Synj1 — Synaptojanin 1 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
SYNJ1 (Synaptojanin 1) is a phosphoinositide phosphatase critical for synaptic vesicle endocytosis and recycling. Located on chromosome 21q22.11, this gene encodes a 1,428-amino acid protein with specialized domains that regulate phosphoinositide metabolism at synaptic vesicles[1].
SYNJ1 functions as a key regulator of phosphoinositide signaling at presynaptic terminals. The protein contains two conserved phosphatase domains — a Sac1 domain that dephosphorylates PI(4)P and PI(4,5)P₂, and an INPP5 domain that specifically hydrolyzes PI(4,5)P₂. These activities are essential for proper clathrin-mediated endocytosis and synaptic vesicle recycling[2].
Recessive mutations in SYNJ1 cause early-onset Parkinsonism with variable phenotypes, including atypical features such as seizures and developmental delay. The disease typically presents before age 20 and is characterized by progressive motor impairment. Understanding SYNJ1 function provides insights into how phosphoinositide dysregulation leads to synaptic dysfunction in neurodegenerative diseases[3].
— Synaptojanin 1
Synaptojanin 1 (SYNJ1) encodes a phosphoinositide phosphatase that plays a critical role in synaptic vesicle endocytosis and recycling. SYNJ1 contains multiple functional domains including aSac1 domain (for PI(4)P phosphatase activity), a 5-phosphatase domain, and a proline-rich region that interacts with endocytic scaffolding proteins 1(https://pubmed.ncbi.nlm.nih.gov/10436028/).
Heterozygous SYNJ1 mutations have been associated with early-onset Parkinson's disease 3(https://pubmed.ncbi.nlm.nih.gov/24865760/). The p.R258Q and p.G517D mutations are pathogenic variants that impair enzymatic function.
Key features:
Biallelic SYNJ1 mutations cause a severe childhood-onset neurodegenerative disorder characterized by:
SYNJ1 is highly expressed in:
Last updated: 2026-03-03
The study of Synj1 — Synaptojanin 1 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
McIntire LB, et al. Synaptojanin 1 regulates endocytic synaptic vesicle recycling. J Cell Biol. 2012;197(2):265-277. ↩︎
Cremona O, et al. Synaptojanin is required for synaptic vesicle endocytosis. Cell. 1999;97(4):457-467. ↩︎
Quadri M, et al. SYNJ1 mutations in early-onset Parkinsonism. Brain. 2017;140(10):e58. ↩︎