Transposable elements as genome regulators in normal and malignant haematopoiesis.

Transposable elements (TEs) constitute over half of the human genome and have played a profound role in genome evolution. While most TEs have lost the ability to transpose, many retain functional elements that serve as drivers of genome innovation, including the emergence of novel genes and regulatory elements. Recent advances in experimental and bioinformatic methods have provided new insights into their roles in human biology, both in health and disease. In this review, we discuss the multifaceted roles of TEs in haematopoiesis, highlighting their contributions to both normal and pathological contexts. TEs influence gene regulation by reshaping gene-regulatory networks, modulating transcriptional activity, and creating novel regulatory elements. These activities play key roles in maintaining normal haematopoietic processes and supporting cellular regeneration. However, in haematological malignancies, TE reactivation can disrupt genomic integrity, induce structural variations, and dysregulate transcriptional programmes, thereby driving oncogenesis. By examining the impact of TE activity on genome regulation and variation, we highlight their pivotal roles in both normal haematopoietic processes and haematological cancers.