Single nucleotide polymorphisms within Adducin 3 and Adducin 3 antisense RNA1 genes are associated with biliary atresia in Thai infants

Genetics of biliary atresia: Approaches, pathological insights and challenges

Biliary atresia (BA) is a severe neonatal cholestatic disorder marked by fibro-obliteration of the extrahepatic and intrahepatic bile ducts. It is the most common cause of pediatric end-stage liver disease and the leading indication for liver transplantation in children. There is significant heterogeneity in the etiology, involving various genetic and environmental factors such as viral infection, immune dysregulation and genetic predisposition to defective hepatobiliary development. In this review, we discuss the strategies to uncover the genetic factors underlying BA and highlight their associated molecular and pathological mechanisms, as well as the challenges faced in this area of research.

The correlation between rs2501577 gene polymorphism and biliary atresia: a systematic review and meta-analysis

IMPORTANCE

Multiple studies indicate a possible correlation between ADD3 rs2501577 and biliary atresia susceptibility; however, a conclusive determination has yet to be made.

OBJECTIVE

Investigate the role of ADD3 rs2501577 in biliary atresia susceptibility across diverse populations.

DATA SOURCES

The study protocol has been registered on PROSPERO, an international platform for systematic review registration (PROSPERO ID: CRD42023384641). The following databases will be searched until February 1, 2023: PubMed, Embase, Cochrane, CBM, Web of Science, and CNKI.

STUDY SELECTION

Eight studies were selected from seven papers to assess the data. A total of 7651 participants were included, consisting of 1662 in the BA group and 5989 in the NC group.

DATA EXTRACTION AND SYNTHESIS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed while conducting the systematic reviews and meta-analyses. Two authors independently assessed the quality of the included studies using the Newcastle-Ottawa Quality Assessment Scale. The significance of the pooled odds ratio (OR) was evaluated with a Z test, and statistical heterogeneity across studies was assessed using the I2 and Q statistics. Publication bias was assessed using Egger's and Begg's tests.

MAIN OUTCOME(S) AND MEASURE(S)

The primary study outcome was the development of biliary atresia. Subgroup analysis was performed based on race, region, and assessment of Hardy-Weinberg equilibrium (HWE).

RESULTS

The studies indicate that the ADD3 rs2501577 susceptibility locus increases the risk of developing biliary atresia, regardless of allelic, homozygote, dominant, and recessive gene inheritance models. Furthermore, ADD3 has been found to be associated with apoptosis, cell cycle, and cell damage repair based on functional analysis.

CONCLUSIONS AND RELEVANCE

The ADD3 rs2501577 polymorphic locus is associated with an increased risk of biliary atresia, particularly in Asian populations. This study recommends further investigation of the ADD3 rs2501577 locus in Asian populations to validate its role in the diagnosis of biliary atresia.

A novel pathogenesis concept of biliary atresia approached by combined molecular strategies

Cholestatic jaundice is one of the most common neonatal conditions. BA, a correctable cholangiopathy, presents with cholestatic jaundice within the first weeks of life. The inflammation of bile ducts leads to progressive fibrosclerosis involving biliary trees, followed by cirrhosis and liver failure. With the use of modern molecular studies, this research aimed to define a novel pathogenesis by exploring variations. We performed genetic discovery by using supervised and unsupervised approaches. Ultimately, a combination of genetic variations and survival data was analyzed to strengthen the novel concept in this study. In this study, coding regions were explored to identify rare deleterious variants within genes from the first analysis together with gene sets reported in PFIC, and diseases with hyperbilirubinemia. Our unsupervised prioritization was primarily designed to identify novel causal genes from nonsynonymous variants derived by three biostatistical algorithms: enrichment analysis, burden test, and trio study. Survival analysis was integratively evaluated with a combination of identified causal genes. The individuals with identified variants from the supervised approach were frequently related to the severity of cirrhosis and poor postoperative outcome. In the unsupervised approach, nonsynonymous variants were enriched. Cilium and muscle related pathways had a significant correlation. CCDC8 was statistically significant gene in which six cases carried mutations identified through burden analysis. Individuals who carried variants in corresponding genes and significant pathways had significantly lower native-liver survival than individuals in whom none of these variants were identified (log-rank p value 0.016). This study explored genetic variations by multiple strategies. Different pathways of cholestatic diseases have been found to be associated with BA. Therefore, BA may be characterized as a shared sequela of many cholestatic disorders. Susceptibility in those pathways suggested an association with BA and strengthened this proposed novel hypothesis. The results emphasized the consequences of many disruptive pathophysiologies.

A novel inflammation-related lncRNAs prognostic signature identifies LINC00346 in promoting proliferation, migration, and immune infiltration of glioma

In this study, a total of 13 inflammation-related lncRNAs with a high prognostic value were identified with univariate, multivariate Cox regression analysis, and LASSO analysis. LINC00346, which is one of the 13 lncRNAs identified, was positively associated with type 2 macrophage activation and the malignant degree of glioma. Fluorescence in situ hybridization (FISH) and immunohistochemical staining showed that LINC00346 was highly expressed in high-grade glioma, while type 2 macrophages key transcription factor STAT3 and surface marker CD204 were also highly expressed simultaneously. LINC00346 high-expression gliomas were more sensitive to the anti-PD-1 and anti-CTLA-4 therapy. LINC00346 was also associated with tumor proliferation and tumor migration validated by EdU, cell colony, formation CCK8, and transwell assays. These findings reveal novel biomarkers for predicting glioma prognosis and outline relationships between lncRNAs inflammation, and glioma, as well as possible immune checkpoint targets for glioma.

Impact of EFEMP1 on the survival outcome of biliary atresia in Thai infants

Genome-wide association studies (GWASs) have identified a genetic associated between EFEMP1 and biliary atresia (BA). To examine the susceptibility of single nucleotide polymorphisms (SNPs) in EFEMP1 in Thai BA patients, we performed an analysis of the genetic associations and biological interactions with previously reported key SNPs in ADD3, a key gene associated with BA. The study also used high-throughput sequencing to detect novel variants in both genes. In addition, the clinical impact of EFEMP1 SNPs in terms of survival association was also evaluated. The genotypes of 60 BA patients and 179 controls were evaluated using a TaqMan genotyping assay for rs2501577 and rs17095355 in ADD3 and rs6761893 and rs727878 in EFEMP1. The genotype frequencies were analyzed together with the SNP-SNP interactions. Fine mapping by whole-exome sequencing was performed to identify deleterious variants within both genes, and the survival analysis results were analyzed with the EFEMP1 SNPs. The recessive genotypes of rs2501577, rs17095355 and rs6761893 showed significantly higher frequencies in the BA patients than the controls, and a logistic regression showed that minor alleles of those SNPs increased the BA risk by ORs of 1.86, 1.67, and 1.84, respectively. Moreover, the SNP-SNP interference suggested that a combination of recessive alleles from the 2 genes resulted in an additive risk to BA. In addition, rare missense variants in the gene coding sequences were identified in 7 cases. Immunohistochemical studies revealed a pattern of ADD3 downregulation and EFEMP1 overexpression in the bile ducts of BA patients. Patients with the AA genotype of rs6761893 had significantly lower 5-year native liver survival (34.0%) than those with AT/TT (75.0%), with a log-rank p value of 0.041. Variants in EFEMP1 are associated with the occurrence of BA in Thai patients. In addition, these variants have an additive influence on BA risk when combined with ADD3 variants. Moreover, rs6761893 in EFEMP1 was indicative of survival in Thai BA patients.

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.

Role of long non-coding RNA-adducin 3 antisense RNA1 in liver fibrosis of biliary atresia

Biliary atresia (BA) is a devastating liver disease in neonates. Liver fibrosis is regarded as a universal and prominent feature of BA. Studies have revealed that long non-coding RNAs (lncRNAs) regulate cellular processes during the development of liver fibrosis in BA. Long non-coding RNA-adducin 3 antisense RNA1 (lnc-ADD3-AS1) has been shown to increase susceptibility to BA. However, the role of lnc-ADD3-AS1 in liver fibrosis in BA remains unclear. Here, we investigated the role of lnc-ADD3-AS1 in the proliferation, migration, and apoptosis of the immortalized human hepatic stellate cell (HSC) line, LX-2. We successfully overexpressed and silenced lnc-ADD3-AS1 in LX-2 cells using adenovirus vectors and evaluated the proliferation of transfected cells using the Cell Counting Kit-8 (CCK8) assay. Cell apoptosis was detected using annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) double staining and flow cytometry. We then analyzed cell migration by performing wound-scratch and transwell migration assays. Our results show that lnc-ADD3-AS1 significantly promoted LX-2 cell proliferation and attenuated apoptosis. More importantly, lncRNA-ADD3-AS1 significantly accelerated the migration of LX-2 cells. Our data indicated that lncRNA-ADD3-AS1 plays a role in the pathogenesis of liver fibrosis in patients with BA and may serve as a potential diagnostic marker for monitoring liver fibrosis in BA or as a therapeutic target for the disease.

Update on Etiology and Pathogenesis of Biliary Atresia

Biliary atresia is a rare inflammatory sclerosing obstructive cholangiopathy that initiates in infancy as complete choledochal blockage and progresses to the involvement of intrahepatic biliary epithelium. Growing evidence shows that biliary atresia is not a single entity with a single etiology but a phenotype resulting from multifactorial events whose common path is obliterative cholangiopathy. The etiology of biliary atresia has been explained as resulting from genetic variants, toxins, viral infection, chronic inflammation or bile duct lesions mediated by autoimmunity, abnormalities in the development of the bile ducts, and defects in embryogenesis, abnormal fetal or prenatal circulation and susceptibility factors. It is increasingly evident that the genetic and epigenetic predisposition combined with the environmental factors to which the mother is exposed are potential triggers for biliary atresia. There is also an indication that a progressive thickening of the arterial middle layer occurs in this disease, suggestive of vascular remodeling and disappearance of the interlobular bile ducts. It is suggested that the hypoxia/ischemia process can affect portal structures in biliary atresia and is associated with both the extent of biliary proliferation and the thickening of the medial layer.

Molecular Landscape for Malignant Transformation in Diffuse Astrocytoma

Background  Malignant transformation (MT) of low-grade gliomas changes dramatically the natural history to poor prognosis. Currently, factors associated with MT of gliomas have been inconclusive, in particular, diffuse astrocytoma (DA).

Objective  The present study aimed to explore the molecular abnormalities related to MT in the same patients with different MT stages.

Methods  Twelve specimens from five DA patients with MT were genotyped using next-generation sequencing (NGS) to identify somatic variants in different stages of MT. We used cross-tabulated categorical biological variables and compared the mean of continuous variables to assess for association with MT.

Results  Ten samples succussed to perform NGS from one male and four females, with ages ranging from 28 to 58 years. The extent of resection was commonly a partial resection following postoperative temozolomide with radiotherapy in 25% of cases. For molecular findings, poly-T-nucleotide insertion in isocitrate dehydrogenase 1 (IDH1) was significantly related to MT as a dose–response relationship (Mann–Whitney's U test, p  = 0.02). Also, mutations of KMT2C and GGT1 were frequently found in the present cohort, but those did not significantly differ between the two groups using Fisher's exact test.

Conclusion  In summary, we identified a novel relationship between poly-T insertion polymorphisms that established the pathogenesis of MT in DA. A further study should be performed to confirm the molecular alteration with more patients.

Genetic aspects of biliary atresia etiology

Biliary atresia (BA) is a cholestatic disorder of infancy that is fatal if untreated. Despite years of study the etiology of BA remains unknown. Three etiopathogenic mechanisms may be involved, such as immune dysregulation, environmental factors and genetic susceptibility. Genetic predisposition is being actively studied. Candidate genes associated with BA in certain populations, genes affecting the cholangiocyte cilia function, as well as genes involved in stress responses have been identified. However, the long-term follow-up of twins with BA suggests that genotype is not of paramount importance for the disease development. Both epigenetic patterns and postzygotic somatic mutations may contribute to etiology of the disease. Recently, some evidence is being accumulated on the possible genetic predisposition to certain outcome of Kasai portoenterostomy performed in patients with BA. However, the presence of a number of factors contributing to the development of the disease makes it difficult to identify the genetic markers.

Association of common variation in ADD3 and GPC1 with biliary atresia susceptibility

Biliary atresia (BA) is an idiopathic neonatal cholestatic disease. Recent genome-wide association study (GWAS) revealed that common variation of ADD3, GPC1, ARF6, and EFEMP1 gene was associated with BA susceptibility. We aimed to evaluate the association of these genes with BA in Chinese population. Twenty single nucleotide polymorphisms (SNPs) in these four genes were genotyped in 340 BA patients and 1,665 controls. Three SNPs in ADD3 were significantly associated with BA, and rs17095355 was the top SNP (P_Allele = 3.23×10^-6). Meta-analysis of published data and current data indicated that rs17095355 was associated with BA susceptibility in Asians and Caucasians. Three associated SNPs were expression quantitative trait loci (eQTL) for ADD3. Two GPC1 SNPs in high linkage disequilibrium (LD) showed nominal association with BA susceptibility (P_Allele = 0.03 for rs6707262 and P_Allele = 0.04 for rs6750380), and were eQTL of GPC1. Haplotype harboring these two SNPs almost reached the study-wide significance (P = 0.0035). No association for ARF6 and EFEMP1 was found with BA risk in the current population. Our study validated associations of ADD3 and GPC1 SNPs with BA risk in Chinese population and provided evidence of epistatic contributions of genetic factors to BA susceptibility.

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.