Modeling ANKRD26 5’-UTR mutation-related thrombocytopenia in zebrafish

Mutations in 5’-untranslated region (5’-UTR) of ANKRD26 (ankyrin repeat domain-containing protein 26) are associated with hereditary thrombocytopenia-2 (THC2). However, the causative role of these mutations and the mechanisms underlying THC2 are not fully established. Here, we report for the first time that zebrafish carrying a deletion of two nucleotides (Δ2) in the 5’-UTR of ankrd26 recapitulate some of the key laboratory features of THC2. Ankrd26^ku6 (homozygous for the Δ2 deletion in the 5’-UTR) fish larvae exhibited significantly increased expression of ankrd26 mRNA and protein. Ankrd26^ku6 adult fish exhibited spontaneous thrombocytopenia. Furthermore, the thrombocytes from ankrd26^ku6 showed an enhanced ability to adhere and aggregate on a collagen surface under flow. Proteomic profiling demonstrated a dramatic upregulation of Ninjurin1 in young thrombocytes from ankrd26^ku6 fish compared with those from wild-type controls. The ankrd26^ku6 fish with a homozygous nacre allele developed myelodysplastic syndrome at old age. ANKRD26 protein levels were also significantly increased in platelets and plasma from patients with immune thrombotic thrombocytopenic purpura compared with those from healthy controls. We conclude that ANKRD26 overexpression, resulting from either hereditary or acquired mechanisms, may contribute to thrombocytopenia, thrombosis, and hematologic malignancies.