Targeted disruption of the surfactant protein B gene disrupts surfactant homeostasis, causing respiratory failure in newborn mice.

TLDR

Surfactant protein B is a small hydrophobic protein that improves surfactant phospholipid spreading and stability in the alveolus. The study aimed to evaluate SP‑B function by disrupting its gene in mouse embryonic stem cells. The SP‑B gene was knocked out via homologous recombination in mouse embryonic stem cells. Homozygous SP‑B knockout mice died at birth from respiratory failure, with atelectatic lungs lacking SP‑B protein, lamellar bodies, and exhibiting disrupted surfactant phospholipid and protein processing.

Abstract

Surfactant protein B (SP-B) is an 8.7-kDa, hydrophobic protein that enhances the spreading and stability of surfactant phospholipids in the alveolus. To further assess the role of SP-B in lung function, the SP-B gene was disrupted by homologous recombination in murine mouse embryonic stem cells. Mice with a single mutated SP-B allele (+/-) were unaffected, whereas homozygous SP-B -/- offspring died of respiratory failure immediately after birth. Lungs of SP-B -/- mice developed normally but remained atelectatic in spite of postnatal respiratory efforts. SP-B protein and mRNA were undetectable and tubular myelin figures were lacking in SP-B -/- mice. Type II cells of SP-B -/- mice contained no fully formed lamellar bodies. While the abundance of SP-A and SP-C mRNAs was not altered, an aberrant form of pro-SP-C, 8.5 kDa, was detected, and fully processed SP-C peptide was markedly decreased in lung homogenates of SP-B -/- mice. Ablation of the SP-B gene disrupts the routing, storage, and function of surfactant phospholipids and proteins, causing respiratory failure at birth.