LBR and systemic lupus erythematosus: To evaluate whether a disruption in nuclear structure can contribute to the development of lupus autoimmunity, lupus-prone NZW mice were crossed with non-autoimmune-prone c57Bl/6 mice that are heterozygous for a mutation in Lbr that causes an impairment in mRNA splicing (B6.Lbric/+ mice).