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Determination of the window of lethality


Determining the developmental window of lethality is essential as it can provide valuable information about the type of defects present in the embryos and/or placentas. To determine the window of lethality, representative stages will be chosen to dissect the embryos or fetuses. These stages represent critical time points in development and the results will help inform subsequent histological analyses.


  • Stereomicroscopes 
  • Automated macroscope equipped with digital camera


Genotyping protocol by PCR is recommended because early stages of development will not provide enough material for genotyping the embryos by Southern.

Characterization of embryonic and perinatal defects


To detect developmental defects in prenatal mice from E5.5 to E18.5. Embryos and fetuses are analyzed macroscopically, then fixed in Bouin's fluid, decalcified (for ages E16.5 and beyond), embedded in paraffin, serially sectioned at 7 µm and stained with hematoxylin and eosin or Mallory's trichrome and hematoxylin stain. Whole skeletal analyses can be performed on E18.5 fetuses (alcian blue and alizarin red staining)



Slide scanner (Nanozoomer 2.0 HT, Hamamatsu Photonics K.K., Hamamatsu City, Japan)




Always use age-matched littermates as controls

Characterization of gene expression pattern

LacZ enzyme activity is evaluated by histochemical staining in order to characterize anatomical structures expressing the targeted gene in embryos carrying a lacZ transgene. See gene expression pattern.

Micron-scale Computed Tomography (µCT) of Embryos


Embryos may be morphologically examined in situ using micron-scale X-ray Computed Tomography (also called µCT). This can be an effective strategy for screening a large number of different groups (e.g. genetic screens, multiple alleles, or drug treatments) for organ-specific or broad effects on embryo anatomy, relieving extensive embryo processing of standard histological techniques.


µCT (PerkinElmer Quantum FX, Waltham , Massachusetts)

Sample Results


  • Macroscopic and microscopic images of the abnormalities
  • Fixed embryos or fetuses
  • Embryos, fetuses or specific embryonic tissues fixed in liquid nitrogen for RNA analysis
  • Sets of stained slides
  • Pathology reports with expert opinion 
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