Humanized SFTPA1 and SFTPA2 transgenic mice reveal functional divergence of SP-A1 and SP-A2: Formation of tubular myelin in vivo requires both gene products

Guirong Wang, Xiaoxuan Guo, Susan DiAngelo, Neal J. Thomas, Joanna Floros

Research output: Contribution to journalArticle

48 Scopus citations

Abstract

Surfactant protein A (SP-A) plays a role in lung innate immunity and surfactant-related functions. Two functional genes, SP-A1 (SFTPA1) and SP-A2 (SFTPA2), are present in humans and primates (rodents have one gene). Single gene SP-A1 or SP-A2 proteins expressed in vitro are functional. To study their role in vivo, we generated humanized transgenic (hTG) C57BL/6 mice, SP-A1(6A4) and SP-A2(1A3). The SP-A cDNA in experimental constructs was driven by the 3.7-kb SP-C promoter. Positive hTG mice were bred with SP-A knock-out mice to generate F8 offspring for study. Epithelial alveolar type II cells were SPA-positive, and Clara cells were negative by immunohistochemistry in hTG mice. The levels of SP-A in lungs of two hTG lines used were comparable with those in human lungs. Southern blot analysis indicated that twocDNAcopies of either SP-A1(6A4) or SP-A2(1A3) were integrated as a concatemer into the genome of each of the two hTG lines. Electron microscopy analysis revealed that hTG mice with a single SP-A1(6A 4) or SP-A2(1A3) gene product lacked tubular myelin (TM), but hTG mice carrying both had TM. Furthermore, TM was observed in human bronchoalveolar lavage fluid only if both SP-A1 and SP-A2 gene products were present and not in those containing primarily (>99.7%) either SP-A1 or SP-A2 gene products. In vivo rescue study confirmed thatTMcan only be restored after administering exogenous SP-A containing both SP-A1 and SP-A2 into the lungs of SP-A knock-out mice. These observations indicate that SP-A1 and SP-A2 diverged functionally at least in terms of TM formation.

Original languageEnglish (US)
Pages (from-to)11998-12010
Number of pages13
JournalJournal of Biological Chemistry
Volume285
Issue number16
DOIs
StatePublished - Apr 16 2010

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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