Identification of an HMGB3 frameshift mutation in a family with an X-linked colobomatous microphthalmia syndrome using whole-genome and X-exome sequencing.

IMPORTANCE: Microphthalmias are rare disorders whose genetic bases are not fully understood. HMGB3 is a new candidate gene for X-linked forms of this disease. OBJECTIVE: To identify the causative gene in a pedigree with an X-linked colobomatous microphthalmos phenotype. DESIGN, SETTING, AND PARTICIPANTS: Whole-genome sequencing and chromosome X-exome-targeted sequencing were performed at the High Throughput Sequencing Laboratory of the Genetic Resources Core Facility at the Johns Hopkins University School of Medicine on the DNA of the male proband and informatically filtered to identify rare variants. Polymerase chain reaction and Sanger sequencing were used to confirm the variant in the proband and the carrier status of his mother. Thirteen unrelated male patients with a similar phenotype were also screened. MAIN OUTCOMES AND MEASURES: Whole-genome and X-exome sequencing to identify a frameshift variant in HMGB3. RESULTS: A 2-base pair frameshift insertion (c.477_478insTA, coding for p.Lys161Ilefs*54) in the HGMB3 gene was found in the proband and his carrier mother but not in the unrelated patients. The mutation, confirmed by 3 orthogonal methods, alters an evolutionarily conserved region of the HMGB3 protein from a negatively charged polyglutamic acid tract to a positively charged arginine-rich motif that is likely to interfere with normal protein function. CONCLUSIONS AND RELEVANCE: In this family, microphthalmia, microcephaly, intellectual disability, and short stature are associated with a mutation on the X chromosome in the HMGB3 gene. HMGB3 should be considered when performing genetic studies of patients with similar phenotypes.

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.

Hypoxia-inducible factor 1alpha polymorphism and coronary collaterals in patients with ischemic heart disease.

STUDY OBJECTIVES: Marked variability exists in coronary artery collaterals in patients with ischemic heart disease. Although multiple factors are thought to play a role in collateral development, the contribution of genetic factors is largely unknown. Hypoxia inducible factor 1 (HIF-1), a transcriptional activator that functions as a master regulator of oxygen homeostasis, is one possible genetic factor that could play an important role in modulating collateral development. DESIGN, SETTING, AND PARTICIPANTS: Collateral vessels were determined in 100 patients with > or = 70% narrowing of at least one coronary artery without acute myocardial infarction or prior revascularization. DNA was genotyped for the presence of a single nucleotide (C to T) polymorphism that changes residue 582 of HIF-1alpha from proline to serine. MEASUREMENTS AND RESULTS: The frequency of the T allele was significantly higher among patients without collaterals compared to patients with collaterals (0.188 vs 0.037, p < 0.001). In multivariate analyses, two variables affecting collateral formation were detected: two- or three-vessel coronary artery disease was a significant positive predictor (odds ratio [OR], 4.17; 95% confidence interval [CI], 1.61 to 10.8; p = 0.001), whereas the presence of HIF-1alpha genotype CT or TT was a negative predictor (OR, 0.19; 95% CI, 0.04 to 0.84; p = 0.03). CONCLUSIONS: These data suggest that variations in HIF-1alpha genotype may influence development of coronary artery collaterals in patients with significant coronary artery disease.