Genes controlling pattern formation in Drosophila embryogenesis
| Gene | Expression Pattern | Mutant Phenotype | Molecular Nature | Developmental Function |
|---|---|---|---|---|
| dicephalic (dic) | Maternal | Abnormal position of nurse cells relative to oocyte | Contributes to anteroposterior polarity of nurse cell oocyte complex | |
| gurken (grk) | Oocyte | Eggs ventralized with dorsal appendages reduced or missing | Similar to vertebrate transforming growth factor alpha (TGF-α), ligand for torpedo | Establishes first posterior and then dorsal identity of ovarian follicle cells |
| spindle (spn) (several loci) | Maternal germ line | Disturbed anteroposterior polarity of oocyte | Determination of prospective oocyte among cystocytes | |
| torpedo (trp) | Ovarian follicle cells | Similar to grk | Receptor tyrosine kinase, receptor for grk | Same as grk |
| Gene | Expression Pattern | Mutant Phenotype | Molecular Nature | Developmental Function |
|---|---|---|---|---|
| bicoid (bcd) | mRNA transcribed in nurse cells and transported to anterior of oocyte. Translated during cleavage. Protein forms anteroposterior gradient. | Head and thorax replaced with mirror image of telson | Transcriptional regulator (homeodomain and paired repeat) | Activates hb transcription; acts as a morphogen on embryonic genes; expressed anteriorly |
| exuperantia (exu) | Testis and ovary | Reducion of head; defective gastrulation | RNA-binding protein | Needed to transport bcd mRNA from nurse cells to oocyte |
| hunchback (hb) | See Zygotic anteroposterior gap class | |||
| staufen (stau) | Maternal germ line, emryonic central nervous system | Most abdominal segments missing, no pole cells, also head defects | Double-stranded RNA-binding protein | Required for bicoid mRNA localization and polar granule assembly |
| swallow (swa) | Maternal germ line | Reduction of head; cellularization defects | Rna-binding protein | Required for localization of bcd mRNA |
| Gene | Expression Pattern | Mutant Phenotype | Molecular Nature | Developmental Function |
|---|---|---|---|---|
| cappuccino (capu) | Maternal | Abdominal segments A2-A7 missing; no pole cells | Putative transmembrane receptor | Required for polar granule assembly |
| nanos | Transcription in oocyte and nurse cells. Partial localization to polar granules. Only this localized mRNA is translated. | Absence of abdomen; pole cells normal | RNA-binding protein, translational repressor | Inhibits translation of maternal hb mRNA and hastens its destruction, hence allows activation of kni in posterior. |
| oskar (osk) | Maternal germ line | Similar to capu | Required for polar granule assembly, localizes nos mRNA | |
| pumilio (pum) | Transcription maternal. Protein probably localized to posterior | Most of abdomen missing; pole cells normal | RNA-binding protein | Recruits nos protein to hb mRNA |
| spire (spir) | Maternal | Similar to capu | Actin-binding protein | Required for polar granule assembly |
| staufen (stau) | See maternal anterior system | |||
| tudor (tud) | Male and female germ line | Similar to capu | Required for pole cell formation | |
| vasa (vas) | Transcription in nurse cells and oocyte; mRNA uniform in early embryo. Protein localized in posterior of oocyte, egg, and in pole cells. | Similar to capu | RNA helicase | Required for pole cell formation |
| Gene | Expression Pattern | Mutant Phenotype | Molecular Nature | Developmental Function |
|---|---|---|---|---|
| NTF-1 | Transcriptional inhibitor | Inhibits transcription of hkb and tll | ||
| torso (tor) | Transcription in nurse cells. Transport to oocyte, where protein distributed uniformly in plasma membrane. | Absence of labrum, reduction of head skeleton, absence of A8 and telson; gain of function; suppression of segmentation in thorax and abdomen | Tyrosine kinase receptor, likely receptor for active trunk protein | Activates tll hkb by inhibiting NTF-1 |
| torsolike (tsl) | Protein secreted by anterior and posterior ovarian follicle cells probably associates with vitelline envelope near egg poles | Similar to tolr (loss of function only) | Modifying protein | Generates active form of trunk near egg poles |
| Trunk (trk) | Maternal mRNA translated in early embryo, protein released into preivitelline space | Similar to tor | Secreted protein | Probably ligand of tor, after processing by tsl |
| Gene | Expression Pattern | Mutant Phenotype | Molecular Nature | Developmental Function |
|---|---|---|---|---|
| empty spiracles | Transcription during blastoderm 78-67% EL; later, in cells forming tracheal pits and spiracles | Defects in antennal segment, tracheal system | Transcriptional regulator (homeodomain) | Specifies procephalic segments |
| giant (gt) | Initial transcription at preblastoderm stage 82-60% and 33-0% EL; changes later | Defects in or absence of labrum, labium, and abdominal segments | Transcriptional regulator (Leucine zipper) | Activates Scr; represses Kr |
| huckebein (hkb) | Anterior and posterior ends of blastoderm | Defects in terminal body structures and gut | Transcriptional regulator (zinc finger domain) | Specifies terminal structures in concert with tll |
| hunchback (hb) | Maternal mRNA initially uniform; protein forms anteroposterior gradient. Embryonic transcription 100-50% EL and 20-10% EL. Posterior domain long-lasting. | Embryonic: deletion of labium, thorax, aA7/pA8 (PS 13). No pure maternal effect, but if mother and sperm are hb-, then deletion of all mouthparts and thoracic segments and A1-A3, with mirror duplication of abdomen. | Transcriptional regulator (zinc finger domain) | Represses kni; represses Kr at high level and activates at low level; regulates eve; regulates h, run, ftz; activates Antp (with ftz); represses Ubx |
| knirps (kni) | Transcription starts at preblastoderm stage forming zone 45-30% EL. Ventral patch and narrow ring form in atnerior by cellular blastoderm stage. | Replacement of A1-A7 by single A-type segment | Transcriptional regulator (zinc finguer) | Represses Kr; regulates h, run, eve, ftz; represses Abd-B and Antp |
| Krüppel (Kr) | Transcription starts at preblastoderm stage in central zone, eventually expanding to 60-30% EL. Later also posterior patch and patch in head. | Purely embryonic. Head normal, deletion of thorax and A1-A5. Duplicated inverted A6. | Trancriptional regulator (zinc finguer) | Activates kni; represses gt; regulates eve; regulates h, run, ftz; represses Scr; activates Antp; represses Abd-B |
| orthodenticle (otd) | Narrow band (75-92% EL) in anterior blastoderm | Defects in eyes and anterior head parts | Transcriptional regulator (homeodomain, paired domain) | Activated by bcd and tor, otd - along with ems - specifies procephalic segments |
| tailless (tll) | Transcription in termini of preblastoderm embryo | Head skeleton reduced but labrum present. Hindgut, Malpighian tubules absent. | Transcriptional regulator (steroid receptor family) | Activates hb; represses Kr; represses kni; activates h |
| Gene | Expression Pattern | Mutant Phenotype | Molecular Nature | Developmental Function |
|---|---|---|---|---|
| even-skipped (eve) | Transcription starts at preblastoderm stage; 7 stripes corresponding to parasegments 1, 3, 5, etc., by cellularization stage. Fades during gastrulation. | Abolishes segmentation, giving lawn of denticles. Weak alleles delete odd parasegments. | Transcriptional regulator (homeodomain) | Represses ftz, odd, run; activates itself; activates en; represses wg; activates Dfd |
| fushi tarazu (ftz) | Transcription starts at preblastoderm stage; 7 stripes corresponding to parasegments 2, 4, 6, etc., by cellularization. Fades during germ band extension. | Deletes even parasegments | Transcriptional regulator (homeodomain) | Activates itself; activates en; activates Antp; activates Ubx; represses wg |
| hairy (h) | Transcription starts at preblastoderm stage; 7 stripes + dorsal head patch by time of cellularization. Fades during gastrulation. | Range from deletion of odd parasegments to formation of lawn of denticles. Also loss of labral tooth. Other alleles give extra hairs in adult. | Transcriptional regulator (helix-loop-helix domain) | Represses run, ftz; activates eve |
| paired (prd) | Transcription starts at preblastoderm stage; 8 stripes with dorsal head patch by cellularization. During germ band extension stripes 2-7 split and then fade. | Deletions about 1 segment wide starting in middle of denticle band affecting mainly odd abdominal segments | Transcriptional regulator (homeodomain) | Activates wg, en |
| runt (run) | Transcription starts at preblastoderm stage; 7 stripes. After cellularization, patter becomes single-segment stripes, which persist through germ band extension. | Deletions more than 1 segment wide centered on T2, A1, A3, A5, A7, with mirror duplication of what is left | Transcriptional regulator (novel) | Represses h, eve; activates ftz |
| Gene | Expression Pattern | Mutant Phenotype | Molecular Nature | Developmental Function |
|---|---|---|---|---|
| engrailed (en) | Transcription starts at blastoderm stage and produces 14 narrow stripes by extended germ band stage, marking the anterior of each parasegment. Expression in posterior compartments of larval imaginal discs | Ventral cuticle a continuous lawn of denticles. Less severe alleles delete even-numbered parasegments | Transcriptional regulator (homeodomain) | Maintains hh and indirectly wg activity; selector gene defining posterior compartment |
| frizzled (fz) | Various imaginal discs | Variable orientation of wing hairs, irregular ommatidia in eye | Seven-pass transmembrane receptor | Receptor for wg |
| frizzled-2 (fz-2) | Apparently redundant with fz | |||
| hedgehog (hh) | Posterior compartments of larval segments and imaginal discs | Posterior compartment replaced with mirror image of anterior compartment |
