Ah-Ra Ko

Identification of signal peptide domain SOST mutations in autosomal dominant craniodiaphyseal dysplasia.

Sclerosteosis and Van Buchem disease are related recessive sclerosing bone dysplasias caused by alterations in the SOST gene. We tested the hypothesis that craniodiaphyseal dysplasia (CDD) (MIM 122860), an extremely rare sclerosing bone dysplasia resulting facial distortion referred to as “leontiasis ossea”, could also be caused by SOST mutations. We discovered mutations c.61G>A (Val21Met) and c.61G>T (Val21Leu) two children with CDD. As these mutations are located in the secretion signal of the SOST gene, we tested their effect on secretion by transfecting the mutant constructs into 293E cells. Intriguingly, these mutations greatly reduced the secretion of SOST. We conclude that CDD, the most severe form of sclerotic bone disease, is part of a spectrum of disease caused by mutations in SOST. Unlike the other SOST-related conditions, sclerosteosis and Van Buchem disease that are inherited as recessive traits seem to be caused by a dominant negative mechanism.

Phase I/II clinical trial of enzyme replacement therapy with idursulfase beta in patients with mucopolysaccharidosis II (Hunter Syndrome)

BackgroundMucopolysaccharidosis II (MPS II, Hunter syndrome) is a rare X-linked lysosomal storage disorder caused by the deficiency of iduronate-2-sulfatase (IDS). In affected patients, glycosaminoglycan (GAG) accumulates in the lysosomes of many organs and tissues contributing to the pathology associated with MPS II. The objective of this phase I/II clinical study was to evaluate the efficacy and safety of recombinant human iduronate-2-sulfatase (idursulfase beta, Hunterase®) in the treatment of MPS II.MethodsThirty-one MPS II patients between 6 and 35 years of age were enrolled in a randomized, single-blinded, active comparator-controlled phase I/II trial for 24 weeks. Patients were randomized to active comparator infusions (N=11), 0.5 mg/kg idursulfase beta infusions (N=10), or 1.0 mg/kg idursulfase beta infusions (N=10). The primary efficacy variable was the level of urinary GAG excretion. The secondary variables were changes in the distance walked in 6 minutes (6-minute walk test, 6MWT), echocardiographic findings, pulmonary function tests, and joint mobility.ResultsPatients in all three groups exhibited reduction in urine GAG and this reduced GAG level was maintained for 24 weeks. Urine GAG was also significantly reduced in the 0.5 mg/kg and 1.0 mg/kg idursulfase beta groups when compared to the active comparator group (P = 0.043, 0.002, respectively). Changes in 6MWT were significantly greater in the 0.5 mg/kg and 1.0 mg/kg idursulfase groups than in the active comparator group (p= 0.003, 0.015, respectively). Both idursulfase beta infusions were generally safe and well tolerated, and elicited no serious adverse drug reactions. The most frequent adverse events were urticaria and skin rash, which were easily controlled with administration of antihistamines.ConclusionsThis study indicates that idursulfase beta generates clinically significant reduction of urinary GAG, improvements in endurance as measured by 6MWT, and it has an acceptable safety profile for the treatment of MPS II.Trial registrationClinicalTrials.gov: NCT01301898

LIN28B polymorphisms are associated with central precocious puberty and early puberty in girls

Purpose Single-nucleotide polymorphism (SNP) markers within LIN28B have been reported to be related to the timing of pubertal growth. However, no study has investigated the frequency of genetic markers in girls with precocious puberty (PP) or early puberty (EP). This study aimed to determine the frequency of putative genetic markers in girls with PP or EP. Methods Genomic DNAs were obtained from 77 and 109 girls that fulfilled the criteria for PP and EP, respectively. The controls in this study were 144 healthy volunteers between 20 and 30 years of age. The haplotypes were reconstructed using 11 SNPs of LIN28B, and haplotype association analysis was performed. The haplotype frequencies were compared. Differences in the clinical and laboratory parameters were analyzed according to the haplotype dosage. Results Eleven SNPs in LIN28B were all located in a block that was in linkage disequilibrium. The haplotype could be reconstructed using 2 representative SNPs, rs4946651 and rs369065. The AC haplotype was less frequently observed in the PP group than in the controls (0.069 vs. 0.144, P=0.010). The trend that girls with non-AC haplotypes tended to have earlier puberty onset (P=0.037) was illustrated even in the EP+PP patient group by Kaplan-Meier analysis. Conclusion The results of the present study showed that non-AC haplotypes of LIN28B had a significant association with PP in girls.

Improvement of CNS Defects Via Continuous Intrathecal Enzyme Replacement by Osmotic Pump in Mucopolysaccharidosis Type II Mice

Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome (OMIM 309900), is a rare, X‐linked lysosomal storage disorder caused by a deficiency of iduronate‐2‐sulfatase (IDS; EC 3.1.6.13), which is involved in the lysosomal degradation of glycosaminoglycans (GAG). Although intermittent intrathecal (IT) injection of the enzyme has been introduced as a method to overcome the blood‐brain barrier, continuous IT infusion of the enzyme would be more physiologic. This study was performed to investigate responses in the brain of MPS II mice to varying doses of continuous IT infusion of recombinant human IDS (rh‐IDS) in MPS II mice by osmotic pump in three different doses (2.4, 4.8, and 12 µg/day) of rh‐IDS for 3 weeks. The results showed that the group treated with 12 µg/day doses of rh‐IDS demonstrated decreased GAG concentrations compared to the untreated KO mice group (P = 0.003). After 3 weeks of continuous IT ERT, the brain tissues of the high‐dose IT‐treated KO mice showed a reduction of vacuolation in the cerebral cortex, thalamus and cerebellar cortex, which was not observed in the low‐ and medium‐dose KO mice groups. Moreover, the anti‐NeuN signal representing intact neuron was restored in the cortexes of the high‐dose group. In conclusion, continuous IT infusion of the deficient enzyme was effective in improving CNS defects in the MPS II mice, and could be a valuable therapeutic method for treating neurological deterioration in patients with MPS II.

Identification of 11 novel mutations in 49 Korean patients with mucopolysaccharidosis type II

Sohn YB, Ki C‐S, Kim C‐H, Ko A‐R, Yook Y‐J, Lee S‐J, Kim SJ, Park SW, Yeau S, Kwon E‐K, Han SJ, Choi EW, Lee S‐Y, Kim J‐W, Jin D‐K. Identification of 11 novel mutations in 49 Korean patients with mucopolysaccharidosis type II.

A polymorphism in the growth hormone receptor is associated with height in children with Prader-Willi syndrome.

The exon‐3 deletion polymorphism (d3, Database of Genomic Variants ID: Variation_64191) in the growth hormone receptor (GHR) gene is associated with increased growth response to growth hormone (GH) therapy in GH‐deficient patients. However, an association of the GHR genotype with height has not yet been reported in Prader–Willi syndrome (PWS). The aim of this study was to assess the association of GHR alleles with height before starting GH therapy in patients with PWS. Seventy‐four patients with PWS were genotyped and their medical records were retrospectively reviewed (45 males and 29 females, median age 8.7 years). One hundred normal controls, with known final height, were also genotyped. The GH‐exon 3 locus was genotyped using a PCR multiplex assay. The distribution of alleles in the patients with PWS was not different from controls [(fl/fl n = 53 (72%), fl/d3 n = 21 (28%)) in PWS vs. (fl/fl n = 72(72%), fl/d3 n = 26(26%), and d3/d3 n = 2(2%)]. However, patients with PWS carrying a d3 allele had significantly greater height standard deviation scores (SDS) (P = 0.025) and higher insulin‐like growth factor I (IGF‐I) level (P = 0.041), although the age at the start of GH therapy, weight, BMI, and body fat were not different. The d3 allele was associated with height and IGF‐I levels before GH therapy and suggests that even before GH therapy, d3 allele may influence height through GH secretion.

Pharmacokinetics, Pharmacodynamics, and Efficacy of a Novel Long-Acting Human Growth Hormone: Fc Fusion Protein

The current recombinant human growth hormone (rhGH) therapy requires daily subcutaneous (sc) injections, which results in poor patient compliance, especially in young children. To reduce the dosing frequency, we generated a chimeric protein of rhGH and the Fc-domain of immunoglobulin G (IgG) (rhGH-Fc). The pharmacokinetics and pharmacodynamics of sc-injected rhGH-Fc were assessed in male Sprague-Dawley rats and hypophysectomized rats, respectively. A single sc injection of rhGH-Fc at a dose of 0.2 mg/kg slowly reached a Cmax of 16.80 ng/mL and remained for 7 days with a half-life of 51.1 h. Conversely, a single sc injection of rhGH 0.2 mg/kg rapidly reached a Cmax of 46.88 ng/mL and declined with a half-life of 0.55 h to baseline values in 4 h. In the efficacy study, the sc-injected rhGH-Fc induced rapid weight gain and tibial width growth at a dose of 240 μg/animal. The effect of two injections of rhGH-Fc separated by 1 week was comparable to that of the same dose of 14 daily injections of rhGH. The rhGH-Fc is a novel candidate for long-acting rhGH therapy with more convenient weekly administration, as it reduces glomerular filtration and receptor-mediated clearance while allowing for the rapid reversal of potential adverse events.

Differential Effects of Insufflated, Subcutaneous, and Intravenous Growth Hormone on Bone Growth, Cognitive Function, and NMDA Receptor Subunit Expression

The objective of this study was to characterize the effect of inhalable growth hormone (GH) delivered by an insufflator to the lungs of hypophysectomized Sprague Dawley rats. In the first cohort, the safety and efficacy of the insufflated GH were evaluated. Three experimental groups (n = 7 per group) were treated with GH for 15 d: One group received sc injection of GH daily at 200 microg/kg (SC200). Two other groups received GH by insufflation daily: 200 microg/kg (INS 200) and 600 microg/kg (INS 600). In the second set of experiments, GH was administered in three routes [SC200, INS200, intravenous (IV200)] (n=10) for 5 d, and escape latency and N-methyl D-aspartate (NMDA) receptor expression were evaluated. In the first cohort, INS200 showed similar bioactivity as SC200 in growth promotion, tibial growth, as well as escape latency on the 12th day of treatment. Insufflated GH was well tolerated without significant inflammatory responses. In the second cohort, expression of the NMDA receptor 1 and 2B in hippocampus measured after 3 or 6 d of daily treatments were significantly higher in INS200 as compared to IV200, consistent with the improvement of the escape latency. In summary, the inhalable form of GH delivered by intratracheal insufflation was safe, and its bioactivity was comparable to sc injection both in promotion of growth and acquisition of learning ability. If applied properly to human, inhalable GH would be effective for growth promotion and possibly for several disorders caused by underexpression of NMDA receptors.

Improvement of cardiac function by short-term enzyme replacement therapy in a murine model of cardiomyopathy associated with Hunter syndrome evaluated by serial echocardiography with speckle tracking 2-D strain analysis

Cardiac systolic function is significantly decreased in a proportion of patients with Hunter syndrome. This study was performed to evaluate the change in myocardial function associated with enzyme replacement therapy (ERT) in a mouse model of cardiomyopathy associated with Hunter syndrome. Thirty 9-week-old iduronate-2-sulfatase (IDS) knockout mice received either intravenous injection of human recombinant IDS (ERT group, N=15) or saline (control group, N=15) for 5 weeks. Echocardiography was performed at baseline and after treatment. Echocardiographic parameters of left ventricular (LV) systolic function and 2-dimensional radial and circumferential strain were assessed. At follow-up, there was a significant increase in LV fractional shortening and radial and circumferential strain in the ERT group only. Notable myocardial fibrosis was observed in the control group only. In the murine model of Hunter syndrome, ERT exerts beneficial effects on cardiac function, which can be evaluated by serial echocardiographic evaluation including 2-dimensional strain analysis.

Calpain-mediated proteolysis of polycystin-1 C-terminus induces JAK2 and ERK signal alterations.

Autosomal dominant polycystic kidney disease (ADPKD), a hereditary renal disease caused by mutations in PKD1 (85%) or PKD2 (15%), is characterized by the development of gradually enlarging multiple renal cysts and progressive renal failure. Polycystin-1 (PC1), PKD1 gene product, is an integral membrane glycoprotein which regulates a number of different biological processes including cell proliferation, apoptosis, cell polarity, and tubulogenesis. PC1 is a target of various proteolytic cleavages and proteosomal degradations, but its role in intracellular signaling pathways remains poorly understood. Herein, we demonstrated that PC1 is a novel substrate for μ- and m-calpains, which are calcium-dependent cysteine proteases. Overexpression of PC1 altered both Janus-activated kinase 2 (JAK2) and extracellular signal-regulated kinase (ERK) signals, which were independently regulated by calpain-mediated PC1 degradation. They suggest that the PC1 function on JAK2 and ERK signaling pathways might be regulated by calpains in response to the changes in intracellular calcium concentration.