North American Indian cirrhosis in children: a review of 30 cases

Early predictors of unfavourable outcome in progressive cholestasis of northwestern Quebec

BACKGROUND

Progressive cholestasis of northwestern Quebec (PCNQ) is a rare and severe form of cirrhosis affecting children from Quebec's First Nations. First described by our group in 1981 and historically named North American Indian childhood cirrhosis, such a condition often requires liver transplantation during the pediatric age. This study aimed at suggesting a more culturally sensitive name for the disease and identifying early prognostic factors for an unfavourable outcome.

METHODS

We retrospectively collected data of all 14 consecutive patients diagnosed with PCNQ over the last 20 years and compared children listed for liver transplant before 18 years of age (LT, n = 7) to those with milder disease progression (no-LT, n = 7).

RESULTS

Compared with the no-LT group, LT children developed serious complications with an unusually high incidence of gastrointestinal bleeding. Over the first 12 months from presentation, a greater increase of alanine aminotransferase plasma levels, decrease of total bilirubin, and increase of alanine aminotransferase-to-total bilirubin ratio was observed in the LT group. Bone mineral density was lower in LT children independently of vitamin D levels. Patients with PCNQ showed poorer bone health than age-matched children with other cholestatic disorders.

CONCLUSIONS

In the name of cultural sensitivity, PCNQ should be the preferred name for this condition. Variation of alanine aminotransferase and total bilirubin plasma levels over the first 12 months from presentation might be used for the early identification of children with PCNQ who are at higher risk of unfavourable outcomes. This might help optimize clinical management to populations that are underserved by health care services.

Ribosomopathies: New Therapeutic Perspectives

Ribosomopathies are a group of rare diseases in which genetic mutations cause defects in either ribosome biogenesis or function, given specific phenotypes. Ribosomal proteins, and multiple other factors that are necessary for ribosome biogenesis (rRNA processing, assembly of subunits, export to cytoplasm), can be affected in ribosomopathies. Despite the need for ribosomes in all cell types, these diseases result mainly in tissue-specific impairments. Depending on the type of ribosomopathy and its pathogenicity, there are many potential therapeutic targets. The present manuscript will review our knowledge of ribosomopathies, discuss current treatments, and introduce the new therapeutic perspectives based on recent research. Diamond–Blackfan anemia, currently treated with blood transfusion prior to steroids, could be managed with a range of new compounds, acting mainly on anemia, such as L-leucine. Treacher Collins syndrome could be managed by various treatments, but it has recently been shown that proteasomal inhibition by MG132 or Bortezomib may improve cranial skeleton malformations. Developmental defects resulting from ribosomopathies could be also treated pharmacologically after birth. It might thus be possible to treat certain ribosomopathies without using multiple treatments such as surgery and transplants. Ribosomopathies remain an open field in the search for new therapeutic approaches based on our recent understanding of the role of ribosomes and progress in gene therapy for curing genetic disorders.

CIRH1A augments the proliferation of RKO colorectal cancer cells

Accumulating evidence suggests that ribosomal proteins may have extraribosomal functions in various physiological and pathological processes, including cancer. We analyzed the expression of the CIRH1A ribosomal protein in colorectal carcinoma and para-carcinoma samples by bioinformatics analyses of data extracted from The Cancer Genome Atlas and in colorectal cancer cell lines in vitro by qPCR. CIRH1A was highly expressed in carcinoma samples and colorectal cancer cells. We also transduced the RKO colorectal cancer (CRC) cell line with lentivirus-mediated small interfering RNAs (siRNAs) and studied the impact that this knockdown of CIRH1A expression had on cell growth. RNA interference (RNAi)-mediated inhibition of CIRH1A expression significantly suppressed proliferation and increased apoptosis of transduced cells, and tended to arrest them in G1 phase. Our data suggest that CIRH1A plays a critical role in the proliferation, cell cycle distribution, and apoptosis of human malignant colorectal cells, and might therefore be a potential target for therapeutic strategies.

Ribosomopathies: Global process, tissue specific defects

Disruptions in ribosomal biogenesis would be expected to have global and in fact lethal effects on a developing organism. However, mutations in ribosomal protein genes have been shown in to exhibit tissue specific defects. This seemingly contradictory finding - that globally expressed genes thought to play fundamental housekeeping functions can in fact exhibit tissue and cell type specific functions - provides new insight into roles for ribosomes, the protein translational machinery of the cell, in regulating normal development and disease. Furthermore it illustrates the surprisingly dynamic nature of processes regulating cell type specific protein translation. In this review, we discuss our current knowledge of a variety of ribosomal protein mutations associated with human disease, and models to better understand the molecular mechanisms associated with each. We use specific examples to emphasize both the similarities and differences between the effects of various human ribosomal protein mutations. Finally, we discuss areas of future study that are needed to further our understanding of the role of ribosome biogenesis in normal development, and possible approaches that can be used to treat debilitating ribosomopathy diseases.

Human diseases of the SSU processome

Ribosomes are the cellular machines responsible for protein synthesis. Ribosome biogenesis, the production of ribosomes, is a complex process involving pre-ribosomal RNA (rRNA) cleavages and modifications as well as ribosomal protein assembly around the rRNAs to create the functional ribosome. The small subunit (SSU) processome is a large ribonucleoprotein (RNP) in eukaryotes required for the assembly of the SSU of the ribosome as well as for the maturation of the 18S rRNA. Despite the fundamental nature of the SSU processome to the survival of any eukaryotic cell, mutations in SSU processome components have been implicated in human diseases. Three SSU processome components and their related human diseases will be explored in this review: hUTP4/Cirhin, implicated in North American Indian childhood cirrhosis (NAIC); UTP14, implicated in infertility, ovarian cancer, and scleroderma; and EMG1, implicated in Bowen-Conradi syndrome (BCS). Diseases with suggestive, though inconclusive, evidence for the involvement of the SSU processome in their pathogenesis are also discussed, including a novel putative ribosomopathy. This article is part of a Special Issue entitled: Role of the Nucleolus in Human Disease.

Diverse diseases from a ubiquitous process: the ribosomopathy paradox

Collectively, the ribosomopathies are caused by defects in ribosome biogenesis. Although these disorders encompass deficiencies in a ubiquitous and fundamental process, the clinical manifestations are extremely variable and typically display tissue specificity. Research into this paradox has offered fascinating new insights into the role of the ribosome in the regulation of mRNA translation, cell cycle control, and signaling pathways involving TP53, MYC and mTOR. Several common features of ribosomopathies such as small stature, cancer predisposition, and hematological defects, point to how these diverse diseases may be related at a molecular level.

p53-mediated biliary defects caused by knockdown of cirh1a, the zebrafish homolog of the gene responsible for North American Indian Childhood Cirrhosis

North American Indian Childhood Cirrhosis (NAIC) is a rare, autosomal recessive, progressive cholestatic disease of infancy affecting the Cree-Ojibway first Nations of Quebec. All NAIC patients are homozygous for a missense mutation (R565W) in CIRH1A, the human homolog of the yeast nucleolar protein Utp4. Utp4 is part of the t-Utp subcomplex of the small subunit (SSU) processome, a ribonucleoprotein complex required for ribosomal RNA processing and small subunit assembly. NAIC has thus been proposed to be a primary ribosomal disorder (ribosomopathy); however, investigation of the pathophysiologic mechanism of this disease has been hindered by lack of an animal model. Here, using a morpholino oligonucleotide (MO)-based loss-of-function strategy, we have generated a model of NAIC in the zebrafish, Danio rerio. Zebrafish Cirhin shows substantial homology to the human homolog, and cirh1a mRNA is expressed in developing hepatocytes and biliary epithelial cells. Injection of two independent MOs directed against cirh1a at the one-cell stage causes defects in canalicular and biliary morphology in 5 dpf larvae. In addition, 5 dpf Cirhin-deficient larvae have dose-dependent defects in hepatobiliary function, as assayed by the metabolism of an ingested fluorescent lipid reporter. Previous yeast and in vitro studies have shown that defects in ribosome biogenesis cause stabilization and nuclear accumulation of p53, which in turn causes p53-mediated cell cycle arrest and/or apoptosis. Thus, the nucleolus appears to function as a cellular stress sensor in some cell types. In accordance with this hypothesis, transcriptional targets of p53 are upregulated in Cirhin-deficient zebrafish embryos, and defects in biliary function seen in Cirhin-deficient larvae are completely abrogated by mutation of tp53. Our data provide the first in vivo evidence of a role for Cirhin in biliary development, and support the hypothesis that congenital defects affecting ribosome biogenesis can activate a cellular stress response mediated by p53.

Alagille syndrome and other hereditary causes of cholestasis

Neonatal conjugated jaundice is a common presentation of hereditary liver diseases, which, although rare, are important to recognize early. Developments in molecular genetic techniques have enabled the identification of causative genes, which has improved diagnostic accuracy for patients and has led to a greater understanding of the molecular pathways involved in liver biology and pathogenesis of liver diseases. This review provides an update of the current understanding of clinical and molecular features of the inherited liver diseases that cause neonatal conjugated jaundice.

An autosomal recessive form of Alagille-like syndrome that is not linked to JAG1

PURPOSE

Alagille syndrome is an autosomal dominant condition characterized by a paucity of interlobular bile ducts and chronic cholestasis, cardiac disease, skeletal abnormalities, ocular abnormalities, and characteristic facies. Most cases harbor a mutation in JAG1. We describe a large consanguineous family with five individuals affected with an Alagille-like syndrome that appears to be autosomal recessive. Our objective was to characterize the disorder clinically and determine whether affected individuals had inherited a mutation in JAG1.

METHODS

Clinical data were obtained through questioning and patient chart review. Linkage analysis using microsatellite markers was used to assess the possibility of a JAG1 mutation.

RESULTS

The clinical phenotype of patients was not entirely consistent with classic Alagille syndrome. All affected individuals had neonatal cholestasis with intrahepatic bile duct paucity, with three having pulmonary stenosis, but the presentation was unusually uniform and severe in childhood. There was no evidence of posterior embryotoxon or vertebral anomalies. Cardiac abnormalities were inconsistent between patients. Most significantly, the pedigree suggested an autosomal recessive form of inheritance. Linkage analysis excluded a mutation in JAG1.

CONCLUSIONS

We have identified a kindred with an Alagille-like syndrome with an autosomal recessive form of inheritance not caused by a mutation in JAG1.

Chronic liver disease in Aboriginal North Americans

A structured literature review was performed to detail the frequency and etiology of chronic liver disease (CLD) in Aboriginal North Americans. CLD affects Aboriginal North Americans disproportionately and is now one of the most common causes of death. Alcoholic liver disease is the leading etiology of CLD, but viral hepatitis, particularly hepatitis C, is an important and growing cause of CLD. High rates of autoimmune hepatitis and primary biliary cirrhosis (PBC) are reported in regions of coastal British Columbia and southeastern Alaska. Non-alcoholic liver disease is a common, but understudied, cause of CLD. Future research should monitor the incidence and etiology of CLD and should be geographically inclusive. In addition, more research is needed on the treatment of hepatitis C virus (HCV) infection and non-alcoholic fatty liver disease (NAFLD) in this population.

[North American Indian childhood cirrhosis (NAIC)]

North American Indian childhood cirrhosis is a distinct form of neonatal familial cholestasis. To date, it has only been described in aboriginal children from northwestern Quebec. The disease rapidly evolves into cirrhosis with early portal hypertension and bleeding from esophageal varices. Twelve of 36 children followed at l'Hôpital Ste-Justine since 1970 received a liver transplant. As of now, there are 17 living NAIC patients, 6 of whom had liver transplantation. We mapped NAIC to chromosome 16q22, and identified mutations in CIRH1A in patients. All are homozygous for the R565W mutation in cirhin, a WD40 repeat protein of unknown function. We showed that cirhin is a resident in the nucleolus. Cirhin interacts with Cirip, a functional, alternative splice variant of the HIVEP1 protein. Their interaction indicates synergistic action. The complete inactivation of mouse homolog, tex292 is likely embryonic lethal. The continued collaboration between patients, their families, clinicians and researchers that has helped to identify the disease gene and to develop a diagnostic test now focuses on finding a new treatment for this unique disease affecting First Nations children from Québec.

Genetics of familial intrahepatic cholestasis syndromes

Bile acids and bile salts have essential functions in the liver and in the small intestine. Their synthesis in the liver provides a metabolic pathway for the catabolism of cholesterol and their detergent properties promote the solubilisation of essential nutrients and vitamins in the small intestine. Inherited conditions that prevent the synthesis of bile acids or their excretion cause cholestasis, or impaired bile flow. These disorders generally lead to severe human liver disease, underscoring the essential role of bile acids in metabolism. Recent advances in the elucidation of gene defects underlying familial cholestasis syndromes has greatly increased knowledge about the process of bile flow. The expression of key proteins involved in bile flow is tightly regulated by transcription factors of the nuclear hormone receptor family, which function as sensors of bile acids and cholesterol. Here we review the genetics of familial cholestasis disorders, the functions of the affected genes in bile flow, and their regulation by bile acids and cholesterol.

Prognosis, with evaluation of general biochemistry, of liver disease in lymphoedema cholestasis syndrome 1 (LCS1/Aagenaes syndrome)

OBJECTIVE

To investigate the prognosis of liver disease in Aagenaes syndrome (lymphoedema cholestasis syndrome 1 (LCS1)), which is an autosomal recessive inherited syndrome consisting of neonatal cholestasis with intermittent cholestatic episodes in childhood into adulthood and development of lymphoedema. Forty Norwegian patients are known to have this condition, 25 of whom are alive. A clinical description of the liver disease is supplied with a case-control study.

MATERIAL AND METHODS

In this paper we review the course of the liver disease in the Norwegian cohort of patients and present results from a case-control study in the patients above 10 years of age. The case-control study was performed on 15 patients without clinical cholestasis (itching and sometimes jaundice) at the time of the study. An evaluation of 11 patients above 15 years of age without chronic biochemical cholestasis (increased alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT) and/or serum bile acids) was also carried out. For each patient one randomly identified control person was included (15 in one study, 11 in the other).

RESULTS

Cirrhosis with either transplantation or death in infancy or early childhood occurred in six patients; slowly developing cirrhosis occurred in three patients. Two patients may be in the process of developing cirrhosis. Significantly increased ALP and GGT levels were found in patients with normal liver biochemistry in the preceding years when compared with the case control group. Additionally, albumin was found to be lower in older patients.

CONCLUSIONS

Compared with that for other types of hereditary neonatal cholestasis, patients with LCS1 have a relatively good prognosis. More than 50% can expect a normal life span.

Nucleolar localization of cirhin, the protein mutated in North American Indian childhood cirrhosis

Cirhin (NP_116219), the product of the CIRH1A gene is mutated in North American Indian childhood cirrhosis (NAIC/CIRH1A, OMIM 604901), a severe autosomal recessive intrahepatic cholestasis. It is a 686-amino-acid WD40-repeat containing protein of unknown function that is predicted to contain multiple targeting signals, including an N-terminal mitochondrial targeting signal, a C-terminal monopartite nuclear localization signal (NLS) and a bipartite nuclear localization signal (BNLS). We performed the direct determination of subcellular localization of cirhin as a crucial first step in unraveling its biological function. Using EGFP and His-tagged cirhin fusion proteins expressed in HeLa and HepG2, cells we show that cirhin is a nucleolar protein and that the R565W mutation, for which all NAIC patients are homozygous, has no effect on subcellular localization. Cirhin has an active C-terminal monopartite nuclear localization signal (NLS) and a unique nucleolar localization signal (NrLS) between residues 315 and 432. The nucleolus is not known to be important specifically for intrahepatic cholestasis. These observations provide a new dimension in the study of hereditary cholestasis.

Colestasis infantil y transportadores biliares

Identification of the transport systems involved in bile secretion and of the genes codifying these systems has allowed the etiology of familial intrahepatic cholestasis to be determined in most affected children. Mutations in ATP8B1 cause a defect in FIC1, an aminophospholipid flipase, and give rise to a variable spectrum of disease, ranging from progressive intrahepatic cholestasis to benign recurrent cholestasis, due to alterations in the lipid composition of the membranes and decreased expression of the nuclear factor FXR. Mutations in ABCB11 cause a defect of the canalicular bile salt export pump (BSEP), with early clinical manifestations and progression to hepatocellular failure in childhood. Mutations in ABCB4 cause an alteration in the MDR3 phospholipid transporter, and a variable spectrum of disease from progressive ductal injury to cirrhosis in children, and gallstones, cholestasis of pregnancy, or late cirrhosis in adults.

Population history and its impact on medical genetics in Quebec

Knowledge of the genetic demography of Quebec is useful for gene mapping, diagnosis, treatment, community genetics and public health. The French-Canadian population of Quebec, currently about 6 million people, descends from about 8500 French settlers who arrived in Nouvelle-France between 1608 and 1759. The migrations of those settlers and their descendants led to a series of regional founder effects, reflected in the geographical distribution of genetic diseases in Quebec. This review describes elements of population history and clinical genetics pertinent to the treatment of French Canadians and other population groups from Quebec and summarizes the cardinal features of over 30 conditions reported in French Canadians. Some were discovered in French Canadians, such as autosomal recessive ataxia of the Charlevoix-Saguenay (MIM 270550), agenesis of corpus callosum and peripheral neuropathy (MIM 218000) and French-Canadian-type Leigh syndrome (MIM 220111). Other conditions are particularly frequent or have special genetic characteristics in French Canadians, including oculopharyngeal muscular dystrophy, hepatorenal tyrosinaemia, cystic fibrosis, Leber hereditary optic neuropathy and familial hypercholesterolaemia. Three genetic diseases of Quebec First Nations children are also discussed: Cree encephalitis (MIM 608505), Cree leukoencephalopathy (MIM 603896) and North American Indian childhood cirrhosis (MIM 604901).

Biliary tract malformations

The biliary tree extends from the canals of Hering at the margin of the most peripheral portal tracts to the ampulla of Vater. Malformations occur at every level of this structure. Phenotypic features dominate present understanding of these malformations and of the disorders with which they are associated. Classifications of disease will likely shift from a phenotypic basis to a genotypic basis as genes implicated in biliary tree development and function are identified. Involvement of such genes in biliary tree disorders now considered inflammatory, such as extrahepatic biliary atresia, awaits study. The concept of "feeble cholangiocytes" postnatally susceptible to the effects of "toxic bile" is presented.

Neonatal hepatitis syndrome

Conjugated hyperbilirubinaemia in an infant indicates neonatal liver disease. This neonatal hepatitis syndrome has numerous possible causes, classified as infective, anatomic/structural, metabolic, genetic, neoplastic, vascular, toxic, immune and idiopathic. Any infant who is jaundiced at 2-4 weeks old needs to have the serum conjugated bilirubin measured, even if he/she looks otherwise well. If conjugated hyperbilirubinaemia is present, a methodical and comprehensive diagnostic investigation should be performed. Early diagnosis is critical for the best outcome. In particular, palliative surgery for extrahepatic biliary atresia has the best chance of success if performed before the infant is 8 weeks old. Definitive treatments available for many causes of neonatal hepatitis syndrome should be started as soon as possible. Alternatively, liver transplantation may be life saving. Supportive care, especially with attention to nutritional needs, is important for all infants with neonatal hepatitis syndrome.

A missense mutation (R565W) in cirhin (FLJ14728) in North American Indian childhood cirrhosis

North American Indian childhood cirrhosis (CIRH1A, or NAIC), a severe autosomal recessive intrahepatic cholestasis described in Ojibway-Cree children from northwestern Quebec, is one of several familial cholestases with unknown molecular etiology. It typically presents with transient neonatal jaundice, in a child who is otherwise healthy, and progresses to biliary cirrhosis and portal hypertension. Clinical and physiological investigations have not revealed the underlying cause of the disease. Currently, liver transplantation is the only effective therapy for patients with advanced disease. We previously identified the NAIC locus by homozygosity mapping to chromosome 16q22. Here we report that an exon 15 mutation in gene FLJ14728 (alias Cirhin) causes NAIC: c.1741C-->T in GenBank cDNA sequence NM_032830, found in all NAIC chromosomes, changes the conserved arginine 565 codon to a tryptophan, altering the predicted secondary structure of the protein. Cirhin is preferentially expressed in embryonic liver, is predicted to localize to mitochondria, and contains WD repeats, which are structural motifs frequently associated with molecular scaffolds.

Hereditary forms of intrahepatic cholestasis

Several genes that are mutated in hereditary forms of intrahepatic cholestasis have been identified or mapped, providing new insights into the process of enterohepatic bile acid circulation in health and disease and new tools with which to study this process. Murine models of several of these disorders have been generated. Unanticipated genetic heterogeneity has been identified.

Common diagnostic problems in pediatric liver pathology

The role of the pathologist in dealing with common problems of liver disease in children is likely to change dramatically as the molecular genetic revolution progresses. For example, microchip arrays for genes involved in bile salt synthesis and transport will pinpoint the specific mutations responsible for infantile cholestasis and similar methods will sort out infectious agents of acute and chronic hepatitis. But even as biochemistry, microbiology, and immunology laboratories already provide essential diagnostic information in such settings, informed histopathologic interpretation will continue to guide investigations of etiology and therapeutics and will remain an important medical necessity [95,96,100,102,104].

Cholestatic syndromes

New insights into the regulation of hepatobiliary transport proteins have provided the basis for a better understanding of the pathogenesis of cholestatic liver diseases. Mutations of transporter genes can cause hereditary cholestatic syndromes, the study of which has shed much light on the basic mechanisms of bile secretion and cholestasis. Important new studies have been published about the pathogenesis, clinical features, and treatment of primary biliary cirrhosis, primary sclerosing cholangitis, cholestasis of pregnancy, total parenteral nutrition-induced cholestasis, and drug-induced cholestasis.