Alteration of Neural Stem Cell Functions in Ataxia and Male Sterility Mice: A Possible Role of ß-Tubulin Glutamylation in Neurodegeneration.

Ataxia and Male Sterility (AMS) is a mutant mouse strain that contains a missense mutation in the coding region of Nna1, a gene that encodes a deglutamylase. AMS mice exhibit early cerebellar Purkinje cell degeneration and an ataxic phenotype in an autosomal recessive manner. To understand the underlying mechanism, we generated neuronal stem cell (NSC) lines from wild-type (NMW7), Nna1 mutation heterozygous (NME), and Nna1 mutation homozygous (NMO1) mouse brains. The NNA1 levels were decreased, and the glutamylated tubulin levels were increased in NMO1 cultures as well as in the cerebellum of AMS mice at both 15 and 30 days of age. However, total ß-tubulin protein levels were not altered in the AMS cerebellum. In NMO1 neurosphere cultures, ß-tubulin protein levels were increased without changes at the transcriptional level. NMO1 grew faster than other NSC lines, and some of the neurospheres were attached to the plate after 3 days. Immunostaining revealed that SOX2 and nestin levels were decreased in NMO1 neurospheres and that the neuronal differentiation potentials were reduced in NMO1 cells compared to NME or NMW7 cells. These results demonstrate that the AMS mutation decreased the NNA1 levels and increased glutamylation in the cerebellum of AMS mice. The observed changes in glutamylation might alter NSC properties and the neuron maturation process, leading to Purkinje cell death in AMS mice.

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.