Localization of complement factor H gene expression and protein distribution in the mouse outer retina

Mol Vis. 2015 Feb 5;21:110-23. eCollection 2015.


Purpose: To determine the localization of complement factor H (Cfh) mRNA and its protein in the mouse outer retina.

Methods: Quantitative real-time PCR (qPCR) was used to determine the expression of Cfh and Cfh-related (Cfhr) transcripts in the RPE/choroid. In situ hybridization (ISH) was performed using the novel RNAscope 2.0 FFPE assay to localize the expression of Cfh mRNA in the mouse outer retina. Immunohistochemistry (IHC) was used to localize Cfh protein expression, and western blots were used to characterize CFH antibodies used for IHC.

Results: Cfh and Cfhr2 transcripts were detected in the mouse RPE/choroid using qPCR, while Cfhr1, Cfhr3, and Cfhrc (Gm4788) were not detected. ISH showed abundant Cfh mRNA in the RPE of all mouse strains (C57BL/6, BALB/c, 129/Sv) tested, with the exception of the Cfh(-/-) eye. Surprisingly, the Cfh protein was detected by immunohistochemistry in photoreceptors rather than in RPE cells. The specificity of the CFH antibodies was tested by western blotting. Our CFH antibodies recognized purified mouse Cfh protein, serum Cfh protein in wild-type C57BL/6, BALB/c, and 129/Sv, and showed an absence of the Cfh protein in the serum of Cfh(-/-) mice. Greatly reduced Cfh protein immunohistological signals in the Cfh(-/-) eyes also supported the specificity of the Cfh protein distribution results.

Conclusions: Only Cfh and Cfhr2 genes are expressed in the mouse outer retina. Only Cfh mRNA was detected in the RPE, but no protein. We hypothesize that the steady-state concentration of Cfh protein is low in the cells due to secretion, and therefore is below the detection level for IHC.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Complement C3b Inactivator Proteins / genetics*
  • Complement C3b Inactivator Proteins / metabolism
  • Complement Factor H / genetics*
  • Complement Factor H / metabolism
  • Epithelial Cells / cytology
  • Epithelial Cells / metabolism*
  • Female
  • Gene Expression
  • Humans
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Molecular Sequence Data
  • Organ Specificity
  • Photoreceptor Cells, Vertebrate / cytology
  • Photoreceptor Cells, Vertebrate / metabolism*
  • RNA, Messenger / genetics*
  • RNA, Messenger / metabolism
  • Retinal Pigment Epithelium / cytology
  • Retinal Pigment Epithelium / metabolism*
  • Sequence Alignment
  • Sequence Homology, Amino Acid


  • Complement C3b Inactivator Proteins
  • RNA, Messenger
  • Complement Factor H