A complementary study pipeline unravels novel players in the pathoetiology of Hirschsprung's disease. A complementary study pipeline unravels novel players in the pathoetiology of Hirschsprung's disease

Purpose: Hirschsprung’s disease (HSCR, OMIM 142623) represents one of the main causes of neonatal intestinal obstruction. It is caused by dysfunction of neural crest cells (NCCs) and their progeny during development of the enteric nervous system (ENS). HSCR is considered a multifactorial disorder, however, associated risk genes only account for a minority of cases. Consequently, defining disease-relevant variants is still a demanding task. Methods: To reduce the number of candidate genes identified by Whole Exome Sequencing (WES) and to examine their disease-causing relevance, we established a complementary study pipeline including transcriptome data of murine embryonic ENS-relevant tissues, literature and database searches, in silico network analyses as well as functional assays using genome-edited candidate-specific cell clones. Results: Applying this strategy on a pilot set of two HSCR patients and their non-affected parents led to the identification of four novel HSCR candidate genes: ATP7A, SREBF1, ABCD1 and PIAS2. This candidate gene selection was corroborated by the discovery of further rare variants in additional HSCR cases. Moreover, expression analyses revealed that all four genes are expressed in embryonic murine gastrointestinal tissues. Functional analyses using candidate gene-specific, neuronal-like CRISPR/Cas9-edited knockout cell clones demonstrated impaired differentiation, proliferation and/or cell survival capacity. Conclusions: Taken together, the presented study pipeline was proven to be suitable for the selection and validation of candidate genes as well as to gain insight into underlying pathomechanisms of HSCR. Overall design: For mRNA expression analyses by microarray profiling, murine embryonic regions of interest (pre-migratory vagal NCCs at stages E8.75 and E9.5; embryonic gut at E13.5, without stomach) were prepared. Embryonic tissues from each litter were pooled and three litters were analyzed per stage.