Project description:Williams Syndrome (WS) is a rare neurodevelopmental disorder caused by heterozygous deletions in a chromosome 7q11.23 region typically encompassing 26-28 genes. WS patients exhibit a wide spectrum of symptoms, including cardiovascular disease, intellectual disability, visuospatial deficits and hypersociability a behavioral profile that contrasts with autism spectrum disorder (ASD). However, the relationship between neuropsychiatric phenotypes and dysregulated gene networks caused by the 7q11.23 deletion is unknown. We report results from a large-scale integrated transcriptome analysis of peripheral blood in clinically evaluated subjects with WS, ASD and matched controls. We identified significantly differential expressed genes in WS as compared with ASD or controls, even after removing genes spanning the 7q11.23 region. Using weighted gene co-expression network analysis (WGCNA), we found that three co-expression modules were upregulated in WS, and were significantly associated with the intermediate phenotypes such as anxiety and attention problems. Notably, these three co-expression modules were only composed of genes located outside of 7q11.23 critical region. One module was associated with immune systems and B cell proliferation. Its top hub gene, BCL11A, is implicated in ASD and chromatin modification. Another module was enriched with genes associated with astrocytes and oligodendrocytes, and the third module was associated with RNA processing and neurons. MicroRNA (miRNA) profiling revealed differentially expressed miRNAs whose targets were enriched in each co-expression module associated with WS. These results identify genes and potential driver miRNAs, located outside of 7q11.23 critical region, that are novel candidates for mediating the neuropsychiatric phenotypes in WS.
Project description:Stargardt disease (STGD1) is an inherited retinopathy affecting approximately 1:8,000 individuals. It is characterised by biallelic mutations in ABCA4, and encodes a vital protein for the recycling of retinaldehyde in the retina. Despite its prevalence and impact, there are currently no treatments available for this condition. Furthermore, 35% of STGD1 cases remain genetically unsolved. Efforts have been directed towards comprehending the fundamental disease mechanisms and identifying all disease-causing variants in the extensive 150kb gene, to better aid with the development of effective therapeutic strategies. In this study, we generated iPSC lines from two monoallelic (PT1 & PT2), late onset STGD1 cases with the heterozygous complex allele - c.[5461-10T>C;5603A>T]. We differentiated these cells alongside a biallelic affected control (AC) - c.4892T>C, and c.4539+2001G>A, to retinal organoids (ROs) allowing us to investigate cellular and molecular characteristics associated with STGD1. We hypothesized that the missing inheritance in our monoallelic cases is due to an RNA defect. Consequently, we utilised a myriad of sequencing strategies including WGS, single-cell RNA sequencing (scRNAseq) and long-read RNA sequencing (LRS) to address this. ROs were grown for 230 days and developed all key retinal neurons with photoreceptor outer segments capable of ABCA4 expression. We observed patient-specific disruption to lamination with OPN1MW/LW+ cone photoreceptor retention in the RO centre during differentiation. Retention was more severe in the AC case affecting both cones and rods, suggesting a genotype/phenotype correlation. scRNAseq suggests retention may be due to the induction of apoptosis in photoreceptors. WGS successfully identified the missing alleles in both cases; PT1 reported c. 5603A>T in homozygous state and PT2 uncovered a rare hypomorph - c.4865T>C. Furthermore, ROs were able to recapitulate the retina-specific splicing defect in PT1 as shown by LRS data. Collectively, these results highlight the suitability of ROs in STGD1 modelling. Their ability to display genotype-phenotype correlations enhances their utility as a platform for therapeutic development. Importantly, both PT1 and PT2 cases were genetically resolved in this study, providing two more individuals their confirmed genetic diagnosis.