FGF10 and the Mystery of Duodenal Atresia in Humans

Abstract

Background: Duodenal atresia (DA) is a congenital obstruction of the duodenum, which affects 1 in 7000 pregnancies and requires major surgery in the 1st days of life. Three morphological DA types are described. In humans, the association between DA and Down syndrome suggests an underlying, albeit elusive, genetic etiology. In mice, interruption of fibroblast growth factor 10 (Fgf10) gene signaling results in DA in 30–50% of embryos, supporting a genetic etiology. This study aims to validate the spectrum of DA in two novel strains of Fgf10 knock-out mice, in preparation for future and translational research.Methods: Two novel CRISPR Fgf10 knock-out mouse strains were derived and embryos generated by heterozygous plug-mating. E15.5–E19.5 embryos were genotyped with respect to Fgf10 and micro-dissected to determine the presence and type of DA.Results: One twenty seven embryos (32 wild-type, 34 heterozygous, 61 null) were analyzed. No wild-type or heterozygous embryos had DA. However, 74% of Fgf10 null embryos had DA (49% type 1, 18% type 2, and 33% type 3).Conclusion: Our CRISPR-derived strains showed higher penetrance of DA due to single-gene deletion of Fgf10 in mice than previously reported. Further, the DA type distribution in these mice more closely reiterated that observed in humans. Future experiments will document RNA and protein expression of FGF10 and its key downstream signaling targets in normal and atretic duodenum. This includes exploitation of modern, high-fidelity developmental tools, e.g., Fgf10flox/+–tomatoflox/flox mice.

The Role of Fibroblast Growth Factor 10 Signaling in Duodenal Atresia

“…FGF10 haploinsufficiency and FGF10 mutations have been linked to human disease, principally to craniofacial syndromes (Entesarian et al, 2005;Milunsky et al, 2006;Rohmann et al, 2006), chronic respiratory disease (Klar et al, 2011), but no human gastrointestinal tract atresia cases to date (Tatekawa et al, 2007). In contrast to this narrative of haploinsufficiency, homozygous Fgf10 invalidation appears necessary for DA in our animal models (Teague et al, 2018), albeit accompanied by non-survivable anomalies such as lung agenesis. Therefore, we hypothesize that DA is caused by conditional tissue-specific deletion in Fgf10, Fgfr2b or their downstream targets (e.g., spatially limited to the duodenum or foregut).…”

“…As will be discussed in detail in this review, murine studies have shown that interruption of the Fgf10-Fgfr2b signaling axis may result in DA in 35-75% of knockout mice (Fairbanks et al, 2004b;Kanard et al, 2005;Botham et al, 2012;Reeder et al, 2012b;Teague et al, 2018). This also supports a genetic etiology for DA in humans, however, no specific genetic cause has been demonstrated to date.…”

“…Importantly, the morphology of the duodenum is normal in Fgf10 hypomorphic mice, with no examples of DA in this setting of Fgf10 under-expression (Teague et al, 2018). Thus, even reduced Fgf10 signaling is sufficient for morphologically normal duodenal development.…”

“…We have recently reported a more human-like distribution of DA types, including type 2 DA, in two strains of CRISPR-derived Fgf10 knockout mouse (Teague et al, 2018). Of note, these newly reported strains; tm1 (B6-Fgf10<c.[464_470dup;506_645del]APNMu>); and tm2 (B6-Fgf10<c.495_507delAPNMu>) (Eppig et al, 2006) each demonstrate all three DA types ( Figures 1F-H), and a significantly higher penetrance of DA than previous animal models [74% (Teague et al, 2018) versus 35-45% (Fairbanks et al, 2004b;Kanard et al, 2005;Botham et al, 2012;Reeder et al, 2012b). The basis for such differences in type-distribution and penetrance when compared with previously reported Fgf10 knockout mouse strains remains unclear.…”

“…Annotations denote scale bars, and location of the pylorus, P. Arrows indicate location of an atresia. Figures (E-H) reused from Teague et al (2018), held under the CC-BY 4.0 license.…”