CHARACTERIZATION OF TWO BABOON SURFACTANT PROTEIN A (SP A) GENES.
Gao, Erwei, Ying Wang, Susan M. McCormick, Jinxing Li, Steven R. Seidner and
Carole R. Mendelson.
Departments of Biochemistry and Obstetrics Gynecology, The University of
Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard,
Dallas, Texas 75235 9038,1 and Department of Pediatrics, University of Texas
Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio,
Texas 78284-78122
APStracts 3:0069L, 1996.
The gene encoding surfactant protein A (SP-A) is expressed in type II
pneumonocytes and is developmentally- and hormonally-regulated in fetal lung
tissue. SP-A is encoded by a single-copy gene in rabbits, dogs, rats and mice.
By contrast, the human genome contains two similar genes, hSP-A1 and hSP-A2,
which are differentially regulated during development, and by cyclic AMP and
glucocorticoid treatment of human fetal lung in culture. In the present study,
we have isolated and characterized baboon genomic clones containing two highly
similar SP-A genes. Restriction mapping of these clones, together with
Southern analysis of genomic DNA, indicates that these comprise two distinct
baboon SP-A genes. Sequence comparison of DNA upstream of the transcription
initiation sites and within the 3’-untranslated regions encoded by exons VI
indicates that one of the baboon SP-A genes (bSP-A1) is more similar to hSP-
A1, whereas, the other (bSP-A2) is more similar to hSP-A2. Primer extension
analysis of baboon lung mRNA indicates that both baboon SP-A genes utilize
conserved transcription initiation sites. Reverse transcriptase-polymerase
chain reaction (RT-PCR) analysis of RNA isolated from lung tissues of fetal
baboons of 160 days gestational age indicates that both bSP-A1 and bSP-A2 are
expressed in baboon fetal lung, and that mRNA transcripts of bSP-A1 and bSP-A2
genes are primarily comprised of sequences encoded by exons I and III-VI;
however, minor transcripts of the bSP-A1 gene containing exon II and exon II
plus an extension also were detected. The presence of two SP A genes in the
baboon suggests that duplication of the SP-A gene occurred more than 26.5
million years ago, prior to divergence of the baboon lineage from the man-
gorilla-chimpanzee clade.
Received 11 December 1995; accepted in final form 10 May 1996.
APS Manuscript Number L362-5.
Article publication pending Am. J. Physiol. (Lung, Cell. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 May 96