GABA also regulates the growth of embryonic and neural stem cells. There is widespread controversy over the use of human embryonic stem cells. Sox2 has a critical role in maintenance of embryonic and neural stem cells. King has also voted against allowing human embryonic stem cell research. A germ layer is a primary layer of cells that forms during embryonic development. He opposed and voted against expanding public funding of embryonic stem cell research. He voted against expanding research to more embryonic stem cell lines. Smith supports efforts to provide alternatives to embryonic stem cell research. There has been more recent interest in the use of extra embryonic mesenchymal stem cells. Physiologic EMH occurs during embryonic and fetal development mainly. Dermoid cysts are formed from the outer layers of embryonic skin cells. He has voted in favor of the expansion of embryonic stem cell research. Yamanaka focused on factors that are important for maintaining pluripotency in embryonic stem (ES) cells. Hemoglobin variants are a part of the normal embryonic and fetal development. Harkin has come out in favor of embryonic stem cell research.