In molecular biology MicroRNA-223 (miR-223) is a short

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms. miR-223 is a

hematopoietic Haematopoiesis (, from Greek , 'blood' and 'to make'; also hematopoiesis in American English; sometimes also h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. ...

specific microRNA with crucial functions in

myeloid Myeloid tissue, in the bone marrow sense of the word '' myeloid'' ('' myelo-'' + ''-oid''), is tissue of bone marrow, of bone marrow cell lineage, or resembling bone marrow, and myelogenous tissue (''myelo-'' + '' -genous'') is any tissue of, ...

lineage development. It plays an essential role in promoting

granulocytic Granulocytes are cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear. They hav ...

differentiation while also being associated with the suppression of

erythrocytic Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

differentiation. miR-223 is commonly repressed in

hepatocellular carcinoma Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults and is currently the most common cause of death in people with cirrhosis. HCC is the third leading cause of cancer-related deaths worldwide. It occurs in t ...

and

leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ' ...

. Higher expression levels of miRNA-223 are associated with extranodal marginal-zone lymphoma of mucosa-associated lymphoid tissue of the stomach and recurrent

ovarian cancer Ovarian cancer is a cancerous tumor of an ovary. It may originate from the ovary itself or more commonly from communicating nearby structures such as fallopian tubes or the inner lining of the abdomen. The ovary is made up of three different c ...

. In some cancers the microRNA-223 down-regulation is correlated with higher tumor burden, disease aggressiveness, and poor prognostic factors. MicroRNA-223 is also associated with

rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are involv ...

sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...

type 2 diabetes Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urination, ...

, and hepatic ischemia.

Characterization

MicroRNA-223 was initially identified bioinformatically and it was subsequently characterized as part of the haematopoietic system. Its gene resembles a myeloid gene and it could be driven by the

PU.1 Transcription factor PU.1 is a protein that in humans is encoded by the ''SPI1'' gene. Function This gene encodes an ETS-domain transcription factor that activates gene expression during myeloid and B-lymphoid cell development. The nuclear pro ...

and

C/EBPα CCAAT-enhancer-binding proteins (or C/EBPs) is a family of transcription factors composed of six members, named from C/EBPα to C/EBPζ. They promote the expression of certain genes through interaction with their promoters. Once bound to DNA, C ...

proteins which are myeloid transcription factors. MicroRNA-223 selectively targets distinct populations of transcripts harboring AU-rich elements. More specifically, it was validated that the RhoB mRNA is a ''bona fide'' miR-223 target. miR-223 also regulates

cyclin E Cyclin E is a member of the cyclin family. Cyclin E binds to G1 phase Cdk2, which is required for the transition from G1 to S phase of the cell cycle that determines initiation of DNA duplication. The Cyclin E/CDK2 complex phosphorylates p27 ...

activity by modulating expression of the

FBXW7 F-box/WD repeat-containing protein 7 is a protein that in humans is encoded by the ''FBXW7'' gene. Function This gene encodes a member of the F-box protein family which is characterized by an approximately 40 amino acid motif, the F-box. The F ...

protein. In particular, overexpression of miR-223 reduces FBXW7 mRNA levels while increasing endogenous cyclin E protein and activity levels.

Role in hematopoiesis

The role of miR-223 in hematopoiesis has been extensively analyzed in the past few years. During granulopoiesis miR-223 acts as fine-tuner of granulocytic differentiation, maturation, and function. More specifically, human granulocytic differentiation is controlled by a regulatory circuitry involving miR-223 and two transcriptional factors,

NFIA Nuclear factor 1 A-type is a protein that in humans is encoded by the ''NFIA'' gene. Function Nuclear factor I (NFI) proteins constitute a family of dimeric DNA-binding proteins with similar, and possibly identical, DNA-binding specificity. T ...

and

. These two factors compete for binding: NFI-A maintains miR-223 at low levels whereas C/EBPα upregulates miR-223 expression. The competition by C/EBPα and the granulocytic differentiation are favored by a negative-feedback loop in which miR-223 represses NFI-A translation. Analysis of expression profiles indicate that miR-223 expression decreases as cells mature during

monocytic Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and conventional dendritic cells. As a part of the vertebrate innate immune system monocytes also infl ...

, erythroid, and mast cell differentiation. miR-223 down-regulation during erythropoiesis is required for erythrocyte proliferation and differentiation at progenitor and precursor level. This down-modulation promotes erythropoiesis favoring translation of the key functional protein

LMO2 LIM domain only 2 (rhombotin-like 1), also known as LMO2, RBTNL1, RBTN2, RHOM2, LIM Domain Only Protein 2, TTG2, and T-Cell Translocation Protein 2, is a protein which in humans is encoded by the ''LMO2'' gene. Function LMO2 encodes a cysteine- ...

resulting in reversible regulation of erythroid and megakaryocytic differentiation. MicroRNA-223 also plays an essential role during osteoclast differentiation. More specifically, miR-223 expression suppresses the differentiation of osteoclast precursors into osteoclast thus making it a potential viable therapeutic target for a range of bone metabolic disorders with excess osteoclast activity.

Involvement in disease

Cancer

MicroRNA-223 is commonly repressed in

chronic lymphocytic leukemia Chronic lymphocytic leukemia (CLL) is a type of cancer in which the bone marrow makes too many lymphocytes (a type of white blood cell). Early on, there are typically no symptoms. Later, non-painful lymph node swelling, feeling tired, fever, nigh ...

acute lymphoblastic leukemia Acute lymphoblastic leukemia (ALL) is a cancer of the lymphoid line of blood cells characterized by the development of large numbers of immature lymphocytes. Symptoms may include feeling tired, pale skin color, fever, easy bleeding or bruisin ...

, acute myeloid leukemia, gastric MALT lymphoma, and recurrent

. Integrative analysis in hepatocellular carcinoma implicates Stathmin 1 ( STMN1) as a downstream target of miR-223. Furthermore, miR-223 could suppress the luciferase activity in reporter construct containing the STMN1 3' untranslated region. The reduced expressions of miR-223 may predispose to the development of hepatocellular carcinoma via the widespread induction of chromosomal instability by STMN1. MicroRNA-223 blocks the translation of

E2F1 Transcription factor E2F1 is a protein that in humans is encoded by the ''E2F1'' gene. Function The protein encoded by this gene is a member of the E2F family of transcription factors. The E2F family plays a crucial role in the control of cell ...

leading to inhibition of cell-cycle progression followed by myeloid differentiation. In acute myeloid leukemia (AML), miR-223 is down-regulated thus leading to E2F1 overexpression. The overexpressed E2F1 could bind to the miR-223 promoter and in turn lead to a further decrease in miR-223 expression through a

negative feedback Negative feedback (or balancing feedback) occurs when some function (Mathematics), function of the output of a system, process, or mechanism is feedback, fed back in a manner that tends to reduce the fluctuations in the output, whether caused by ...

loop followed by myeloid cell-cycle progression at the expense of differentiation. Overexpression of E2F1 has been shown to be an oncogenic event that predisposes cells to transformation. While there is some indication of the miR-223 role in AML there is still little known about this microRNA function in chronic lymphocytic and acute lymphoblastic leukemia. Nevertheless, MicroRNA-223 expression levels decreased significantly with the progression of these two diseases thus associating miR-223 down-regulation with higher tumor burden, disease aggressiveness, and poor prognostic factors. Gastric MALT lymphoma and recurrent ovarian cancer are associated with higher levels of MicroRNA-223 expression making them a potential biomarker.

Rheumatoid arthritis

MicroRNA-223 is overexpressed in the T-lymphocytes cells of

patients suggesting that its expression in this cell type could contribute to the etiology of the disease.

Sepsis

There is some evidence that MicroRNA-223 and MicroRNA-146a are significantly reduced in septic patients compared with systemic inflammatory response syndrome (SIRS) patients and/or healthy controls. This suggests that miR-223 can be used as a biomarker for distinguishing sepsis from SIRS.

Diabetes

Quantitative miRNA expression analyses revealed that miR-223 was consistently upregulated in the insulin-resistant hearts of patients with

. This effect was associated with miR-223 role in Glut4 regulation and

glucose metabolism Carbohydrate metabolism is the whole of the biochemical processes responsible for the metabolic formation, breakdown, and interconversion of carbohydrates in living organisms. Carbohydrates are central to many essential metabolic pathways. Plants ...

Hepatic ischemia

A recent study concluded that hepatic ischemia/reperfusion injury might be another form of liver disease that is associated with the alteration in miR-223 expression. Correlation analysis revealed that hepatic miR-223 expression levels are significantly positively correlated with the serum markers of hepatic ischemia. Further, prediction assay of miRNA targets mRNA, acyl-CoA synthetase long-chain family member 3, ephrin A1, and ras homolog gene family member B were predicted to be downstream targets of miR-223.

References

External links

* {{miRNA precursor families MicroRNA