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 |
