Embryonic germ cells as well as germline stem cells from neonatal mouse testis are pluripotent and have differentiation potential similar to embryonic stem cells, suggesting that the germline lineage may retain the ability to generate pluripotent cells. However, until now there has been no evidence for the pluripotency and plasticity of adult spermatogonial stem cells (SSCs), which are responsible for maintaining spermatogenesis throughout life in the male. Here we show the isolation of SSCs from adult mouse testis using genetic selection, with a success rate of 27%. These isolated SSCs respond to culture conditions and acquire embryonic stem cell properties. We name these cells multipotent adult germline stem cells (maGSCs). They are able to spontaneously differentiate into derivatives of the three embryonic germ layers in vitro and generate teratomas in immunodeficient mice. When injected into an early blastocyst, SSCs contribute to the development of various organs and show germline transmission. Thus, the capacity to form multipotent cells persists in adult mouse testis. Establishment of human maGSCs from testicular biopsies may allow individual cell-based therapy without the ethical and immunological problems associated with human embryonic stem cells. Furthermore, these cells may provide new opportunities to study genetic diseases in various cell lineages.

Mutations in the homologous presenilin 1 (PS1) and presenilin 2 (PS2) genes cause the most common and aggressive form of familial Alzheimer's disease. Although PS1 function and dysfunction have been extensively studied, little is known about the function of PS2 in vivo. To delineate the relationships of PS2 and PS1 activities and whether PS2 mutations involve gain or loss of function, we generated PS2 homozygous deficient (؊͞؊) and PS1͞PS2 double homozygous deficient mice. In contrast to PS1 ؊͞؊ mice, PS2 ؊͞؊ mice are viable and fertile and develop only mild pulmonary fibrosis and hemorrhage with age. Absence of PS2 does not detectably alter processing of amyloid precursor protein and has little or no effect on physiologically important apoptotic processes, indicating that Alzheimer's disease-causing mutations in PS2, as in PS1, result in gain of function. Although PS1 ؉͞؊ PS2 ؊͞؊ mice survive in relatively good health, complete deletion of both PS2 and PS1 genes causes a phenotype closely resembling full Notch-1 deficiency. These results demonstrate in vivo that PS1 and PS2 have partially overlapping functions and that PS1 is essential and PS2 is redundant for normal Notch signaling during mammalian embryological development.

Recent studies have demonstrated that somatic stem cells have a more flexible potential than expected, whether put into tissue or cultured under different conditions. Bone marrow (BM)-derived stem cells can transdifferentiate into multilineage cells, such as muscle of mesoderm, lung and liver of endoderm, and brain and skin of ectoderm origin. Here we show that BM stem cells are able to transdifferentiate into male germ cells. For derivation of male germ cells from adult BM stem (BMS) cells, we used the Stra8-enhanced green fluoresence protein (EGFP) transgenic mouse line expressing EGFP specifically in male germ cells. BMS cellderived germ cells expressed the known molecular markers of primordial germ cells, such as fragilis, stella, Rnf17, Mvh and Oct4; as well as molecular markers of spermatogonial stem cells and spermatogonia including Rbm, c-Kit, Tex18, Stra8, Piwil2, Dazl, Hsp90a, b1-and a6-integrins. Our ability to derive male germ cells from BMS cells reveals novel aspects of germ cell development and opens the possibilities for use of these cells in reproductive medicine.