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The third egg envelope subunit in fish: cDNA cloning and analysis, and gene expression
H Sugiyama1, S Yasumasu, K Murata
1Life Science Institute, Sophia University, Tokyo, Japan.
Development, Growth & Differentiation
|May 1, 1998
Summary
Researchers discovered a new protein subunit in the medaka fish egg envelope. This novel protein, expressed in the liver, is the third major component of the egg's inner layer.
Area of Science:
- Reproductive biology
- Molecular biology
- Fish reproduction
Background:
- The medaka fish egg envelope's inner layer comprises ZI-1,2 and ZI-3 subunits.
- ZI-1,2 glycoproteins originate from choriogenin H (Chg H), and ZI-3 from choriogenin L (Chg L).
Purpose of the Study:
- To identify and characterize a novel protein subunit within the medaka fish egg envelope's ZI-1,2 group.
Main Methods:
- Partial purification of ZI-1,2 from oocyte envelopes and V8 protease digestion.
- RT-PCR using primers based on the novel protein's amino acid sequence.
- cDNA library screening from spawning female liver.
- Northern blot analysis for gene expression.
Main Results:
- A novel protein fraction, absent in Chg H, was identified in V8 digests of ZI-1,2.
- A full-length cDNA clone (2025 bp) encoding a 634-amino acid protein was obtained.
- The novel protein contains Pro-X-Y repeat sequences and is expressed in the liver, not the ovary.
Conclusions:
- A third major subunit protein has been identified in the inner layer of the medaka fish egg envelope.
- This novel protein is synthesized in the liver and incorporated into the egg envelope.