The iron-sulphur cluster in human DNA2 is required for all biochemical activities of DNA2.

The nuclease/helicase DNA2 plays important roles in DNA replication, repair and processing of stalled replication forks. DNA2 contains an iron-sulphur (FeS) cluster, conserved in eukaryotes and in a related bacterial nuclease. FeS clusters in DNA maintenance proteins are required for structural integrity and/or act as redox-sensors. Here, we demonstrate that loss of the FeS cluster affects binding of human DNA2 to specific DNA substrates, likely through a conformational change that distorts the central DNA binding tunnel. Moreover, we show that the FeS cluster is required for DNA2's nuclease, helicase and ATPase activities. Our data also establish that oxidation of DNA2 impairs DNA binding in vitro, an effect that is reversible upon reduction. Unexpectedly, though, this redox-regulation is independent of the presence of the FeS cluster. Together, our study establishes an important structural role for the FeS cluster in human DNA2 and discovers a redox-regulatory mechanism to control DNA binding.

Osteogenesis imperfecta caused by PPIB mutation with severe phenotype and congenital hearing loss.

Osteogenesis imperfecta (OI) is an inherited disorder of connective tissue typically caused by defects in either COL1A1 or COL1A2. A number of other genes causative of this disorder have been found, including PPIB, which forms one subunit of the prolyl 3-hydroxylase enzyme complex. Patients with homozygous or compound heterozygous mutations in this gene have OI with a trend toward lethal or severe phenotype. We present a Native American female with prenatal diagnosis of OI. Long bones were shortened with significant rhizomelia. At birth, fractures were present in ribs, humerii, and femurs. She had significant respiratory disease at birth, and required oxygen throughout her life. She also had recurrent pneumonias, one of which ultimately caused her death at age 16 mo. She also had significant bilateral sensorineural hearing loss. Molecular testing showed that the patient was homozygous for a single nucleotide substitution in PPIB (c. 136-2A>G). Patients with OI caused by PPIB mutations have had variable disease, but with majority of either with perinatal lethality or progressively deforming severe disease. Patients with OI due to PPIB mutation have shown some differences in phenotype. There appears to be a trend toward rhizomelic shortening and less severe bowing of the extremities, as compared to patients with comparably severe OI caused by COL1A1 or COL1A2 mutation. Congenital hearing loss may be an inconsistent feature of this condition, or may have co-occurred in our patient for unrelated reasons. Still, patients with OI caused by PPIB mutation should have appropriate early and regular management of their hearing.

Prevalence of pilomatricoma in Turner syndrome: findings from a multicenter study.

IMPORTANCE: The absence of data on the prevalence of pilomatricoma among patients with Turner syndrome served as the catalyst for this multicenter investigation. OBJECTIVES: To ascertain the prevalence of pilomatricoma among patients with Turner syndrome and to determine any association between the development of pilomatricomas and the use of exogenous hormones in patients with Turner syndrome. DESIGN: A retrospective medical record review from January 1, 2000, through January 1, 2010, was performed of all patients with Turner syndrome. Data on pilomatricomas and the use of hormone therapy were collected. SETTING: University of California-Davis Medical Center, University of Nebraska Medical Center, and The University of North Carolina at Chapel Hill. PARTICIPANTS: Patients with a diagnosis of Turner syndrome. MAIN OUTCOME MEASURES: Prevalence of concomitant pilomatricoma and diagnosis of Turner syndrome. Secondary outcome measures included the use of the exogenous hormones estrogen or recombinant human growth hormone (rhGH). RESULTS: In total, 311 patients with Turner syndrome were identified from these 3 institutions. Among them, 8 patients (2.6%) were diagnosed as having pilomatricomas. Before the development of pilomatricomas, 5 patients had been treated with rhGH but not estrogen, 1 patient had received estrogen but not rhGH, and 2 patients did not receive either therapy. CONCLUSIONS AND RELEVANCE: Although the prevalence of pilomatricoma among the general population is unknown, this study demonstrates a high prevalence (2.6%) of pilomatricomas among patients with Turner syndrome. No apparent relationship was noted among our patients or in the literature between the use of rhGH and the development of pilomatricomas.

Enzyme-replacement therapy in life-threatening hypophosphatasia.

BACKGROUND: Hypophosphatasia results from mutations in the gene for the tissue-nonspecific isozyme of alkaline phosphatase (TNSALP). Inorganic pyrophosphate accumulates extracellularly, leading to rickets or osteomalacia. Severely affected babies often die from respiratory insufficiency due to progressive chest deformity or have persistent bone disease. There is no approved medical therapy. ENB-0040 is a bone-targeted, recombinant human TNSALP that prevents the manifestations of hypophosphatasia in Tnsalp knockout mice. METHODS: We enrolled infants and young children with life-threatening or debilitating perinatal or infantile hypophosphatasia in a multinational, open-label study of treatment with ENB-0040. The primary objective was the healing of rickets, as assessed by means of radiographic scales. Motor and cognitive development, respiratory function, and safety were evaluated, as well as the pharmacokinetics and pharmacodynamics of ENB-0040. RESULTS: Of the 11 patients recruited, 10 completed 6 months of therapy; 9 completed 1 year. Healing of rickets at 6 months in 9 patients was accompanied by improvement in developmental milestones and pulmonary function. Elevated plasma levels of the TNSALP substrates inorganic pyrophosphate and pyridoxal 5'-phosphate diminished. Increases in serum parathyroid hormone accompanied skeletal healing, often necessitating dietary calcium supplementation. There was no evidence of hypocalcemia, ectopic calcification, or definite drug-related serious adverse events. Low titers of anti-ENB-0040 antibodies developed in four patients, with no evident clinical, biochemical, or autoimmune abnormalities at 48 weeks of treatment. CONCLUSIONS: ENB-0040, an enzyme-replacement therapy, was associated with improved findings on skeletal radiographs and improved pulmonary and physical function in infants and young children with life-threatening hypophosphatasia. (Funded by Enobia Pharma and Shriners Hospitals for Children; ClinicalTrials.gov number, NCT00744042.).