Identifying endotypes in monogenic osteoporosis using a multifaceted approach

Precision Medicine Project - Identifying endotypes in monogenic osteoporosis using a multifaceted approach

Supervisor(s): Dr Erika Kague, Dr Athina Spiliopoulou, Prof Stuart Ralston & Prof Outi Makitie (Karolinska Institutet)
Centre/Institute: Institute of Genetics and Cancer

Background

Fragility fractures are a major public health concern. In the UK alone, over 3.5 million individuals are affected, with an estimated annual global healthcare cost of over $400 billion. The most common cause is low bone mineral density (BMD) in the form of osteopenia or osteoporosis. The causal genes for bone fragility and underlying biological pathways remain largely unknown so there is a fundamental gap in our understanding of disease mechanisms for bone fragility and an urgent need for a precision medicine approach. Genome wide association studies have identified over 500 loci associated with BMD but only a handful of these variants have been associated with fragility fractures. In contrast, genetic analysis in rare inherited diseases associated with fragility fractures have identified pathogenic variants in genes which have a large effect size on fractures. Accordingly, studies of rare, inherited forms of bone disease, provide a unique opportunity to understand the disease mechanisms implicated in Our collaborators at the Karolinska Institute, led by Prof. Outi Makitie, have established unique familial cohorts with rare monogenic osteoporosis caused by mutations in WNT1, PLS3, and the newly identified gene SGMS2. While all these genes are implicated in osteocyte function, the specific disease mechanisms driven by PLS3 and SGMS2 mutations and bone fragility are not well-understood. Osteocytes, the most abundant cells in bone, act as endocrine regulators, releasing factors into the circulation. We therefore hypothesise that pathogenic variants in bone fragility may lead to unique patterns of osteocyte dysfunction, which can be detected as a specific "protein signature" in the serum plasma. The identification of these signatures will advance our current knowledge about the molecular mechanisms associated tih bone fragility, enabling the discovery of novel disease endotypes and therapeutic targets.

Aims 

The overarching goal of this project is to identify distinctive protein signatures in rare monogenic disease associated with fragility fractures and to apply this understanding to define why some patients with osteoporosis are predisposed to fragility fractures whereas others are not. 

Aim 1: Identify distinct plasma protein signatures in rare monogenic osteoporosis cohorts. 

  • Objective 1.1: Perform quantitative proteomics on plasma samples from cohorts with WNT1, PLS3, and SGMS2 mutations and with Pregnancy Associated Osteoporosis (PAO) to identify differentially expressed proteins compared to healthy controls from the same families.
  • Objective 1.2: Use bioinformatics and pathway analysis to identify biological processes and signalling networks that are specifically dysregulated in each monogenic osteoporosis cohort. Perform univariate analysis to identify common proteins associated with osteoporosis from UK-Biobank.

Aim 2: Connect protein plasma signature with functional disruption of bone endochrine cells. 

  • Objective 2.1: Generate a SGMS2 knock-in osteocyte cell model using CRISPR-Cas9. Analyse the impacts with a focus on changes in secreted proteins (secretome), bone matrix regulation, and cell morphology. Compare proteins from secretome of osteocytes to those identified in human bone fragility cohorts and osteoporosis in UK Biobank.
  • Objective 2.2: Support our functional findings of osteocytes through development of the zebrafish with genetic perturbations on sgms2a and sgms2b. We will not only analyse skeletal changes and osteocyte organisation in adult fish, but also bone quality and strength thorugh advanced methodologies, such as assessment of collagen aligment in in vivo.

Training outcomes

This PhD project offers an exceptional opportunity for the student to acquire a diverse range of skills essential for a career in precision medicine and translational research. 

  • Data Analysis and Bioinformatics: Data processing, statistical analysis, and advanced pathway and network analysis of large-scale proteomic datasets
  • Molecular and Cell Biology: mammalian cell culture and maintenance of zebrafish, genetic manipulation of cells and fish using CRISPR-Cas9.
  • Organismal Biology: zebrafish maintenance, skeletal formation, skeletal phenotyping, advanced high-resolution imaging modalities (micro-computed tomography, confocal microscopy, 3D imaging analysis
  • Research & Communication: Scientific writing for publications and proposals, public speaking and presenting at international conferences, and collaborative teamwork within a multidisciplinary environment.

References

  1. Pekkinen M, Terhal PA, Botto LD, Henning P, Mäkitie RE, Roschger P, Jain A, Kol M, Kjellberg MA, Paschalis EP, van Gassen K, Murray M, Bayrak-Toydemir P, Magnusson MK, Jans J, Kausar M, Carey JC, Somerharju P, Lerner UH, Olkkonen VM, Klaushofer K, Holthuis JC, Mäkitie O. Osteoporosis and skeletal dysplasia caused by pathogenic variants in SGMS2. JCI Insight. 2019 Apr 4;4(7):e126180. doi: 10.1172/jci.insight.126180. PMID: 30779713; PMCID: PMC6483641.
  2. Mäkitie RE, Hackl M, Weigl M, Frischer A, Kämpe A, Costantini A, Grillari J, Mäkitie O. Unique, Gender-Dependent Serum microRNA Profile in PLS3 Gene-Related Osteoporosis. J Bone Miner Res. 2020 Oct;35(10):1962-1973. doi: 10.1002/jbmr.4097. Epub 2020 Jul 2. PMID: 32453450.
  3. Mäkitie RE, Blouin S, Välimäki VV, Pihlström S, Määttä K, Pekkinen M, Fratzl-Zelman N, Mäkitie O, Hartmann MA. Abnormal Bone Tissue Organization and Osteocyte Lacunocanalicular Network in Early-Onset Osteoporosis Due to SGMS2 Mutations. JBMR Plus. 2021 Aug 20;5(11):e10537. doi: 10.1002/jbm4.10537. PMID: 34761145
  4. Laine, C. M., K. S. Joeng, P. M. Campeau, R. Kiviranta, K. Tarkkonen, M. Grover, J. T. Lu, M. Pekkinen, M. Wessman, T. J. Heino, V. Nieminen-Pihala, M. Aronen, T. Laine, H. Kroger, W. G. Cole, A. E. Lehesjoki, L. Nevarez, D. Krakow, C. J. Curry, D. H. Cohn, R. A. Gibbs, B. H. Lee and O. Makitie (2013). "WNT1 mutations in early-onset osteoporosis and osteogenesis imperfecta." N Engl J Med 368(19): 1809-1816.
  5. Kague, E., Turci, F., Newman, E., Yang, Y., Brown, K. R., Aglan, M. S., Otaify, G. A., Temtamy, S. A., Ruiz-Perez, V. L., Cross, S., Royall, C. P., Witten, P. E. and Hammond, C. L. “3D assessment of intervertebral disc degeneration in zebrafish identifies changes to bone density that prime disc disease” (2021). Nat Bone Res.

Apply Now

Click here to Apply Now

  • The deadline for 26/27 applications is Monday 12th January 2026
  • Applicants must apply to a specific project. Please ensure you include details of the project on the Recruitment Form below, which you must submit to the research proposal section of your EUCLID application.
  • Please ensure you upload as many of the requested documents as possible, including a CV, at the time of submitting your EUCLID application.  

Q&A Sessions

Supervisor(s) of each project will be holding a 30 minute Q&A session in the first two weeks of December. 

If you have any questions regarding this project, you are invited to attend the session on TBC via Microsoft Teams. Click here to join the session.

This article was published on