Table 1.

Functional analysis of Xenopus pronephric genes by microinjectiona

Gene ExpressedMaterial InjectedPosition of InjectionPhenotype in Pronephros
xWT1 (12)mRNA transcribed in vitro from both KTS plus and minus formsInjected into the C tier at the 32-cell stageReduced size of pronephric tubules as a result of failure to form a pronephric anlagen of the appropriate size
Xlim-1 (29)mRNA transcribed in vitroInjected into the C tier at the 32-cell stage15% enlarged and 19% ectopic tubules; no abnormality was found in the duct
Xpax8/2 (29)mRNA transcribed in vitroInjected into the C tier at the 32-cell stage7% enlarged and 23% ectopic tubules; no abnormality was found in the duct; a similar effect was observed with Pax-2
Xpax8 + Xlim-1 (29)mRNA transcribed in vitroInjected into the C tier at the 32-cell stage19% enlarged and 47% with ectopic tubules with multiple branches; no abnormality was found in the duct
Xlim-1, Xlim-1enR Xlim1-VP16 +/- Xldb-1 (11)mRNA transcribed in vitroInjected into the animal pole of embryos and then dissected as animal caps and incubated in combinations of RA and activinConstitutively active or wild-type Lim-1 failed to induce pronephros with RA or activin treatment alone but augmented pronephros when treated with both; the dominant negative Xlim-1enR inhibited kidney formation
Xlim-1enR (11)mRNA transcribed in vitroInjected into the C tier at the 32-cell stageA functional deficit of Xlim1 prevents the process of tubulogenesis, embryos failing to progress pass the tor stage
GR-Su(H)VP16 GR-Su(H)DBM GR-notch ICD (14)mRNA transcribed in vitroInjected into one ventro-vegetal blastomere and expression induced with dexamethasone at stage 20Obliteration of duct markers after the activation by dexamethasone of GR-Su(H)VP16 or GR-notch ICD as a result of increased notch signaling; dominant negative inhibition of notch signaling increased duct formation and expression of glomus markers
XCIRP-1 (28)Antisense and sense RNA transcripts transcribed in vitroInjected into both cells of the two-cell embryoAntisense inhibited pronephros development; no phenotype with mRNA overexpression
Annexin IV (21)MO oligonucleotide and mRNA transcribed in vitroInjected into the one-cell embryoMO generated a shortened, uncoiled tubule with wider diameter of lumen compared with wild type; partial rescue with wild-type mRNA; no phenotype with mRNA overexpression
Xwnt-4 (13)MO oligonucleotide and mRNA transcribed in vitroInjected into the V2 blastomere of the eight-cell embryoMO generated a phenotype with complete loss of tubules, although dust was unaffected; overexpression generated a phenotype with abnormal and fused nephrostomes
XC3H-3b (26)MO oligonucleotide and mRNA transcribed in vitroInjected into C2 and C3 of the 32-cell embryoMO inhibited the formation of the three dorsal tubules, although the ventral common tubule and duct were normal; overexpression generated either shortened or missing tubules
Xlmx-1b (30)MO oligonucleotide and mRNA transcribed in vitroInjected into the V2 blastomere of the eight-cell embryoMO generated a phenotype with a reduced glomus; no glomus phenotype with overexpression
  • a MO, morpholino.