Abstract
We investigated the genetic landscape of Parkinson's disease (PD) on the island of Crete. DNA samples from 360 PD patients and 251 controls were analyzed using a combination of genotyping, whole-exome sequencing, and targeted screening for GBA1 variants p.N409S and p.L483P. A molecular diagnosis (heterozygous dominant/homozygous recessive pathogenic/likely pathogenic non-GBA1 variant) was identified in 3.1% of patients, including LRRK2-PD (n = 4) and SNCA-PD (n = 1). A novel homozygous PINK1 variant (p.Y295Ter) and a rare homozygous FIG4 variant (p.I41T) were detected in two early-onset cases. About 10.3% of patients carried a GBA1 variant, including four rare variants (p.C55S, p.H294Q, p.K237T, p.R502H), and had an adjusted earlier disease onset of 7.3 years. GBA1 carriers had a 4.3-fold higher risk for PD compared to non-carriers. The proportion of GBA1 in Crete is substantially higher than on the Greek mainland, highlighting the distinct genetic PD profile in this population and supporting targeted genetic testing and counseling.