Monoallelic expression of mouse <Emphasis Type="Italic">Cd4</Emphasis> gene

A 7-bp deletion in the Cd4 gene, present in the strain MOLF/Ei of Mus musculus molossinus and absent in laboratory mouse strains (Mus musculus musculus), provided the means to distinguish the parental origin of the Cd4 alleles expressed in single cells of F₁ (AKR × MOLF/Ei) and F₁ (Balb/C × MOLF/Ei) hybrids. Single-cell RT-PCR showed that the individual CD4⁺ lymphocyte expresses either the maternal or the paternal Cd4 allele, never both. In situ hybridization proved that Cd4 alleles replicate asynchronously, as expected in the case of genes expressed monoallelically.