PgmNr M312: Driving discovery and characterisation of novel genes important for bone biology by combining high-throughput mouse phenotyping and a tissue-based deep phenotyping platform.

Authors:
C. J. Lelliott 1 ; J. Logan 2 ; S. Beck-Cormier 3 ; D. Lafont 1 ; A. Swiatkowska 1 ; H. Protheroe 2 ; S. Pearson 1 ; S. Maguire 1 ; A. Gogakos 2 ; N. Butterfield 2 ; V. Leitch 2 ; J. K. White 1 ; L. Beck 3 ; G. R. Williams 2 ; J. H. Bassett 2 ; Sanger Mouse Pipelines

Institutes
1) Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK; 2) Molecular Endocrinology Group, Department of Medicine, Imperial College London, London, UK; 3) Institut National de la Sante et de la recherche Medicale, U791, LIOAD, Nantes, France.

Abstract:

Bone diseases causing abnormal development or maintenance of structure and function are an area of intense scientific investigation. Bone mineralization measurements by dual-energy X-ray absorptiometry (DEXA) are performed by many International Mouse Phenotyping Consortium members and could identify new candidate genes for focussed study. Data from 717 alleles from Sanger Mouse Pipelines (C57BL/6N, LabDiet #5021), was analysed by a Mixed-Model approach. 58 lines (8%) had hits for one or more bone mineral measurement: bone mineral density (BMD – 42 hits), volumetric BMD (vBMD – 19 hits) and bone mineral content accounting for body weight (BMC+BW – 37 hits).  Hits were distributed: 1 hit – 26 alleles, 2 hits – 26, 3 hits – 6. Using the power of the Origins of Bone and Cartilage Disease platform (http://www.boneandcartilage.com), we further characterised two lines that displayed reduced bone parameters.  Mice lacking the phosphate transporter Slc20a2 have reduced BMD and BMC+BW (BMC+BW effect size: Females -9.77%; Males -9.38%) in DEXA. Using microcomputed tomography and histology, we found that femurs from Slc20a2tm1a(EUCOMM)Wtsi-/- mice show impaired linear growth, particularly at younger ages.  Slc20a2-/- femurs display delayed ossification linked to reduced growth plate width, as well as reduced trabecular bone content and reduced mineralization in both trabecular and cortical bone.  Consequently, the mechanical properties of Slc20a2-/- femurs were altered in a three-point bend test, resulting in weak, brittle but flexible bones. Similarly, mice lacking Tram2, a component of the translocon, had significantly reduced BMD, vBMD and BMC+BW (BMC+BW effect size: Females -18.67%; Males -17.93%) in DEXA.  Femurs from Tram2tm1a(KOMP)Wtsi-/- mice were short, with thinner cortical bone, less trabecular bone and were weak yet flexible in the three-point bend test.  As well as long-bone phenotypes, both Slc20a2-/- and Tram2-/- mice had abnormal skull and craniofacial morphologies. In Tram2-/- mice, this, combined with disrupted ossicle shape, correlates with a substantially raised hearing threshold without indication of auditory sensorineural impairment.  Overall, this data shows the additive value of combining high-throughput phenotyping with specialist platforms to enhance the knowledge generated for specific areas of high medical need.