Allele-specific occurrence of multiple C4 and Slp mRNAs

Area of Science:

• Immunogenetics
• Molecular Biology
• Genetics

Background:

• The H-2 S region contains highly homologous genes for the fourth complement component (C4) and sex-limited protein (Slp).
• Different alleles (C4high, Slpa vs. C4low, Slpo) exhibit distinct C4 and Slp protein expression levels in plasma.
• Mice with C4high, Slpa alleles express single mRNA species, while C4low, Slpo alleles are associated with low protein levels.

Purpose of the Study:

• To investigate the molecular basis for differential C4 and Slp gene expression in mice.
• To characterize the messenger RNA (mRNA) transcripts of C4 and Slp genes in different H-2 haplotypes.
• To explore the genetic polymorphism at the RNA level in the H-2 S region.

Main Methods:

• Analysis of mRNA species transcribed from the C4 and Slp genes using techniques like Northern blotting (implied).
• Comparison of RNA profiles between mice carrying different H-2 haplotypes (e.g., H-2k vs. others).
• Investigation to rule out alternative transcription initiation sites as the cause of multiple RNA species.

Main Results:

• Mice carrying the H-2k haplotype (C4low, Slpo alleles) express multiple C4 and Slp mRNA species (RNA doublets).
• Mice with other S regions express a single, indistinguishable mRNA species.
• The observed RNA doublets are not due to alternative upstream transcription initiation.

Conclusions:

• A genetic polymorphism exists at the level of RNA multiplicity in the H-2 S region.
• Alternative splicing or alternative polyadenylation are hypothesized mechanisms for the generation of RNA doublets.
• The occurrence of multiple RNA species in C4low, Slpo strains may be linked to their characteristically low C4 protein expression.