Homeobox protein NANOG

Last updated
NANOG
NANOG.png
Available structures
PDB Ortholog search: PDBe RCSB
Identifiers
Aliases NANOG , entrez:79923, Nanog, Nanog homeobox
External IDs OMIM: 607937 MGI: 1919200 HomoloGene: 78027 GeneCards: NANOG
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_001297698
NM_024865

NM_028016
NM_001289828
NM_001289830
NM_001289831

RefSeq (protein)

NP_001284627
NP_079141

NP_001276757
NP_001276759
NP_001276760
NP_082292

Location (UCSC) Chr 12: 7.79 – 7.8 Mb Chr 6: 122.68 – 122.69 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Homeobox protein NANOG(hNanog) is a transcriptional factor that helps embryonic stem cells (ESCs) maintain pluripotency by suppressing cell determination factors. [5] hNanog is encoded in humans by the NANOG gene. Several types of cancer are associated with NANOG. [6]

Contents

Etymology

The name NANOG derives from Tír na nÓg (Irish for "Land of the Young"), a name given to the Celtic Otherworld in Irish and Scottish mythology. [7] [8]

Structure

The human hNanog protein coded by the NANOG gene, consists of 305 amino acids and possesses 3 functional domains: the N-terminal domain, the C- terminal domain, and the conserved homeodomain motif. The homeodomain region facilitates DNA binding. The NANOG is located on chromosome 12, and the mRNA contains a 915 bp open reading frame (ORF) with 4 exons and 3 introns. [8]

The N-terminal region of hNanog is rich in serine, threonine and proline residues, and the C-terminus contains a tryptophan-rich domain. The homeodomain in hNANOG ranges from residues 95 to 155. There are also additional NANOG genes (NANOG2, NANOG p8) which potentially affect ESCs' differentiation. Scientists have shown that NANOG is fundamental for self-renewal and pluripotency, and NANOG p8 is highly expressed in cancer cells. [9]

Function

Transcription programs in embryonic stem cells Transcription programs in stem cells..jpg
Transcription programs in embryonic stem cells

NANOG is a transcription factor in embryonic stem cells (ESCs) and is thought to be a key factor in maintaining pluripotency. NANOG is thought to function in concert with other factors such as POU5F1 (Oct-4) and SOX2 to establish ESC identity. These cells offer an important area of study because of their ability to maintain pluripotency. In other words, these cells have the ability to become virtually any cell of any of the three germ layers (endoderm, ectoderm, mesoderm). It is for this reason that understanding the mechanisms that maintain a cell's pluripotency is critical for researchers to understand how stem cells work, and may lead to future advances in treating degenerative diseases.

NANOG has been described to be expressed in the posterior side of the epiblast at the onset of gastrulation. [10] There, NANOG has been implicated in inhibiting embryonic hematopoiesis by repressing the expression of the transcription factor Tal1. [11] In this embryonic stage, NANOG represses Pou3f1, a transcription factor crucial for the anterior-posterior axis formation. [10]

Analysis of arrested embryos demonstrated that embryos express pluripotency marker genes such as POU5F1, NANOG and Rex1. Derived human ESC lines also expressed specific pluripotency markers:

These markers allowed for the differentiation in vitro and in vivo conditions into derivatives of all three germ layers. [12]

POU5F1, TDGF1 (CRIPTO), SALL4, LECT1, and BUB1 are also related genes all responsible for self-renewal and pluripotent differentiation. [13]

The NANOG protein has been found to be a transcriptional activator for the Rex1 promoter, playing a key role in sustaining Rex1 expression. Knockdown of NANOG in embryonic stem cells results in a reduction of Rex1 expression, while forced expression of NANOG stimulates Rex1 expression. [14]

Besides the effects of NANOG in the embryonic stages of life, ectopic expression of NANOG in the adult stem cells can restore the proliferation and differentiation potential that is lost due to organismal aging or cellular senescence. [15] [16] [17] [18] [19]

Clinical significance

Cancer

NANOG is highly expressed in cancer stem cells and may thus function as an oncogene to promote carcinogenesis. High expression of NANOG correlates with poor survival in cancer patients. [20] [21] [22]

Recent research has shown that the localization of NANOG and other transcription factors have potential consequences on cellular function. Experimental evidence has shown that the level of NANOG p8 expression is elevated specially in cancer cells, which mean that NANOG p8 gene is a critical member in (CSCs) Cancer stem cells, so knocking it down could reduce the cancer malignancy. [9]

Diagnostics

NANOG p8 gene has been evaluated as a prognostic and predictive cancer biomarker. [23]

Cancer stem cells

Nanog is a transcription factor that controls both self-renewal and pluripotency of embryonic stem cells. Similarly, the expression of Nanog family proteins is increased in many types of cancer and correlates with a worse prognosis. [9]

Evolution

Humans and chimpanzees share ten NANOG pseudogenes (NanogP2-P11) during evaluation, two of them are located on the X chromosome and they characterized by the 5’ promoter sequences and the absence of introns as a result of mRNA retrotransposition [8] all in the same places: one duplication pseudogene and nine retropseudogenes. Of the nine shared NANOG retropseudogenes, two lack the poly-(A) tails characteristic of most retropseudogenes, indicating that copying errors occurred during their creation. Due to the high improbability that the same pseudogenes (copying errors included) would exist in the same places in two unrelated genomes, evolutionary biologists point to NANOG and its pseudogenes as providing evidence of common descent between humans and chimpanzees. [24]

See also

Related Research Articles

<span class="mw-page-title-main">Stem cell</span> Undifferentiated biological cells that can differentiate into specialized cells

In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell in a cell lineage. They are found in both embryonic and adult organisms, but they have slightly different properties in each. They are usually distinguished from progenitor cells, which cannot divide indefinitely, and precursor or blast cells, which are usually committed to differentiating into one cell type.

<span class="mw-page-title-main">Cellular differentiation</span> Developmental biology

Cellular differentiation is the process in which a stem cell changes from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover. Some differentiation occurs in response to antigen exposure. Differentiation dramatically changes a cell's size, shape, membrane potential, metabolic activity, and responsiveness to signals. These changes are largely due to highly controlled modifications in gene expression and are the study of epigenetics. With a few exceptions, cellular differentiation almost never involves a change in the DNA sequence itself. However, metabolic composition does get altered quite dramatically where stem cells are characterized by abundant metabolites with highly unsaturated structures whose levels decrease upon differentiation. Thus, different cells can have very different physical characteristics despite having the same genome.

<span class="mw-page-title-main">Embryonic stem cell</span> Type of pluripotent blastocystic stem cell

Embryonic stem cells (ESCs) are pluripotent stem cells derived from the inner cell mass of a blastocyst, an early-stage pre-implantation embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells. Isolating the inner cell mass (embryoblast) using immunosurgery results in destruction of the blastocyst, a process which raises ethical issues, including whether or not embryos at the pre-implantation stage have the same moral considerations as embryos in the post-implantation stage of development.

<span class="mw-page-title-main">Oct-4</span> Mammalian protein found in Homo sapiens

Oct-4, also known as POU5F1, is a protein that in humans is encoded by the POU5F1 gene. Oct-4 is a homeodomain transcription factor of the POU family. It is critically involved in the self-renewal of undifferentiated embryonic stem cells. As such, it is frequently used as a marker for undifferentiated cells. Oct-4 expression must be closely regulated; too much or too little will cause differentiation of the cells.

In biology, reprogramming refers to erasure and remodeling of epigenetic marks, such as DNA methylation, during mammalian development or in cell culture. Such control is also often associated with alternative covalent modifications of histones.

<span class="mw-page-title-main">Leukemia inhibitory factor</span> Mammalian protein found in Homo sapiens

Leukemia inhibitory factor, or LIF, is an interleukin 6 class cytokine that affects cell growth by inhibiting differentiation. When LIF levels drop, the cells differentiate.

<span class="mw-page-title-main">Induced pluripotent stem cell</span> Pluripotent stem cell generated directly from a somatic cell

Induced pluripotent stem cells are a type of pluripotent stem cell that can be generated directly from a somatic cell. The iPSC technology was pioneered by Shinya Yamanaka and Kazutoshi Takahashi in Kyoto, Japan, who together showed in 2006 that the introduction of four specific genes, collectively known as Yamanaka factors, encoding transcription factors could convert somatic cells into pluripotent stem cells. Shinya Yamanaka was awarded the 2012 Nobel Prize along with Sir John Gurdon "for the discovery that mature cells can be reprogrammed to become pluripotent."

<span class="mw-page-title-main">FOXP1</span> Protein-coding gene in the species Homo sapiens

Forkhead box protein P1 is a protein that in humans is encoded by the FOXP1 gene. FOXP1 is necessary for the proper development of the brain, heart, and lung in mammals. It is a member of the large FOX family of transcription factors.

<span class="mw-page-title-main">SOX2</span> Transcription factor gene of the SOX family

SRY -box 2, also known as SOX2, is a transcription factor that is essential for maintaining self-renewal, or pluripotency, of undifferentiated embryonic stem cells. Sox2 has a critical role in maintenance of embryonic and neural stem cells.

<span class="mw-page-title-main">TBX3</span> Protein-coding gene in the species Homo sapiens

T-box transcription factor TBX3 is a protein that in humans is encoded by the TBX3 gene.

<span class="mw-page-title-main">SALL4</span> Protein-coding gene in the species Homo sapiens

Sal-like protein 4(SALL4) is a transcription factor encoded by a member of the Spalt-like (SALL) gene family, SALL4. The SALL genes were identified based on their sequence homology to Spalt, which is a homeotic gene originally cloned in Drosophila melanogaster that is important for terminal trunk structure formation in embryogenesis and imaginal disc development in the larval stages. There are four human SALL proteins with structural homology and playing diverse roles in embryonic development, kidney function, and cancer. The SALL4 gene encodes at least three isoforms, termed A, B, and C, through alternative splicing, with the A and B forms being the most studied. SALL4 can alter gene expression changes through its interaction with many co-factors and epigenetic complexes. It is also known as a key embryonic stem cell (ESC) factor.

<span class="mw-page-title-main">Rex1</span> Known marker of pluripotency, and is usually found in undifferentiated embryonic stem cells

Rex1 (Zfp-42) is a known marker of pluripotency, and is usually found in undifferentiated embryonic stem cells. In addition to being a marker for pluripotency, its regulation is also critical in maintaining a pluripotent state. As the cells begin to differentiate, Rex1 is severely and abruptly downregulated.

<span class="mw-page-title-main">DPPA3</span> Protein-coding gene in humans

Developmental pluripotency-associated protein 3 is a protein that in humans is encoded by the DPPA3 gene.

<span class="mw-page-title-main">FOXD3</span> Protein-coding gene in the species Homo sapiens

Forkhead box D3 also known as FOXD3 is a forkhead protein that in humans is encoded by the FOXD3 gene.

<span class="mw-page-title-main">Cell potency</span> Ability of a cell to differentiate into other cell types

Cell potency is a cell's ability to differentiate into other cell types. The more cell types a cell can differentiate into, the greater its potency. Potency is also described as the gene activation potential within a cell, which like a continuum, begins with totipotency to designate a cell with the most differentiation potential, pluripotency, multipotency, oligopotency, and finally unipotency.

miR-296

miR-296 is a family of microRNA precursors found in mammals, including humans. The ~22 nucleotide mature miRNA sequence is excised from the precursor hairpin by the enzyme Dicer. This sequence then associates with RISC which effects RNA interference.

Embryonic stem cells are capable of self-renewing and differentiating to the desired fate depending on their position in the body. Stem cell homeostasis is maintained through epigenetic mechanisms that are highly dynamic in regulating the chromatin structure as well as specific gene transcription programs. Epigenetics has been used to refer to changes in gene expression, which are heritable through modifications not affecting the DNA sequence.

Induced stem cells (iSC) are stem cells derived from somatic, reproductive, pluripotent or other cell types by deliberate epigenetic reprogramming. They are classified as either totipotent (iTC), pluripotent (iPSC) or progenitor or unipotent – (iUSC) according to their developmental potential and degree of dedifferentiation. Progenitors are obtained by so-called direct reprogramming or directed differentiation and are also called induced somatic stem cells.

In molecular biology, mir-720 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.

<span class="mw-page-title-main">UTF1</span> Protein-coding gene in the species Homo sapiens

Undifferentiated embryonic cell transcription factor 1 is a protein in humans that is encoded by the UTF1 gene. UTF1, first reported in 1998, is expressed in pluripotent cells including embryonic stem cells and embryonic carcinoma cells. Its expression is rapidly reduced upon differentiation. UTF1 protein is localized to the cell nucleus, where it functions to regulate the pluripotent chromatin state and buffer mRNA levels by promoting degradation of mRNA.

References

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Further reading