Haspin, also known as haploid germ cell-specific nuclear protein kinase, is an atypical serine/threonine kinase. It lacks sequence similarity with other eukaryotic protein kinases. Haspin is crucial for cell cycle progression, especially in mitosis, where it phosphorylates threonine 3 of histone 3 (H3T3), which recruits the chromosomal passenger complex to the inner centromere and ensures proper chromosome alignment and segregation. It also seems to have a role in post-meiotic spermatogenesis as it is highly expressed in the testis [1,2,3].

Depletion of Haspin by RNA interference in human cell lines causes premature loss of centromeric cohesin from chromosomes in mitosis, failure of metaphase chromosome alignment, and subsequent mitotic arrest [3]. In gallbladder carcinoma, knockdown of HASPIN inhibited cell proliferation, clone-formation ability, and promoted apoptosis both in vitro and in vivo, indicating its role in promoting cancer progression [4]. Inhibiting Haspin using small molecule inhibitors like CHR-6494 or 5-ITu can delay mitotic entry at the G1/S or S/G2 boundaries, suggesting its role in regulating cell cycle progression at multiple stages [5].

In conclusion, Haspin is essential for normal mitosis and cell cycle regulation. Its overexpression or deletion leads to defective mitosis. The study of Haspin through loss-of-function experiments, such as knockdown in cell lines, has revealed its significance in cancer development, making it a promising target for anticancer drug design.