Tanycytes in Alzheimer's Disease and Frontotemporal Dementia

Inclusion Criteria: * Subjects able to undergo a lumbar puncture * Subjects registered with the French Social Security, in agreement with the French law on biomedical experimentation To be assigned in the study subgroups, subjects will have to fulfill the specific following criteria: Group 1: Controls * absence of cognitive complaint (completion of the memory complaint questionnaire) * absence of significant cognitive impairment: normal MMSE according to age and education levels * Subjects capable of and willing to comply with the protocol and to give their written informed consents after having received and understood the subject information Group 2: Alzheimer's Disease * Diagnosis of probable Alzheimer's disease dementia according to the NIA 2011 criteria1 * MMSE ≥ 16 * Subjects who have a study partner. The study partner is required to complete several scales and to drive back the subject after the lumbar puncture for safety reasons. If the subjects or their study partners are not able to drive, their transport fees will be reimbursed by the promotor * Subjects and study partners capable of and willing to comply with the protocol and to give their written informed consents after having received and understood the subject information. According to the legal protection or the mental capacities of the subject, the subject will be accompanied by a legally acceptable representative during this procedure Group 3: Frontotemporal Dementia * Diagnosis of probable frontotemporal dementia according to the FTDC 2011 criteria2 * MMSE ≥ 16 * Subjects who have a study partner. The study partner is required to complete several scales and to drive back the subject after the lumbar puncture for safety reasons. If the subjects or their study partners are not able to drive, their transport fees will be reimbursed by the promotor * Subjects and study partners capable of and willing to comply with the protocol and to give their written informed consents after having received and understood the subject information. According to the legal protection or the mental capacities of the subject, the subject be accompanied by a legally acceptable representative during this procedure Exclusion Criteria: * General exclusion criteria: * Subjects with dementia caused by a non-neurodegenerative disease, including patients with severe cerebrovascular risk factor load * Subjects who have contraindications to perform a lumbar puncture * Subjects who have contraindications to perform a MRI scan * Weighted less than 45 kg Associated illnesses or conditions: * Subjects with other neurodegenerative disease such as Lewy body dementia and Parkinson's disease * Subjects with other serious neurological disorder such as brain tumor, stroke, epilepsy, hydrocephalus and any condition which contraindicates, in the investigator's judgment, entry to the study; * Subjects with severe metabolic or endocrine disorder (excluding hypothyroidism under stable hormone replacement therapy, controlled type 2 diabetes or common dyslipidaemia), previously known or identified at screening * Subjects under metformin treatment. Biological exclusion criteria: * Subjects with known active HCV, HBV or HIV * Subjects with clinical or significant laboratory abnormalities, previously known or identified at screening, in the judgment of the investigator Others: * Pregnancy or breastfeeding or Women of childbearing age without effective contraception (a pregnancy test will be done) * Subjects with excessive alcohol intake or drug abuse, in the judgment of the investigator * Subjects who, in the opinion of the investigator, have a risk of non-compliance to the study procedures or who are otherwise not appropriate to include in this clinical trial (for example, being impossible to contact in case of emergency)