ID4

Key takeaways

ID4 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect ID4 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of ID4 from memory before moving on to harder problems.

Reference excerpt

ID4 is a protein coding gene. In humans, it encodes the protein known as DNA-binding protein inhibitor ID-4. This protein is known to be involved in the regulation of many cellular processes during both prenatal development and tumorigenesis. This is inclusive of embryonic cellular growth, senescence, cellular differentiation, apoptosis, and as an oncogene in angiogenesis.

Structure The gene spans 3.3kb on the plus strand. It is composed of 3 exons and during transcription its mRNA is 2343 bp. The encoded protein consists of 161 amino acids, is 16.6 KDa and contains a poly-Ala segment from amino acid 39 to 48, a helix-loop-helix motif from amino acid 65 to 105 and a poly-Pro region from amino acid 118 to 124. This protein is expressed in various tissues.

Function The ID4 gene is part of the ID gene family. This family is also known as inhibitors of DNA binding protein family and are composed of transcription inhibitory proteins which modulate a number of processes. They are transcriptional regulators that work by negatively regulating their basic helix-loop-helix (bHLH) transcription factors by forming heterodimers. The heterodimer is what inhibits their DNA binding and transcriptional activity. Transcription factors containing a basic helix-loop-helix (bHLH) motif regulate expression of tissue-specific genes in a number of mammalian and insect systems. DNA-binding activity of the bHLH proteins is dependent on formation of homo- and/or heterodimers. Dominant-negative (antimorph) HLH proteins encoded by Id-related genes, such as ID4, also contain the HLH-dimerization domain but lack the DNA-binding basic domain. Consequently, ID proteins inhibit binding to DNA and transcriptional transactivation by heterodimerization with bHLH proteins.

Regulation during embryogenesis The ID4 gene plays a pivotal role in development and is a key player in many pathways of embryogenesis and foetal development. ID4 expression is upregulated in embryogenesis during days 9.5 and 13.5 of gestation and restricted to specific cells of the central and peripheral nervous system. ID4 transcription control has both negative and positive regulatory elements inclusive of novel inhibitory functions. ID4 expression has been shown to be discrete in the early stages, with transcription transiently expressed in subsets of migrating neural crest cells, the dorsal myocardium, the segmental plate mesoderm, and the tail bud. Later stages show ID4 expression in the telencephalic vesicles and corneal epithelium. ID4 expression is only detected in neuronal tissues and the ventral portion of the epithelium in the developing stomach during embryogenesis. ID4 is expressed in the central nervous system and is required for G1-S transition and to enhance proliferation in early cortical progenitors. It is complexly involved in regulating neural stem cell proliferation and differentiation by inhibiting proliferation of differentiating neurons through enhancement of RB1-mediated pathways. This is either by direct interaction or through interaction with other molecules of the cell cycle machinery. ID4 also regulates the lateral expansion of the proliferative zone in the developing cortex and hippocampus. This is integral to normal brain size formation. ID4 regulates neural progenitor proliferation and differentiation. Its expression is seen in the neural tube much later than other ID genes. ID4 was also shown to be involved in the regulation of cardiac mesoderm function in frog embryos and human embryonic stem cells. Ablation of the ID gene family mouse embryos showed failure of anterior cardiac progenitor specification and the development of heartless embryos. This study also demonstrated that ID4 protein is involved in the regulating cardiac cell fate by a pathway which represses two inhibitors of cardiogenic mesoderm formation (TCF3 and FOXA2) whilst activating inducers (EVX1, GRRP1, and MESP1).

Clinical significance

Role in endometriosis ID4 has been linked to the molecular pathogenicity of endometriosis. These pathways are still poorly understood. It is thought that ID4 plays a role in the transcription of HOXA9 and CDKN1A which are known to be associated with endometriosis. A genome wide association study revealed over 100 candidate genes associated with endometriosis. Of these, six were shown to have a highly reliable association, of which the ID4 gene was identified. This is thought to be due to an independent single nucleotide polymorphism at loci rs7739264 near ID4 on chromosome 6p22.3. ID4 is implicated in the molecular pathogenicity of endometriosis as being differentially expressed between the proliferative, early and mid-secretory phases.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with ID4

Start with the simplest possible case. Write down what ID4 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 ID4 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 ID4 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 ID4

In research: ID4 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 ID4 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: ID4 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Genes on human chromosome 6, Transcription factors, so understanding it makes those chapters shorter.
In everyday life: Look for ID4 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.

How to study ID4 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what ID4 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain ID4 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is ID4 in simple terms?

ID4 is a protein coding gene. In humans, it encodes the protein known as DNA-binding protein inhibitor ID-4.

Why does ID4 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.

How should I study ID4?

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.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on ID4.