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The myelin proteolipid DMα in fishes
1Institute of Biochemistry, Ludwig-Maximilians Universität München, Germany. christian.broesamle@med.uni-muenchen.de
Abstract:
Vertebrate myelin membranes are compacted and held in close apposition by three structural proteins of myelin, myelin basic protein, myelin protein zero (MPZ) and myelin proteolipid protein (PLP1/DMalpha). PLP1/DMalpha is considered to function as a scaffolding protein and play a role in intracellular trafficking in oligodendrocytes. In humans, point mutations, duplications or deletions of PLP1 are associated with Pelizaeus-Merzbacher disease and spastic paraplegia Type 2. PLP1 is highly conserved between mammals, but less so in lower vertebrates. This has led some researchers to question whether certain fish species express PLP1 orthologues at all, and to suggest that the function of PLP1/DMalpha in the central nervous system (CNS) may have been taken over by MPZ. Here, we review the evidence for the conservation of orthologues of PLP1/DMalpha in actinopterygian fishes and provide a comparison of currently available sequence data across 17 fish species. Our analysis demonstrates that orthologues of PLP1/DMalpha have been retained and are functionally expressed in many, if not all, extant species of bony fish. Many of the amino acids that, when mutated, are associated with severe CNS pathology are conserved in teleosts, demonstrating conservation of essential functions and justifying the development of novel disease models in species such as the zebrafish.
Insights
Myelin proteolipid protein (PLP1/DMalpha) is essential for central nervous system (CNS) development and is conserved in bony fish. This finding supports using fish models to study PLP1-related human neurological disorders.
Area of Science:
- Neuroscience
- Molecular Biology
- Evolutionary Biology
Background:
- Myelin basic protein, myelin protein zero (MPZ), and myelin proteolipid protein (PLP1/DMalpha) are crucial for vertebrate CNS myelin structure.
- PLP1/DMalpha is implicated in oligodendrocyte intracellular trafficking, and its mutations cause Pelizaeus-Merzbacher disease and spastic paraplegia Type 2 in humans.
- PLP1 is highly conserved in mammals but less so in lower vertebrates, prompting questions about its presence and function in fish.
Purpose of the Study:
- To investigate the conservation of PLP1/DMalpha orthologues in actinopterygian (bony) fishes.
- To compare available PLP1/DMalpha sequence data across 17 fish species.
- To assess the functional conservation of PLP1/DMalpha in fish for potential disease modeling.
Main Methods:
- Literature review of evidence for PLP1/DMalpha orthologues in fish.
- Comparative sequence analysis of PLP1/DMalpha across 17 diverse fish species.
- Identification of conserved amino acid residues critical for protein function.
Main Results:
- Orthologues of PLP1/DMalpha are retained and functionally expressed in most bony fish species.
- Key amino acid residues associated with human CNS diseases are conserved in teleost fish.
- Evidence suggests PLP1/DMalpha function is maintained across bony fish, not replaced by MPZ.
Conclusions:
- PLP1/DMalpha orthologues are widely conserved in bony fish, indicating essential, retained functions.
- The conservation of critical residues supports the use of fish, like zebrafish, as models for PLP1-related human neurological disorders.
- This research validates the evolutionary importance of PLP1/DMalpha in CNS development across vertebrates.
