samenvatting H7: patterning and anteroposterior patterning P. callaerts

H7: PATTERNING-
ANTEROPOSTERIOR PATTERNING
P. CALLAERTS




Inhoudsopgave
7.1 MATERNAL AND SEGMENTATION GENES REVISITED............................................2
7.2 THE BODY PLAN AND HOMEOTIC GENES............................................................3
7.2.1 HOMEOTIC TRANSFORMATIONS: CHANGE OF DEVELOPMENTAL FATE.................................................4

7.3 THE LEWIS MODEL............................................................................................ 4
7.4 DROSOPHILA HOX GENES ARE ORGANIZED IN TWO CLUSTERS............................5
7.5 THE HOMEOBOX ENCODES THE HOMEODOMAIN.................................................5
7.6 COLINEAR HOX GENE EXPRESSION....................................................................6
7.7 HOX GENES IN OTHER SPECIES – VERTEBRATES AND MAMMALS..........................6
7.7.1 VERTEBRATE HOX CLUSTERS................................................................................................... 6
7.7.2 MAMMALIAN HOX CLUSTERS.................................................................................................... 7

7.8 HOX GENES: AN ANCIENT SYSTEM FOR BODY PATTERNING.................................7
7.9 HOX GENES: LIMB PATTERNING – MEDICAL RELEVANCE......................................8
7.9.1 MUTATION IN HOXD13........................................................................................................... 8

7.10 HOX GENES: A MODEL TO STUDY EVOLUTION...................................................9
7.11 A CASE STUDY: CHANGING LIMB NUMBERS IN ARTHROPODS............................9
7.11.1 CHANGING HOX PROTEIN FUNCTION........................................................................................ 9
7.11.2 CHANGING HOX GENE EXPRESSION......................................................................................... 9
7.11.3 CHANGING HOX TARGET GENES............................................................................................. 9




Goals:

 To define homeotic transformations and give examples in Drosophila and mouse

1

,  To explain the Lewis model
 To know the organization of the Hox genes in Drosophila and in mouse
 To define the homeobox and the homeodomain
 To define colinearity of Hox genes
 To know and explain an example in biomedicine of Hox genes and their relevance
 To know how limb numbers in Arthropods can change in evolution




How is developmental fate along the anteroposterior axis determined?

Hox genes: a Swiss army knife for development and evolution. Hox genes are a key component
in this process.




7.1 MATERNAL AND SEGMENTATION GENES REVISITED

How is each segment distinguished from the next segment?

Hox genes were first defined and identified in drosophila

Previous class (H5)
 Anterior and posterior determinants: bicoid and nanos which have localized mRNA
which become proteins and form an opposing gradient. Maternally deposited genes
generate a gradient

 These gradients are then subsequently converted into increasingly defined expression
patterns of the 3 categories of segmentation genes:
1) Gap genes
2) Pair-rule genes
3) Segment polarity genes

We know how to make segments, but we don’t know how each segment is gaining its
identity!

We have seen this in H5 (positional information)




2