FGF10 and the Mystery of Duodenal Atresia

Abstract

The cause of duodenal atresia (DA) is not known. Tandler’s “solid cord” hypothesis conflicts with current biological evidence. In humans, a genetic aetiology is supported by the association with Trisomy 21. Interruption of Fgf10 is the strongest genetic link to DA in mice, but the lethality of associated defects means it is an unlikely cause of DA in humans. It is hypothesised that DA is caused by a genetic change downstream of the FGF10/FGFR2b signalling pathway. This thesis aims to identify gene signalling changes that may cause DA.

Aim 1 was to validate the spectrum of DA present in CRISPR-derived Fgf10-/- embryos. These embryos demonstrated a higher penetrance of DA than previously reported, with morphology distribution closely reiterating that observed in humans. DA penetrance and phenotype severity increased with gestational age, suggesting an evolutionary nature.

Aim 2 was to evaluate gene expression associated with DA, through the use of RNA-seq and RT-qPCR. Whilst multiple genes were up- and downregulated in the absence of Fgf10, a cluster, otherwise associated with pyloric muscle specification, was of particular interest. This possible interplay between pyloric development and DA unveils a new hypothesis, that: in the duodenum of Fgf10-/- mice, anterior-posterior mis-patterning with ectopic pyloric specification may be the basis of DA formation, and loss luminal continuity.

Aim 3 was to develop an organoid model to facilitate future ex vivo DA research. Normal organoids were shown to grow from wild-type duodenum and growth patterns differed between Fgf10 genotypes.

This thesis forms a foundation for future research into DA aetiology. Further animal research must combine gene analysis of human patients born with DA, to identify putative causative genes/pathways. Determining the cause of DA in humans is a clinical and scientific imperative, with immediate therapeutic relevance to antenatal counselling and future clinical research to ameliorate or prevent DA.