A new mutation, ataxia and male sterility (ams), of autoimmune-prone MRL/lpr mouse is not linked to lpr gene but associated with reduction of spleen size and alteration of lymphocyte subpopulations.

We describe changes in the immune system of the newly established mutant line, ataxia and male sterility (AMS) mouse, and that the putative ams mutation is independent of lpr but seemed to affect lymphoproliferation in its mother strain, MRL/lpr. The mean weights of the spleen and lymph nodes of ams-lpr double-homozygous mouse were reduced compared with lpr single-homozygous mouse. Comparison between ams single-homozygous and control mice revealed 45-50% reduction of the spleen weight in the former for which reduction of the number of nucleated cells contributed greatly. In the lymphocyte/monocyte fraction of the spleen, there were significant changes in the proportion of lymphocyte subpopulations, with a reduction of B cells, an increase in CD4 and CD8 T cells, and a decrease in the CD4 : CD8 ratio. In vitro response of splenocytes to concanavalin A showed inconspicuous dose- and time-dependent responses in ams homozygous spleen, suggesting functional alteration of the immunological response. Our results indicate that ams mutation affects the immune system in addition to its two other major effects on the central nervous system and male reproductive system.

Ataxia and male sterility (AMS) mouse. A new genetic variant exhibiting degeneration and loss of cerebellar Purkinje cells and spermatic cells.

We describe a novel genetic variant mouse that exhibited ataxia and male sterility, named the AMS mouse. It arose in autoimmune-prone MRL/lpr strain and putative ams mutation showed an autosomal recessive inheritance pattern. Clinical symptoms were first discernible at approximately 21 days of age and consisting of subtle sway of the trunk followed by failure to maintain still posture and appearance of abnormal walk, but no further worsening was noted with advancement of age. The abnormal motor coordination was ascribed to almost complete loss of Purkinje cells of the cerebellum. The cell loss in the Purkinje cell layer began before onset of ataxia and rapidly progressed towards near-complete loss by 6 weeks of age. Another symptom was male sterility due to severe oligozoospermia associated with cellular degeneration during spermatic differentiation in the seminiferous tubules. Thus, the effects of the genetic variation were apparent in two different organs after the development of their basic histological structures, and degeneration and loss of particular cell types in these two tissues produced overt clinical symptoms. Genetic pleiotropism, provided that the nature of genetic variation is of a single gene mutation, is discussed.