Key points about Doppel (PRND):

Structure:

• Prion protein paralog
• Three α-helices, two-stranded β-sheet
• Lacks octapeptide repeat region
• Downstream of PRNP gene

Expression:

• Primarily in testis
• Limited during normal growth
• Highest in spermatids and mature sperm

Reproductive Role:

• Critical for sperm development
• Aids acrosome formation
• Influences sperm motility
• Controls calcium levels

Molecular Characteristics:

• GPI anchor attachment
• More stable protein fold
• Ancient gene duplication (500 million years ago)

Neurological Implications:

• Normally absent from nervous system
• Abnormal brain presence linked to neurotoxicity
• Can cause cerebellar degeneration

Pathological Potential:

• Associated with neurological disorders
• Disrupts neuronal calcium balance
• Possible target for neurodegenerative disease research