MAPT and X-linked retinoschisis: Progressive supranuclear palsy (PSP) is a neurodegenerative disease defined by theaggregation and spread of tau protein isoforms with four microtubule-binding repeat domains(4R-tau) in neurons, astrocytes and oligodendrocytes of the central nervous system.1 Most frequently, PSP presents clinicallywith a combination of supranuclear gaze palsy and postural instability, commonly referred toas Richardson’s syndrome (PSP-RS).