Brain-derived neurotrophic factor is more highly conserved in structure and function than nerve growth factor during...

Area of Science:

• Neuroscience
• Evolutionary Biology
• Molecular Biology

Background:

• Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are crucial neurotrophins with conserved domains.
• Their distinct sequence motifs mediate diverse neuronal functions.
• Understanding their evolutionary conservation provides insights into neurobiology.

Purpose of the Study:

• To investigate the structural and functional evolution of NGF and BDNF.
• To compare fish (Xiphophorus) NGF and BDNF with their mammalian counterparts.
• To determine the evolutionary rates and divergence times of NGF and BDNF.

Main Methods:

• Isolation of genomic clones for fish NGF and BDNF using cross-hybridization.
• Expression and purification of recombinant fish NGF and BDNF via vaccinia viruses.
• Assessment of neuronal survival specificities and half-maximal survival concentrations.
• DNA sequencing and comparative analysis of amino acid sequences.
• RNA gel blot analysis for mRNA expression patterns.

Main Results:

• Fish and mammalian NGF/BDNF exhibited similar neuronal survival specificities.
• Recombinant fish and mammalian BDNF showed equal potency for chick sensory neuron survival (60 pg/ml).
• Recombinant fish NGF was 75-fold less potent than mouse NGF for chick neurons (6 ng/ml).
• Amino acid sequence identity to mouse was 63% for fish NGF and 90% for fish BDNF.
• NGF reached an optimized structure later in evolution than BDNF.

Conclusions:

• NGF and BDNF evolved at significantly different rates from a common ancestor approximately 600 million years ago.
• NGF shows less functional and structural conservation compared to BDNF.
• These findings highlight the distinct evolutionary trajectories of neurotrophic factors.