Chapter 4: Molecular Basis for Embryonic Development Flashcards

1
Q

transcription factors

A

proteins possessing domains that bind to the DNA of promoter or enhancer regions of specific genes

also possess domain that interacts with RNA polymerase II or other transcription factors and consequently regulates the amount of mRNA produced by that gene

some are general that can be found in virtually all cells while others are extremely specific for certain types of cells and stages of development

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2
Q

signaling molecules

A

leave the cells that produce them and exert their effects on others, which can be neighboring cells or cells located at greater distances

many are members of the growth factor family

signaling molecules bind as ligands to receptor molecules that are often transmembrane proteins protruding through the plasma membrane of cells that they affect

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3
Q

signal transduction pathway

A

set off by the formation of a signaling molecule-receptor molecule complex; result in cascade of events that transmits the molecular signal to the nucleus of the responding cell

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4
Q

homeodomain proteins

A

contain a highly conserved homeodomain region of 60 amino acids

homeodomain: type of helix-loop-helix region

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5
Q

homeobox

A

the 180 nucleotides in the gene that encode the homeodomain

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6
Q

maternal effect genes

A

in Drosophila, establish the dorsoventral and anteroposterior axes of the embryo

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7
Q

gap genes

A

control the first step of segmentation in Drosophila; subdivide the embryo into broad regional domains

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8
Q

pair-rule genes

A

control the second step of segmentation in Drosophila; involved in the formation of seven pairs of stripes along the craniocaudal axis of the embryo

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9
Q

segment-polarity genes

A

control the third step of segmentation in Drosophila; work at the level of individual segments and are involved in their anteroposterior segmentation

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10
Q

homeotic genes in Drosophila

A

impart specific or regional characteristics to the newly formed segments;

found in the antennapedia complex and the bithorax complex

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11
Q

antennapedia-bithorax complex in Drosophila

A

consists of 8 homeobox-containing genes located in 2 clusters on the chromosome

mice and humans have at least 39 homologous homeobox genes

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12
Q

vertebrate Hox genes

A

paly a prominent role in craniocaudal segmentation of the body and their spatiotemporal expression proceeds according to very regular rules

genes are activated and expressed according to a strict sequence in the 3’ to 5’ direction

originally described to operate along the main body axis;; later discovered to be involved in developing organs or regions such as the gut, limbs, and internal and external genitalia

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13
Q

loss-of-function mutations

A

result in posterior-to-anterior transformations (cells of a given segment form the structural equivalent of the next most anterior segment)

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14
Q

gain-of-function mutations

A

result in anterior-to-posterior structural transformations (cells of a given segment form the structural equivalent of the previous most posterior segment)

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15
Q

Pax gene family

A

consists of 9 known members;

homologous to Drosophila pair-rule segmentation genes

all contain a paired domain of 128 amino acids that bind to DNA;; some also contain entire or partial homeobox domains and conserved octapeptide sequence

play important role in sense organs and developing nervous system; also involved in cellular differentiative processes when epithelial-mesenchymal transition occurs

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16
Q

POU gene family

A

Pit1: gene uniquely expressed in the pituitary

Oct1 and Oct2; Oct4 plays important role in early cleavage

Unc86: expressed in nematode

contain a homeobox, region encoding 75 amino acids, which also bind to DNA through a helix-loop-helix structure

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17
Q

Lim proteins

A

large family of homeodomain proteins; some bind to DNA in the nucleus and others are localized in the cytoplasm

involved in some stage of formation of virtually all parts of the body

no Lim=headless mammal

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18
Q

Dlx gene family

A

group of genes that have been phylogenetically conserved; six members

play important role in patterning, especially outgrowing structures, in early embryo

operate in pairs which are closely associated with Hox genes

involved in morphogenesis of jaws and inner ear and in early development of the placenta

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19
Q

Msx genes

A

small, highly conserved family of homeobox-containing genes; only two in humans;

play important roles in embryonic development; especially in epitheliomesenchymal interactions in the limbs and face

generally inhibitors of cell differentiation in prenatal development

in postnatal life; maintain proliferative capacity of tissues

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20
Q

T-box (tbx) gene

A

takes name from brachyury (T) locus; recognized originally to cause short tails in heterozygotic mice

involved in development, with roles such as inducing the mesodermal germ layer, and coordinating outgrowth or either the arm or the leg

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21
Q

basic helix-loop-helix proteins

A

contain a short stretch of amino acids in which two alpha-helices are separated by an amino acid loop

helices region (with adjacent basic regions) allows the regulator protein to bind to specific DNA sequences

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22
Q

forkhead (Fox) genes

A

family of transcription factors

contain a winged helix structure; expressed in many developing organs throughout the body; tend to have microscopically distinct domains within the developing organ and can work together to direct the morphogenesis of a structure

23
Q

zinc finger transcription factors

A

proteins with regularly placed cystidine and histidine units that are bound by zinc ions and cause he polypeptide chain to pucker into fingerlike structures which can then be inserted into specific regions of the DNA helix

24
Q

Sox genes

A

large family that have in common HMG domain

SRY gene is one example;

work in concert with other transcription factors to influence the expression of their target genes

25
HMG (high mobility group) domain
found on Sox genes; unusually for a transcription factor in that, with a partner protein, it binds to 7 nucleotide on the minor instead of the major groove on the DNA helix and causes a pronounced conformational change in the DNA
26
WT1 gene
isolated gene that in prenatal life plays a prominent role in formation of both the kidneys and the gonads crucial for the development of early forms of kidney and for formation of definitive adult kidney; necessary for formation of the gonads
27
transforming growth factor-beta family
numerous molecules that play a wide variety role during embryogenesis and postnatal life regulated by several molecules that bind to them in the extracellular space
28
TGF-beta 1-5
mesodermal induction myoblast proliferation invasion of cardiac jelly by atrioventricular endothelial cells
29
activin
granulosa cell proliferation | mesodermal induction
30
inhibin
inhibition of gonadotropin secretion by hypophysis
31
Mullerian inhibiting substance
regression of paramesonephric ducts
32
decapentaplegic
signaling of limb development
33
Vg1
mesodermal and primitive streak induction
34
BMP-1 to BMP-15
induction of neural plate, induction of skeletal differentiation, and other inductions exert their effects by inhibiting other processes in the embryo
35
nodal
formation of mesoderm and primitive streak, left-right axial fixation
36
glial cell line-derived neurotrophic factor
induction of outgrowth of ureteric bud, neural colonization of gut
37
lefty
determination of body asymmetry
38
fibroblast growth factor family
play important roles in a variety of phases of embryonic development and in fulfilling functions, such as stimulation of capillary growth, post natal body mainly regulated farther downstream; secreted FGFs are closely associated with extracellular matrix and must bind to heparan sulfate to activate their receptors
39
means of regulating FGF
modification of their interaction with heparan proteoglycans in the receptor complex regulation at the membrane of the responding cell through the actions of transmembrane proteins intracellular regulation by molecules, such as SPROUTY, which complex with parts of the signal transduction machinery of the responding cell
40
hedgehog family and sonic hedgehog
protein with highly conserved N-terminal region and a more divergent C-terminal region after its synthesis and release from RER, the signaling peptide is cleaved off and glycosylation occurs on the remaining peptide; still within the cell, shh peptide undergoes autocleavage through the catalytic activity of its C-terminal portion, while the N-terminal segment becomes covalently bonded with cholesterol the N-terminal peptide is secreted from the cell, but it remains bound to the surface off the cell that produced it;; all the signaling activity of shh resides in the N-terminal segment through the activity of another gene product, the N-terminal segment of shh, still bound to cholesterol is released from the cell; C-terminus plays no role in signaling
41
shh signaling pathway on target cell
shh, still with cholesterol, binds to Patched (Ptc) receptor, closely associated with transmembrane smoothened (smo) Ptc normally inhibits smo, but shh inhibits Ptc, thus allowing smo to give off intracellular signal
42
Wnt family
plays dramatically different roles in different classes of vertebrates; in mammals, plays important role during gastrulation (stimulate cellular proliferation that is required to bring organs to their normal proportions) often interact with components of the ECM; Wnt-inhibitory factor-1 (WIF-1) and Cerberus directly bind to the Wnt molecule, inhibiting it dickkopf effect inhibition by binding to receptor complex
43
chordin, noggin, gremlin
inhibit activity of BMP, which itself is an inhibitor inhibiting the inhibitor a common trend in developmental biology signaling molecules
44
positive and negative regulators of growth
positive: shh and FGF negative: some BMP
45
cell surface receptors
typically transmembrane proteins with extracellular, transmembrane and cytoplasmic domains extracellular domain has a binding site for the ligand; binding of ligand affects conformational change in the cytoplasmic domain two main types: (1) intrinsic protein kinase activity and (2) receptors that use a secondary messenger system to activate cytoplasmic protein kinases
46
lateral inhibition
when one cell from a group of developmentally equivalent cell differentiates into a dominant mature cell type and signals its subservient neighbors to prevent them from differentiating into the same cell type
47
Notched signaling pathway
common mechanism of lateral inhibition cell surface receptor with a large extracellular domain and a smaller intracellular domain becomes activated when combines with ligands Delta or Jagged that extend from the surface of the dominant cell, setting off pathway that inhibits the neighboring cell from differentiating into the dominant phenotype complexing of Notch with ligand stimulates an intracellular protease reaction that cleaves off the intracellular domain of the Notch molecule intracellular domain translocated to nucleus; on the way becomes associated with regulatory proteins such as deltex; in the nucleus, intracellular domain of Notch combines with several helix-loop-helix transcription factors and complex binds to DNA of gene called enhancer of split product of enhancer of split is a transcription factor that regulates other genes
48
signal transduction
process by which signal provided by the first messenger is translated into an intracellular response binding of signaling molecule to receptor resulting in a conformational change of the receptor sets of chain reaction that carries the signal to the nucleus, where it ultimately influences gene expression
49
receptor tyrosine kinase (TRK) pathway
members of FGF family do this FGF binds to receptor, G protein near receptor becomes activated and results in RAS ==> RAF ==> MAP kinase ==> ERK which enters nucleus and phosphorylates transcription factors
50
TGF-beta and Smad proteins
TGF-beta binds to type II serine-threonine kinase receptor which complexes with type I receptor two different Smad proteins, R-Smad and Co-Smad dimerize and enter the nucleus; binds with cofactor and is then capable of binding with some regulatory element on DNA
51
Wnt pathway
binding of Wnt to transmembrane receptor, Frizzled, Frizzled interacts with Disheveled, which ties up a complex of numerous molecules (destruction complex) which in the absence of Wnt causes the degradation of beta-catenin if beta-catenin is not destroyed, it enters the nucleus where it acts as a powerful adjunct to transcription factors that determine patterns of gene expression
52
Hippo pathway
regulates the growth of organs throughout the animal kingdom
53
small RNAs
small noncoding RNA molecules that exert an enormous array of influence on gene expression, mainly at posttranscriptional levels can be divided into two groups: those that act during gametogenesis and those that act during embryogenesis gametogenesis: Piwi-interacting RNAs (piRNAs) important in spermatogenesis and endogenous small interfering RNAs (endo-siRNAs) play vital roles in oogenesis miRNAs expressed in somatic tissues during embryonic development
54
vitamin A (retinol) and its metabolite, retinoic acid
retinol binds to retinol-binding protein, which attaches to specific cell surface receptors retinol then released and binds to cellular retinol binding protein (CRBP I); all-trans retinol then converted into all-trans retinoid CRBP I and CRABPI (cellular retinoic acid-binding protein) regulate the amount of retinoids that enter the nucleus retinoic acid enters the nucleus when released from CRABP and binds with dimer heterodimer retinoic acid receptor (RAR), retinoid X receptor (RXR) this complex then binds to retinoic acid response element (RARE) on DNA in the enhancer region of a gene