BACKGROUNDDespite evidence that genetic factors contribute to the duration of gestation and the risk of preterm birth, robust associations with genetic variants have not been identified. We used large data sets that included the gestational duration to determine possible genetic associations. METHODSWe performed a genomewide association study in a discovery set of samples obtained from 43,568 women of European ancestry using gestational duration as a continuous trait and term or preterm (<37 weeks) birth as a dichotomous outcome. We used samples from three Nordic data sets (involving a total of 8643 women) to test for replication of genomic loci that had significant genomewide association (P<5.0×10 −8 ) or an association with suggestive significance (P<1.0×10 −6 ) in the discovery set. RESULTSIn the discovery and replication data sets, four loci (EBF1, EEFSEC, AGTR2, and WNT4) were significantly associated with gestational duration. Functional analysis showed that an implicated variant in WNT4 alters the binding of the estrogen receptor. The association between variants in ADCY5 and RAP2C and gestational duration had suggestive significance in the discovery set and significant evidence of association in the replication sets; these variants also showed genomewide significance in a joint analysis. Common variants in EBF1, EEFSEC, and AGTR2 showed association with preterm birth with genomewide significance. An analysis of mother-infant dyads suggested that these variants act at the level of the maternal genome. CONCLUSIONSIn this genomewide association study, we found that variants at the EBF1, EEFSEC, AGTR2, WNT4, ADCY5, and RAP2C loci were associated with gestational duration and

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The present study was undertaken to determine if a synthetic peptide, KLLLLKLLLLKLLLLKLLLLK (KL4), in which K = lysine and L = leucine, in an aqueous dispersion of phospholipids (DPPC and POPG), would expand pulmonary alveoli and improve gas exchange in premature human infants with respiratory distress syndrome (RDS). The KL4 peptide was synthesized to resemble the amino acid pattern of surfactant protein B (SP-B). Forty-seven infants with RDS were treated within 4 h of birth with the KL4-peptide/phospholipid mixture, called KL4-Surfactant. The average arterial-to-alveolar oxygen tension ratios (a/A O2) of 39 patients included in efficacy analyses rose from pretreatment values of 0.14 +/- 0.02 (mean +/- SEM) to 0.40 +/- 0.04 (normal value > or = 0.40) by 12 h of age. Mean airway pressures and oxygenation index values fell concomitantly, and expansion of the lungs was observed on radiographs. The median duration of mechanical ventilation was 5.0 d. Of the 39 included infants, 29 required only a single dose. Radiographic data indicate that those patients requiring a second instillation of KL4-Surfactant but not showing a sustained rise in a/A O2 ratios did, in fact, exhibit expansion of alveoli in the lung. There were no RDS-related deaths; the incidence of complications was no higher than found in other comparable published studies. The data demonstrate that the synthetic peptide, KL4, which mimics the hydrophobic and hydrophilic pattern of SP-B, when formulated in an aqueous dispersion with the phospholipids DPPC and POPG, creates a strong and durable surfactant activity as judged by expansion of pulmonary alveoli and improvement of gas exchange in infants with RDS.

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ABSTRACf. Synthetic pulmonary surfactants consisting of mixtures of phospholipids with synthetic peptides based on the amino acid sequence of human surfactant apoprotein SP-B were prepared. These surfactants were analyzed for their ability to lower surface tension on a pulsating bubble surfactometer and for their capacity to improve lung compliance and increase alveolar expansion in a fetal rabbit model of surfactant deficiency. The data demonstrate that several peptides, ranging from 17 to 45 residues in length, matching the carboxy-terminal sequence of the SP-B protein, when appropriately recombined with the phospholipids dipalmitoylphosphatidylcholine and phosphatidylglycerol (3:1), are capable of producing a synthetic surfactant with biophysical and biologicactivity approaching that of human surfactant derived from amniotic fluid. (Pediatr Res 29: 460-465, 1991) Abbreviations DPPC, dipalmitoylphosphatidylcholine lA, iodoacetic acid PG, phosphatidylglycerol PL, phospholipid SP, surfactant protein or swine, or synthetic lipids, generally in combination with SPBand SP-C (7, 10, 11, 13-15, 17-19, 21-23, 27), are being evaluated for their potential use in surfactant replacement therapies.Our previous studies (10) and those of Curstedt et al. (2), and Yu and Possmayer (19), suggested that when recombined with PL, SP-B resulted in greater surface tension lowering and biologic activity than did SP-C. For this reason, we decided to focus our attention on this protein. SP-B, also called SP-18 (4, 10), SPL(Phe) (3), PSP-B (5), and SAP-6-14 (7,16,17,23), has been shown to be a disulfide-linked dimer of two identical polypeptides of approximately 9000 D having an amino terminal sequence of phe-pro-ile-pro-leu-pro-tyr-(human) (3, 5, 10). Data based on amino acid compositions (10) and fast atom bombardment mass spectroscopy (unpublished observations) have led us to conclude that human SP-B is 80-81 residues in length. The sequence is shown in Figure I.To investigate the mechanisms by which SP-B protein augments the surfactant capacity of PL, peptides were synthesized that conform to portions of the native sequence of this protein. These peptides could be combined with PL to reconstitute the biophysical and biologic activities of natural surfactant. We report here the results of studies, using the pulsating bubble surfactometer to measure the capacity of these synthetic surfactants to lower surface tension at an air/liquid interface and the fetal rabbit model to determine their ability to increase lung compliance and alveolar expansion. MATERIALS AND METHODS Preparation ofpurified SP-B monomer, dimer, and oligomers.SP-B was isolated from human amniotic fluid surfactant ad escribed previously (10). One hundred J.Lg of SP-B, in a volume of 206 J.LL methanol, were incubated with 5.14 mg DTT (Sigma Chemical Co, St. Louis, MO) in 17 J.LL methanol, for 1 h at 37°C. Analysis of 2 J.LL on SDS-PAGE showed the SP-B to be approximately 70% reduced as noted by a shift in band position from 18000 D to approximately 9000 D. The SP-B/...