Comment on "Critical role of the potential O-linked glycosylation sites of CXCR4 in cell migration and bone marrow homing of hematopoietic stem progenitor cells".

This study by Pan et al. reveals the critical role of O-linked glycosylation at Ser-5 and Ser-9 of mouse CXCR4 in HSPC migration and BM homing. Using CRISPR/Cas9-mediated mutagenesis, in vitro assays, and in vivo models, they show these sites are essential for CXCL12 binding, downstream signaling, and HSPC engraftment. CXCR4[SSA59A] mutants display impaired FAK/MEK/PI3K phosphorylation and reduced homing efficiency without embryonic lethality, offering new insights into CXCR4 glycosylation's structural-functional relationship. The validation across multiple cell types and lectin blot use highlight the methodological rigor. These findings revolutionize chemokine receptor biology understanding and could optimize clinical HSPC transplantation. However, the O-glycosylation characterization is indirect. Future studies using advanced techniques like site-specific O-glycosylation mapping or glycosylation-deficient cell lines could provide more direct evidence. Overall, this work is a significant contribution to glycobiology and stem cell homing mechanisms, setting a high standard for studying receptor post-translational modifications and aligning with STEM CELLS' mission of publishing impactful translational research.