Elevated expression of four apolipoprotein genes during the 32-35 week gestation window in the human developing lung.
BACKGROUND
Co-expression of four apolipoproteins with a sex difference was observed in the mouse developing lung with an increase during the day of the surge of surfactant synthesis and a causal relationship was proposed.


OBJECTIVE
To determine whether these apolipoproteins and lipoprotein lipase (LPL) are expressed in the human fetal lung. To compare the distribution patterns of apoC-II and LPL proteins at different developmental ages.


METHODS
Real-time PCR with RNA samples and immunohistochemistry with tissues from lungs of fetuses deceased between 19 and 40 weeks' pregnancy.


RESULTS
Elevated apolipoprotein A-I (apoA-I), apoA-II, apoC-II, and apoH expression was observed only during a short gestation time window from 32 to 35 weeks' gestation. LPL was expressed at relatively constant levels over gestation time. The gene encoding for the essential co-factor of LPL, apoC-II, was expressed at similar levels than LPL gene only during the 32-35 week gestation window. ApoC-II and LPL protein distribution vary according to gestation time, with obvious co-localization in capillaries at 32 weeks' gestation, but not in samples collected at 22-24 weeks' gestation.


CONCLUSIONS
ApoA-I, apoA-II, apoC-II, and apoH genes are expressed with a human-specific narrow peak of elevated expression in late gestation. Specific and developmental time-dependent distribution profiles were observed for apoC-II and LPL proteins. The 32-35 weeks' gestation window, where high levels of expression of apolipoproteins and co-localization of apoC-II and LPL protein were observed, correlates with the reported decrease in the incidence and severity of respiratory distress syndrome (RDS) consequently to the surge of surfactant synthesis.
Provost
Pierre R
PR
Reproduction Axis, Perinatal and Child Health, Room T-1-49, CHUQ Research Center, Québec City, Québec, Canada.
Tremblay
Yves
Y
D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism*; D016633:Apolipoprotein A-II / Q000378:metabolism*; D053304:Apolipoprotein C-II / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007150:Immunohistochemistry; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008168:Lung / Q000196:embryology* / Q000378:metabolism; D008297:Male; D051379:Mice; D016133:Polymerase Chain Reaction; D053482:beta 2-Glycoprotein I / Q000378:metabolism*
C505693:APOA1 protein, human; C115794:APOA2 protein, human; D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D053304:Apolipoprotein C-II; D017931:DNA Primers; D018076:DNA, Complementary; D053482:beta 2-Glycoprotein I; D008071:Lipoprotein Lipase