To improve some problems accompanying gene introduction to human hematopoietic cells using either of retroviral vector or physical technique of gene introduction.

Polypeptides are provided, for examples, that include a haemoglobin alpha chain wherein the C-terminal hydrophobic domain has been substituted or deleted, polypeptides that include a haemoglobin alpha chain wherein the C-terminal haptoglobin joint domain has been substituted or deleted, or polypeptides including amino acid 1-97 of a human haemoglobin alpha chain.