Inherited surfactant deficiency caused by uniparental disomy of rare mutations in the surfactant protein-B and ATP binding cassette, subfamily a, member 3 genes.

OBJECTIVE: To characterize inheritance of homozygous, rare, recessive loss-of-function mutations in surfactant protein-B (SFTPB) or ATP binding cassette, subfamily A, member 3 (ABCA3) genes in newborns with lethal respiratory failure. STUDY DESIGN: We resequenced genes from parents whose infants were homozygous for mutations in SFTPB or ABCA3. For infants with only 1 heterozygous parent, we performed microsatellite analysis for chromosomes 2 (SFTPB) and 16 (ABCA3). RESULTS: We identified 1 infant homozygous for the g.1549C > GAA mutation (121ins2) in SFTPB for whom only the mother was heterozygous and 3 infants homozygous for mutations in ABCA3 (p.K914R, p.P147L, and c.806_7insGCT) for whom only the fathers were heterozygous. For the SP-B-deficient infant, microsatellite markers confirmed maternal heterodisomy with segmental isodisomy. Microsatellite analysis confirmed paternal isodisomy for the 3 ABCA3-deficient infants. Two ABCA3-deficient infants underwent lung transplantation at 3 and 5 months of age, respectively, and 2 infants died. None exhibited any nonpulmonary phenotype. CONCLUSIONS: Uniparental disomy should be suspected in infants with rare homozygous mutations in SFTPB or ABCA3. Confirmation of parental carrier status is important to provide recurrence risk and to monitor expression of other phenotypes that may emerge through reduction to homozygosity of recessive alleles.

Gene variants of the phosphatidylcholine synthesis pathway do not contribute to RDS in the Chinese population.

BACKGROUND: To determine population-based prevalence and disease contribution of phosphatidylcholine synthetic pathway-associated gene variants in a native southern Chinese cohort. METHODS: We used bloodspots from 2010 that were obtained from the Guangxi Neonatal Screening Center in Nannning China and included the Han (n = 443) and Zhuang (n = 313) ethnic groups. We sequenced the exons of cholinephosphate cytidylyltransferase (PCYT1B) lysophospholipid acyltransferase 1 (LPCAT1), and cholinephosphotransferase (CHPT1) genes, and analyzed both rare and common exonic variants. RESULTS: We obtained five mutations (G199D, A299V, G434C, Y490C, L312S) with eight alleles in the three candidate genes. The collapsed minor allele frequency for candidate genes was not significantly different between the Han and Zhuang populations (0.0045 vs. 0.0064, respectively, P = 0.725). The combined Han and Zhuang pool collapsed carrier frequency of rare mutation allele was found to be 1.06%, which is much higher than previously reported for the Missouri population (0.1%). Further, we detected six exonic common variants (three in LPCAT1 and three in CHPT1), with three non-synonymous variants (F162S, F341L, M427K) among them. Two of the non-synonymous exonic variants (F341L, M427K) were not found in CHB; F341L was also not previously reported in exome sequencing project. CONCLUSIONS: The population-based frequency of mutations in the phosphatidylcholine synthesis pathway-associated genes PCYT1B LPCAT1, CHPT1 is low in southern Chinese newborns and there is no evidence of contribution to population-based disease burden of respiratory distress syndrome. As a population-based study of rare mutations and common variants, this work is valuable in directing future research.

Population-based frequency of surfactant dysfunction mutations in a native Chinese cohort.

BACKGROUND: Rare mutations in surfactant-associated genes contribute to neonatal respiratory distress syndrome. The frequency of mutations in these genes in the Chinese population is unknown. METHODS: We obtained blood spots from the Guangxi Neonatal Screening Center in Nanning, China that included Han (n=443) and Zhuang (n=313) ethnic groups. We resequenced all exons of the surfactant proteins-B (SFTPB), -C (SFTPC), and the ATP-binding cassette member A3 (ABCA3) genes and compared the frequencies of 5 common and all rare variants. RESULTS: We found minor differences in the frequencies of the common variants in the Han and Zhuang cohorts. We did not find any rare mutations in SFTPB or SFTPC, but we found three ABCA3 mutations in the Han [minor allele frequency (MAF)=0.003] and 7 in the Zhuang (MAF=0.011) cohorts (P=0.10). The ABCA3 mutations were unique to each cohort; five were novel. The collapsed carrier rate of rare ABCA3 mutations in the Han and Zhuang populations combined was 1.3%, which is significantly lower than that in the United States (P<0.001). CONCLUSION: The population-based frequency of mutations in ABCA3 in south China newborns is significantly lower than that in United States. The contribution of these rare ABCA3 mutations to disease burden in the south China population is still unknown.

[Pulmonary surfactant associated gene variants in mixed ethnic population of Han and Zhuang].

OBJECTIVE: To explore the prevalence of pulmonary surfactant associated pathway genes functional variants in Chinese population. METHOD: Using a cohort of 258 mixed ethnic population of Han and Zhuang, we pooled DNA samples from 146 term male infants and 112 term female infants and then used an Ill umina next generation sequencing platform to perform the complete exonic resequencing in 6 target genes:surfactant protein-B (SFTPB), surfactant protein-C (SFTPC), ATP-binding cassette transporter A3 (ABCA3), lysophospholipid acyltransferase 1 (LPCAT1), choline phosphotransferase 1 (CHPT1), phosphate cytidylyltransferase 1, choline, beta (PCYT1B). Collapsing methods was used to determine the functional allele frequency. RESULT: (1) Altogether, 128 variants were found, including 44 synonymous variants, 66 nonsynonymous variants and 18 insertions-deletions. Of these, 28 variants were predicted to alter protein function. Two of these variants were seen twice, the rest variants were only seen once, for a total of 30 functional alleles; (2) ABCA3 had the most functional variants in both male and female groups with the minor allele frequencies of 0.014 (1.4%) and 0.04 (4%), respectively. The total functional allele frequencies of 6 genes were 0.041 (4.1%) and 0.08 (8%) in the two groups, respectively (P = 0.06). CONCLUSION: (1) Functional variants in pulmonary surfactant associated pathway genes are present in the mixed Han-Zhuang population. (2) ABCA3 contained the most functional variants suggesting that ABCA3 could contribute significantly to neonatal respiratory distress syndrome and other lung disease.

Single ABCA3 mutations increase risk for neonatal respiratory distress syndrome.

BACKGROUND AND OBJECTIVE: Neonatal respiratory distress syndrome (RDS) due to pulmonary surfactant deficiency is heritable, but common variants do not fully explain disease heritability. METHODS: Using next-generation, pooled sequencing of race-stratified DNA samples from infants ≥34 weeks' gestation with and without RDS (n = 513) and from a Missouri population-based cohort (n = 1066), we scanned all exons of 5 surfactant-associated genes and used in silico algorithms to identify functional mutations. We validated each mutation with an independent genotyping platform and compared race-stratified, collapsed frequencies of rare mutations by gene to investigate disease associations and estimate attributable risk. RESULTS: Single ABCA3 mutations were overrepresented among European-descent RDS infants (14.3% of RDS vs 3.7% of non-RDS; P = .002) but were not statistically overrepresented among African-descent RDS infants (4.5% of RDS vs 1.5% of non-RDS; P = .23). In the Missouri population-based cohort, 3.6% of European-descent and 1.5% of African-descent infants carried a single ABCA3 mutation. We found no mutations among the RDS infants and no evidence of contribution to population-based disease burden for SFTPC, CHPT1, LPCAT1, or PCYT1B. CONCLUSIONS: In contrast to lethal neonatal RDS resulting from homozygous or compound heterozygous ABCA3 mutations, single ABCA3 mutations are overrepresented among European-descent infants ≥34 weeks' gestation with RDS and account for ~10.9% of the attributable risk among term and late preterm infants. Although ABCA3 mutations are individually rare, they are collectively common among European- and African-descent individuals in the general population.