Thus, we generated a knock-in (PEX1-G844D) mouse model representing the common human PEX1-c.2528G>A allele (encoding PEX1-G843D) to study pathophysiology and develop therapies, and found that it has classic features of milder ZSD, including retinal degeneration (5). Here, PEX1 is linked to peroxisome biogenesis disorder.