General Introduction 
The Stem Cell Research Laboratory in Shaare Zedek, headed by Dr. R. Eiges, was found in 2008 as part of the Medical Genetics Institute. The laboratory is mainly engaged with basic research studies related to genetic disorders, using mutant human embryonic stem cells as a model system. Specifically, we are focusing on the research of genetic conditions that are associated with unstable repeat expansions (microsatellites) in the DNA like fragile X syndrome, myotonic dystrophy type 1, a heritable form of ALS, as well as Dyskeratosis Congenital. In addition, it is charged with establishing and providing diseased human embryonic stem cell (HESC) lines as a universally available resource.

What are stem cells?
Stem cells are unspecialized cells that are the source of all cell types and tissues in the body. They are responsible for structuring the body during embryo development, and provide a continuous supply of cells thereafter. Unlike any other cell type in the body, they can self-renew by replicating themselves while maintaining their broad developmental potential. In mammals there are two types of stem cells; adult and embryonic. Adult stem cells, also termed somatic stem cells, are formed beginning from 9 weeks gestation. They are found in small numbers in organs/tissues throughout the lifetime of an individual, and give rise to nascent cells of the tissues they reside in. Their function is to serve as a reservoir of cells for tissue homeostasis, and as a repair system when tissues are damaged. Unlike adult stem cells, embryonic stem cells appear transiently during embryo development, at the blastocyst stage, for a very short period (day 5-7 post-fertilization). They are less specialized cells than adult stem cells and give rise to all tissues and
 cell types in the body and, in principle, can form a complete viable fetus on their own. 

What are the potential applications of hESCs? 
Embryonic stem cells are present in the blastocyst as a clump of cells, termed inner cell mass (ICM). The ICM, which normally remains pluripotent for only a short time in vivo, can be isolated and maintained in the culture dish without losing its undifferentiated phenotype or wide developmental potential. Moreover, unlike any other primary cell culture, the ICM cells can be expanded practically without limit once they are removed from their natural environment in the embryo. The resulting cell lines, termed human embryonic stem cell lines (HESCs), can differentiate into a wide range of cell types in culture and in vivo. The advantages of these cells in basic and applied research are far reaching; they can be utilized as an unlimited cell source for cell based therapy and tissue regeneration. In addition, they can be employed for investigating underlying mechanisms of diverse human pathologies. They can also be exceptionally useful for drug development, screening and evaluation since they offer the potential to generate a plentiful supply of specific cell types in culture.