**Background**
Beckwith–Wiedemann Syndrome (BWS) is a condition where some tissues in the body grow too much, especially in the liver. This happens due to changes in a specific part of chromosome 11 (11p15). These changes can lead to problems like an enlarged liver and a higher chance of developing liver cancer, specifically a type called hepatoblastoma. However, we don’t fully understand how these changes in the chromosome lead to the liver overgrowth seen in BWS.
Our previous research showed that liver tissue near BWS tumors, as well as the tumors themselves, had signs that suggest a higher risk of cancer. We also know that babies with BWS often have higher levels of a protein called alpha-fetoprotein (AFP), which is normally made by the liver. This suggests that BWS livers are more active than usual.
Based on these findings, we created a detailed map of liver tissue in BWS children to understand it better at a very detailed level (single-nucleus level). We used advanced technology to study the cells in BWS livers and identify which types of cells are more common. To confirm our findings, we also used lab-grown BWS liver cells from induced pluripotent stem cells or iPSCs to support what we discovered in the liver tissue samples.
**Findings**
Using single-nucleus RNA sequencing (snRNA-seq) which looks at expression levels of genes, we found that the types of cells in the livers of BWS patients were similar to those in non-BWS livers. However, certain pathways related to fat and lipid metabolism, along with PPARA signaling, were more active in BWS liver cells compared to normal liver cells (**Figure 1**). Further, single-nucleus ATAC sequencing (snATAC-seq) which looks at chromatin (a complex of DNA and protein in nucleus forming the basic structure of a chromosome) showed that the DNA in BWS liver cells was more open in the regions related to these pathways, suggesting that these pathways were more easily activated.
When we compared the lab-grown BWS liver cells – hepatocytes (from induced pluripotent stem cells or iPSCs) to control cells, we found similar changes. Specifically, the BWS liver cells showed more activity in fat and lipid metabolism pathways, just like the cells from BWS patients' livers (**Figure 1**). We also noticed that the gene called PPARA was more active in the BWS cells during their development into hepatocytes. This demonstrated that the cell-model of BWS was similar to the actual BWS liver samples and can be used for further studies of BWS.
We tested further and observed that the BWS liver cells had fewer fat droplets and were burning fat (through a process called fatty acid β-oxidation) more quickly. This points to an alteration in their metabolism. Finally, we saw that these BWS liver cells had an increased response to reactive oxygen species (ROS), which are harmful molecules that can damage DNA. This oxidative damage may be a part of the process that leads to liver cancer in BWS. Based on these findings, we suggest that the changes in metabolism could be driving the transition to cancerous cells in BWS livers.
.png)
**Figure 1**: Single nuclei multiome sequencing analysis and BWS liver cell differentiation of iPSCs depict the PPARA driven metabolic nature of BWS liver.
**Conclusion**
In this study, we explored the complex molecular landscape of Beckwith-Wiedemann Syndrome (BWS) to better understand the metabolic problems and highlighted the important role of PPARA signaling in BWS liver cells, which may contribute to the increased risk of liver cancer (hepatoblastoma) in BWS. Our multi-omic approach allowed us to identify distinct cell types and differences between the livers of BWS patients and those without the condition. These discoveries offer new insights into this rare genetic disorder and could pave the way for more targeted treatments to help prevent BWS-related liver cancer (hepatoblastoma).