biology

Microphthalmia-associated transcription factor

Microphthalmia-associated transcription factor is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Microphthalmia-associated transcription factor rather than just read about it. In short: Microphthalmia-associated transcription factor also known as class E basic helix-loop-helix protein 32 or bHLHe32 is a protein that in humans is encoded by the MITF gene. MITF is a basic helix-loop-helix leucine zipper transcription factor involved in lineage-specific pathway regulation of many types of cells including melanocytes, osteoclasts, and mast cells.

Key takeaways

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Reference excerpt

Microphthalmia-associated transcription factor also known as class E basic helix-loop-helix protein 32 or bHLHe32 is a protein that in humans is encoded by the MITF gene. MITF is a basic helix-loop-helix leucine zipper transcription factor involved in lineage-specific pathway regulation of many types of cells including melanocytes, osteoclasts, and mast cells. The term "lineage-specific", since it relates to MITF, means genes or traits that are only found in a certain cell type. Therefore, MITF may be involved in the rewiring of signaling cascades that are specifically required for the survival and physiological function of their normal cell precursors. MITF, together with transcription factor EB (TFEB), TFE3 and TFEC, belong to a subfamily of related bHLHZip proteins, termed the MiT-TFE family of transcription factors. The factors are able to form stable DNA-binding homo- and heterodimers. The gene that encodes for MITF resides at the mi locus in mice, and its protumorogenic targets include factors involved in cell death, DNA replication, repair, mitosis, microRNA production, membrane trafficking, mitochondrial metabolism, and much more. Mutation of this gene results in deafness, bone loss, small eyes, and poorly pigmented eyes and skin. In human subjects, because it is known that MITF controls the expression of various genes that are essential for normal melanin synthesis in melanocytes, mutations of MITF can lead to diseases such as melanoma, Waardenburg syndrome, and Tietz syndrome. Its function is conserved across vertebrates, including in fishes such as zebrafish and Xiphophorus. An understanding of MITF is necessary to understand how certain lineage-specific cancers and other diseases progress. In addition, current and future research can lead to potential avenues to target this transcription factor mechanism for cancer prevention.

Clinical significance

Mutations As mentioned above, changes in MITF can result in serious health conditions. For example, mutations of MITF have been implicated in both Waardenburg syndrome and Tietz syndrome. Waardenburg syndrome is a rare genetic disorder. Its symptoms include deafness, minor defects, and abnormalities in pigmentation. Mutations in the MITF gene have been found in certain patients with Waardenburg syndrome, type II. Mutations that change the amino acid sequence of that result in an abnormally small MITF are found. These mutations disrupt dimer formation, and as a result cause insufficient development of melanocytes. The shortage of melanocytes causes some of the characteristic features of Waardenburg syndrome. Tietz syndrome, first described in 1923, is a congenital disorder often characterized by deafness and leucism. Tietz is caused by a mutation in the MITF gene. The mutation in MITF deletes or changes a single amino acid base pair specifically in the base motif region of the MITF protein. The new MITF protein is unable to bind to DNA and melanocyte development and subsequently melanin production is altered. A reduced number of melanocytes can lead to hearing loss, and decreased melanin production can account for the light skin and hair color that make Tietz syndrome so noticeable.

Melanoma Melanocytes are commonly known as cells that are responsible for producing the pigment melanin which gives coloration to the hair, skin, and nails. The exact mechanisms of how melanocytes become cancerous are relatively unclear, but there is ongoing research to gain more information about the process. For example, it has been uncovered that the DNA of certain genes is often damaged in melanoma cells, most likely as a result of damage from UV radiation, and in turn increases the likelihood of developing melanoma. Specifically, it has been found that a large percentage of melanomas have mutations in the B-RAF gene which leads to melanoma by causing an MEK-ERK kinase cascade when activated. In addition to B-RAF, MITF is also known to play a crucial role in melanoma progression. Since it is a transcription factor that is involved in the regulation of genes related to invasiveness, migration, and metastasis, it can play a role in the progression of melanoma.

Target genes MITF recognizes E-box (CAYRTG) and M-box (TCAYRTG or CAYRTGA) sequences in the promoter regions of target genes. Known target genes (confirmed by at least two independent sources) of this transcription factor include,

Additional genes identified by a microarray study (which confirmed the above targets) include the following,

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Microphthalmia-associated transcription factor

Start with the simplest possible case. Write down what Microphthalmia-associated transcription factor claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Microphthalmia-associated transcription factor before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Microphthalmia-associated transcription factor ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Microphthalmia-associated transcription factor

In research: Microphthalmia-associated transcription factor appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Microphthalmia-associated transcription factor in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Microphthalmia-associated transcription factor is common in secondary-school and first-year university syllabi. It links to neighbouring topics Gene expression, Genes on human chromosome 3, Human proteins, so understanding it makes those chapters shorter.
In everyday life: Look for Microphthalmia-associated transcription factor outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Frequently asked questions

What is Microphthalmia-associated transcription factor in simple terms?

Why does Microphthalmia-associated transcription factor matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

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Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

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