Recent advances show that human focal segmental glomerulosclerosis (FSGS) is a primary podocytopathy caused by podocyte-specific gene mutations including NPHS1, NPHS2, WT-1, LAMB2, CD2AP, TRPC6, ACTN4 and INF2.
While earlier reports suggested that mutations causing FSGS-CMT are restricted to exons 2 and 3 of the INF2 gene, we found one CMT-FSGS causing mutation (p.Glu184Lys) in exon 4 extending the critical region of INF2 for rapid CMT-FSGS molecular genetic diagnosis.
In our center, more than 30% (278/911) of kidney transplant (KTx) recipients were diagnosed with a causal nephropathy: Prevalence of rare genetic disorders in this group was 4.32% (12/278), including 2,8-dihydroxyadeninuria (2,8-DHA) disease (n = 2), HNF-1B-associated nephropathy (n = 2), UMOD-related nephropathy (n = 5), Fabry disease (n = 1), INF2focal segmental glomerulosclerosis (n = 1), and Senior-Løken syndrome (n = 1).
Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology.
Recently, mutations in the INF2 gene, which encodes inverted formin-2, were identified in patients with focal segmental glomerulosclerosis and a dominant intermediate form of CMT (CMTDIE, OMIM #614455).
In three distinct models of FSGS (5/6-nephrectomy + DOCA-salt; the murine transgenic chronic Thy1.1 model; or the MWF rat) and in human biopsies, the primary injury to induce FSGS associated with focal activation of PECs and the formation of cellular adhesions to the capillary tuft.
INF2 mutations appear to cause many cases of FSGS-associated Charcot-Marie-Tooth neuropathy, showing that INF2 is involved in a disease affecting both the kidney glomerulus and the peripheral nervous system.