Dominant and recessive mutations in
podocalyxin (PODXL) are associated with human
kidney disease. Interestingly, some PODXL mutations manifest as
anuria while others are associated with proteinuric
kidney disease. PODXL heterozygosity is associated with adult-onset
kidney disease and
podocalyxin shedding into the urine is a common
biomarker of a variety
nephrotic syndromes. It is unknown, however, how various lesions in PODXL contribute to these disparate disease pathologies. Here we generated two mouse stains: one that deletes Podxl in developmentally mature podocytes (Podxl∆Pod) and a second that is heterozygous for
podocalyxin in all tissues (Podxl+/-). We used histologic and ultrastructural analyses, as well as clinical chemistry assays to evaluate kidney development and function in these strains. In contrast to null knockout mice (Podxl-/-), which die shortly after birth from
anuria and
hypertension, Podxl∆Pod mice develop an acute congenital
nephrotic syndrome characterized by
focal segmental glomerulosclerosis (FSGS) and
proteinuria. Podxl+/- mice, in contrast, have a normal lifespan, and fail to develop
kidney disease under normal conditions. Intriguingly, although wild-type C57Bl/6 mice are resistant to
puromycin aminonucleoside (PA)-induced
nephrosis (PAN), Podxl+/- mice are highly sensitive and PA induces severe
proteinuria and collapsing FSGS. In summary, we find that the developmental timepoint at which
podocalyxin is ablated (immature vs. mature podocytes) has a profound effect on the urinary phenotype due to its critical roles in both the formation and the maintenance of podocyte ultrastructure. In addition, Podxl∆Pod and Podxl+/- mice offer powerful new mouse models to evaluate early
biomarkers of proteinuric
kidney disease and to test novel
therapeutics.