ACTB and myeloproliferative neoplasm: Tg(β-actin:loxP-eGFP-loxP:K-RASG12D) zebrafish crossed to a zebrafish carrying a heat shock promoter (hsp70) driving cre expression resulted in the development of a myeloproliferative neoplasm (MPN) between 34 to 66 days of life, with increased myelomonocytes and myeloid precursors in kidney marrow, and a significant loss of mature erythrocytes [51].