Multiple neurofilament subunits are present in lamprey CNS

Area of Science:

• Neuroscience
• Molecular Biology
• Evolutionary Biology

Background:

• Mammalian neurofilaments (NFs) consist of three subunits: NF-L, NF-M, and NF-H.
• Previously, only one NF, NF180, was identified in lamprey, but it could not self-assemble.
• This suggested lamprey NFs might be heteropolymers, requiring additional subunits.

Purpose of the Study:

• To investigate the existence of additional NF subunits in lamprey.
• To characterize newly identified NF genes in lamprey.

Main Methods:

• Gene isolation and characterization of potential NF subunits.
• In situ hybridization to determine expression patterns in the central nervous system (CNS).
• Northern blotting to assess gene expression levels.

Main Results:

• Evidence for a lamprey NF-L homolog (L-NFL) was found.
• Two new NF-M isoforms, NF132 and NF95, were isolated and characterized.
• All three newly cloned NFs (L-NFL, NF132, NF95) are expressed in spinal cord and brainstem neurons.
• NF132 and NF95 lack KSP motifs, similar to NF180.
• NF95 shows high identity to NF180.
• NF95 expression may be low in older larvae.

Conclusions:

• The identification of L-NFL supports the hypothesis that lamprey NFs are obligate heteropolymers, requiring NF-L.
• The findings indicate a greater complexity of NF composition in lamprey than previously thought.
• This expands our understanding of NF evolution and function across vertebrates.