The Tissue atlas is based on immunohistochemical staining of tissue microarrays from 44 different normal tissue types. In addition to the standard setup, extended tissue profiling is performed for selected proteins, to give a more complete overview on where the protein is expressed. Extended tissue samples include mouse brain, human lactating breast, eye, and additional samples of adrenal gland, skin and brain. For eye, full section of eye and 1 mm diameter cores of retina were used.
The full list of proteins analyzed in eye and retina is found in Table 1.
The eye globe is covered by a fibrous coat which includes an anterior translucent surface called cornea. Light enters the eye through the pupil, behind the cornea, and is refracted by the lens, a transparent disc suspended by muscular fibers behind the pupil. The refracted light is focused on the retina, the innermost layer of the eye which transforms light into nerve signals that are then transmitted by the optical nerve to the brain. A vascular layer, called choroid, provides nutrients to the cells of the eye. An example of a protein essential for the structure and function of lens is crystallin B2 (CRYBB2) (Figure 1). It is a major component of lens fiber and maintains transparency and refractive index of the lens.
Figure 1. Immunohistochemical staining of human eye using an antibody toward CRYBB2 shows strong positivity in lens.
The layer of neural retina nearest the choroid contains photoreceptor cells: rods and cones. Rods register presence of light and allow night vision while cones register red, green and blue colors and allow color vision. Between the photoreceptors and choroid is a layer of pigment epithelium which provides nutrients and protection against oxidative stress to the photoreceptor cells. Nerve signals are transmitted from the photoreceptors to cells in the inner nuclear and ganglion cell layers through nerve fibers in the inner and outer plexiform layers, and are finally collected in the optical nerve. The protein cGMP phosphodiesterase (PDE6B) is expressed in the outer segments of photoreceptor cells and is involved in transmission and amplification of visual signals (Figure 2).
Figure 2. Immunohistochemical staining of human retina using an antibody toward PDE6B shows strong positivity in outer segments of photoreceptor cells.
Table 1. The following 53 genes have been analyzed using extended eye (10 genes) and retina (43 genes) tissue samples.
Relevant links and publications
UhlÚn M et al, 2015. Tissue-based map of the human proteome. Science
PubMed: 25613900 DOI: 10.1126/science.1260419
Yu NY et al, 2015. Complementing tissue characterization by integrating transcriptome profiling from the Human Protein Atlas and from the FANTOM5 consortium. Nucleic Acids Res.
PubMed: 26117540 DOI: 10.1093/nar/gkv608
Fagerberg L et al, 2014. Analysis of the human tissue-specific expression by genome-wide integration of transcriptomics and antibody-based proteomics. Mol Cell Proteomics.
PubMed: 24309898 DOI: 10.1074/mcp.M113.035600