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Pattern formation Flashcards

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1
Q

What is the process of ordered spatial arrangements of differentiated cells creating tissues and organs called?

A

Pattern formation

Pattern formation is crucial during embryogenesis, leading to the development of organs and appendages.

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2
Q

What are the general steps involved in regional specification during pattern formation?

A
  • Definition of the cells of a region
  • Establishment of signaling centers for positional information
  • Differentiation of cells in response to cues
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3
Q

What must cells in the developing vertebrate upper limb differentiate into?

A
  • Muscle (myocytes)
  • Cartilage (chondrocytes)
  • Bone cells (osteocytes)
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4
Q

What is the role of the Shh protein in pattern formation?

A

Involved in patterning of the vertebrate neural tube, somites, and limbs, and distinguishing left from right

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5
Q

What can point mutations in the human Shh gene, SHH, cause?

A
  • Abnormal midline brain development (holoprosencephaly)
  • Severe intellectual disability
  • Early death
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6
Q

What is gastrulation?

A

The process of cell and tissue movements rearranging the blastula cells into new positions and neighbors

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7
Q

What three germ layers are formed during human gastrulation?

A
  • Ectoderm (outer layer)
  • Endoderm (inner layer)
  • Mesoderm (middle layer)
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8
Q

What is the major structural feature of mammalian gastrulation?

A

The primitive streak

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9
Q

What is neurulation?

A

The process by which the dorsal mesoderm and overlying ectoderm interact to form the hollow neural tube

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10
Q

What role does the Spemann–Mangold organizer play in neurulation?

A

Controls induction of the neural tube and transformation of mesoderm

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11
Q

What are the three cell populations formed from the ectoderm during neurulation?

A
  • Neural tube (brain and spinal cord)
  • Epidermis of the skin
  • Neural crest cells
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12
Q

What is the primary function of embryonic endoderm?

A

To form the linings of the digestive tract and respiratory tree

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13
Q

What are the five components of mesoderm?

A
  • Notochord
  • Dorsal mesoderm
  • Intermediate mesoderm
  • Lateral mesoderm
  • Head mesenchyme
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14
Q

What is the role of fibroblast growth factor receptor 3 (FGFR3) in development?

A

Mutations can cause skeletal dysplasias, including thanatophoric dysplasia

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15
Q

True or False: The anterior/posterior axis of a developing mammalian embryo is defined by the primitive streak.

A

True

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16
Q

What is the function of Hox genes in vertebrate development?

A

Identify various regions along the anterior/posterior axis of the body and limbs

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17
Q

What do dorsalizing signals do in dorsal/ventral patterning?

A

Promote dorsal structures and repress ventralizing signals

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18
Q

What is organogenesis?

A

The formation of organs and limbs occurring after gastrulation

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19
Q

How does craniofacial development relate to the central nervous system?

A

Neural crest cells contribute to structures forming the face and jaw

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20
Q

What is the outcome of functional inactivation of Hoxa3 in mice?

A

Small or absent thymuses and thyroid, malformations of the heart and blood vessels

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21
Q

What common process is involved in endoderm-derived structures?

A

Budding and branching

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22
Q

Fill in the blank: The major structural feature of mammalian gastrulation is the _______.

A

primitive streak

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23
Q

What do mutations in genes that disrupt earlier developmental events often lead to?

A

Lethality

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24
Q

What is the significance of the expression of Hox genes in vertebrate development?

A

Provides patterning information corresponding to the axial level of differentiation

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25
What are Hox genes?
Hox genes are a group of related genes that control the body plan of an embryo along the anterior/posterior axis.
26
How many Hox genes are clustered in Drosophila?
8 Hox genes.
27
How many Hox genes are distributed among clusters on chromosomes in humans?
39 Hox genes.
28
What are paralogs?
Paralogs are Hox genes that share the same number but are located in different clusters.
29
In which direction are Hox genes expressed along the anterior/posterior axis?
From 3′ to 5′.
30
What happens when Hoxb4 expression is eliminated?
The combinatorial code in the third segment is altered, resulting in a homeotic transformation.
31
What is a homeotic transformation?
The transformation of one structure into another due to changes in gene expression.
32
What are some challenges in studying human development genes?
Ethical concerns, small family sizes, and long generation times.
33
Why are mice commonly used as animal models for human disease?
They are well-understood, easily manipulated, and many developmental genes are conserved.
34
What is a transgenic mouse?
A mouse that has had human genes inserted into its embryonic stem cells.
35
What is a knockout model?
A model where a specific mouse gene is disrupted so that it is not expressed.
36
Which diseases have been studied using mouse knockouts?
* Neurofibromatosis type 1 * Gaucher disease * Huntington disease * Myotonic dystrophy * Fragile X syndrome * Cystic fibrosis * Alzheimer's disease
37
What is a conditional knockout?
A model where gene disruption occurs only in specific cells, tissues, or at specific times.
38
What is the role of the Fgf8 gene in limb development?
Disruption of Fgf8 in the limb results in severe truncation of forelimbs.
39
What are Zinc-finger nucleases (ZFNs)?
Engineered nucleases used for producing targeted mutations in the genome.
40
What is the CRISPR/Cas system?
A genome editing system based on bacterial enzymes that can generate mutations in multiple species.
41
What is the significance of motile cilia in L/R asymmetry?
They create a leftward flow of fluid that is crucial for establishing left/right asymmetry.
42
What is situs inversus?
A complete mirror image of organ arrangement along the midline.
43
What is situs ambiguus?
Randomization of the arrangement of organs along the midline.
44
Which proteins are essential for the function of cilia?
* Left-right dynein (lrd) * Polycystin-2
45
What gene mutations are commonly associated with laterality defects in humans?
* ZIC3 * LEFTY2 * CFC1 * ACVR2B
46
What is the role of dHAND and eHAND in heart development?
They are transcription factors involved in patterning the right and left ventricles.
47
What is the link between cilia dysfunction and primary ciliary dyskinesias?
Cilia dysfunction can lead to disorders including situs inversus and other anomalies.
48
What is the effect of knocking out both Hoxa11 and Hoxd11 genes?
Severe reduction in the length of the radius and ulna.
49
What are common abnormalities found in human conjoined twins?
More frequent abnormalities of L/R asymmetry compared to singleton or dizygotic twins.
50
What role do motile cilia play in organ symmetry?
Establish normal left-right symmetry and asymmetric positioning of organs
51
What can mutations in genes encoding cilia proteins lead to?
A variety of conditions characterized by overlapping anomalies of organs
52
What is Joubert syndrome caused by?
Mutations in more than 30 different genes encoding cilia proteins
53
From what do the bones of the skull develop?
Mesenchyme produced by neural crest cells
54
What is craniosynostosis?
Premature fusion of skull bones causing misshapen head and potential brain growth impairment
55
What gene mutations are often associated with craniosynostosis?
Mutations in FGFR genes and MSX2
56
What disorder is caused by mutations in the GLI3 gene?
Greig cephalopolysyndactyly
57
What does the GLI3 gene encode?
At least seven conserved domains including DNA-binding and zinc-finger domains
58
What syndrome is characterized by hypothalamic hamartomas and polydactyly?
Pallister–Hall syndrome
59
What is the function of IFT in cilia?
Bidirectional transport system moving cargo into and out of the cilium
60
What are the main characteristics of Primary Ciliary Dyskinesia?
Chronic airway disease and laterality defects
61
What is the primary signaling factor in the zone of polarizing activity (ZPA)?
Shh (Sonic hedgehog)
62
What gene mutations cause Holt–Oram syndrome?
Mutations in the gene TBX5
63
What are the roles of Tbx4 and Tbx5 in limb development?
Essential for hindlimb and forelimb development, respectively
64
What is the apical ectodermal ridge (AER)?
A specialized region that extends from anterior to posterior along the limb bud
65
What is the function of Fgf10 in limb bud initiation?
Regulates expression to initiate limb bud formation
66
What is the outcome of Wnt7a expression in the mesoderm?
Instructs the mesoderm to adopt dorsal characteristics
67
What type of defects are associated with mutations in Hox genes?
Birth defects, including synpolydactyly and hand–foot–genital syndrome
68
What does the transcription factor IPF1 do in pancreatic development?
Stimulates transcription of insulin in beta cells
69
What is the significance of interactions between mesenchymal and epithelial cells?
Prominent in the development of various organs and structures
70
Fill in the blank: Mutations in the human homolog of the mouse gene hairless cause loss of _______.
All body hair
71
What is the role of Bmp-4 during tooth development?
Signals mesenchyme to express transcription factors for tooth formation
72
What is the primary function of Hox genes in limb development?
Control growth and differentiation of cells along the proximal/distal axis
73
What is the role of MSX1 mutations in humans?
Disrupt tooth formation and cause loss of the second premolars ## Footnote MSX1 is a gene associated with tooth development.
74
What is the effect of mutations in the human homolog of the mouse gene hairless?
Cause loss of all body hair, including scalp, eyebrows, axillae, and pubis ## Footnote This gene is involved in hair follicle development.
75
What is the significance of p63 in epithelial tissue?
Promotes growth and differentiation of the epithelium ## Footnote p63 is a homolog of the tumor suppressor gene p53.
76
What happens when p63 function is perturbed?
Decreases availability of epithelial progenitor cells and causes abnormalities in limbs, skin, teeth, hair, and nails ## Footnote This can lead to at least six different malformation syndromes.
77
What are osteoblasts and their role in the body?
Bone-forming cells essential for skeletal formation ## Footnote Osteoblasts are critical for bone development and maintenance.
78
Which transcription factor regulates the differentiation of osteoblasts?
Runx2 ## Footnote Runx2 is an osteoblast-specific transcription factor.
79
What are the effects of targeted disruption of Runx2 in mice?
Complete lack of ossification of the skeleton, widened cranial sutures, shortened digits, and abnormalities of the shoulder girdle ## Footnote These defects resemble those in humans with cleidocranial dysplasia.
80
What is cleidocranial dysplasia caused by?
Mutations in Runx2 ## Footnote This condition affects bone development and growth.
81
How do organ formations occur?
Through reciprocal interactions between epithelium and mesenchyme ## Footnote This interaction is crucial for proper organ development.
82
What mediates the interaction between epithelium and mesenchyme during organ formation?
Secreted signaling molecules that bind to receptors ## Footnote These molecules conduct signals through interconnected pathways to influence DNA transcription.

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