We first tested whether galectin-1 expression correlated with fibrosis progression in patients with myeloproliferative neoplasms, quantifying galectin-1 protein in bone marrow biopsies of 30 patients, including those with myelofibrosis (n = 14), non-fibrotic MPNs (essential thrombocythemia [ET], n = 9 and polycythemia vera [PV], n = 7) and age-matched healthy controls (n = 7, Table S4). Here, LGALS1 is linked to essential thrombocythemia.