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#apoptosis

41 public questions tagged with this topic.

Limb Development -l

Which molecule regulates apoptosis in the interdigital mesenchyme?

Programmed death sculpting free digits from webbed paddle is executed in interdigital mesenchyme regulated by bone morphogenetic protein signaling. BMP4 secreted interdigitally phosphorylates Smad1-5-8 and activates MAPK and caspase cascades resulting in apoptosis, counterbalanced by apical ridge-derived FGF8 and BMP antagonist Gremlin protecting condensing digits. Wnt3a induces ridge, SHH sustains loop via Gremlin induction, retinoic acid modulates field boundaries. Experimental implantation of Noggin beads or reduction of BMP signaling inhibits interdigital death causing syndactyly, establis

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 19: BMP4 regulation of interdigital apoptosis and syndactyly.

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Limb Development -l

Which structure undergoes apoptosis for digit separation?

Digit individualization from initially webbed autopod paddle occurs via selective apoptosis of interdigital mesenchyme situated between digit condensations. Interdigital cells express BMP2, BMP4, BMP7 which activate Smad and caspase pathways triggering cell death, protected in digit regions by AER-derived FGFs and Gremlin antagonism. Zone of polarizing activity secretes SHH posteriorly, ridge eventually regresses, lateral plate mesoderm is skeletal origin. Failure of interdigital apoptosis results in soft-tissue syndactyly with retained webbing, underscoring precise spatiotemporal BMP-FGF inte

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 19: Interdigital BMP-mediated apoptosis and digit separation.

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Limb Development -lll

Which molecule regulates interdigital cell death?

Interdigital cell death is tightly regulated by BMP family members, primarily BMP2 BMP4 BMP7 secreted in interdigital mesenchyme under control of retinoic acid and Msx transcription. BMP binds type I receptors activating Smad1-5-8, inducing Msx2 and proapoptotic genes leading to caspase activation and DNA fragmentation. FGF8 from AER and Gremlin from digit tips normally inhibit BMP to protect digit chondrogenesis driven by Sox9 and Bmpr1b. Manipulating BMP signaling converts free digits to webbed or truncates digits. Wnt7a patterns DV axis, Gremlin antagonizes BMP upstream, but execution depen

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 20: BMP regulation of interdigital apoptosis.

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Limb Development -lll

Which molecule inhibits BMP signaling and prevents apoptosis in the interdigital webbing of ducks?

Interdigital sculpting divergence between ducks and chicks illustrates differential BMP antagonism controlling webbing. In chick, BMP2 BMP4 BMP7 in interdigital mesenchyme activate Smad signaling, upregulate Msx genes and drive caspase-dependent apoptosis, freeing digits into separate units. In duck, persistently elevated Gremlin1, a DAN family BMP antagonist, is maintained in interdigital tissue, binding BMPs and blocking apoptotic cascade, retaining webbing for swimming adaptation. Ectopic Gremlin in chick mimics webbing, Gremlin inhibition restores apoptosis. SHH maintains Gremlin loop, Wnt

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 20: BMP Gremlin and duck interdigital webbing.

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Tetrapod

Which molecule plays a crucial role in interdigital apoptosis in tetrapod limbs?

Digit separation requires elimination of interdigital mesenchyme via programmed cell death regulated by bone morphogenetic proteins. BMP2, BMP4, BMP7 are expressed in interdigital regions activating SMAD1/5/8 to induce ROS production, Msx1/2, and apoptotic effectors, while digit condensations express antagonists Gremlin, Noggin, FGFs protecting chondrogenic cells. Blocking BMP signaling with Noggin beads retains webbing causing syndactyly, whereas exogenous BMP widens death zones. FGF8 from digit tips counteracts BMP to fine-tune boundaries. Hence BMP4 constitutes major inducer of interdigital

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 19: BMP4 signaling and interdigital apoptosis, syndactyly.

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Plasma Membrane

Which of the following phospholipids is primarily involved in apoptosis?

Phosphatidylserine is normally confined to the cytoplasmic leaflet of the plasma membrane at greater than 85% asymmetry, maintained by P4-ATPase flippases ATP11A and ATP11C that use ATP to translocate aminophospholipids inward while floppases move lipids outward. Early in apoptosis, effector caspase-3 cleaves and inactivates flippases and simultaneously activates calcium-dependent scramblases such as Xkr8 and ANO6, causing rapid collapse of asymmetry and exposure of phosphatidylserine on the external surface. This externalized lipid functions as dominant eat-me signal recognized by dedicated p

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 10: Lipid Asymmetry and Apoptosis.

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Properties of Plasma Membrane

Which phospholipid is associated with apoptosis when it flips to the outer leaflet?

Phosphatidylserine externalization is tightly regulated apoptotic signature converting silent inner lipid into eat me signal for phagocytes and coagulation cofactor. In viable cells phosphatidylserine restricted inside by flippase ATP11C ATP11A requiring CDC50A chaperone maintaining aminophospholipid gradient preventing thrombin generation and immune recognition. Apoptotic executioner caspases three and seven cleave ATP11C at conserved DEVD site inactivating inward pumping and cleave Xkr8 at C terminus unmasking scramblase activity requiring binding to basigin neuroplastin heterodimer. Externa

Ref: Nagata et al., Cell Death & Differentiation 2016, PS exposure via flippase scramblase in apoptosis and coagulation.

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Flow cytometry, FACS, ELISA

Which assay is best to detect apoptotic cells?

Viability assays measure different aspects of cell health. MTT measures metabolic activity of mitochondria, trypan blue assesses membrane permeability, chromium release measures cytotoxic lysis. None specifically identify programmed cell death early stage. Annexin V FITC flow cytometry detects externalized phosphatidylserine, earliest membrane event in apoptosis while membrane remains impermeable to PI, allowing distinction of early and late apoptosis versus necrosis. Quantitative fluorescence per cell and population percentages make it sensitive, specific and standard for apoptosis kinetics i

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Apoptosis

Anoikis is apoptosis triggered by

The extrinsic pathway is initiated by binding of death ligands such as FasL or TNF to their cognate death receptors. Receptor clustering recruits adaptor proteins and caspase-8, forming the death-inducing signaling complex. Anoikis is a specialized form of apoptosis triggered by loss of integrin-mediated attachment to the extracellular matrix, thereby preventing survival of detached cells.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Apoptosis

The extrinsic apoptotic pathway is initiated by

The extrinsic pathway is initiated by binding of death ligands such as FasL or TNF to their cognate death receptors. Receptor clustering recruits adaptor proteins and caspase-8, forming the death-inducing signaling complex. Anoikis is a specialized form of apoptosis triggered by loss of integrin-mediated attachment to the extracellular matrix, thereby preventing survival of detached cells.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Apoptosis

Smac/DIABLO promotes apoptosis by

XIAP is a potent inhibitor of caspases-3, -7 and -9. The mitochondrial protein Smac/DIABLO, released during MOMP, binds XIAP and neutralizes its inhibitory activity, thereby facilitating full activation of the caspase cascade. This dual control—release of both cytochrome c and Smac—ensures robust commitment to apoptosis once mitochondria are permeabilized. Careful

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Apoptosis

Which protein directly inhibits caspase-3, -7, and -9?

XIAP, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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