Extracellular proteolysis: developmentally regulated activity during chick spinal cord histogenesis

Area of Science:

• Developmental Biology
• Neuroscience
• Biochemistry

Background:

• Extracellular proteolysis, specifically the plasmin-generating system, plays a role in tissue development.
• Understanding the temporal and spatial expression of proteases during embryonic development is crucial for deciphering tissue morphogenesis.

Purpose of the Study:

• To identify the stages of spinal cord histogenesis where the plasmin-generating system, particularly plasminogen activator, is expressed.
• To investigate the developmental regulation and spatial distribution of plasminogen activator activity in the embryonic chick spinal cord.

Main Methods:

• Daily monitoring of plasminogen activator specific activity in whole embryonic chick spinal cords (days 4-hatching) and dissected ventral/dorsal halves (days 6-17).
• Biochemical determination of enzyme activity using a fibrinolytic assay.
• Assessment of cell proliferation by measuring spinal cord DNA content (micrograms DNA/mg protein).

Main Results:

• Plasminogen activator specific activity is low during early neuroblast proliferation and markedly increases (14-fold) during later stages of neuronal maturation and glial cell proliferation.
• Enzyme activity exhibits a developmentally regulated pattern, with decreases and enhancements across three distinct temporal stages of spinal cord histogenesis, correlating with glial proliferation.
• On embryonic days 7-9, ventral halves of the spinal cord show significantly higher plasminogen activator activity than dorsal halves, aligning with the ventral-to-dorsal differentiation gradient.

Conclusions:

• Plasminogen activator expression is developmentally regulated during embryonic chick spinal cord histogenesis.
• The observed spatio-temporal pattern of plasminogen activator activity suggests its involvement in neuronal differentiation and glial proliferation.
• Differential activity between ventral and dorsal spinal cord halves points to a role in establishing the ventral-to-dorsal differentiation axis.