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Pathology Evaluation of Genetically Engineered Mice (GEM)


The Pathology/Histotechnology Laboratory provides high quality pathology evaluation/phenotyping of GEM to NCI and NIH investigators. Pathology data generated by PHL has been used in numerous publications in peer-reviewed scientific journals. This service has been ongoing for over ten years.

Our approach to phenotyping of GEM is global since manifestation of gene over- or under-expression may occur during embryogenesis, the perinatal/neonatal period, the first six months of age or as the mice age.

To provide phenotyping service, PHL pathologists interact closely with each investigator in order to customize phenotyping of GEM. The following PHL resources may be used in phenotyping:

  • Necropsy examination by trained technicians: description of gross lesions and collection of tissues for fixation, body and organ weights, snap freezing of designated tissues for later molecular analysis; sterile collection of tissue/tumors; collection of tissues in cryomolds for later cryomicrotomy, collection of blood for hematology/serum for clinical chemistry. Digital photography of gross lesions.


  • Comprehensive histopathology evaluation of H&E slides: pathology diagnoses are entered into a computerized database (Zaphod); pathology reports include individual animal reports, project summary reports of neoplastic and nonneoplastic lesions, tabulated animal data, tumor incidence data (if applicable), correlation of gross-to-microscopic findings and a narrative summary. Digital photomicrography capability is also available.


  • Target organs evaluation: when target organs are identified, the necropsy and histopathology evaluation can be focused, with in-depth analysis using:


  • Blood analysis including:
      - Hematology using the Hemavet 850:
        Complete blood count (CBC)
        Leucocytes (total, absolute and differential)
        Erythrocytes (total, hemoglobin, hematocrit, MCV, MCHC, RDW, RSD)
        Thrombocytes (total, MPV)
      - Clinical chemistry: serum plasma or urine analyzed for a range of biochemical parameters; up to fifteen tests done per sample.


  • Embryo analysis
      - Removal of embryos from timed-pregnant dams
      - Precise orientation
      - Serial and step-serial sections
      - Location of microscopic structures
      - Beta galactosidase staining
    Because GEM phenotyping is customized to each study, costs can be variable.

PHL staff provide investigators with cost estimates prior to starting a project as well as updates as the project progresses.

A sample cost estimate for phenotyping one adult GEM from necropsy examination through pathology evaluation, including hematology and clinical chemistry, is $345 per mouse.

Prices for immunohistochemistry, apoptosis and special stains and additional information on PHL services can be accessed at PHL's pricing page.

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