Alternative splicing regulates Prdm1/Blimp-1 DNA binding activities and corepressor interactions

Area of Science:

• Developmental Biology
• Molecular Biology
• Gene Regulation

Background:

• Prdm1/Blimp-1 is a key regulator of gene expression in development and adult tissues.
• It possesses a C-terminal domain critical for nuclear import, DNA binding, and corepressor recruitment.
• Alternative splicing produces a Blimp-1Δexon7 isoform lacking exon 7, predicted to have different functions.

Purpose of the Study:

• To investigate the in vivo functional significance of alternative splicing in Prdm1/Blimp-1.
• To characterize the molecular and developmental properties of the Blimp-1Δexon7 isoform.
• To determine the necessity of the short isoform for normal development and cellular function.

Main Methods:

• Engineered novel mouse strains using embryonic stem (ES) cell technology to study Prdm1/Blimp-1 alternative splicing.
• Generated mice with targeted deletion of exon 7, exclusively expressing Blimp-1Δexon7.
• Created mice with an exon 6-exon 7 fusion allele expressing only full-length Blimp-1.

Main Results:

• The Blimp-1Δexon7 isoform lacks DNA binding and corepressor interactions but retains PRMT5 binding.
• Embryos exclusively expressing Blimp-1Δexon7 die at E10.5 due to placental defects, similar to null mutants.
• Mice expressing only full-length Blimp-1 develop normally, are fertile, and generate mature plasma cells, indicating the short isoform is dispensable.

Conclusions:

• The short Blimp-1Δexon7 isoform is dispensable for mouse development and function.
• Alternative splicing of Prdm1/Blimp-1 is developmentally regulated and fine-tunes its functional repertoire.
• Chromatin structure at the Prdm1 locus likely influences alternative splicing patterns.