Hye Young Jin

Spectrum of Mutations in Noonan Syndrome and Their Correlation with Phenotypes

OBJECTIVES To investigate mutation spectrums and their correlations to phenotypes in Noonan syndrome (NS) and NS-related disorders that share functional alterations of the Ras-mitogen-activated protein kinase pathway. STUDY DESIGN Clinical characteristics and genotypes of 10 previously known and 2 candidate genes, SPRY1-4 and SPRED1, were investigated in 59 patients with NS, 17 with cardiofaciocutaneous syndrome, 5 with Costello syndrome, and 2 with LEOPARD syndrome. RESULTS PTPN11 (39.0%), SOS1 (20.3%), RAF1 (6.8%), KRAS (5.1%), and BRAF (1.7%) mutations were identified in NS; BRAF (41.2%), SHOC2 (23.5%), and MEK1 (5.9%) mutations in cardiofaciocutaneous syndrome; and HRAS and PTPN11 mutations in Costello syndrome and LEOPARD syndrome, respectively. No additional mutations were identified in 28.9% of NS and 35.3% of cardiofaciocutaneous syndrome. Functional characterizations of 2 RAF1 novel variants, p.P261T and p.S259T, and one SOS1 variant, p.K170E, showed enhanced activity of Ras-mitogen-activated protein kinase pathway. Normal stature was frequent in SOS1 mutations, hypertrophic cardiomyopathy in RAF1, and developmental delay in RAF1, BRAF, or SHOC2 mutations. CONCLUSIONS By identifying genotype-phenotype correlations, our study highlights the role of molecular genetic testing in the process of differential diagnosis of NS and NS-related disorders. Pathophysiologies that underlie these correlations are needed to be investigated in terms of their effects on Ras-mitogen-activated protein kinase pathway.

Clinical and Functional Characteristics of a Novel Heterozygous Mutation of the IGF1R Gene and IGF1R Haploinsufficiency due to Terminal 15q26.2->qter Deletion in Patients with Intrauterine Growth Retardation and Postnatal Catch-Up Growth Failure

CONTEXT Mutations in the IGF1R gene result in intrauterine growth retardation and postnatal growth failure. OBJECTIVE The objective of this study was to describe the clinical features of subjects with a mutation in the IGF1R gene and to evaluate the molecular and functional characteristics of a novel IGF1R mutation. SUBJECTS Three children with unexplained intrauterine growth retardation (birth weight <-1.5 SD score) and persistent short stature (<-2.0 SD score) were included in the study. METHODS Auxological and endocrinological profiles were measured. All coding regions, including the intron-exon boundaries of the IGF1R gene, were amplified via PCR and directly sequenced. To study the functional effect of the IGF1R gene mutation on IGF-I signaling, total IGF1R protein expression, and IGF-I-dependent Akt and ERK phosphorylation were assessed by Western blotting. RESULTS Two children and their father possessed a novel c.420del (p.A110fsX20) mutation in exon 2 of the IGF1R gene. After recombinant human GH therapy, the growth deficit decreased in these two children. Our data show that IGF-I-induced autophosphorylation of the phosphorylated tyrosine and phosphorylated Akt of IGF1R increased in a dose-dependent manner but did so less efficiently in patients. Array comparative genomic hybridization of chromosome 15 identified a heterozygous deletion of 15q26.2 to 15qter in subject 3. CONCLUSIONS The novel heterozygous mutation described in this study reduced IGF1R expression and represents haploinsufficiency of the IGF1R gene. Our results indicate that this mutation in the IGF1R gene leads to abnormalities in the function of IGF1R and also retards intrauterine and subsequent growth in humans.

Distinct clinical courses according to presenting phenotypes and their correlations to ATP7B mutations in a large Wilson's disease cohort.

Introduction and aims: Wide phenotypic and genotypic heterogeneities in Wilsons disease (WD) have been reported, hampering the study of their correlations. The goal of this study was to identify the factors related to these diversities.

High frequency of DUOX2 mutations in transient or permanent congenital hypothyroidism with eutopic thyroid glands.

Background/Aims: This study aimed to clarify the frequency, phenotypes, and molecular spectrum of DUOX2, TPO, TSHR, and TG mutations in patients with congenital hypothyroidism (CH) with enlarged or normal-sized eutopic thyroid glands. Methods: The study cohort included 43 subjects from 41 unrelated families who had CH with eutopic thyroid glands. Mutation analyses of DUOX2, TPO, and TSHR were performed. The functional capacities of novel missense variants of DUOX2 were verified by measuring H2O2 generation in vitro. Results: Of the 43 subjects, 23 (53.5%) had sequence variants in at least one gene. Twelve different DUOX2 variants, including seven novel variants, were identified in 20 subjects. A functional analysis of the DUOX2 variants revealed that most variants, other than p.G206V and p.H678R, caused a significant reduction in H2O2 generation. Therefore, 15 subjects harbored functionally deleterious DUOX2 variants. Of these, 5 subjects had transient CH, and 10 were found to have permanent CH. Sequence variants in TSHR were identified in 5 subjects. One of the 43 subjects (2.3%) had sequence variants in two different genes. Conclusions:DUOX2 variants are a relatively common cause of CH with normal-sized or enlarged eutopic thyroid glands. Variable phenotypes were associated with partial loss of the functional activity of DUOX2 variants.

Clinical characterization and identification of two novel mutations of the GNAS gene in patients with pseudohypoparathyroidism and pseudopseudohypoparathyroidism

Objective  Pseudohypoparathyroidism (PHP) and pseudopseudohypoparathyroidism (PPHP) are rare disorders resulting from genetic and epigenetic aberrations in the GNAS locus.

Argininemia Presenting With Progressive Spastic Diplegia

Argininemia is caused by a deficiency of arginase 1, which catalyzes the final step in the urea cycle, i.e., the cytosolic hydrolysis of arginine to ornithine and urea. In contrast to other urea cycle disorders, hyperammonemic encephalopathy is rarely observed in patients with argininemia. Rather, most exhibit an insidious onset and progression of neurologic manifestations, including spastic diplegia. We describe the first Korean patient with argininemia, manifesting as slowly progressive spastic diplegia. Our patient carries c.[32T>C]+[913G>A] (p.[Ile11Thr]+[Gly305Arg]) mutations in the ARG1 gene. The latter mutation was not previously reported. Although argininemia is a very rare disease, it is recognized as a pan-ethnic disorder. We conclude that argininemia should be considered more frequently in the differential diagnosis of a patient with slowly progressive neurologic manifestations, especially progressive spastic diplegia, even in a population where argininemia was previously unknown.

Response to Growth Hormone Therapy in Children with Noonan Syndrome: Correlation with or without PTPN11 Gene Mutation

Background/Aims: The objective of this study was to evaluate the efficacy of recombinant human growth hormone (rhGH) therapy and the influence of genotype on the response to rhGH therapy in children with Noonan syndrome (NS). Methods: 14 male and 4 female subjects with NS with short stature, whose height was <3rd percentile, were included. The rhGH was subcutaneously administered at a dose of 66 µg/kg/day. Mutations in the PTPN11 gene were identified in 10 subjects (55.6%). Mutations in the SOS1 (2 children, 11.1%), MEK1 (1 child, 5.6%) and KRAS (1 child, 5.6%) genes were also found. Results: Height SDS increased from –2.8 ± 0.9 at the start of rhGH therapy to –2.0 ± 0.9 12 months later (p < 0.001). Height velocity increased from 5.0 ± 0.9 cm/year in the year before treatment to 8.9 ± 1.6 during treatment (p < 0.001). Changes in height SDS, height velocity, and serum IGF-1 level did not differ significantly between those children with or without PTPN11 mutations. Conclusion: The rhGH therapy significantly improved the growth velocity and increased the serum IGF-1 level. Long-term correlation between genotype and rhGH therapy responsiveness needs to be addressed in a large population.

Proteomic analysis of the hepatic tissue of Long–Evans Cinnamon (LEC) rats according to the natural course of Wilson disease

Copper‐induced toxicity is important in the pathogenic process of Wilsons disease (WD). Using Long–Evans Cinnamon (LEC) rats, an animal model of WD, the study was undertaken to identify proteins involved in the process of WD and to investigate their functional roles in copper‐induced hepatotoxicity. In early stages, expression levels of mitochondrial matrix proteins including agmatinase, isovaleryl coenzyme A dehydrogenase, and cytochrome b5 were downregulated. As mitochondrial injuries progressed, along with subsequent apoptotic processes, expressions of malate dehydrogenase 1, annexin A5, transferrin, S‐adenosylhomocysteine hydrolase, and sulfite oxidase 1 were differentially regulated. Notably, the expression of malate dehydrogenase 1 was downregulated while the annexin A5 was overexpressed in an age‐dependent manner, indicating that these proteins may be involved in the WD process. In addition, pronounced under‐expression of S‐adenosylhomocysteine hydrolase in elderly LEC rats, also involved in monoamine neurotransmitter metabolism, indicates that this protein might be related to the development of neurological manifestations in WD. The results of our study help to understand the pathogenic process of WD in hepatic tissues, identifying the important proteins associated with the disease process of WD, and to investigate the molecular pathogenic process underlying the development of neurological manifestations in WD.

Nonalcoholic fatty liver disease in 2 siblings with adult-onset type II citrullinemia.

682 ty liver disease (NAFL ic enzymes, radiolog N onalcoholic fat D) is characterized by elevated hepat ical feature of fatty change, and steatosis with inflammation and fibrosis in liver biopsy (1). Excluding infectious diseases, autoimmune diseases, drugs, a1antirypsin deficiency, and Wilson disease, NAFLD in the preadolescent and adolescent periods is suggested to be mainly associated with obesity due to rapidly growing prevalence (1–3). Diverse inherited metabolic disorders including citrin deficiency can exhibit hepatic manifestations, mostly in the neonate or infant periods; however, citrin deficiency can also present in the late adolescent to adult period. The typical presentation of citrullinemia type II (CTLN2) is hyperammonemic encephalopathy accompanying hepatic dysfunction and NAFLD, which is called adult-onset CTLN2 (Online Mendelian Inheritance in Man no. 603471) (4–7). In contrast to a urea cycle disorder or citrullinemia type I (CTLN1), citrullinemia is not prominent and the plasma arginine level is usually normal in CTLN2. The patients have peculiar dietary habits, preference for proteinor lipid-rich foods, such as eggs, meat, fish, and beans, but dislike of carbohydrate-rich foods like rice, bread, and sweets; however, they show stunted growth patterns. Once a patient experiences hyperammonemic encephalopathy, the prognosis is believed to be poor due to repeated hyperammonemic episodes and accompanying liver cirrhosis, and liver transplantation is the only curative management (4,5,7). Therefore, early identification and adequate management are important for the patient prognosis. Here, we report 2 teenage siblings with CTLN2 manifesting as NAFLD before they experienced hyperammonemic encephalopathy, indicating that NAFLD is an important early sign of CTLN2.

Functional effects of DAX-1 mutations identified in patients with X-linked adrenal hypoplasia congenita.

X-linked adrenal hypoplasia congenita with hypogonadotropic hypogonadism and adrenal insufficiency is a rare disorder caused by mutations of DAX-1. In this study, we investigated the functional defects of DAX-1 caused by mutations identified in 3 unrelated Korean patients with adrenal hypoplasia congenita. The DAX-1 gene was directly sequenced using genomic DNA isolated from peripheral blood leukocytes. The functional defects of DAX-1 caused by mutations were evaluated using an in vitro promoter assay. After mutagenesis of DAX-1 complementary DNA in the pcDNA3.1 vector, steroidogenic factor 1 and the promoter region of steroidogenic acute regulatory protein (StAR) genes in pGL4.10[luc2] were transiently cotransfected into human embryonic kidney 293 cells, followed by luminometry measurements of the luciferase activity of StAR. Mutation analysis of 3 patients revealed p.L386delfsX2, p.W105X, and p.Q252X mutations of the DAX-1 gene. The mutant DAX-1 proteins showed lower repressive activity on the StAR gene promoter when compared with normal DAX-1. Nonsense and frameshift mutations of the DAX-1 gene partially eliminated the ability of DAX-1 to repress the transcription of StAR in an in vitro assay.