Extended brain samples

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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, hair and additional samples of adrenal gland, skin and brain. For extended brain samples, both tissue microarrays with 1 mm diameter cores and tissue section samples are used.

The full list of proteins analyzed in extended brain samples is found in Table 1.

Hypothalamus

The hypothalamus, a part of the diencephalon (interbrain), is located below the thalamus and above the pituitary gland. The hypothalamus is considered to be the link between the nervous and endocrine system, and plays an essential role in metabolism and homeostasis – by regulating the autonomic nervous system, production of hormones (via the pituitary gland), and controlling body temperature. The hypothalamus is also involved in regulation of behavior, food intake and circadian rhythm. The hypothalamus can be divided into three different regions based on structure and function; the anterior, tuberal and posterior regios, which further can be structured into several nuclei and areas. Extended protein profiling in human hypothalamus was performed using large tissue sections (20 x 30 mm). Only images representing regions of interest are selected for inclusion on the Human Protein Atlas.

The pro-melanin concentrating hormone (PMCH) encodes a preproprotein, and is proteolytically processed to generate multiple proteins. PMCH is mainly expressed in a subset of hypothalamic neurons (Figure 1).

Figure 1. Immunohistochemical staining of human hypothalamus using an antibody towards PMCH shows strong cytoplasmic staining in neuronal cells.

Hippocampal formation

Located in the medial temporal lobes, surrounded by the entorhinal, parahippocampal and perirhinal cortices, lies the hippocampus. The hippocampus belongs to the limbic system. The dorsal part is involved in episodic memory and spatial navigation, while the ventral hippocampus is implicated in emotion-related connections. The hippocampus is included in the standard tissue microarray setup. Extended protein profiling of human hippocampus, using a tissue section (20 x 30 mm) which includes the dentate gyrus/hippocampal cornus ammonis (CA) areas, was performed in order to give a wider perspective of the protein localization and assess protein expression in cells that are not included in the standard setup due to tissue sampling. Only images representing regions of interest are selected for inclusion on the Human Protein Atlas.

Cerebral cortex

The cerebral cortex (also known as the neocortex) is a complex, multilayered (six layers), highly organized structure, and the outer layer of the brain in humans and most mammals. The cerebral cortex contains a high number of different neuronal and glial cells types. The cortical neurons comprise mainly of two classes: the interneurons and the pyramidal (projection) neurons, which can further be classified based on morphological and molecular signatures. The cerebral cortex is included in the standard tissue microarray setup. Extended protein profiling using a tissue section (15 x 20 mm) from the human cerebral cortex frontal lobe was performed in order to give a wider perspective of the protein localization and assess protein expression in cells that are not included in the standard setup due to tissue sampling.

Pituitary gland

The pituitary gland (also called hypophysis) consists of two glands, the anterior (adeno) pituitary gland, and the posterior (neuro) pituitary gland. The anterior pituitary gland is divided into three regions: pars distalis, pars tuberalis and pars intermedia. These structures consist mainly of hormone-producing epithelial cells that store hormones in secretory granules, to later be released in the blood stream. The hormones act on various tissues. One example is the peptide hormone prolactin (PRL) that stimulates the mammary glands to produce milk. Prolactin is expressed in the anterior pituitary gland (Figure 2). The posterior pituitary gland consists mainly of unmyelinated axons of secretory neuronal cells located in the supraoptic and periventricular nuclei of the hypothalamus. The neurons produce a neurosecretory material, containing antidiuretic hormones and oxytocin, which travels along the axons from the hypothalamic neurons to the nerve endings in the posterior pituitary, specifically to the pars nervosa - the main structure of the posterior gland. Extended protein profiling in human pituitary gland was performed using a tissue microarray with 1 mm diameter cores.

Figure 2. Immunohistochemical staining of human pituitary gland towards PRL shows strong cytoplasmic positivity in endocrine cells.

Table 1. The following 40 genes have been analyzed using extended brain samples.

Relevant links and publications

Uhlén 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