MBNL proteins in health, disease, and therapeutic applications.

The Muscleblind-like (MBNL) family comprises evolutionarily conserved RNA-binding proteins that interact with target RNAs via zinc finger domains. MBNLs orchestrate RNA processing, particularly alternative splicing, driving the developmental fetal-to-adult isoform switch across numerous target transcripts. This transition is a cornerstone in the process of MBNL-maintained cellular homeostasis and fails in many pathological conditions associated with deregulated expression or function of specific MBNL paralogs. This review provides current insights into the roles of MBNL genes and proteins in both health and disease. We examine their genomic architecture and protein organization and synthesize key insights from animal models to delineate the selective and compensatory functions of individual MBNL paralogs in physiology. To illustrate the roles of MBNLs in disease, we outline nucleotide repeat expansion disorders marked by their functional depletion, with a primary focus on myotonic dystrophy (DM). We also highlight selected cancer studies that have demonstrated the dual roles of MBNLs in tumorigenesis, encompassing both pro-oncogenic and tumor suppressive functions. Finally, using DM as a model, we review evidence for the therapeutic potential of endogenous MBNL gene modulation and argue that analogous strategies could be adapted and tailored to restore MBNL homeostasis in other disorders involving their dysregulation.