Production of mouse ES cells homozygous for Cdk5-phosphorylated site mutation in c-Src alleles

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• c-Src protein's cellular functions are not fully understood due to functional redundancy with other Src family members.
• Cyclin-dependent kinase 1 (Cdk1) and Cdk5 phosphorylate c-Src at Ser75 in its unique N-terminal domain.
• Studying c-Src's specific roles requires cells with a homozygous mutation at Ser75, which have been difficult to generate.

Purpose of the Study:

• To develop an efficient procedure for generating mouse embryonic stem (ES) cell clones with a homozygous Ser75 to Asp mutation in the c-src gene.
• To enable the assessment of c-Src's specific cellular functions through targeted mutagenesis.

Main Methods:

• Combined a novel point mutation introduction strategy (no exogenous sequence) with high-geneticin (G418) selection for homozygous mutation.
• Utilized gene targeting in mouse embryonic stem cells to introduce a specific point mutation at the Ser75 site of the c-src gene.

Main Results:

• Successfully generated ES cell clones with a homozygous Ser75 to Asp mutation in the c-src gene.
• Mutant clones exhibited normal levels of c-Src protein and autophosphorylation activity compared to wild-type cells.
• The mutant c-Src protein was not phosphorylated at Ser75 during mitosis, confirming the mutation's functional impact.

Conclusions:

• The developed procedure efficiently produces ES cells homozygous for subtle mutations, specifically demonstrated for the c-src Ser75 to Asp mutation.
• This method is a significant advancement for studying gene function, particularly for genes with redundant family members.
• The technique is expected to be broadly applicable to generating homozygous mutant somatic cell lines for various genes.