Hotaka Kamasaki

Functional analysis of PTPN11/SHP-2 mutants identified in Noonan syndrome and childhood leukemia

AbstractNoonan syndrome (NS) is characterized by short stature, characteristic facial features, and heart defects. Recently, missense mutations of PTPN11, the gene encoding protein tyrosine phosphatase (PTP) SHP-2, were identified in patients with NS. Further, somatic mutations in PTPN11 were detected in childhood leukemia. Recent studies showed that the phosphatase activities of five mutations identified in NS and juvenile myelomonocytic leukemia (JMML) were increased. However, the functional properties of the other mutations remain unidentified. In this study, in order to clarify the differences between the mutations identified in NS and leukemia, we examined the phosphatase activity of 14 mutants of SHP-2. We identified nine mutations, including a novel F71I mutation, in 16 of 41 NS patients and two mutations, including a novel G503V mutation, in three of 29 patients with leukemia. Immune complex phosphatase assays of individual mutants transfected in COS7 cells showed that ten mutants identified in NS and four mutants in leukemia showed 1.4-fold to 12.7-fold increased activation compared with wild-type SHP-2. These results suggest that the pathogenesis of NS and leukemia is associated with enhanced phosphatase activity of mutant SHP-2. A comparison of the phosphatase activity in each mutant and a review of previously reported cases showed that high phosphatase activity observed in mutations at codons 61, 71, 72, and 76 was significantly associated with leukemogenesis.

Novel and recurrent TRPV4 mutations and their association with distinct phenotypes within the TRPV4 dysplasia family

Background Mutations in TRPV4, a gene that encodes a Ca2+ permeable non-selective cation channel, have recently been found in a spectrum of skeletal dysplasias that includes brachyolmia, spondylometaphyseal dysplasia, Kozlowski type (SMDK) and metatropic dysplasia (MD). Only a total of seven missense mutations were detected, however. The full spectrum of TRPV4 mutations and their phenotypes remained unclear. Objectives and methods To examine TRPV4 mutation spectrum and phenotype−genotype association, we searched for TRPV4 mutations by PCR-direct sequencing from genomic DNA in 22 MD and 20 SMDK probands. Results TRPV4 mutations were found in all but one MD subject. In total, 19 different heterozygous mutations were identified in 41 subjects; two were recurrent and 17 were novel. In MD, a recurrent P799L mutation was identified in nine subjects, as well as 10 novel mutations including F471del, the first deletion mutation of TRPV4. In SMDK, a recurrent R594H mutation was identified in 12 subjects and seven novel mutations. An association between the position of mutations and the disease phenotype was also observed. Thus, P799 in exon 15 is a hot codon for MD mutations, as four different amino acid substitutions have been observed at this codon; while R594 in exon 11 is a hotspot for SMDK mutations. Conclusion The TRPV4 mutation spectrum in MD and SMDK, which showed genotype−phenotype correlation and potential functional significance of mutations that are non-randomly distributed over the gene, was presented in this study. The results would help diagnostic laboratories establish efficient screening strategies for genetic diagnosis of the TRPV4 dysplasia family diseases.

Mutation analysis of the SHOC2 gene in Noonan-like syndrome and in hematologic malignancies.

Noonan syndrome is an autosomal dominant disease characterized by dysmorphic features, webbed neck, cardiac anomalies, short stature and cryptorchidism. It shows phenotypic overlap with Costello syndrome and cardio-facio-cutaneous (CFC) syndrome. Noonan syndrome and related disorders are caused by germline mutations in genes encoding molecules in the RAS/MAPK pathway. Recently, a gain-of-function mutation in SHOC2, p.S2G, has been identified as causative for a type of Noonan-like syndrome characterized by the presence of loose anagen hair. In order to understand the contribution of SHOC2 mutations to the clinical manifestations of Noonan syndrome and related disorders, we analyzed SHOC2 in 92 patients with Noonan syndrome and related disorders who did not exhibit PTPN11, KRAS, HRAS, BRAF, MAP2K1/2, SOS1 or RAF1 mutations. We found the previously identified p.S2G mutation in eight of our patients. We developed a rapid detection system to identify the p.S2G mutation using melting curve analysis, which will be a useful tool to screen for the apparently common mutation. All the patients with the p.S2G mutation showed short stature, sparse hair and atopic skin. Six of the mutation-positive patients showed severe mental retardation and easily pluckable hair, and one showed leukocytosis. No SHOC2 mutations were identified in leukemia cells from 82 leukemia patients. These results suggest that clinical manifestations in SHOC2 mutation-positive patients partially overlap with those in patients with typical Noonan or CFC syndrome and show that easily pluckable/loose anagen hair is distinctive in SHOC2 mutation-positive patients.

FBN2, FBN1, TGFBR1, and TGFBR2 analyses in congenital contractural arachnodactyly

FBN2, FBN1, TGFBR1, and TGFBR2 were analyzed by direct sequencing in 15 probands with suspected congenital contractural arachnodactyly (CCA). A total of four novel FBN2 mutations were found in four probands (27%, 4/15), but remaining the 11 did not show any abnormality in either of the genes. This study indicated that FBN2 mutations were major abnormality in CCA, and TGFBR and FBN1 defects may not be responsible for the disorder. FBN2 mutations were only found at introns 30, 31, and 35 in this study. Thus analysis of a mutational hotspot from exons 22 to 36 (a middle part) of FBN2 should be prioritized in CCA as previously suggested.

A significant improvement in lower limb pain after treatment with alendronate in two cases of Camurati–Engelmann disease

Camurati–Engelmann disease, also known as progressive diaphyseal dysplasia, is a rare osteosclerotic dysplasia of bone that is characterized by endosteal and periosteal thickening of the diaphysis of the long bones. The most common symptoms are severe, bilateral, and symmetrical bone pain in the limbs, waddling gait, muscle weakness, and easy fatigability [1,2]. Camurati–Engelmann disease is inherited in an autosomic dominant manner, and alterations in the sequence in the transforming growth factor-β1 (TGF-β1) gene in the chromosomal region 19q13.1 have been found to be associated with the disorder [3]. Radiographically, symmetrical osteosclerosis is observed in the diaphyses and metaphyses of the long bones [4], and bone scintigraphy reveals a marked increase in radioactivity at the affected regions [5]. These radiologic fi ndings provide a meaningful assessment of disease extent and activity. A few previous reports showed that biochemical markers of bone turnover were useful to evaluate the disease activity of Camurati–Engelmann disease [6]. Concerning the treatment of Camurati–Engelmann disease, corticosteroids have been reported to be effective in reducing the symptoms in some cases [7], whereas there were no defi nitive data on the effectiveness of corticosteroids on disease activity in a previous report [8]. Recently, several reports showed that bisphosphonates have been used in Camurati–Engelmann disease because of the experience of treatment with these drugs in Paget’s disease. However, most of the studies indicated that the administration of bisphosphonates was ineffective for treating Camurati–Engelmann disease [8–10]. In this study, treatment of two cases of Camurati–Engelmann disease was attempted with alendronate. The drug markedly improved bone pain, and a correlative decrease in cross-linked Ntelopeptides of type I collagen (NTX), a bone resorption marker, was noted.

A Case of Graves’ Disease Diagnosed in the Course of Bilateral Carotid Artery Stenoses (Moyamoya Disease); A Case Report and Review of the Literature

A 14-year-old boy was admitted to our hospital after being diagnosed at a local clinic with bilateral carotid artery stenoses (Moyamoya disease) and mild thyrotoxicosis. A blood examination showed suppressed TSH and elevated triiodothyronine and thyroxine levels; however, he was negative for anti-thyrotropin receptor antibody (TRAB) and thyroid stimulating antibody (TSAB). Concern about a possible thyroid crisis led us to administer thiamazole (MMI) and potassium iodide (KI), following which encephalo-duro-arterio-synangiosis (EDAS) of the left side was performed successfully. After about 1 mo, he became positive for TRAB and TSAB. He was thought to have Graves’ disease and Moyamoya disease coincidentally. Several factors are considered to be involved in the coincidental onset of these two diseases.

A novel heterozygous intronic mutation in POU1F1 is associated with combined pituitary hormone deficiency

POU class 1 homeobox 1 (POU1F1) regulates pituitary cell-specific gene expression of somatotropes, lactotropes, and thyrotropes. In humans, two POU1F1 isoforms (long and short isoform), which are generated by the alternative use of the splice acceptor site for exon 2, have been identified. To date, more than 30 POU1F1 mutations in patients with combined pituitary hormone deficiency (CPHD) have been described. All POU1F1 variants reported to date affect both the short and long isoforms of the POU1F1 protein; therefore, it is unclear at present whether a decrease in the function of only one of these two isoforms is sufficient for disease onset in humans. Here, we described a sibling case of CPHD carrying a heterozygous mutation in intron 1 of POU1F1. In vitro experiments showed that this mutation resulted in exon 2-skipping of only in the short isoform of POU1F1, while the long isoform remained intact. This result strongly suggests the possibility, for the first time, that isolated mutations in the short isoform of POU1F1 could be sufficient for induction of POU1F1-related CPHD. This finding improves our understanding of the molecular mechanisms, and developmental course associated with mutations in POU1F1.

An adolescent case of familial hyperparathyroidism with a germline frameshift mutation of the CDC73 gene

Abstract. A 13-yr-old boy who complained of persistent nausea, vomiting and weight loss had hypercalcemia and an elevated intact PTH level. Computed tomography confirmed two tumors in the thyroid gland. The tumors were surgically removed and pathologically confirmed as parathyroid adenoma. Because his maternal aunt and grandmother both had histories of parathyroid tumors, genetic investigation was undertaken for him, and a germline frameshift mutation of the CDC73 gene was identified. CDC73 gene analysis should be done on individuals who are at risk of familial hyperparathyroidism, including those who are asymptomatic, and they should be followed for potential primary hyperparathyroidism and associated disorders including resultant parathyroid carcinoma.

Treatment of Hypothyroidism due to Iodine Deficiency Using Daily Powdered Kelp in Patients Receiving Long-term Total Enteral Nutrition

We investigated thyroid function and urinary iodine concentration (UIC) in seven patients with severe motor intellectual disabilities. All seven received total enteral nutrition (TEN) for more than three years with a daily iodine intake of less than 20 µg. They were diagnosed as hypothyroidism due to iodine deficiency (HID) because of high TSH levels (7.6–82.3 µIU/ml), lower free T4 (FT4 0.4–1.5 ng/dl), negative anti-thyroid antibodies (anti-thyroglobulin antibody, anti-thyroidal peroxidase antibody) and extremely low UIC (<25–58 µg/l) levels. We gave them 1–2 g powdered kelp (200–400 µg as iodine) once a day, which restored their thyroid function and normalized their UICs. We proposed that daily powdered kelp would be effective and safe to treat HID in patient receiving long term TEN.

Incidence and Characteristics of Adrenal Crisis in Children Younger than 7 Years with 21-Hydroxylase Deficiency: A Nationwide Survey in Japan

Background/Aims: We aimed to evaluate the incidence and characteristics of adrenal crisis in Japanese children with 21-hydroxylase deficiency (21-OHD). Methods: We conducted a retrospective nationwide survey for the councilors of the Japanese Society for Pediatric Endocrinology (JSPE) regarding adrenal crisis in children under 7 years with 21-OHD, admitted to hospitals from 2011 through 2016. We defined adrenal crisis as the acute impairment of general health due to glucocorticoid deficiency with at least two of symptoms, signs, or biochemical abnormalities. Results: The councilors of the JSPE in 83 institutions responded to this survey (response rate, 60.1%). Data analyses of 378 patients with 1,101.4 person-years (PYs) revealed that 67 patients (17.7%) experienced at least 1 episode of hospital admission for adrenal crisis at the median age of 2 years. The incidence of adrenal crisis was calculated as 10.9 per 100 PYs (95% confidence interval [CI] 9.6–12.2). Infections were the most common precipitating factors, while no factor was observed in 12.5%. Hypoglycemia occurred concomitantly in 27.4%. One patient died from severe hypoglycemia, resulting in a mortality rate of 0.09 per 100 PYs (95% CI 0.0–0.2). Conclusion: Adrenal crisis is not rare and can be accompanied by disastrous hypoglycemia in children with 21-OHD.