Heterogeneous nuclear ribonucleoprotein F deficiency in mouse podocyte promotes podocytopathy mediated by methyltransferase-like 14 nuclear translocation resulting in Sirtuin 1 gene inhibition

Heterogeneous nuclear ribonucleoprotein F (HnRNP F) is a key regulator for nucleic acid metabolism; however, whether HnRNP F expression is important in maintaining podocyte integrity is unclear. Nephroseq analysis from a registry of human kidney biopsies was performed. Age- and sex-matched podocyte-specific HnRNP F knockout (HnRNP F^POD KO) mice and control (HnRNP F^fl/fl) were studied. Podocytopathy was induced in male mice (more susceptible) either by adriamycin (ADR)- or low-dose streptozotocin treatment for 2 or 8 weeks. The mouse podocyte cell line (mPODs) was used in vitro. Nephroseq data in three human cohorts were varied greatly. Both sexes of HnRNP F^POD KO mice were fertile and appeared grossly normal. However, male 20-week-old HnRNP F^POD KO than HnRNP F^fl/fl mice had increased urinary albumin/creatinine ratio, and lower expression of podocyte markers. ADR- or diabetic- HnRNP F^POD KO (vs. HnRNP F^fl/fl) mice had more severe podocytopathy. Moreover, methyltransferase-like 14 (Mettl14) gene expression was increased in podocytes from HnRNP F^POD KO mice, further enhanced in ADR- or diabetic-treated HnRNP F^POD KO mice. Consequently, this elevated Mettl14 expression led to sirtuin1 (Sirt1) inhibition, associated with podocyte loss. In mPODs, knock-down of HnRNP F promoted Mettl14 nuclear translocation, which was associated with podocyte dysmorphology and Sirt1 inhibition-mediated podocyte loss. This process was more severe in ADR- or high glucose- treated mPODs. Conclusion: HnRNP F deficiency in podocytes promotes podocytopathy through activation of Mettl14 expression and its nuclear translocation to inhibit Sirt1 expression, underscoring the protective role of HnRNP F against podocyte injury.