Neurons differ in invertebrates from mammalian cells. At present , retroviral vectors are popular for cloning genes in mammalian cells. Half of the membrane mass in human and most mammalian red blood cells are proteins. Other diseases involving the mammalian prion protein are known. Fibroblasts are cells involved in wound healing and cell structure formation in mammalian cells. Bidirectional promoters are a common feature of mammalian genomes. There are 9 major proteins involved in NER in mammalian cells. MC1R is one of the key proteins involved in regulating mammalian skin and hair color. The avian herpes viruses diverged from the branch leading to the mammalian species. There was also variation in different tissues and mammalian species. These remaining DNA damages accumulate with age in mammalian postmitotic tissues. Glutamate is the principal excitatory neurotransmitter in the mammalian CNS. "Cunninghamella elegans" is a candidate for use as a model for mammalian drug metabolism. It has a crucial role in restricting axonal regeneration in adult mammalian central nervous system. It is serologically similar to structures found on mammalian glycoproteins.