Acetylcholine synthesis and possible functions during sea urchin development

Area of Science:

• Marine Biology
• Developmental Biology
• Neurobiology

Background:

• The cholinergic system, crucial for neurotransmission, is implicated in fertilization and early development across various organisms.
• Acetylcholine (ACh) is synthesized by choline acetyltransferase (ChAT) and degraded by acetylcholinesterase (AChE).

Purpose of the Study:

• To investigate the presence and function of choline acetyltransferase (ChAT) in the gametes of the sea urchin, Paracentrotus lividus.
• To explore the role of the cholinergic system in sea urchin fertilization and early embryonic development.

Main Methods:

• Indirect immunofluorescence and immuno-gold methods were used to localize ChAT in oocytes, eggs, zygotes, and sperm.
• In vivo experiments exposed sea urchin gametes and embryos to acetylcholine (ACh) and acetylcholinesterase (AChE) to assess functional impacts.

Main Results:

• ChAT-like molecules were detected in oocytes, eggs, and zygotes, indicating the capacity for autonomous acetylcholine (ACh) synthesis.
• ChAT was localized in the acrosome of unreacted sperm and on the head surface of reacted sperm.
• Exposure to ACh and AChE induced polyspermy and developmental anomalies in sea urchin embryos, highlighting functional roles.

Conclusions:

• The cholinergic system in sea urchins contributes to fertilization through sperm-derived ACh and to post-fertilization development via maternal ChAT.
• Autonomous ACh synthesis by both sperm and eggs suggests a significant role for the cholinergic system in early sea urchin development.