Molecular mechanisms of recessive and dominant mutations in the small vessel disease-related high temperature requirement protease HTRA1

• Applicants: Dr. Nathalie Beaufort; Professor Dr. Martin Dichgans
• Subject Area: Molecular and Cellular Neurology and Neuropathology ; Clinical Neurology; Neurosurgery and Neuroradiology ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 320697423

Cerebral small vessel diseases (SVDs) are a major cause of both stroke and dementia but therapeutic options are still very limited. Mendelian conditions have been instrumental in defining the molecular, cellular, and pathophysiological basis of SVDs. Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a recessive early onset familial SVD caused by loss-of-function mutations in the high temperature requirement protein HTRA1 gene. HTRA1, a secreted protease, assembles as trimers and higher order oligomers to form a mature and proteolytically active complex. Our previous results indicate that SVD-related mutations in HTRA1 result in molecularly diverse effects including but not limited to assembly defects. In collaboration with others, we further found that heterozygous mutations in HTRA1 associate with autosomal dominant late onset SVD but the distinguishing features of recessive and dominant HTRA1 mutations remain to be defined. The current application addresses three major aims: i) to determine the effects of pathogenic mutations on key molecular and cellular aspects of HTRA1 function (mRNA stability, protein stability, trimer assembly, ECM integration, substrate recognition); ii) to investigate, whether heterozygous HTRA1 mutations have a dominant negative effect on enzyme function and determine the underlying mechanisms; iii) to explore strategies to restore HTRA1 function as a potential basis for future targeted therapies. This aim is motivated by our preliminary results indicating it is be possible to restore enzymatic activity for individual mutations. To achieve these aims we will employ a variety of genetic tools, biochemical techniques and cell biology approaches, which will be applied to both transfected cells and primary cells from patients and control subjects. Regardless of the specific outcomes this project will provide novel insights into key mechanisms of CARASIL as well as autosomal dominant forms of HTRA1-related SVD. In addition, the project might open a therapeutic perspective for patients carrying mutations with defined molecular properties.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Professorin Dr. Elisabeth Tournier-Lasserve