Cathepsin D and 2',3'-cyclic nucleotide 3'-phosphohydrolase in developing human foetal brain

Area of Science:

• Biochemistry
• Neuroscience
• Developmental Biology

Background:

• Proteinase activity in the prenatal human cerebral cortex is crucial for neural development.
• Understanding enzyme function and distribution aids in characterizing developmental processes like neurogenesis and gliogenesis.

Purpose of the Study:

• To characterize proteinase activity in the prenatal human cerebral cortex.
• To investigate the role of Cathepsin D in early brain development.
• To correlate the expression of neuronal and glial markers during gestation.

Main Methods:

• Assay of proteinase activity using hemoglobin, bovine serum albumin, and casein substrates at varying pH.
• Partial purification of Cathepsin D using Concanavalin A-Sepharose affinity chromatography.
• Inhibition studies with specific proteinase inhibitors.
• Immunohistochemical analysis of cathepsin D and 2',3'-cyclic nucleotide 3'-phosphohydrolase distribution in fetal brain regions.

Main Results:

• Three distinct proteinase activity peaks were identified at pH 3.5, 6.5, and 8.5.
• Cathepsin D was the most prominent proteinase, with hemoglobin as its preferred substrate.
• Benzethonium chloride demonstrated strong inhibitory effects on Cathepsin D, similar to pepstatin A.
• Coincident expression of the neuronal marker cathepsin D and the oligodendroglial marker 2',3'-cyclic nucleotide 3'-phosphohydrolase was observed.
• High glial marker acquisition was noted in the medulla and spinal cord between 20-25 weeks of gestation.

Conclusions:

• Cathepsin D plays a significant role in the prenatal human cerebral cortex.
• Neurogenesis and gliogenesis occur concurrently from early gestational periods.
• The study provides insights into the developmental timeline of neuronal and glial differentiation in the human fetal brain.