ABCA3 Research Articles

Increased Risk of Interstitial Lung Disease in Children with a Single R288K Variant of ABCA3.

The ABCA3 gene encodes a lipid transporter in type II pneumocytes critical for survival and normal respiratory function. The frequent ABCA3 variant R288K increases the risk for neonatal respiratory distress syndrome among term and late preterm neonates, but its role in children's interstitial lung disease has not been studied in detail. In a retrospective cohort study of 228 children with interstitial lung disease related to the alveolar surfactant system, the frequency of R288K was assessed and the phenotype of patients carrying a single R288K variant further characterized by clinical course, lung histology, computed tomography and bronchoalveolar lavage phosphatidylcholine PC 32:0. Cell lines stably transfected with ABCA3-R288K were analyzed for intracellular transcription, processing and targeting of the protein. ABCA3 function was assessed by detoxification assay of doxorubicin, and the induction and volume of lamellar bodies. We found nine children with interstitial lung disease carrying a heterozygous R288K variant, a frequency significantly higher than in the general Caucasian population. All identified patients had neonatal respiratory insufficiency, recovered and developed chronic interstitial lung disease with intermittent exacerbations during early childhood. In vitro analysis showed normal transcription, processing, and targeting of ABCA3-R288K, but impaired detoxification function and smaller lamellar bodies. We propose that the R288K variant can underlie interstitial lung disease in childhood due to reduced function of ABCA3, demonstrated by decelerated detoxification of doxorubicin, reduced PC 32:0 content and decreased lamellar body volume.

Phylogenetic analysis of the ATP-binding cassette transporter family in three mosquito species

The ATP-binding cassette (ABC) transporter family functions in the ATP-dependent transportation of various substrates across biological membranes. ABC proteins participate in various biological processes and insecticide resistance in insects, and are divided into eight subfamilies (A–H). Mosquitoes are important vectors of human diseases, but the mechanism by which the ABC transporter family evolves in mosquitoes is unknown. In this study, we classified and compared the ABC transporter families of three mosquitoes, namely, Anopheles gambiae, Aedes aegypti, and Culex pipiens quinquefasciatus. The three mosquitoes have 55, 69, and 70 ABC genes, respectively. The C. p. quinquefasciatus had approximately 40% and 65% expansion in the ABCG subfamily, mainly in ABCG1/G4, compared with the two other mosquito species. The ABCB, ABCD, ABCE, and ABCF subfamilies were conserved in the three mosquito species. The C. p. quinquefasciatus transcriptomes during development showed that the ABCG and ABCC genes were mainly highly expressed at the egg and pupal stages. The pigment-transport relative brown, white, and scarlet, as well as the ABCF subfamily, were highly expressed at the egg stage. The highly expressed genes in larvae included three ABCA3 genes. The majority of the highly expressed genes in adults were ABCG1/4 genes. These results provided insights into the evolution of the ABC transporter family in mosquitoes.

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

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. 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. 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). 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.

The Haplotype TGGAG in the ABCA3 Gene Increases the Risk of Respiratory Distress Syndrome in Preterm Infants in Southern China

Rare mutations in the ATP-binding cassette (ABC) transporter A3 (ABCA3) gene are associated with neonatal respiratory distress syndrome (RDS). The contribution of common single nucleotide polymorphisms (SNPs) to preterm RDS differs between ethnicities and remains unclear in Chinese infants. This study evaluated whether common SNPs and consequent haplotypes increase susceptibility to RDS in a population of preterm infants from the Guangxi Zhuang Autonomous Region of China. Using a tagging SNP (tSNP) strategy and real-time polymerase chain reaction, we genotyped four tSNPs (i.e., rs150929, rs4787273, rs11867129, and rs17135889) and one coding SNP (p.F353F) of the ABCA3 gene in preterm infants with RDS (n=83) and without RDS (n=83). We predicted the haplotypes. Minor allele frequencies (MAFs) and haplotype distributions were compared between the two groups. We analyzed correlations between the clinical data and the genotypes. Seven haplotypes existed at a frequency of 0.01 or greater. The haplotype TGGAG was significantly more frequent in RDS infants than in non-RDS infants (p=0.026; odds ratio 3.41; 95% confidence interval 1.088-10.685). The MAF of rs17135889 SNP, a crucial SNP of the haplotype TGGAG located in the transcription factor binding site of ABCA3, was significantly higher in RDS infants (p<0.05); however, the Bonferroni correction test showed no significant difference (p>0.05). No significant correlation existed between the rs17135889 genotypes (AG/GG) and any clinical characteristic (e.g., oxygen supplementation duration and hospitalization, requirement for ventilation, bronchopulmonary dysplasia complications, and mortality rate). The TGGAG haplotype may be a risk factor for RDS in preterm infants in this Chinese population. Further study is needed with a larger sample size to verify the association between the rs17135889 SNP and increased risk of RDS in preterm infants, and to determine whether rs17135889 can be a reference in further population-based studies of ABCA3.

ABCA3, a key player in neonatal respiratory transition and genetic disorders of the surfactant system.

Genetic disorders of the surfactant system are rare diseases with a broad range of clinical manifestations, from fatal respiratory distress syndrome (RDS) in neonates to chronic interstitial lung disease (ILD) in children and adults. ABCA3 [ATP-binding cassette (ABC), subfamily A, member 3] is a lung-specific phospholipid transporter critical for intracellular surfactant synthesis and storage in lamellar bodies (LBs). Its expression is developmentally regulated, peaking prior to birth under the influence of steroids and transcription factors. Bi-allelic mutations of the ABCA3 gene represent the most frequent cause of congenital surfactant deficiency, indicating its critical role in lung function. Mutations affect surfactant lipid and protein processing and LBs' morphology, leading to partial or total surfactant deficiency. Approximately 200 mutations have been reported, most of which are unique to individuals and families, which makes diagnosis and prognosis challenging. Various typesof mutations, affecting different domains of the protein, account in part for phenotype diversity. Disease-causing mutations have been reported in most coding and some non-coding regions of the gene, but tend to cluster in the first extracellular loop and the second nucleotide-binding domain (NBD), leading to defective glycosylation and trafficking defects and interfering with ATP binding and hydrolysis respectively. Mono-allelic damaging and benign variants are often subclinical but may act as disease modifiers in lung diseases such as RDS of prematurity or associate with mutations in other surfactant-related genes. Diagnosis is complex but essential and should combine pathology and ultrastructure studies on lung biopsy with broad-spectrum genetic testing of surfactant-related genes, made possible by recent technology advances in the massive parallel sequencing technology.

Alveolar Type II Cells from Mice Expressing a Lung Disease‐Associated ABCA3 E292V Mutation Exhibit Alterations in Organellar Homeostasis and Autophagy

The lipid transporter, ATP binding cassette class A3, ABCA3, plays a critical role in the biogenesis of alveolar type II (AT2) cell lamellar bodies (LBs). A relatively large number of mutations in the ABCA3 gene have been identified in association with interstitial lung disease (ILD). The most common mutation is a valine for glutamate missense mutation at residue 292 (E292V) which results in a functional impairment of lipid transport in vitro. To characterize the cellular consequences induced by this mutation in vivo, a novel knockin (KI) mouse model carrying allelic ABCA3 E292V mutations was produced. Lung ultrastructure from E292V homozygous mice revealed smaller size but increased numbers of LBs accompanied by increased AT2 cell mitochondrial counts. Examination of 16 wk and 32 wk homozygous E292V mice showed age‐dependent increase in bronchoalveolar lavage cellularity as well as reduction in alveolar wall thickness coupled with enlarged alveolar air spaces. While isolated E292V AT2 cells demonstrated no alterations in the unfolded protein response, an age‐dependent increase in autophagy components LC3‐I/LC3‐II and P62 also developed in these mice. Furthermore, AT2 cell lysates from 32 wk mice showed accompanying increases in the levels of marker antigens for both mitochondria (Tom20) and lysosomes (Lamp1). We conclude that expression of the ABCA3 E292V mutation produces changes in AT2 organellar homeostasis which result in time‐dependent disruption of macroautophagy‐dependent cellular quality control pathways. We speculate that these changes contribute to the phenotype of a vulnerable epithelium susceptible to second hit injuries that promote the pathogenesis of ILD.

Relationship between ABCA3 gene polymorphisms and susceptibility with neonatal respiratory distress syndrome

Objective To investigate ABCA3 gene polymorphism and its relationship with neonatal respiratory distress syndrome (NRDS) in the Guangxi Zhuang Autonomous Region of China by genotyping and haplotype analysis. Methods Using a tagging single nucleotide polymorphism (tSNP) strategy and TaqMan (r) real-time PCR, we genotyped 4 tSNPs (rs4787273, rs150929, rs11867129, and rs17135889) and one additional coding SNP (rs13332514) of the ABCA3 gene in preterm infants with NRDS (NRDS group, n=45) and without NRDS (non-NRDS group, n=45) and subsequently predicted the haplotypes. The minor allele frequency and the haplotype `distribution were compared between the two groups. Results The minor allele A (0.14 vs.0.05, P=0.046) and genotype AG (0.289 vs.0.111, P=0.035) frequency of SNP rs17135889 in NRDS group were significantly higher than those in non-NRDS group. Totally 6 haplotypes occurred at a frequency ≥0.01, among which, the haplotype TGGAG, depended on rs17135889, was significantly higher in NRDS group than that in non-NRDS group (0.061 vs.0.000, P=0.014). Conclusion The results suggested that SNP rs17135889 of ABCA3 gene might be related to NRDS in preterm population of the Guangxi Zhuang Autonomous Region. Allele A contributes to NRDS susceptibility in preterm infants. Key words: Neonatal respiratory distress syndrome; ABCA3; Single nucleotide polymorphism

Skipping of ATP-Binding Cassette Transporter A3 Exon 19 in AML Cells Is an Independent Prognostic Factor in Patients with Normal Cytogenetics

ATP binding cassette (ABC) transporters are a superfamily of highly conserved membrane proteins that transport a wide variety of substrates across cell membranes and confer drug resistance against a wide range of chemotherapeutic agents. We recently found that WT1, which is regularly overexpressed in AML and interact with the splicing machinery, modifies the splicing of ABC transporters A2, A3, A5, and C2. For ABCA3, WT1 knock-down in three AML cell line coupled with Affymetrix HTA2 exon arrays analysis confirmed by exon-specific PCR revealed that WT1 influences the skipping of exon 19. ABCA3 belongs in the ABC subclass and induces a significant reduction in cytotoxicity observed following exposure to DNR, mitoxantrone, etoposide, Ara-C and vincristine. The ABCA3 domain encoded by exon 19 (amino acid 805-847) is localized at the junction of the first nucleotide-binding domain and the second transmembrane domain, and is involved in ATP hydrolysis. In silico, skipping of exon 19 deletes a sequence of 32 amino acids rich in positively charged residues and is thereby assumed to increase drug efflux through increased ATP hydrolysis. The effects of the skipping of exon 19 on chemoresistance and DNR efflux are currently investigated while for the present study, we hypothesized that skipping of exon 19 of ABCA3 might negatively influence outcome in AML patients.Analyzing 132 bone marrow AML samples harvested at diagnostic confirmed the statistically significant correlation between WT1 expression and ABCA3 splicing in vivo (p<10-4, Spearman Rank Correlation). This correlation was specific because it was not observed in 37 control samples deriving from bone marrow donors or in the AML cases with 2 TET2 alternative exon usages found WT1-independent ex vivo. In the 106 patients treated with intensive chemotherapy (IC), skipping of ABCA3 exon 19 was associated with a significantly lower response rate: 39/55 (70.9%) vs 44/51 (86.3%, p = 0.045, Pearson’s chi-squared test). In complete remitters, skipping of ABCA3 exon 19 was associated with a significantly higher relapse rate: 77.1% vs 52.6% (p=0.026, Pearson’s chi-squared test). Median follow-up was 25 months. The 25 allografted patients were censored at the time of allograft. By univariate analysis ABC-A3 exon skipping of exon 19 significantly affected OS (HR=4.50 (95% confidence interval: 2.10-9.63), p<10-4), DFS (HR=3.76 (95% confidence interval: 1.87-7.42), p<10-4), and EFS (HR 3.73 (95% confidence interval: 1.38-5.13), p=0.004); higher the level of exon 19 skipping, poorer the outcome. In multivariate analysis, age, cytogenetic, and ABC A3 exon 19 skipping were identified to be independent prognostic factors for OS, EFS and DFS. Age and ABC-A3 exon exclusion were identified to be independent prognostic factor for OS in the 49 patients with normal karyotype.In order to confirm these results we investigated the prognostic impact of ABC A3 exon 19 skipping in a validation cohort of 108 additional AML case with normal cytogenetics. FLT3 internal tandem duplication (FLT3-ITD) and nucleophosmin (NPM1) exon-12 gene mutation were identified in 37 (34.3%) and 66 cases (61.1%). In the 86 patients treated with IC, the CR rate was 89,5% without significant difference between patients with or without exon 19 skipping. The relapse rate was higher in cases with exon 19 skipping (47,1% vs 23.5%) but the difference was not statistically significant. The 29 allografted patients were censored at the time of allograft. Median follow-up was 12 months. By univariate analysis ABC-A3 exon skipping of exon 19 significantly affected DFS (HR=2.03 (95% confidence interval: 1.22-3.39), p=0.007, and EFS (HR 1.62 (95% confidence interval: 1.06-2.48), p=0.027); higher the level of exon 19 skipping, poorer the outcome. In multivariate analysis, age, FLT3-ITD, ABC A3 exon 19 skipping but not NPM1 mutation were identified to be independent prognostic factors for EFS while FLT3-ITD and ABC A3 exon 19 skipping were independent prognostic factors for DFS.In conclusion ABC-A3 missplicing possesses a strong prognostic impact in AML indicating that besides whole gene transcription, quantitative analysis of alternative splicing might represent a promising tool for assessing AML aggressiveness at the time of diagnostic in patients with normal or abnormal karyotype. DisclosuresNicolini:Novartis: Consultancy.

Sequencing of idiopathic pulmonary fibrosis-related genes reveals independent single gene associations

BackgroundPrevious studies investigating a genetic basis for idiopathic pulmonary fibrosis (IPF) have focused on resequencing single genes in IPF kindreds or cohorts to determine the genetic contributions to IPF. None...

Hereditary interstitial lung diseases manifesting in early childhood in Japan.

Genetic variations associated with interstitial lung diseases (ILD) have not been extensively studied in Japanese infants. Forty-three infants with unexplained lung dysfunction were studied. All 43, 22, and 17 infants underwent analyses of surfactant protein (SP)-C gene (SFTPC) and ATP-binding cassette A3 gene (ABCA3), SP-B gene (SFTPB), and SP-B western blotting, respectively. Two and four underwent assessment of granulocyte macrophage colony-stimulating factor-stimulating phosphorylation of signal transducer and activator of transcription-5 (pSTAT-5) and analyses of FOXF1 gene (FOXF1), respectively. ILD were diagnosed clinically in nine infants: four, three, and two had interstitial pneumonitis, hereditary pulmonary alveolar proteinosis (hPAP), and alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV), respectively. Genetic variations considered responsible were detected in six (67%) of the nine infants with ILD: three with hPAP (SFTPC p.Leu45Arg and p.Gln145fs, and ABCA3 p.Arg1583Trp/p.Val1495CysfsX21), two with interstitial pneumonitis (SFTPC p.Lys63Glu and p.Ser72Asn/p.Gly100Ala), and one with ACD/MPV (FOXF1 p.Leu300ArgfsX79). None showed SFTPB mutations or defects in pSTAT-5. The 17 bronchoalveolar lavage or tracheal aspirates contained enough SP-B protein. The SP-C abnormality was most prevalent, and SP-B deficiency was rare in Japanese infants with hereditary ILD.

Genotype-phenotype correlations for infants and children with ABCA3 deficiency.

Recessive mutations in the ATP-binding cassette transporter A3 (ABCA3) cause lethal neonatal respiratory failure and childhood interstitial lung disease. Most ABCA3 mutations are private. To determine genotype-phenotype correlations for recessive ABCA3 mutations. We reviewed all published and unpublished ABCA3 sequence and phenotype data from our prospective genetic studies of symptomatic infants and children at Washington and Johns Hopkins Universities. Mutations were classified based on their predicted disruption of protein function: frameshift and nonsense mutations were classified as "null," whereas missense, predicted splice site mutations, and insertion/deletions were classified as "other." We compared age of presentation and outcomes for the three genotypes: null/null, null/other, and other/other. We identified 185 infants and children with homozygous or compound heterozygous ABCA3 mutations and lung disease. All of the null/null infants presented with respiratory failure at birth compared with 75% of infants with null/other or other/other genotypes (P = 0.00011). By 1 year of age, all of the null/null infants had died or undergone lung transplantation compared with 62% of the null/other and other/other children (P < 0.0001). Genotype-phenotype correlations exist for homozygous or compound heterozygous mutations in ABCA3. Frameshift or nonsense ABCA3 mutations are predictive of neonatal presentation and poor outcome, whereas missense, splice site, and insertion/deletions are less reliably associated with age of presentation and prognosis. Counseling and clinical decision making should acknowledge these correlations.

Drug transporter expression profiling in chemoresistant variants of the A2780 ovarian cancer cell line

Ovarian cancer is characterized by the higher mortality among gynecological cancers. In results of MDR development during chemotherapy cancer cells become resistant to further treatment. Microarray techniques can provide information about MDR development at gene expression level. ABC and SLC transporters are most important proteins responsible for this phenomenon. In this study changes of ABC and SLC genes expression pattern in drugs resistant sublines of the A2780 ovarian cancer cell line were demonstrated. The cytostatic resistant sublines were generated by culture of A2780 cell line with an increasing concentration of the indicated drugs. As screening methods, we used Affymetrix U219 Human Genome microarrays. Independent t-tests were used to determinate statistical significances of results. Genes that expression levels were higher than assumed threshold (upregulated above threefold and downregulated under −3 fold) were visualized using scatter plot method, selected and listed in table. Between the ABC genes increased expression of seven genes and decreased expression of three genes were observed. Expression of two genes was increased or decreased depending on the cell line. We observed significant (more than tenfold) increase in expression of four ABC genes: ABCA8, ABCB1, ABCB4 and ABCG2 and decreased expression of ABCA3 gene. We also observed changes in expression of 32 SLC genes. Between them we observe increased expression of 17 genes and decreased expression of 15 genes. Expression of four genes was increased or decreased dependent on cell line. The expression of nine SLC genes increased or decreased very significantly (more than tenfold). Five genes were significantly upregulated: SLC2A9, SLC16A3, SLC16A14, SLC38A4 and SLC39A8. Four additional genes were significantly downregulated: SLC2A14, SLC6A15, SLC8A1 and SLC27A2. Expression profiles of these genes give strong arguments for assumption of correlation between expression of ABC and SLC genes and drug resistance phenomenon. Identifying correlations between specific drug transporters and cytostatic drug resistance will require further investigation.

MRNA expression profile of multidrug-resistant genes in acute lymphoblastic leukemia of children, a prognostic value for ABCA3 and ABCA2

Multidrug resistance (MDR) is an important cause of treatment failure in acute lymphoblastic leukemia (ALL). The ABC family of membrane transporters is proposed, albeit with controversy, to be involved in this process. The present study aims to investigate the mRNA expression profile of several genes of this family, including ABCA2, ABCA3, ABCB1/MDR1, MRP1/ABCC1, MRP3/ABCC3, ABCG2/BCRP, and the intracellular transporter MVP/LRP, in childhood ALL, and to evaluate their association with response to therapy. Some genes in the present research are being studied for the first time in Iran. Using quantitative real-time PCR, we evaluated 27 children with ALL at diagnosis and 15 children with normal bone marrow. The status of response to therapy was assessed one year after the onset of therapy through investigating the IgH/TCRγ gene rearrangements. Our findings indicate a considerable and direct relationship between mRNA expression levels of ABCA2, ABCA3, MDR1, and MRP1 genes and positive minimal residual disease (MRD) measured after one year of treatment. Statistical analysis revealed that expression of these genes higher than the cutoff point will raise the risk of MRD by 15-, 6.25-, 12-, and 9-fold, respectively. No relationship was found between of MVP/LRP, MRP3 and ABCG2 genes expression and ALL prognoses. Considering the direct and significant relationship between the increased expression of ABCA2, ABCA3, MDR1, and MRP1 genes and positive risk of MRD in children with ALL, evaluating the expression profile of these genes on diagnosis may identify high risk individuals and help plan a more efficient treatment strategy.

Disruption of N-linked glycosylation promotes proteasomal degradation of the human ATP-binding cassette transporter ABCA3

The lipid transport protein, ABCA3, expressed in alveolar type 2 (AT2) cells, is critical for surfactant homeostasis. The first luminal loop of ABCA3 contains three putative N-linked glycosylation sites at residues 53, 124, and 140. A common cotranslational modification, N-linked glycosylation, is critical for the proper expression of glycoproteins by enhancing folding, trafficking, and stability through augmentation of the endoplasmic reticulum (ER) folding cycle. To understand its role in ABCA3 biosynthesis, we utilized EGFP-tagged fusion constructs with either wild-type or mutant ABCA3 cDNAs that contained glutamine for asparagine substitutions at the putative glycosylation motifs. In A549 cells, inhibition of glycosylation by tunicamycin increased the electrophoretic mobility (Mr) and reduced the expression level of wild-type ABCA3 in a dose-dependent manner. Fluorescence imaging of transiently transfected A549 or primary human AT2 cells showed that although single motif mutants exhibited a vesicular distribution pattern similar to wild-type ABCA3, mutation of N124 and N140 residues resulted in a shift toward an ER-predominant distribution. By immunoblotting, the N53 mutation exhibited no effect on either the Mr or ABCA3 expression level. In contrast, substitutions at N124 or N140, as well a N124/N140 double mutation, resulted in increased electrophoretic mobility indicative of a glycosylation deficiency accompanied by reduced overall expression levels. Diminished steady-state levels of glycan-deficient ABCA3 isoforms were rescued by treatment with the proteasome inhibitor MG132. These results suggest that cotranslational N-linked glycosylation at N124 and N140 is critical for ABCA3 stability, and its disruption results in protein destabilization and proteasomal degradation.

Ten‐year follow up of hydroxychloroquine treatment for ABCA3 deficiency

We present a child with interstitial lung disease (ILD) who was diagnosed with desquamative interstitial pneumonitis following CT thorax and open lung biopsy aged 2 years. Subsequently, surfactant protein gene analysis revealed mutations in the ABCA3 gene. This case of ABCA3 deficient ILD describes a stable clinical course over 10 years and highlights the potential benefit of hydroxychloroquine for this condition.

Different course of lung disease in two siblings with novel ABCA3 mutations

Mutations in the gene for adenosine triphosphate-binding cassette transporter subfamily A member 3 (ABCA3) have been reported in infants and children with surfactant deficiency and interstitial lung disease. We report a case of siblings found to be compound heterozygotes for two novel ABCA3 gene mutations but developing very different course of lung disease. The index case is a baby girl with severe interstitial lung disease that manifested on the first days of life. Her 4-year-old brother carrying the same mutations has no signs of lung disease so far. Our findings suggest the contribution of other genetic, epigenetic and environmental factors to discordant phenotype observed in patients carrying the same mutations in the ABCA3 gene. The clinical course of the index case suggests benefit of combined medical therapy in treating infants with ABCA3 deficiency.

Interstitial lung disease in two brothers with novel compound heterozygous ABCA3 mutations

Mutations in genes critical for surfactant metabolism, including surfactant protein C (SP-C) and ABCA3, are well-recognized causes of interstitial lung disease. Recessive mutations in ABCA3 were first attributed to fatal respiratory failure in full-term neonates, but they are also increasingly being recognized as a cause of respiratory disorders with less severe phenotypes in older children and also adults. Here, we report a 20-month-old boy with interstitial lung disease caused by two distinct ABCA3 mutations. Initial treatment with methylprednisolone was unsuccessful, but the additional administration of hydroxychloroquine was effective. The family history revealed that the patient's older brother had died of idiopathic interstitial lung disease at 6 months of age, suggesting a genetic etiology of the disease. Sequence analyses of SP-C and ABCA3 genes were performed using DNA samples from the patient himself, his parents, and his brother. These analyses revealed novel compound heterozygous mutations in the coding exons of ABCA3 in both the patient and his brother: c.2741A > G, of paternal origin, and c.3715_3716insGGGGGG, of maternal origin. Conclusion Since ABCA3 mutations seem to be a heterogeneous entity with various phenotypes, we recommend genetic testing for mutations in SP-C and ABCA3 genes to be considered in children with unexplained interstitial lung disease.

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

To explore the prevalence of pulmonary surfactant associated pathway genes functional variants in Chinese population. 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. (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). (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.

Functional rescue of mutant ABCA1 proteins by sodium 4-phenylbutyrate

Mutations in the ATP-binding cassette transporter A1 (ABCA1) are a major cause of decreased HDL cholesterol (HDL-C), which infers an increased risk of cardiovascular disease (CVD). Many ABCA1 mutants show impaired localization to the plasma membrane. The aim of this study was to investigate whether the chemical chaperone, sodium 4-phenylbutyrate (4-PBA) could improve cellular localization and function of ABCA1 mutants. Nine different ABCA1 mutants (p.A594T, p.I659V, p.R1068H, p.T1512M, p.Y1767D, p.N1800H, p.R2004K, p.A2028V, p.Q2239N) expressed in HEK293 cells, displaying different degrees of mislocalization to the plasma membrane and discrete impacts on cholesterol efflux, were subject to treatment with 4-PBA. Treatment restored localization to the plasma membrane and increased cholesterol efflux function for the majority of mutants. Treatment with 4-PBA also increased ABCA1 protein expression in all transfected cell lines. In fibroblast cells obtained from low HDL-C subjects expressing two of the ABCA1 mutants (p.R1068H and p.N1800H), 4-PBA increased cholesterol efflux without any increase in ABCA1 expression. Our study is the first to investigate the effect of the chemical chaperone, 4-PBA on ABCA1 and shows that it is capable of restoring plasma membrane localization and enhancing the cholesterol efflux function of mutant ABCA1s both in vitro and ex vivo. These results suggest 4-PBA may warrant further investigation as a potential therapy for increasing cholesterol efflux and HDL-C levels.

The differential expression pattern of the BMI-1, SALL4 and ABCA3 genes in myeloid leukemia

Background and methodsIn order to characterize the expression pattern of SALL4, BMI-1 and ABCA3 genes in patients with myeloid leukemia and those who achieved complete remission (CR) after chemotherapy. Real-time PCR was used to determine the expression level of these genes in peripheral blood mononuclear cells from 24 patients with AML, eight patients with AML-CR, 13 patients with CML in the chronic phase (CML-CP), 12 patients with CML in blast crisis (CML-BC), 13 patients with CML-CR and 11 healthy individuals (HI).ResultsOverexpression of the BMI-1 gene was found in the AML, CML-CP and CML-BC groups as compared with HI group, while the BMI-1 expression level was lower in patients who achieved CR. In contrast, significantly increased SALL4 expression was only found in AML group, additionally, SALL4 expression was lower in the CML-CP and CML-CR groups compared with the HI group, while the SALL4 expression level in the CML-BC group was higher and significantly greater than that in the CML-CP and CML-CR groups. Moreover, a positive correlation between the expression of SALL4 and BMI-1 genes was found in samples from most groups. There was no significant difference of ABCA3 expression level in AML and CML-BC group in comparison with HI group. Interestingly, the ABCA3 expression level was significantly decreased in the CML-CP, AML-CR and CML-CR in comparison with the HI group. Moreover, the ABCA3 expression level in all of the CR groups was lower than that in their corresponding groups.ConclusionsThese results describe the altered SALL4, ABCA3 and BMI-1 expression pattern in different phases of myeloid leukemia, which may relate to the development and progression to different diseases. SALL4 expression was strongly correlated with BMI-1 in most of the myeloid leukemia patient groups, providing a potential link between SALL4 and BMI-1 in leukemogenesis.