Two new large deletions of the AVPR2 gene causing nephrogenic diabetes insipidus and a review of previously published deletions

Abstract

In this paper, we report two new original deletions and present an extended review of the previously characterized AVPR2 gene deletions to better understand the underlying deletion mechanisms. The two novel deletions were defined using polymerase chain reaction mapping and junction fragment sequencing. Bioinformatic analysis was performed on both the previously mapped deletions and the novel ones through several web tools. In our two patients with nephrogenic diabetes insipidus, we found a 23 755 bp deletion and a 9264 bp deletion both comprising the entire AVPR2 gene and part of the ARHGAP4 gene. Through bioinformatic studies, the smallest overlapping region as well as several motifs and repeats that are known to promote rearrangements were confirmed. Through this study, it was determined that the deletion mechanisms in the AVPR2 region do not follow the rules of non-allelic homologous recombination. Two of the 13 deletions can be attributed to the fork stalling and template switching (FoSTeS) mechanism, whereas the remaining 11 deletions could be caused either by non-homologous end joining or by the FoSTeS mechanism. Although no recurrence was found, several groupings of deletion breakpoints were identified.