The 2019 and 2021 International Workshops on Alport Syndrome

Abstract

In 1927 Arthur Cecil Alport, a South African physician, described a British family with an inherited form of kidney disease that affected males more severely than females and was sometimes associated with hearing loss. In 1961, the eponymous name Alport syndrome was adopted. In the late twentieth century three genes responsible for the disease were discovered: COL4A3, COL4A4, and COL4A5 encoding for the α3, α4, α5 polypeptide chains of type IV collagen, respectively. These chains assemble to form heterotrimers of type IV collagen in the glomerular basement membrane. Scientists, clinicians, patient representatives and their families, and pharma companies attended the 2019 International Workshop on Alport Syndrome, held in Siena, Italy, from October 22 to 26, and the 2021 online Workshop from November 30 to December 4. The main topics included: disease re-naming, acknowledging the need to identify an appropriate term able to reflect considerable clinical variability; a strategy for increasing the molecular diagnostic rate; genotype-phenotype correlation from monogenic to digenic forms; new therapeutics and new therapeutic approaches; and gene therapy using gene editing. The exceptional collaborative climate that was established in the magical medieval setting of Siena continued in the online workshop of 2021. Conditions were established for collaborations between leading experts in the sector, including patients and drug companies, with the aim of identifying a cure for Alport syndrome.

Fig. 1. Visual summary of current standard of care treatment recommendations and individual lifetime risk for ESRF according to the gene variant and additional risk factors.

Red: patients with—classical‖ Alport syndrome and a 100% risk for early ESRF. Therapy should be initiated at diagnosis (in children 2 years and older) at very early stages of disease. Nephroprotective therapy has the potential to reduce lifetime risk for ESRF to 50% in those with less severe missense variants. Yellow: heterozygous patients with an intermediate lifetime risk of 5 to 40% for ESRF. If therapy is initiated early at microalbuminuria (or even micro-haematuria in patients with additional risk factors), nephroprotective therapy has the potential to reduce lifetime risk to 1 to 5%, only. Green: heterozygous individuals with a low risk for ESRF, which is <1%, if patients remain in a disease management programme to check for additional risk factors for their lifetime.

Fig. 2. Current and possible future treatment options.

Summary of current and possible future treatment options and postulated effects on (the high) cardiovascular risk of patients with Alport syndrome, which also needs to be addressed.

Fig. 3. Gene editing approaches: comparison between direct and indirect strategies.

The CRISPR/Cas9 direct approaches are targeting straightforward mutated genes (A, B). The CRISPR/Cas9 indirect approaches are based on the action of endonuclease deficient activity dCas9 fused to either transcriptional activators or repressors that either upregulate (CRISPRa) or silence (CRISPRi) genes (respectively) relevant to the pathophysiology of AS (C, D). A TTR gene mutated sequence is edited in humans by spCas9 alone. Indel (insertion/deletion) is created after the cut and the gain of function variant (the protein precipitates in aggregates dangerous for the cell) is edited in a loss of function allele. B The loss of function variant in COL4A5 gene is edited to the normal sequence, by means of spCas9, in cultured cells and animal models employing CRISPR/Cas9 approach. C The COL4A6 gene, a minor basement membrane gene, is forced by dCas9/CRISPRa to be overexpressed in podocytes, which should replace the missing α3α4α5(IV) network with the α5α5α6(IV) network; this could slow kidney disease progression. D The LAMA2 downstream gene is silenced by the dCas9/CRISPRi in glomerular cells, which should reduce laminin α2 in the GBM and slow kidney disease progression.

Fig. 4. Basic science approaches.

In the upper panel are summarised the new studies and approaches on podocytes, GEC and GBM ranging from CRISPR/Cas9 application to miRs that stimulate podocyte biology, proteomics and chaperones in combination with studies on podocytes cytoskeleton. In the lower panel the downstream applications of these: imagine technology, organoids in 3D culture, glomerulus on a chip to mimic the glomerular structure in vitro, and preclinical animal model testing in dog and mice.

Fig. 5. World map representation of AS patients distribution.

World map represents the scale and scope of the ASF Facebook user community on a global scale, quantifying patients in a unique database.