A Fly by Any Other Name …

Segmentation of Larvae

Three Classes of Segmentation Genes mutant wild type

Gradients of Maternal Effect Gene Products Direct Subsequent Patterning Gap gene expression is regulated by bcd, hb, & cad Gap genes in turn regulate pair-rule & segment polarity genes and autoregulate themselves

Expression of Gap Genes Ems, btd, otd – expression pattern similar to hb activated by bcd

Interaction of Maternal Effect & Gap Genes

Gap Genes as Txn Regulators Eve txn reg sequences

Transgenic Analysis of Eve Expression

Expression of Pair-rule Genes Expressed in 7 vertical stripes corresponding to parasegments Expression is at border of segments

Refinement of Pair-rule Gene Expression Ftz expression (brown) in 7 stripes corresponding to even numbered parasegments co-stained for eve expression (blue) in odd numbered parasegments

Segment Polarity Genes Pair-rule genes define every other parasegment In turn, pair-rule genes regulate segment polarity genes

Segment Polarity Genes Expressed in a single column of cells at the posterior/anterior border of every parasegment PA

Segment Polarity Genes wg, hh, en signaling specify individual cell types within parasegment

Gradients of Wg & Hh

Homeotic Genes Gap genes & pair-rule genes initiate homeotic gene expression in proper domains Segment polarity genes confine homeotic gene expression to appropriate parasegments Homeotic genes regulate their own expression

Homeotic Selector Genes

Autoregulation of Homeotic Genes Each homeotic gene is negatively regulated by the more posteriorly expressed homeotic genes Antp txn is repressed by Ubx LOF mutations in homeotic genes causes anterior transformation GOF mutations in homeotic genes causes posterior transformation

Ultrabithorax LOF Mutation

Dominant Antennapedia Mutation