MicroRNA-499 Rs3746444 polymorphism and biliary atresia

MicroRNAs in chronic pediatric diseases (Review)

MicroRNAs are small non-coding RNAs with a length of 20-24 nucleotides. They bind to the 3'-untranslated region of target genes to induce the degradation of target mRNAs or inhibit their translation. Therefore, they are involved in the regulation of development, apoptosis, proliferation, differentiation and other biological processes (including hormone secretion, signaling and viral infections). Chronic diseases in children may be difficult to treat and are often associated with malnutrition resulting from a poor diet. Consequently, further complications, disease aggravation and increased treatment costs impose a burden on patients and their families. Existing evidence suggests that microRNAs are involved in various chronic non-neoplastic diseases in children. The present review discusses the roles of microRNAs in five major chronic diseases in children, namely, diabetes mellitus, congenital heart diseases, liver diseases, bronchial asthma and epilepsy, providing a theoretical basis for them to become therapeutic biomarkers in chronic pediatric diseases.

Genetic Contributions to Biliary Atresia: A Developmental Cholangiopathy

Biliary atresia (BA) is the most prevalent serious liver disease of infancy and childhood, and the principal indication for liver transplantation in pediatrics. BA is best considered as an idiopathic panbiliary cholangiopathy characterized by obstruction of bile flow and consequent cholestasis presenting during fetal and perinatal periods. While several etiologies have been proposed, each has significant drawbacks that have limited understanding of disease progression and the development of effective treatments. Recently, modern genetic analyses have uncovered gene variants contributing to BA, thereby shifting the paradigm for explaining the BA phenotype from an acquired etiology (e.g., virus, toxin) to one that results from genetically altered cholangiocyte development and function. Herein we review recently reported genetic contributions to BA, highlighting the enhanced representation of variants in biological pathways involving ciliary function, cytoskeletal structure, and inflammation. Finally, we blend these findings as a new framework for understanding the resultant BA phenotype as a developmental cholangiopathy.

Current Understanding in the Clinical Characteristics and Molecular Mechanisms in Different Subtypes of Biliary Atresia

Biliary atresia is a severe obliterative cholangiopathy in early infancy that is by far the most common cause of surgical jaundice and the most common indicator for liver transplantation in children. With the advanced knowledge gained from different clinical trials and the development of research models, a more precise clinical classification of BA (i.e., isolated BA (IBA), cystic BA (CBA), syndromic BA (SBA), and cytomegalovirus-associated BA (CMVBA)) is proposed. Different BA subtypes have similar yet distinguishable clinical manifestations. The clinical and etiological heterogeneity leads to dramatically different prognoses; hence, treatment needs to be specific. In this study, we reviewed the clinical characteristics of different BA subtypes and revealed the molecular mechanisms of their developmental contributors. We aimed to highlight the differences among these various subtypes of BA which ultimately contribute to the development of a specific management protocol for each subtype.

Genetic Factors and Their Role in the Pathogenesis of Biliary Atresia

Biliary Atresia, a common basis for neonatal cholestasis and primary indication for Liver Transplantation, accounts for 60% of pediatric Liver Transplantations. While the pathogenesis of Biliary Atresia remains obscure, abnormalities within bile ducts and the liver, inflammation, fibrosis and cilia defects are thought to comprise the pathological basis for this condition. The findings of genetic variants in Biliary Atresia, such as Copy Number Variations and Single Nucleotide Polymorphism, are considered as essential factors in the development of this condition. In this review, we summarize and analyze these Biliary Atresia variants from a perspective of their pathological characteristics. In conclusion, such analyses may offer novel insights into the pathogenesis of Biliary Atresia and provide a foundation for future studies directed toward a better understanding and treatment of Biliary Atresia.

MicroRNA-499 rs3746444 polymorphism in Egyptian children with biliary atresia

Aim of the study

We aimed to evaluate the association of microRNA-499 rs3746444 polymorphism and biliary atresia (BA) risk and its correlation with clinic-pathologic features of BA.

Material and methods

This study was performed on 300 Egyptian children (100 BA cases, 100 cases with cholestatic liver diseases other than BA and 100 healthy controls). Routine laboratory investigations, clinical examination and abdominal ultrasound were done. All infants were genotyped for miR-499 single nucleotide polymorphisms (SNPs) (rs3746444 A>G) by real-time polymerase chain reaction (PCR) fluorescence detection on a Rotor Gene Real Time PCR System (QIAGEN, GmbH) using fluorescent labeled probes.

Results

The AG genotype was the most prevalent genotype of miR-499 rs3746444 among the studied groups. A significantly higher frequency of the rs3746444 G allele was found in the BA cases than the other groups (odds ratio = 1.62). This polymorphism was also correlated with the degree of fibrosis in BA cases (p < 0.05). The miR-499 rs3746444 polymorphism (GG genotype) was significantly associated with severe form of BA and bad prognosis after the Kasai operation (p < 0.05). miR-499 rs3746444 polymorphism had no effect on the clinic-pathological features or the liver function status in the non-BA group.

Conclusions

There is an association between the miR-499 SNP genotypes and the occurrence of BA. The variant allele G is the predominant allele in the BA group and is associated with severe liver inflammation and bad prognosis after the Kasai operation.

Genetics in biliary atresia

PURPOSE OF REVIEW

Biliary atresia is a poorly understood deadly disease. Genetic predisposition factors are suspected albeit not firmly established. This review summarizes recent evidence of genetic alterations in biliary atresia.

RECENT FINDINGS

Whole-genome association studies in biliary atresia patients identified four distinct predisposition loci with four different genes potentially involved in the disease occurrence. Variations in these genes were searched for, but none were found in patients with biliary atresia suggesting complex mechanisms.

SUMMARY

Despite decades since its description and decades of intensive researches, cause of biliary atresia disease remains enigmatic. The inheritance of biliary atresia is not Mendelian. Genetic predisposition factor is one of the explored fields to explain biliary atresia pathogenicity. Biliary atresia has been associated with several inborn syndromes, chromosome anomalies, and gene polymorphisms in specific populations. Four predisposition loci encompassing genes relevant to the disease have been identified, but no pathogenic variations were found in biliary atresia patients. Few reported cases of isolated biliary atresia manifestation in the context of known genetic diseases suggest coincidental findings. Alternatives to classic genetic alterations are proposed to explain genetic predisposition in biliary atresia including noncoding and epigenetic factors. Biliary atresia is most likely related to complex traits making its genetic exploration challenging.

Associations of microRNA single nucleotide polymorphisms and disease risk and pathophysiology

Single nucleotide polymorphisms (SNPs) are genetic variations that contribute to human phenotypes associated with various diseases. SNPs are involved in the regulation of a broad range of physiological and pathological processes, such as cellular senescence, apoptosis, inflammation, and immune response, by upregulating the expression of classical inflammation markers. Recent studies have suggested that SNPs located in gene-encoding microRNAs (miRNAs) affect various aspects of diseases by regulating the expression or activity of miRNAs. In the last few years, miRNA polymorphisms that increase and/or reduce the risk of developing many diseases, such as cancers, autoimmune diseases, and cardiovascular diseases, have attracted increasing attention not only because of their involvement in the pathophysiology of diseases but also because they can be used as prognostic biomarkers for a variety of diseases. In this review, we summarize the relationships between miRNA SNPs and the pathophysiology and risk of diseases.

Association between rs17095355 polymorphism on 10q24 and susceptibility to biliary atresia: a meta-analysis

OBJECTIVE

Recent studies have identified 10q24-rs17095355 as a susceptibility locus for biliary atresia (BA). To more precisely estimate the association between the rs17095355 polymorphism and BA risk, a meta-analysis was performed.

METHODS

A comprehensive search was conducted to examine all the eligible studies by electronic databases including Elsevier Science Direct, Pubmed, Google Scholar, China National Knowledge Infrastructure (CNKI) and Chinese Biomedical Literature (CBM) up to December 2015. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of the association.

RESULTS

A total of 6 comparisons from 5 relevant studies involving 1000 patients and 3257 controls were included to analyze the association between rs17095355 and BA risk. The pooled OR for T allele of rs17095355 was 1.72 (95%CI 1.53-1.92, p < 0.01) in BA. Stratification by ethnicity indicated the degree of risk of rs17095355 with BA susceptibility was similar in populations of Asian origin. The pooled OR was 1.81 (95%CI 1.60-2.06, p < 0.01).

CONCLUSIONS

This meta-analysis confirms the association of rs17095355 polymorphism and BA development, especially in Asians. More original studies with large sample are needed to replicate this genetic association in different ethnic groups.