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Lecture 6 Anterior posterior axis formation-the posterior signal Anterior posterior axis formation-down the hierarchy.

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Presentation on theme: "Lecture 6 Anterior posterior axis formation-the posterior signal Anterior posterior axis formation-down the hierarchy."— Presentation transcript:

1 Lecture 6 Anterior posterior axis formation-the posterior signal Anterior posterior axis formation-down the hierarchy

2 Lab or 210: P{hsp ftz  ry + } 226: P{hsp ftz ry + }

3 Lab refers to embryos laid by DH502 females crossed with DH302 males. 167 refers to embryos laid by DH502 females crossed with DH301 males. Consult Hyduk and Percival-Smith for the genotypes associated with the above strain names. See Table 1 and Figure 5.

4 The mutant allele used for the engrailed and wingless experiments was ftz 13.

5 Pole cell transplantation Mosaic analysis Cellular Blastoderm Egg chamber

6 Example pipe (pip)Toll (Tll) What cells, follicle or germ-line, are pipe and Toll required in?

7 Pole cell transplantation Mosaic analysis Ovo D No eggs

8 Pole cell transplantation Mosaic analysis Ovo D Wild type

9 Pole cell transplantation Mosaic analysis Ovo D Wild type Active egg chamber get eggs produced

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11 Toll

12 pipe

13 Posterior signal

14 Three classes of maternal effect phenotypes Nusslein-Volhard et al., Science 238,

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16 What was done to show that nanos was the best candidate to encode the posterior signal?

17 Pole cell formation

18 nanos Injection of oocyte cytoplasm

19 nanos Injection of nurse cell cytoplasm

20 Injection of stage 10 cytoplasm

21 Nanos isolation expression Wang and Lehmann Cell 66,

22 Nanos isolation localization Wang and Lehmann Cell 66,

23 Nanos isolation rescue Wang and Lehmann Cell 66,

24 Nanos and maternal Hunchback expression Nanos Hunchback

25 Expression of Hunchback from maternal mRNA

26 NanosMaternal Hunchback expression

27 Larvae lacking both maternal and zygotic hb exhibit a stronger phenotype hb/hb Irish et al., Nature 338,

28 Larvae lacking both maternal and zygotic hb exhibit a stronger phenotype hb/hb Ovo D mat hb - hb - hb + Pole cell transplantation Irish et al., Nature 338,

29 Larvae lacking both maternal and zygotic hb exhibit a stronger phenotype hb/hb mat hb - hb - Irish et al., Nature 338,

30 Maternal Hunchback is dispensable for normal development hb/hb mat hb - hb + hb - Irish et al., Nature 338,

31 Nanos phenotype Irish et al., Nature 338,

32 hb/hb nos/nos Ovo D mat nos - hb - hb + Pole cell transplantation Nanos has no role when mat hb is removed Irish et al., Nature 338,

33 Two polar centers regulate Hunchback expression Wharton and Struhl Cell 67,

34 Nanos regulatory sequences in the 3’ UTR of mat hb Wharton and Struhl Cell 67,

35 Hunchback expression Wharton and Struhl Cell 67,

36 Nanos represses bicoid translation mRNA protein Wang and Lehmann Cell 66,

37 What Nanos and Pumilio do to suppress Hunchback Gilbert Developmental Biology 7th ed

38 Microtubules and the transport of Nanos and Bicoid mRNA Gilbert Developmental Biology 7th ed

39 Hunchback lacks anterior segments Nusslein-Volhard and Wieschaus 1980 Nature 287, 795

40 Gap proteins Transcription factors Hunchback is a morphogen Delineate blocks of pattern along the A-P axis Gap information used to set up the striped expression of pair-rule genes

41 100% egg length 0% HB TLLa TLLp GTa GTp KrKni Expression of some Gap proteins

42 100% egg length 0% HB TLLa TLLp GT KrKni Posterior signal is permissive because the terminal protein Tailless supresses GT expression. The termini provide polarity.

43 100% egg length 0% HB GTp KrKni Hunchback gradient and the regulation of gap genes

44 Regulatory rules medium [HB] activates Kr medium [HB] represses Kni low [HB] represses gtp

45 100% egg length 0% HB GTpKrKni Outcome of the regulatory rules

46 Expression of FTZ and EVE Lawrence The making of a fly

47 Eve stripe 2 regulatory element Gilbert Developmental Biology 7th ed

48 lacZ Stripe two element expression

49 100% egg length 0% HB GTa Kr BCD

50 100% egg length 0% HB GTa Kr BCD EVE stripe two

51 Stripe 2 regulatory rules BIC and HB activate EVE stripe 2 expression KR and GT repress EVE stripe 2 expression

52 Stripe 2 cis-regulatory elements lacZ HBKRBCDGT lacZ

53 100% egg length 0% HB GTa Kr BCD EVE stripe two

54 Stripe 2 cis-regulatory elements lacZ HBKRBCDGT lacZ

55 Stripe 2 trans-regulatory factors lacZ HBKRBCDGT lacZ hb/hb gt/gt Kr/Kr

56 Expression of FTZ and EVE The expression of pair-rule gene is the first evidence of segmentation; however, the cellular blastoderm embryo is not overtly segmented morphologically. Prepattern. Lawrence The making of a fly

57 Establishing wingless and engrailed expression Gilbert Developmental Biology 7th ed

58 Maintaining the boundary Gilbert Developmental Biology 7th ed

59 You are segmented but not all segments are equal. Homeotic selector genes are required for determining segmental identity.

60 Homeosis Homeotic mutation

61 Antennapedia can be misexpressed either by spontaneous mutation or by genetic engineering. Antenna to second leg transformation

62 The classic Ultrabithorax phenotype: the four winged fly wild type Ubx

63

64 Proboscipedia pb tarsus proboscis

65 Homeotic gene complexes and expression Gilbert Developmental Biology 7th ed


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