.

Liver resection and transplantation in Caroli disease and syndrome

INTRODUCTION

Caroli disease (CD) is a congenital dilatation of the intrahepatic bile ducts. In combination with liver fibrosis or cirrhosis, it is called Caroli syndrome (CS). Infectious complications and intrahepatic cholangiocarcinoma are secondary problems. The aim of this study was to analyse the clinical pattern and outcome in patients with CD/CS who underwent liver surgery.

METHODS

Between January 2004 and December 2016, 21 patients with CD/CS were treated with liver resection or transplantation (LTX) and post-operative data of patients with CD/CS were retrospectively analysed in a database.

RESULTS

Two patients underwent LTX, and 19 patients underwent liver resection due to CD/CS. During follow-up, one patient developed lung cancer nine years after LTX. Patients resected due to CD/CS were predominantly females (74%) with an overall low incidence of co-morbidities. The median post-operative Clavien-Dindo score was 1 (range: 0-3). There was no death during a median follow-up period of over five years. In four patients, cholangiocarcinoma was confirmed. Tumor recurrence was seen in three patients, and was treated with chemotherapy or repeated liver resection.

CONCLUSIONS

LTX and liver resections due to CD/CS are rare and associated with an acceptable post-operative morbidity and low mortality. Surgical treatment should be performed as early as possible to avoid recurrent episodes of cholangitis or carcinogenesis.

Pediatric cholangiopathies: diseases of the gallbladder and biliary tract

Pediatric gallbladder and bile duct disease encompasses a broad spectrum of processes, from congenital to developmental to neoplastic. We describe normal pediatric biliary anatomy and summarize the most common pathologic entities, with a focus on non-invasive imaging techniques and findings. Ultrasound is the first-line imaging modality in children with suspected biliary pathology based on its widespread availability, cost effectiveness, and lack of ionizing radiation. MRI and MRCP are often used for further evaluation in cases of diagnostic uncertainty and for surgical planning.

Gastrointestinal Manifestations of Autosomal-Dominant Polycystic Kidney Disease

Autosomal-dominant polycystic kidney disease (ADPKD) is the most commonly inherited kidney disease, and the fourth most common cause of end-stage renal disease. ADPKD is a systemic disorder, associated with numerous extrarenal manifestations, including polycystic liver disease, the most common gastrointestinal manifestation, and diverticular disease, inguinal, and ventral hernias, pancreatic cysts, and large bile duct abnormalities. All of these gastrointestinal manifestations play a significant role in disease burden in ADPKD, particularly in the later decades of life. Thus, as ADPKD becomes more recognized, it is important for gastroenterologists to be knowledgeable of this monogenic disorder's effects on the digestive system.

Clinical classification of Caroli's disease: an analysis of 30 patients

BACKGROUND

Caroli's disease (CD) is a rare congenital disorder. The early diagnosis of the disease and differentiation of types I and II are of extreme importance to patient survival. This study was designed to review and discuss observations in 30 patients with CD and to clarify the clinical characteristics of the disease.

METHODS

The demographic and clinical features, laboratory indicators, imaging findings and pathology results for 30 patients with CD were reviewed retrospectively.

RESULTS

Caroli's disease can occur at any age. The average age of onset in the study cohort was 24 years. Patients who presented with symptoms before the age of 40 years were more likely to develop type II CD. Approximately one-third of patients presented without positive signs at original diagnosis and most of these patients were found to have type I CD on pathology. Anaemia, leucopoenia and thrombocytopoenia were more frequent in patients with type II than type I CD. Magnetic resonance cholangiopancreatography (MRCP) and computed tomography (CT) examinations were most useful in diagnosing CD.

CONCLUSIONS

No typical symptoms, signs or laboratory indicators are able to distinguish CD from other conditions. Both MRCP and CT were most valuable in diagnosis. The two types of CD may be differentiated by age of onset and routine blood tests.

Cystic hepatic lesions: a review and an algorithmic approach

OBJECTIVE

The purpose of this article is to review the different cystic hepatic lesions, with an emphasis on the imaging features that help to differentiate them, and to propose a practical algorithm for approaching the diagnosis of these lesions.

CONCLUSION

The number and morphology of the lesions and determination of whether there is a solid component are key imaging features that are helpful for approaching the diagnosis of cystic hepatic lesions. Familiarity with these features and knowledge of the clinical associations will help the radiologist to establish a definitive diagnosis or provide a reasonable differential diagnosis.

Renal transplantation in autosomal dominant polycystic kidney disease

In patients with autosomal dominant polycystic kidney disease (ADPKD) evaluated for kidney transplantation, issues related to native nephrectomy, cystic liver involvement, screening for intracranial aneurysms and living-related kidney donation deserve special consideration. Prophylactic native nephrectomy is restricted to patients with a history of cyst infection or recurrent haemorrhage or to those in whom space must be made to implant the graft. Patients with liver involvement require pretransplant imaging. Selection of patients for pretransplant screening of intracranial aneurysms should follow the general recommendations for patients with ADPKD. In living related-donor candidates aged <30 years and at-risk of ADPKD, molecular genetic testing should be carried out when ultrasonography and MRI findings are normal or equivocal. After kidney transplantation, patient and graft survival rates are excellent and the volume of native kidneys decreases. However, liver cysts continue to grow and treatment with a somatostatin analogue should be considered in patients with massive cyst involvement. Cerebrovascular events have a marginal effect on post-transplant morbidity and mortality. An increased risk of new-onset diabetes mellitus and nonmelanoma skin cancers has been reported, but several studies have challenged these findings. Finally, no data currently support the preferential use of mammalian target of rapamycin inhibitors as immunosuppressive agents in transplant recipients with ADPKD.

Ex vivo modeling of chemical synergy in prenatal kidney cystogenesis

Cyclic adenosine monophosphate (cAMP) drives genetic polycystic kidney disease (PKD) cystogenesis. Yet within certain PKD families, striking differences in disease severity exist between affected individuals, and genomic and/or environmental modifying factors have been evoked to explain these observations. We hypothesized that PKD cystogenesis is accentuated by an aberrant fetal milieu, specifically by glucocorticoids. The extent and nature of cystogenesis was assessed in explanted wild-type mouse embryonic metanephroi, using 8-Br-cAMP as a chemical to mimic genetic PKD and the glucocorticoid dexamethasone as the environmental modulator. Cysts and glomeruli were quantified by an observer blinded to culture conditions, and tubules were phenotyped using specific markers. Dexamethasone or 8-Br-cAMP applied on their own produced cysts predominantly arising in proximal tubules and descending limbs of loops of Henle. When applied together, however, dexamethasone over a wide concentration range synergized with 8-Br-cAMP to generate a more severe, glomerulocystic, phenotype; we note that prominent glomerular cysts have been reported in autosomal dominant PKD fetal kidneys. Our data support the idea that an adverse antenatal environment exacerbates renal cystogenesis.

Caroli's Disease: Current Knowledge of Its Biliary Pathogenesis Obtained from an Orthologous Rat Model

Caroli's disease belongs to a group of hepatic fibropolycystic diseases and is a hepatic manifestation of autosomal recessive polycystic kidney disease (ARPKD). It is a congenital disorder characterized by segmental saccular dilatations of the large intrahepatic bile duct and is frequently associated with congenital hepatic fibrosis (CHF). The most viable theory explaining its pathogenesis suggests that it is related to ductal plate malformation. The development of the polycystic kidney (PCK) rat, an orthologous rodent model of Caroli's disease with CHF as well as ARPKD, has allowed the molecular pathogenesis of the disease and the therapeutic options for its treatment to be examined. The relevance of the findings of studies using PCK rats and/or the cholangiocyte cell line derived from them to the pathogenesis of human Caroli's disease is currently being analyzed. Fibrocystin/polyductin, the gene product responsible for ARPKD, is normally localized to primary cilia, and defects in the fibrocystin from primary cilia are observed in PCK cholangiocytes. Ciliopathies involving PCK cholangiocytes (cholangiociliopathies) appear to be associated with decreased intracellular calcium levels and increased cAMP concentrations, causing cholangiocyte hyperproliferation, abnormal cell matrix interactions, and altered fluid secretion, which ultimately result in bile duct dilatation. This article reviews the current knowledge about the pathogenesis of Caroli's disease with CHF, particularly focusing on studies of the mechanism responsible for the biliary dysgenesis observed in PCK rats.

Nephrectomy in patients with Caroli's and ADPKD may be associated with increased morbidity

Autosomal dominant polycystic kidney disease (ADPKD), characterized by multiple bilateral renal cysts, is the most common inherited disorder of the kidney and an important cause of end-stage renal disease (ESRD). Caroli's disease is a much less frequent condition with ectasia of the intrahepatic biliary system. A clear association between autosomal recessive and Caroli's disease has been described, but only 4 cases of ADPKD and Caroli's disease have been reported with 2 postoperative mortalities. The aim of this case is to increase the awareness of intra-operative and postoperative complications. A 66 year-old male was diagnosed with ADPKD and Caroli's disease with hepatosplenomegaly and 4 episodes of ascending cholangitis. After 3 years of hemodialysis for ESRD, he received a cadaveric renal allograft. Subsequently, he developed paroxysmal atrial fibrillation. Upon anticoagulation, he developed multiple episodes of gross hematuria from the left native kidney. After the anticoagulation therapy was discontinued, he underwent bilateral nephrectomies of his native kidneys. Intra-operatively, a splenic laceration could not be managed conservatively. Therefore, splenectomy was performed. In addition, he developed ascending cholangitis post-operatively that was treated with antibiotics. He was discharged on postoperative day 18. Genetic testing revealed that the patient is heterozygote for a large deletion in PKD1 gene, which encompasses all tested exons (exons 1-44).

Glomerular and proximal tubule cysts as early manifestations of Pkd1 deletion

BACKGROUND

The homozygous deletion of Pkd1 in the mouse results in embryonic lethality with renal cysts and hydrops fetalis, but there is no precise data on the segmental origin of cysts and potential changes associated with polyhydramnios.

METHODS

We used Pkd1-null mice to investigate cystogenesis and analyze the amniotic fluid composition from embryonic day 12.5 (E12.5) to birth (n = 257 embryos).

RESULTS

Polyhydramnios was consistently observed from E13.5 in Pkd1(-/-) embryos, in absence of placental abnormalities but with a significantly higher excretion of sodium and glucose from E13.5 through E16.5, and increased cyclic adenosine 3'5-monophosphate (cAMP) levels at E14.5 and E15.5. The Pkd1(-/-) embryos started to die at E13.5, with lethality peaking at E15.5, corresponding to the onset of cystogenesis. The first cysts in Pkd1(-/-) kidneys emerged at E15.5 in mesenchyme-derived segments at the cortico-medullary junction, with a majority of glomerular cysts and fewer proximal tubule cysts (positive for megalin). The cysts extended to ureteric bud-derived collecting ducts (positive for Dolichos biflorus agglutinin lectin) from E16.5.

CONCLUSIONS

These studies indicate that Pkd1 deletion is associated with a massive loss of solutes (from E13.5) and increased cAMP levels (E14.5) associated with polyhydramnios. These abnormalities precede renal cysts (E15.5), first derived from glomeruli and proximal tubules and later from the collecting ducts, reflecting the expression pattern of Pkd1 in maturing epithelial cells.

Frequency and clinical profile of patients with polycystic kidney disease in southern Brazil

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common genetic nephropathies, affecting one in every 800-1000 individuals in the worldwide general population and 5-10% of hemodialysis patients. Little data concerning the prevalence of ADPKD in Brazil are available. Thus, the aim of the present study was to investigate both the frequency and clinical profile of ADPKD among hemodialysis patients in south of Brazil.

METHODS

This cross-sectional study consisted of patients from 24 hemodialysis centers. Patients were screened for ADPKD by clinical, laboratorial, and image examination in medical records.

RESULTS

Of 1326 patients on hemodialysis in the south of Brazil that composed this study, 99 (7.5%) had polycystic kidney as primary cause for chronic renal failure. Comparisons between ADPKD and non-ADPKD patients revealed no differences regarding mean age, gender, and ethnicity.

CONCLUSIONS

Our data revealed that ADPKD is prevalent among patients on hemodialysis in the south of Brazil. In addition, the clinical profile of ADPKD is similar to reported data from North America and Europe, putatively due to the similar ethnic composition mainly based on European descents.

Variation in age at ESRD in autosomal dominant polycystic kidney disease

BACKGROUND

Heterogeneity manifest as more severe disease in successive generations has been attributed to genetic anticipation in patients with autosomal dominant polycystic kidney disease (ADPKD). We evaluated variation in age at end-stage renal disease (ESRD) in ADPKD families for evidence of anticipation.

STUDY DESIGN

Retrospective.

SETTING & PARTICIPANTS

413 families with ADPKD seen at our single center between 1985 and 2004 (including 95 families with documented polycystic disease type 1 [PKD1] and 213 ADPKD families with parents born before 1930).

PREDICTOR

Generational status.

OUTCOME

Age at ESRD onset.

MEASUREMENTS

Time to ESRD was evaluated by using survival analysis, Cox regression, and descriptive statistics. Unstable trinucleotide repeat expansion was evaluated by means of genotyping in 6 PKD1 families.

RESULTS

We analyzed 413 ADPKD families (1,391 parent-offspring pairs) with known age at ESRD or last known age without ESRD (informative pairs). There was no difference in age at ESRD between parents and offspring by means of Cox regression after adjusting for correlations among family members and sex (hazard ratio, 1.019; 95% confidence interval, 0.919 to 1.13; P = 0.7). Similar analysis of PKD1 informative pairs and those with parents born before 1930 showed no differences in age at ESRD. Male ADPKD patients were 42% more likely to reach ESRD (P < 0.001), and male patients with documented PKD1 were 41% more likely to reach ESRD (P = 0.01) than female patients.

LIMITATIONS

Hypertension treatment unknown.

CONCLUSIONS

We found no evidence for anticipation of ESRD in patients with ADPKD; thus, the observed variation in age at ESRD may result from other genetic, sex, or environmental causes.

Caroli's disease: identification and treatment strategy

Caroli's disease is a rare congenital disease of the liver characterized by cystic dilation of the intrahepatic bile duct. Classic Caroli's disease involves malformations of the biliary tract alone, whereas Caroli's syndrome refers to the presence of associated congenital hepatic fibrosis. Caroli's disease usually presents during childhood and early adulthood. The clinical features of Caroli's disease include jaundice, right upper abdominal pain, and fever due to the associated complications of hepatolithiasis or bacterial cholangitis. Endoscopic or percutaneous cholangiography is the traditional method of diagnosis, but magnetic resonance cholangiopancreatography is emerging as the diagnostic modality of choice. The treatment for Caroli's disease includes supportive care with antibiotics for cholangitis and ursodeoxycholic acid for hepatolithiasis. Surgical resection has been used successfully in patients with monolobar disease. For patients with diffuse involvement, the treatment of choice is orthotopic liver transplantation.

Prognosis of autosomal dominant polycystic kidney disease diagnosed in utero or at birth

The use of prenatal ultrasonography has resulted in increased numbers of fetuses being diagnosed with autosomal dominant polycystic kidney disease (ADPKD), but the long-term prognosis is still not well-known. Between 1981 and 2006 we followed 26 consecutive children with enlarged hyperechoic kidneys detected between the 12th week of pregnancy and the first day of life (Day 1) as well as one affected parent. Three other fetuses were excluded following the termination of the pregnancy. The mother was the transmitting parent in 16 of the 26 children (ns, p=0.1). Clinical features that presented during follow-up were oligoamnios (5/26), neonatal pneumothorax (3/26), pyelonephritis (5/26), gross hematuria (2/26), hypertension (5/26), proteinuria (2/26) and chronic renal insufficiency (CRI) (2/26). At the last follow-up (mean duration of follow-up: 76 months; range: 0.5-262 months), 19 children (mean age: 5.5 years) were asymptomatic, five (mean age: 8.5 years) had hypertension, two (mean age: 9.7 years) had proteinuria and two (mean age: 19 years) had CRI. Children presenting enlarged kidneys postnatally tended to have more clinical manifestations than their counterparts who did not. Of 25 siblings of the patients, seven had renal cysts; these were detected during childhood in five siblings and in utero in two siblings. In conclusion, prognosis is favourable in most children with prenatal ADPKD, at least during childhood. The sex of the transmitting parent is not a risk factor of prenatal ADPKD. A high proportion of siblings develop early renal cysts. Abnormalities visualized by ultrasonography appear to be associated to more clinical manifestations.

Primäres Cholangiokarzinom auf dem Boden einer Caroli-Erkrankung

Caroli's disease is a liver disease with segmental cystic dilatation of the intrahepatic bile ducts. It belongs to the group of congenital ductal plate malformations. With an incidence of only 0.05% of all liver cases in the Liver Registry of the University of Cologne, it is a very rare disorder. Caroli's disease is usually combined with cholangitis and bile duct stones. Control of these infections and maintenance of biliary drainage are the main therapeutic aims. The development of intra epithelial neoplasia and invasive carcinoma are rare complications. We report a case of Caroli's disease with the development of cholangiocarcinoma and review the literature.

Prenatal diagnosis of familial type I choledochal cyst

Familial choledochal cysts are extremely rare. High-resolution ultrasound now allows for the antenatal diagnosis of these anomalies. After delivery, elective surgical resection should be planned; however, increases in size, deterioration of liver function, and ascending cholangitis frequently force early intervention. We report an unusual occurrence of siblings with type I choledochal cysts and review the existing literature on cause, genetics, classification, diagnosis, and management of this disease.

Caroli's disease and orthotopic liver transplantation

Caroli's disease is a rare congenital hepatic disease, characterized by segmental dilatation of the biliary tree. Patients who have recurrent bouts of biliary infection, particularly those with complications related to portal hypertension, may require orthotopic liver transplantation (OLT). Few case reports have described the outcome of OLT in patients with Caroli's disease and to date there is no large series reported in the literature. We retrospectively analyzed the outcome of OLT in patients with Caroli's disease who underwent OLT between 1982 and 2002 at Starzl Transplantation Institute, University of Pittsburgh. Patients were identified and data was collected by computerized search of the electronic database system. All patients had confirmation of diagnosis by histopathology of explanted liver. A total of 33 patients with Caroli's disease were listed for liver transplantation, 3 of whom were excluded, as they were not transplanted. A total of 90% had signs of hepatic decompensation at the time of OLT. Median posttransplantation follow-up was 7.7 yr. Short-term graft and patient survival at 1 month was 83% and 86%, whereas overall long-term graft survival rates at 1, 5, and 10 yr were 73%, 62%, and 53%, respectively, and patient survival rates were 76%, 65%, and 56%, respectively. Long-term outcome in patients who survived the first year after transplantation was significantly better. Their survival rate at 5 and 10 yr was 90% and 78%. On univariable analysis, recipient age, donor male gender, coexistent congenital hepatic fibrosis, and re-OLT were associated with poor patient survival. Eight patients were retransplanted, 3 of whom had primary nonfunction. A total of 13 patients died; the most common cause of death being sepsis and cardiovascular complications. Patients who died of sepsis had cholangitis pre-OLT. In conclusion, OLT is a form of curative and life-saving therapy in patients with Caroli's disease, especially in those with decompensated liver disease. Overall survival is better with liver transplantation and is comparable with the survival of recipients who undergo OLT for other etiologies of chronic liver disease. Survival was poor in patients with congenital hepatic fibrosis (Caroli's syndrome) and in those who had cholangitis at the time OLT.

The hepatic fibrocystic diseases

The hepatic fibrocystic diseases present with variable intrahepatic biliary abnormalities, which range from portal tract enlargement and fibrosis to cystic formations. They may present as autosomal recessive or dominant polycystic kidney diseases, with associated dilatation of the renal collecting system, or as incompletely characterized cystic diseases. Symptoms from the liver disease often result from complications of fibrosis or dilated ducts/cyst (sludge, lithiasis, infection). The treatment is supportive, with careful attention to associated renal disease. Liver transplantation is an option in selected patients.

An incredible decade for the primary cilium: a look at a once-forgotten organelle

Since the discovery that numerous proteins involved in mammalian disease localize to the basal bodies and cilia, these organelles have emerged from relative obscurity to the center of intense research efforts in an expanding number of disease- and developmental-related fields. Our understanding of the association between cilia and human disease has benefited substantially from the use of lower organisms such as Chlamydomonas and Caenorhabditis elegans and the availability of murine models and cell culture. These research endeavors led to the discovery that loss of normal ciliary function in mammals is responsible for cystic and noncystic pathology in the kidney, liver, brain, and pancreas, as well as severe developmental patterning abnormalities. In addition, the localization of proteins involved in rare human disorders such as Bardet-Biedl syndrome has suggested that cilia-related dysfunction may play a role in modern human epidemics such as hypertension, obesity, and diabetes. Although we have made great advances in demonstrating the importance of cilia over the past decade, the physiological role that this organelle plays in most tissues remains elusive. Research focused on addressing this issue will be of critical importance for a further understanding of how ciliary dysfunction can lead to such severe disease and developmental pathologies.

Caroli's disease: Liver resection and liver transplantation. Experience in 33 patients

BACKGROUND

The aim of this study was to review and discuss our observations on 33 patients who underwent surgical treatment for Caroli's disease (CD), focusing on diagnosis, current surgical management, and long-term outcome.

METHODS

Between May 1993 and June 2004, 642 liver resections and 286 liver transplantations in 252 patients were performed in our department of surgery. Thirty-three patients were referred to our center for diagnostic and therapeutic management of CD. Prior surgical interventions for hepatobiliary disorders, current diagnostic and surgical procedures, procedure-specific complications, duration of hospital stay, duration of follow-up, outpatient information, and long-term outcome were reviewed.

RESULTS

Fifteen male and 18 female patients were treated in this study. Initial symptoms and signs of the disease noted in our patients included right upper quadrant pain, fever, and jaundice. In 2 of the 33 patients, we noted clinical evidence of cirrhosis followed by histologic confirmation. One patient suffered from variceal bleeding. In 26 patients, diagnoses were established by a combined endoscopic retrograde cholangiopancreatography, ultrasonography, and computed tomographic studies. The disease was localized in 25 and diffuse in 8 patients. Liver resection was carried out in 29 patients. Partial hepatectomies were performed in 27 of these 29 at our institution. Two female patients with the diffuse disease underwent orthotopic liver transplantation. Thirteen of the 31 patients who underwent surgery at our institution had an uneventful postoperative course. Fourteen patients had minor postoperative complications and responded well to medical management. Four patients had major complications that required further surgical treatment. Two patients died of complications related to postoperative hemorrhage and sepsis. Two patients with intrahepatic cholangiocarcinoma died because of primary tumor progress. One patient with cholangiocarcinoma died 1 year after a successful left hepatectomy because of metastatic disease recurrence. The long-term results of the 26 surviving patients were assessed during a mean follow-up of 3.7 years (range, 1-11 years). All 26 patients remained free of biliary symptoms or complications. In 25 patients, surgery including liver transplantation was curative.

CONCLUSIONS

Partial hepatectomy for localized CD is potentially curative. In patients with diffuse CD, liver transplantation provides gratifying long-term results.

Cardiovascular, skeletal, and renal defects in mice with a targeted disruption of the Pkd1 gene

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by cyst formation in the kidney, liver, and pancreas and is associated often with cardiovascular abnormalities such as hypertension, mitral valve prolapse, and intracranial aneurysms. It is caused by mutations in PKD1 or PKD2, encoding polycystin-1 and -2, which together form a cell surface nonselective cation ion channel. Pkd2-/- mice have cysts in the kidney and pancreas and defects in cardiac septation, whereas Pkd1(del34) -/- and Pkd1(L) -/- mice have cysts but no cardiac abnormalities, although vascular fragility was reported in the latter. Here we describe mice carrying a targeted mutation in Pkd1 (Pkd1(del17-21betageo)), which defines its expression pattern by using a lacZ reporter gene and may identify novel functions for polycystin-1. Although Pkd1(del17-21betageo) +/- adult mice develop renal and hepatic cysts, Pkd1(del17-21betageo) -/- embryos die at embryonic days 13.5-14.5 from a primary cardiovascular defect that includes double outflow right ventricle, disorganized myocardium, and abnormal atrio-ventricular septation. Skeletal development is also severely compromised. These abnormalities correlate with the major sites of Pkd1 expression. During nephrogenesis, Pkd1 is expressed in maturing tubular epithelial cells from embryonic day 15.5. This expression coincides with the onset of cyst formation in Pkd1(del34) -/-, Pkd1(L) -/-, and Pkd2-/- mice, supporting the hypothesis that polycystin-1 and polycystin-2 interact in vivo and that their failure to do so leads to abnormalities in tubule morphology and function.

Sonographic pattern of recessive polycystic kidney disease in young adults. Differences from the dominant form

BACKGROUND

To study the sonographic pattern of autosomal recessive polycystic kidney disease (ARPKD) in early adulthood in order to identify imaging criteria to diagnose this disease and to distinguish between recessive and autosomal dominant polycystic kidney disease (ADPKD) in that age group.

METHODS

An abdominal ultrasound was performed on four ARPKD subjects (with a mean age of 20.2) and on 33 ADPKD subjects in early adulthood (29 without renal failure with a mean age of 20.5, and four with renal failure with a mean age of 26.5). Linkage studies with ADPKD and ARPKD markers were compatible with the clinical diagnosis in all cases.

RESULTS

The renal sonographic features in ARPKD subjects included multiple small cysts in a normal-sized kidney, increased cortical echogenicity and loss of corticomedullary differentiation. In ADPKD subjects without renal failure, sonographic features included few or multiple cysts of different sizes, in normal-sized kidneys in 22 out of 29 patients (75.8%), normal cortical echogenicity and conserved corticomedullary differentiation, except in patients with nephromegaly. All ADPKD subjects with renal failure had nephromegaly and loss of corticomedullary differentiation. The hepatic sonographic features in ARPKD patients included portal fibrosis and in some cases Caroli's disease, while in ADPKD patients a normal hepatic echostructure was detected in all but one case, in addition to simple hepatic cysts in a few cases.

CONCLUSIONS

The evaluation of the sonographic features of the kidneys and those of the liver may help in the differential diagnosis between ARPKD and ADPKD in early adulthood.

Mutational analysis within the 3' region of the PKD1 gene

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common genetic diseases in humans, affecting 1 out of 1000 individuals. At least three different genes are involved in this disease. The search for mutations in PKD1 is complicated because most of the transcript is encoded by a genomic region reiterated more proximally on chromosome 16, and no prevalent mutation has been reported.

METHODS

We have screened DNA from exon 43 through exon 46 and intron 40 of the PKD1 sequence by single-stranded conformational polymorphism (SSCP) analysis in 175 ADPKD patients.

RESULTS

We have found 25 differences with respect to the reported PKD1 DNA sequence, seven of which are mutations (Q4041X, Q4124X, IVS44-1G-->C, IVS45-1G-->A, 12801del28, R4275W, and Q4224P). We found different phenotypical expressions of the same mutation in the families studied. We have detected several common polymorphisms, and some of them cosegregate, suggesting a common origin of these alleles in PKD1.

CONCLUSIONS

The detection of only seven mutations in 175 unrelated ADPKD patients for this region of the PKD1 analyzed suggests that mutations could be widespread throughout all of the gene and that a prevalent mutation is not expected to occur. The identified PKD1 missense mutations may help to refine critical regions of the protein. Until a quicker and more sensitive method for the detection of mutations becomes available, linkage studies will continue to be the basis for the molecular diagnosis of ADPKD families.

Early development of the zebrafish pronephros and analysis of mutations affecting pronephric function

The zebrafish pronephric kidney provides a simplified model of nephron development and epithelial cell differentiation which is amenable to genetic analysis. The pronephros consists of two nephrons with fused glomeruli and paired pronephric tubules and ducts. Nephron formation occurs after the differentiation of the pronephric duct with both the glomeruli and tubules being derived from a nephron primordium. Fluorescent dextran injection experiments demonstrate that vascularization of the zebrafish pronephros and the onset of glomerular filtration occurs between 40 and 48 hpf. We isolated fifteen recessive mutations that affect development of the pronephros. All have visible cysts in place of the pronephric tubule at 2–2.5 days of development. Mutants were grouped in three classes: (1) a group of twelve mutants with defects in body axis curvature and manifesting the most rapid and severe cyst formation involving the glomerulus, tubule and duct, (2) the fleer mutation with distended glomerular capillary loops and cystic tubules, and (3) the mutation pao pao tang with a normal glomerulus and cysts limited to the pronephric tubules. double bubble was analyzed as a representative of mutations that perturb the entire length of the pronephros and body axis curvature. Cyst formation begins in the glomerulus at 40 hpf at the time when glomerular filtration is established suggesting a defect associated with the onset of pronephric function. Basolateral membrane protein targeting in the pronephric duct epithelial cells is also severely affected, suggesting a failure in terminal epithelial cell differentiation and alterations in electrolyte transport. These studies reveal the similarity of normal pronephric development to kidney organogenesis in all vertebrates and allow for a genetic dissection of genes needed to establish the earliest renal function.