HOP-1 Presenilin Deficiency Causes a Late-Onset Notch Signaling Phenotype That Affects Adult Germline Function in .

Functionally redundant genes present a puzzle as to their evolutionary preservation, and offer an interesting opportunity for molecular specialization. In , either one of two presenilin genes ( or ) facilitate Notch activation, providing the catalytic subunit for the γ secretase proteolytic enzyme complex. For all known Notch signaling events, can mediate Notch activation, so the conservation of remains a mystery.