Project Details
Projekt
Identification of novel disease genes for monogenic forms of early-onset low BMD disorders
Applicant
Professorin Dr. Kerstin Kutsche
Subject Area
Orthopaedics, Traumatology, Reconstructive Surgery
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 517063424
Primary early-onset low bone mineral density (BMD) disorders belong to monogenic forms of osteoporosis that are caused by pathogenic variant(s) in a single gene. Routine genetic testing in patients with a primary low BMD disorder by gene panels or whole-exome sequencing (WES) followed by a phenotype-driven virtual gene panel can detect a pathogenic variant in a disease gene. In the cohort of patients with early-onset low BMD disorder (P1), genetic testing revealed a variant of unknown significance (VUS) in 264 patients. We will reassess all VUSs to potentially reclassify them that will lead to a molecular diagnosis in several patients. Reclassification is based on the strength of available evidence, which includes the presence of the VUS in human variant databases, the allele frequency of the VUS in population databases, computational and predictive data, and functional data from the scientific literature. A VUS will be segregated in the patient’s family (P1) and a few convincing VUSs will be selected for functional studies. To identify novel disease genes (candidate genes) in genetically unsolved patients with early-onset low BMD disorder, we will re-analyze existing proband-only WES and whole-genome sequencing (WGS) data of 56 and 100 patients, respectively. First, we will design and use a phenotype-driven virtual panel for recently published disease genes to identify a pathogenic variant. Second, we will use a gene-based candidate gene prioritization approach to discover genes that show an enrichment of rare variants in the patient cohort. Using reverse phenotyping in patient subsets sharing variants in the same gene, we will search for a specific combination of clinical features, osteological parameters, immunological and/or serum metabolic alterations (P1, P6, P7, CP2). For patients who have not been molecularly diagnosed and do not have WGS data, we will use WGS to discover novel disease genes. We selected 22 patients with early-onset low BMD disorder or non-classical hypophosphatasia. Family-based WGS data analysis will be carried out for all variant types in the exome and selected non-genic regions. Changes in several parameters will help in candidate gene prioritization. Candidate genes will be analyzed in the existing WES and WGS datasets to find unrelated patients with a potential pathogenic variant. Following the identification of candidate genes, we will perform functional studies to confirm the pathogenicity of variants and investigate the pathomechanism. We have a wide range of biochemical and cell biological methods available and will collaborate with P1, P4, P6 and/or P7 depending on the gene. As an exemplary project, we will perform functional studies using fibroblasts from a patient who carries the homozygous variant p.(Leu236_Arg238dup) in the disease gene TMEM53. Overall, the goal of this project is to increase our knowledge of novel disease genes for this group of osteological disorders.
DFG Programme
Clinical Research Units
