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Identification of a cDNA clone that contains the complete coding sequence for a 140-kD rat NCAM polypeptide
S J Small1, G E Shull, M J Santoni
1Division of Basic Research, Children's Hospital Research Foundation, Cincinnati, Ohio 45229.
The Journal of Cell Biology
|November 1, 1987
Summary
Researchers isolated a novel rat brain cDNA clone, pR18, representing the 140-kD Neural Cell Adhesion Molecule (NCAM) form. This discovery provides the complete amino acid sequence for this NCAM variant, enabling further structural and functional studies.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- Neural Cell Adhesion Molecules (NCAMs) are crucial for cell-cell adhesion in vertebrates.
- NCAMs exist in multiple isoforms, including 180, 140, and 120 kD forms, differing in membrane association.
- Understanding NCAM isoform structure is vital for comprehending neural development and function.
Purpose of the Study:
- To isolate and characterize cDNA clones encoding NCAM isoforms from adult rat brain.
- To determine the complete coding sequence of a specific NCAM polypeptide.
- To investigate the structural basis of NCAM diversity.
Main Methods:
- Isolation of NCAM cDNA clones from an adult rat brain library.
- DNA sequencing and sequence analysis of isolated clones.
- Northern blot analysis using specific probes to detect mRNA size classes.
Main Results:
- Isolation of clone pR18, containing a 2,574-nucleotide open reading frame.
- Sequence analysis suggests pR18 encodes a full-length 140-kD NCAM form with a single membrane-spanning region.
- Northern analysis revealed pR18 corresponds to specific mRNA size classes in adult rat brain, distinct from liver and muscle.
- pR18 contains a unique 30-base pair segment not observed in NCAM cDNAs from other species.
Conclusions:
- pR18 represents the first cDNA with the complete coding sequence of an NCAM polypeptide, likely the rat 140-kD form.
- The study unambiguously demonstrates the predicted amino acid sequence of this rat NCAM isoform.
- The unique sequence segment in pR18 offers new avenues for studying NCAM structure-function relationships.