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Bovine alpha s2-casein D is generated by exon VIII skipping
C Bouniol1, C Printz, J C Mercier
1Laboratoire de Génétique Biochimique, INRA-CRJ, Jouy-en-Josas, France.
Gene
|June 30, 1993
Summary
Bovine alpha s2-casein D (CasD) results from exon skipping, not a DNA deletion. A specific nucleotide substitution likely causes altered splicing, leading to the CasD variant in cows.
Area of Science:
- Genetics
- Molecular Biology
- Dairy Science
Background:
- Bovine alpha s2-casein (Cas) protein exhibits genetic variations, including the common type A and the less common type D (CasD).
- CasD is characterized by a deletion of approximately nine amino acids compared to CasA, but the precise molecular basis has been unclear.
Purpose of the Study:
- To elucidate the genetic mechanism underlying the bovine alpha s2-casein D (CasD) variant.
- To identify the specific genetic alteration responsible for the amino acid deletion in CasD.
Main Methods:
- PCR amplification and sequencing of genomic DNA from cows with CasD and CasA alleles.
- Analysis of nucleotide sequences to identify deletions or substitutions in the alpha s2-casein gene.
Main Results:
- Sequencing revealed no DNA deletion in the analyzed region of CasD alleles.
- Two identical nucleotide substitutions were identified in the region encoding codons 43-75 in both CasD alleles.
- These findings suggest that CasD arises from the skipping of exon VIII, encoding amino acids 51-59.
- A G to T transversion at the 5' splice site of exon VIII is implicated in the altered splicing event.
Conclusions:
- The bovine alpha s2-casein D variant is caused by alternative splicing, specifically the skipping of exon VIII.
- A nucleotide substitution at the exon VIII splice site is the likely molecular driver of this splicing defect.
- This study clarifies the genetic basis of CasD, contributing to a better understanding of casein polymorphism in cattle.