Towards a Central Role of ISL1 in the Bladder Exstrophy–Epispadias Complex (BEEC): Computational Characterization of Genetic Variants and Structural Modelling

Genetic factors play a critical role in the development of human diseases. Recently, several molecular genetic studies have provided multiple lines of evidence for a critical role of genetic factors in the expression of human bladder exstrophy-epispadias complex (BEEC). At this point, ISL1 (ISL LIM homeobox 1) has emerged as the major susceptibility gene for classic bladder exstrophy (CBE), in a multifactorial disease model. Here, GWAS (Genome wide association studies) discovery and replication studies, as well as the re-sequencing of ISL1, identified sequence variants (rs9291768, rs6874700, c.137C > G (p.Ala46Gly)) associated with CBE. Here, we aimed to determine the molecular and functional consequences of these sequence variants and estimate the dependence of ISL1 protein on other predicted candidates. We used: (i) computational analysis of conserved sequence motifs to perform an evolutionary conservation analysis, based on a Bayesian algorithm, and (ii) computational 3D structural modeling. Furthermore, we looked into long non-coding RNAs (lncRNAs) residing within the ISL1 region, aiming to predict their targets. Our analysis suggests that the ISL1 protein specific N-terminal LIM domain (which harbors the variant c.137C > G), limits its transcriptional ability, and might interfere with ISL1-estrogen receptor α interactions. In conclusion, our analysis provides further useful insights about the ISL1 gene, which is involved in the formation of the BEEC, and in the development of the urinary bladder.