Fgfr3 enhancer deletion markedly improves all skeletal features in a mouse model of achondroplasia
Marco Angelozzi, Arnaud Molin, Anirudha Karvande, Ángela Fernández-Iglesias, Samantha Whipple, Andrew M. Bloh, Véronique Lefebvre
Marco Angelozzi, Arnaud Molin, Anirudha Karvande, Ángela Fernández-Iglesias, Samantha Whipple, Andrew M. Bloh, Véronique Lefebvre
View: Text | PDF
Research Article Bone biology Genetics

Fgfr3 enhancer deletion markedly improves all skeletal features in a mouse model of achondroplasia

Abstract

Achondroplasia, the most prevalent short-stature disorder, is caused by missense variants overactivating the fibroblast growth factor receptor 3 (FGFR3). As current surgical and pharmaceutical treatments only partially improve some disease features, we sought to explore a genetic approach. We show that an enhancer located 29 kb upstream of mouse Fgfr3 (–29E) is sufficient to confer a transgenic mouse reporter with a domain of expression in cartilage matching that of Fgfr3. Its CRISPR/Cas9-mediated deletion in otherwise WT mice reduced Fgfr3 expression in this domain by half without causing adverse phenotypes. Importantly, its deletion in mice harboring the ortholog of the most common human achondroplasia variant largely normalized long bone and vertebral body growth, markedly reduced spinal canal and foramen magnum stenosis, and improved craniofacial defects. Consequently, mouse achondroplasia is no longer lethal, and adults are overall healthy. These findings, together with high conservation of –29E in humans, open a path to develop genetic therapies for people with achondroplasia.

Authors

Marco Angelozzi, Arnaud Molin, Anirudha Karvande, Ángela Fernández-Iglesias, Samantha Whipple, Andrew M. Bloh, Véronique Lefebvre

×

Figure 5

–29E deletion lessens skull and vertebral malformations of achondroplastic mice.

Options: View larger image (or click on image) Download as PowerPoint
–29E deletion lessens skull and vertebral malformations of achondroplas...
(A) μCT reconstruction images of the skulls of representative P25 mice with the indicated genotypes. Top row, lateral view; bottom row, apical view. Scale bar: 3 mm. (B) Skull length, width, and base lengths of mice from same groups as those shown in A. Left, measurement schematic. Bars and brackets represent means and SDs, respectively. Each symbol represents a distinct mouse. Blue dots, males; pink triangles, females. The percentages of average values for each genotype group relative to WT mice are indicated. Statistical analysis was performed using 1-way ANOVA followed by Tukey’s multiple comparison tests. *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001; ****P ≤ 0.0001. (C) μCT reconstruction images of the skull base of representative mice. BO, basioccipital bone; BS, basisphenoid bone; PS, presphenoid bone. Red arrows, spheno-occipital and inter-sphenoid synchondroses. Scale bar: 100 μm. (D) μCT reconstruction images of the occipital area of skulls from representative mice showing the foramen magnum (FM). Scale bar: 2 mm. (E) Foramen magnum areas measured for the same mice as in B. (F) μCT reconstruction images of the L4 vertebrae from representative mice. Top row, coronal views; bottom row, transverse views. Scale bar: 0.5 mm. (G) Vertebral body length, interpedicular distance and spinal canal area measured for the L4 vertebrae of same mice as in B. Left, measurement schematic.