Isoform-specific roles of QKI-6 and QKI-7 direct Schwann cell lineage progression and enhance peripheral nerve regeneration

Peripheral nerve injury presents a major therapeutic challenge owing to limited endogenous repair and incomplete functional recovery. Schwann cells (SCs), the principal glia of the peripheral nervous system, support axonal integrity and regeneration, but the post-transcriptional mechanisms regulating their development and reparative function remain poorly defined. Here, we investigated the isoform-specific roles of the RNA-binding protein Quaking (QKI), which is alternatively spliced into nuclear (QKI-5) and cytoplasmic (QKI-6 and QKI-7) variants, in governing human Schwann lineage progression. Using a human pluripotent stem cell-derived Schwann cell precursor (SCP) platform, we found that QKI-6 and QKI-7 are selectively upregulated during SCP-to-SC transition, whereas QKI depletion disrupts SCP viability, differentiation, and splicing fidelity. Transcriptomic and rMATS analysis identified more than 800 QKI-dependent splicing events, including disease-relevant isoform shifts in PLP1 and PMP22. Isoform-specific rescue and gain-of-function assays revealed that QKI-6 supports SCP expansion and mitotic progression, whereas QKI-7 promotes SC maturation and neurotrophic output. In a mouse sciatic nerve transection model, transplantation of QKI-7-overexpressing SCPs or SCs significantly enhanced axonal regeneration, remyelination, and motor recovery compared with unmodified or QKI-6-expressing counterparts. Histological analysis confirmed improved donor cell engraftment, myelin protein expression, and neurotrophin levels in QKI-7-modified grafts. These findings establish a sequential, isoform-dependent mechanism of Schwann lineage control and nominate QKI-7 as a candidate for engineering reparative glial cells with enhanced regenerative capacity. Isoform-targeted modulation of RNA-binding proteins may represent a strategy to overcome intrinsic limitations in glial cell therapy for peripheral nerve disorders.