Exome-wide benchmark of difficult-to-sequence regions using short-read next-generation DNA sequencing.

Next-generation DNA sequencing (NGS) in short-read mode has recently been used for genetic testing in various clinical settings. NGS data accuracy is crucial in clinical settings, and several reports regarding quality control of NGS data, primarily focusing on establishing NGS sequence read accuracy, have been published thus far. Variant calling is another critical source of NGS errors that remains unexplored at the single-nucleotide level despite its established significance. In this study, we used a machine-learning-based method to establish an exome-wide benchmark of difficult-to-sequence regions at the nucleotide-residue resolution using 10 genome sequence features based on real-world NGS data accumulated in The Genome Aggregation Database (gnomAD) of the human reference genome sequence (GRCh38/hg38). The newly acquired metric, designated the 'UNMET score,' along with additional lines of structural information from the human genome, allowed us to assess the sequencing challenges within the exonic region of interest using conventional short-read NGS. Thus, the UNMET score could provide a basis for addressing potential sequential errors in protein-coding exons of the human reference genome sequence GRCh38/hg38 in clinical sequencing.

Challenges of secondary finding disclosure in genomic medicine in rare diseases: A nation-wide survey of Japanese facilities outsourcing comprehensive genetic testing.

Comprehensive genome analysis may reveal secondary findings (SFs) including pathogenic variants of genes other than those originally targeted. Comprehensive genetic analysis of rare diseases is generally performed as research in Japan. Therefore, the status and difficulties in SF disclosure remain unclear. To obtain information for the appropriate disclosure of SFs in rare diseases, we conducted a survey on how SFs are handled in clinical practice by facilities that outsource comprehensive genetic testing to other facilities. The response rate was 66.7% (40/60). Among the responding facilities, 55% had a policy of disclosing SFs with clinical utility and considered targeting actionable SFs with high penetrance. These facilities had difficulties in determining the disclosure targets (51%) and in genetic counseling (38%). Improving genetic literacy, establishment of surveillance systems, and providing insurance coverage for medical care to unaffected carriers were commonly cited as solutions to these difficulties. A comparison of the willingness to disclose SFs between overseas and in Japan showed more reluctance in Japan (86% vs. 65% for actionable SFs and 62% vs. 16% for non-actionable SFs). The group with difficulty in determining disclosure targets was significantly more likely to discuss this at conferences with other facilities and to refer guidelines. This suggests that the group with difficulties was unable to make decisions solely at their own facility and sought collaboration with other facilities. These findings suggest the necessity for a system that allows consultation with experts across facilities and guidelines that set forth policies for determining SFs.

Establishment of FXS-A9 panel with a single human X chromosome from fragile X syndrome-associated individual.

Fragile X syndrome (FXS) is the most common inheritable form of intellectual disability. FMR1, the gene responsible for FXS, is located on human chromosome Xq27.3 and contains a stretch of CGG trinucleotide repeats in its 5' untranslated region. FXS is caused by CGG repeats that expand beyond 200, resulting in FMR1 silencing via promoter hypermethylation. The molecular mechanism underlying CGG repeat expansion, a fundamental cause of FXS, remains poorly understood, partly due to a lack of experimental systems. Accumulated evidence indicates that the large chromosomal region flanking a CGG repeat is critical for repeat dynamics. In the present study, we isolated and introduced whole human X chromosomes from healthy, FXS premutation carriers, or FXS patients who carried disease condition-associated CGG repeat lengths, into mouse A9 cells via microcell-mediated chromosome transfer. The CGG repeat length-associated methylation status and human FMR1 expression in these monochromosomal hybrid cells mimicked those in humans. Thus, this set of A9 cells containing CGG repeats from three different origins (FXS-A9 panel) may provide a valuable resource for investigating a series of genetic and epigenetic CGG repeat dynamics during FXS pathogenesis.

sp2-Iminosugars targeting human lysosomal ß-hexosaminidase as pharmacological chaperone candidates for late-onset Tay-Sachs disease.

The late-onset form of Tay-Sachs disease displays when the activity levels of human ß-hexosaminidase A (HexA) fall below 10% of normal, due to mutations that destabilise the native folded form of the enzyme and impair its trafficking to the lysosome. Competitive inhibitors of HexA can rescue disease-causative mutant HexA, bearing potential as pharmacological chaperones, but often also inhibit the enzyme O-glucosaminidase (GlcNAcase; OGA), a serious drawback for translation into the clinic. We have designed sp2-iminosugar glycomimetics related to GalNAc that feature a neutral piperidine-derived thiourea or a basic piperidine-thiazolidine bicyclic core and behave as selective nanomolar competitive inhibitors of human Hex A at pH 7 with a ten-fold lower inhibitory potency at pH 5, a good indication for pharmacological chaperoning. They increased the levels of lysosomal HexA activity in Tay-Sachs patient fibroblasts having the G269S mutation, the highest prevalent in late-onset Tay-Sachs disease.

Online questionnaire on genetic testing for intractable diseases in Japan: response to and issues associated with the revised medical care act.

In Japan, most genetic testing for intractable diseases has been conducted in research laboratories in the past. However, since the Revised Medical Care Act came into effect on December 1, 2018, genetic testing in compliance with this act has become a major issue. To collect information on this topic, we conducted an online survey of members of the research groups for intractable diseases, which play a central role in medical care and research on intractable diseases with the support of the Ministry of Health, Labor and Welfare, five months after the enactment of the act. We separated the surveyed facilities into those that conducted genetic testing in their own laboratories ("testing facilities") and those that outsourced genetic testing ("outsourcing facilities"). Ninety-five and 66 responses regarding genetic testing were obtained from the testing and outsourcing facilities, respectively. Genetic analysis was the most commonly conducted genetic testing method, accounting for 60% or more of the tests. At the testing facilities that conducted comprehensive analysis with a next-generation sequencer, the number of target diseases for genetic testing was observed to be higher. In these testing facilities, more than 70% were research laboratories. In contrast, at the outsourcing facilities, testing was outsourced to registered clinical laboratories in many cases or to research laboratories. The proportion of genetic testing covered by public medical insurance at the outsourcing facilities was two times higher than that at the testing facilities. The importance of quality control for genetic testing was generally well acknowledged, but there was apprehension regarding the increased cost and burden on staff of quality control assurance, and many testing facilities viewed genetic testing as difficult. The research groups could handle the examination and interpretation of the genetic testing results, and many groups gathered and registered patient information. Within the intractable disease medical support network, there was a relatively large number of collaborations, with studies supported by the Japan Agency for Medical Research and Development (AMED) and Initiative on Rare and Undiagnosed Diseases (IRUD) projects. There were many requests for genetic testing to be covered by public medical insurance. In the future, the implementation of genetic testing using a next-generation sequencer at clinical laboratories with guaranteed quality control and the development of a system for collaboration with research groups will be necessary.

Isolated cortical tuber in an infant with genetically confirmed tuberous sclerosis complex 1 presenting with symptomatic West syndrome.

Tuberous sclerosis complex (TSC) is an autosomal dominant hereditary disorder caused by mutations in either TSC1 on chromosome 16 or TSC2 on chromosome 9, clinically characterized mainly by facial angiofibroma, epilepsy, and intellectual disability. Cortical dysplasias, subependymal nodules, and subependymal giant cell astrocytoma are characteristic central nervous system lesions among 11 major features in the current clinical diagnostic criteria for TSC. We encountered an unusual case of genetically confirmed TSC1 presenting with symptomatic West syndrome due to an isolated cortical dysplasia in the left occipital lobe of a six-month-old male infant who did not meet the clinical diagnostic criteria for TSC. The patient underwent left occipital lesionectomy at age 11 months and has been seizure-free for nearly six years since then. Histological examination of the resection specimen revealed cortical neuronal dyslamination with abundant dysmorphic neurons and ballooned cells, consistent with focal cortical dysplasia (FCD) type IIb. However, the lesion was also accompanied by unusual features, including marked calcifications, dense fibrillary gliosis containing abundant Rosenthal fibers, CD34-positive glial cells with abundant long processes confined to the dysplastic cortex, and multiple nodular lesions occupying the underlying white matter, consisting exclusively of ballooned cell and/or balloon-like astrocytes with focal calcifications. Genetic testing for TSC1 and TSC2 using the patient's peripheral blood revealed a germline heterozygous mutation in exon 7 (NM_000368.5: c.526dupT, p.Tyr176fs) in TSC1. Isolated FCD with unusual features such as calcification, dense fibrillary gliosis, Rosenthal fibers and/or subependymal nodule-like lesions in the white matter may indicate the possibility of a cortical tuber even without a clinical diagnosis of TSC. Identification of such histopathological findings has significant implications for early and accurate diagnosis and treatment of TSC, and is likely to serve as an important supplementary feature for the current clinical diagnostic criteria for TSC.

An autopsy case of GM1 gangliosidosis type II in a patient who survived a long duration with artificial respiratory support.

GM1 gangliosidosis is a storage disorder with autosomal recessive inheritance caused by deficiency of ß-galactosidase (GLB1), which is a lysosomal hydrolase, due to mutations in GLB1. We describe here an autopsy case of GM1 gangliosidosis in a female patient who survived for 38 years with a long period of artificial respiratory support (ARS). She was born after a normal pregnancy and delivery. Although development was normal until one year old, she was unable to walk at two years old and started having seizures by nine years old. At 21 years old, she became unable to communicate and was bed-ridden. At 36 years old, she suffered from pneumonia and required ARS. She died of pneumonia at 40 years old. Neuropathological examination revealed severe atrophy, predominantly found in the frontal lobes. Microscopically, severe gliosis and neuronal loss were observed in the cerebral cortex, putamen, cerebellum, the latter including Purkinje cell and granule cell layers. The hippocampus was relatively preserved. Severe neuronal swelling was observed in the limbic regions and stored a material in these neurons negative for periodic acid-Schiff (PAS). A PAS-positive granular storage material in neurons and macrophages was mainly observed in the brainstem and limbic regions. Exome analysis showed a known c.152T>C (p.I51T) variant that has been described in type III patients and a novel c.1348-2A>G variant in GLB1. Detailed analysis of reverse transcription-polymerase chain reaction products of GLB1 mRNA revealed that these variants were present in a compound heterozygous state. In our case, clinical features and neuropathological findings were most consistent with type II, although the entire course was longer than any previously reported cases. This may be explained by the residual enzyme activity in this patient whose severity lay between types II and III. Our finding of relative preservation of the limbic regions suggests that neuronal loss in GM1 gangliosidosis has regional selectivity.

[Successful treatment with enzyme replacement therapy for pelvic fragile fracture in an elderly case of type I Gaucher's disease].

A 76-year-old male with lower-limb weakness was admitted to our hospital where thrombocytopenia and anemia were noticed. CT showed massive splenomegaly and multiple nodules inside the spleen. Bone marrow examination showed an increase of macrophages with large cytoplasm. Suspected of splenic lymphoma, the patient underwent splenectomy. Spleen specimens were histologically analyzed and suggested the probability of Gaucher's disease (GD). Leukocyte glucocerebrosidase (GBA) enzyme activity had decreased to 1.25 nmol/mg, and mutation analysis of GBA revealed two missense variants, p.D448H (D409H), p.L483P (L444P), which confirmed the diagnosis of type I GD. Fourteen months after splenectomy, he developed right buttock pain, and pelvic magnetic resonance imaging showed a fragile right pubic and pelvic fracture. We initiated injection of imiglucerase as enzyme replacement therapy (ERT) and administered bisphosphonate. His symptoms gradually improved without surgical treatment. In addition, thrombocytopenia and anemia also improved, and angiotensin-converting enzyme levels decreased. Type I GD should be considered a differential diagnosis of giant splenomegaly and thrombocytopenia, even in the elderly. ERT or substrate reduction therapy should be administrated to GD patients, while paying attention to the development of bone lesions.

Phenotypic variability of Niemann-Pick disease type C including a case with clinically pure schizophrenia: a case report.

BACKGROUND: Niemann-Pick disease type C (NPC) is a lysosomal storage disorder with severe prognosis. Disease-specific therapy is crucial to prevent disease progression; however, diagnosing NPC is quite difficult because of remarkably variable clinical presentations. The NPC Suspicion Index (NPC-SI) was developed to overcome this problem. Identifying preclinical cases is important for prevention and therapy. Here, we report three newly diagnosed NPC cases, one typical juvenile-onset case and the cases of two sisters with symptoms neurologically/psychiatrically indistinguishable from dystonia and schizophrenia, respectively. CASE PRESENTATION: In Case 1, a 25-year-old man presented with a 14-year history of intellectual disability, clumsiness, spastic ataxia, dysphagia, and frequent falls. Neurological examination revealed vertical supranuclear gaze palsy and involuntary movements. Ultrasonography revealed mild splenomegaly, and filipin staining of skin fibroblasts was positive with a variant staining pattern. NPC1 gene analysis showed compound heterozygous mutations, including c.1421C > T (p.P474L), a known causative mutation, and c.3722 T > C (p.L1241S), a new mutation. In Case 2, a 28-year-old woman, the proband, who had marked splenomegaly in her childhood, survived well, contrary to the expected severe prognosis of infantile NPC. She had minor neuropsychiatric symptoms including auditory hallucinations, nocturnal urination, and sleep paralysis. At the age of 28 years, she presented with a 1-year history of orofacial and oromandibular painful dystonia. The patient's 35-year-old sister (Case 3) was diagnosed with schizophrenia. In both cases, filipin staining of skin fibroblasts was positive with variant staining patterns, as well as elevated levels of urinary bile acids. NPC1 gene analysis showed compound heterozygous mutations including c.3011C > T (p.S1004 L), a known causative mutation, and c.160_161insG (p.D54GfsX4), a new mutation. Their mother, who was under therapy with modafinil for narcolepsy, shared the latter mutation. CONCLUSIONS: Marked clinical variability was observed in our three cases. NPC could masquerade as a pure neuropsychiatric disorder such as dystonia or schizophrenia. Abdominal ultrasonography, history evaluation, and neurological examination were quite important in the diagnostic process.

Probing the Inhibitor versus Chaperone Properties of sp²-Iminosugars towards Human ß-Glucocerebrosidase: A Picomolar Chaperone for Gaucher Disease.

A series of sp²-iminosugar glycomimetics differing in the reducing or nonreducing character, the configurational pattern (d-gluco or l-ido), the architecture of the glycone skeleton, and the nature of the nonglycone substituent has been synthesized and assayed for their inhibition properties towards commercial glycosidases. On the basis of their affinity and selectivity towards GH1 ß-glucosidases, reducing and nonreducing bicyclic derivatives having a hydroxylation profile of structural complementarity with d-glucose and incorporating an N'-octyl-isourea or -isothiourea segment were selected for further evaluation of their inhibitory/chaperoning potential against human glucocerebrosidase (GCase). The 1-deoxynojirimycin (DNJ)-related nonreducing conjugates behaved as stronger GCase inhibitors than the reducing counterparts and exhibited potent chaperoning capabilities in Gaucher fibroblasts hosting the neuronopathic G188S/G183W mutation, the isothiourea derivative being indeed one of the most efficient chaperone candidates reported up to date (70% activity enhancement at 20 pM). At their optimal concentration, the four selected compounds promoted mutant GCase activity enhancements over 3-fold; yet, the inhibitor/chaperoning balance became unfavorable at much lower concentration for nonreducing as compared to reducing derivatives.

Severe demyelination in a patient with a late infantile form of Niemann-Pick disease type C.

Niemann-Pick disease type C (NPC) is a cholesterol storage disease caused by defective cellular cholesterol transportation. The onset and progression of NPC are variable, and autopsy findings have mainly been reported for the adult and juvenile forms of this disease. Here we report the clinical and pathological findings from a 9-year-old female patient with the late infantile form of NPC due to NPC1 gene mutation. She had notable splenomegaly at 4 months of age. She lost the ability to speak at 18 months of age. She learned to walk, but often fell and could no longer walk after 30 months. At 3 years of age, she was diagnosed with NPC. Sequence analysis of the NPC1 gene revealed compound heterozygous mutation of T2108C (F703S) and C2348G (S813X) (both novel). Thereafter, the patient suffered repeated respiratory infections and died of respiratory failure at 9 years of age. Pathological findings included cerebral atrophy (particularly of white matter), severe demyelination, and the loss of neurons from the cerebrum and from the nuclei of the brain stem. Remnant neuronal cells and microglia in the cerebrum, cerebellum, and brain stem had become swollen and foamy. Neurons of the hippocampal CA1 and Purkinje cells were relatively spared, and senile plaques and axonal spheroids were not present. Foamy cells were also observed in other organs, especially the spleen and bone marrow. The F703S mutation in this patient was localized in a sterol-sensing domain (SSD). Severe neurological phenotypes have been previously reported in patients with missense mutations in an SSD. It is considered that the combination of a nonsense mutation and missense mutation in an SSD was responsible for the severe neurological phenotype of our present patient. While pathological findings of adult/juvenile forms of NPC have included swollen neurons and glia, neuronal cell loss, and NFTs, demyelination may be a predominant finding in the infantile form of NPC.

[Clinical characteristics of early juvenile GM2 gangliosidosis: a case report].

We describe the case of a 15-year-old male with early juvenile type GM2 gangliosidosis. He first manifested with progressive clumsiness in his extremities at the age of 1.5 years, followed by motor regression. Intellectual disability became evident as late as age 6 years. This discrepancy along with rapid motor deterioration after varicella infection, lack of startle response or macrocephaly, and paucity of myoclonus were thought to be characteristic of juvenile GM2 gangliosidosis. In contrast to the cerebellar atrophy as the initial finding in usual juvenile GM2 gangliosidosis, magnetic resonance imaging revealed initially cerebral, and subsequently cerebellar, progressive atrophy. Autistic behavioral problems, including phonophobia, during intellectual regression in this patient was also unusual in juvenile GM2 gangliosidosis. Thus, recognition of these features would prompt proper diagnosis and insights into the pathomechanisms of GM2 gangliosidosis.

Clinical and laboratory outcomes after umbilical cord blood transplantation in a patient with mucolipidosis II alpha/beta.

Mucolipidosis (ML) II alpha/beta is an autosomal recessive disease caused by reduced enzyme activity of N-acetylglucosamine-1-phosphotransferase. Clinical symptoms of ML II are severe psychomotor delay and dysostosis multiplex; death usually occurs by 5-8 years of age from cardiopulmonary complications. Allogeneic hematopoietic stem cell transplantation (HSCT) has been attempted for ML; however, few reports have documented the detailed outcomes of HSCT for ML. A 26-month-old girl received a human leukocyte antigen 3/6-allele-matched transplant from cord blood. The preparative regimen consisted of fludarabine, cyclophosphamide, 6-Gy total body irradiation, and rabbit antithymocyte globulin. Although comparing before and after cord blood transplantation results, we observed that lysosomal enzyme activities in the plasma decreased by approximately 20-40%. Low serum levels of immunoglobulin A, G2, and G4 were also observed before HSCT; however, these values normalized after transplantation. Despite undergoing HSCT, she was treated twice for bacterial pneumonia with acute respiratory distress syndrome at ages 37 and 38 months. Although HSCT effects on the clinical manifestations were limited, laboratory data including plasma lysosomal enzyme activities and serum levels of immunoglobulin showed improvement.

[Mother and son with enlarged parietal foramina, persistent fetal vein, and ALX4 mutation].

Enlarged parietal foramina (EPF) are rare congenital skull defects. These round or oval defects are situated on each parietal bone approximately 1 cm from the midline. Most patients with EPF have a positive family history. The condition is inherited as an autosomal dominant trait with relatively high, but not full, penetrance. Mutation in either MSX2 or ALX4 genes is associated with enlarged parietal foramina. Case 1 is a boy who was noticed to have a large anterior fontanelle, large posterior fontanelle, and widely opened sagittal suture at 2 months. During development, the anterior fontanelle and sagittal suture closed at 3 years and the posterior fontanelle subsequently divided into two foramina with ossification of the midline bridge by 4 years. The foramina were about 2.5 x 2.5 cm in diameter at 8 years. Case 2 is the 34-year-old mother of Case 1. She showed similar bone defects in her cranium, again about 2.5 x 2.5 cm in diameter. Neither patient showed any neurological symptoms. Genetic analysis revealed a mutation in the ALX4 gene in both patients, and magnetic resonance imaging showed a persistent falcine sinus and a hypoplastic straight sinus. Further evaluation revealed that the mother of Case 2 also had a mutation in the ALX4 gene, but no enlarged parietal foramina. Although high penetrance of this condition has been reported, this family suggests incomplete penetrance of this disorder.

Recurrent micronucleation through cell cycle progression in the presence of microtubule inhibitors.

Although most cell lines undergo mitotic arrest after prolonged exposure to microtubule inhibitors, some cells subsequently exit this state and become tetraploid. Among these cells, limited numbers of rodent cells are known to undergo multinucleation to generate multiple small independent nuclei, or micronuclei by prolonged colcemid treatment. Micronuclei are thought to be formed when cells shift to a pseudo G1 phase, during which the onset of chromosomal decondensation allows individual chromosomes distributed throughout the cell to serve as sites for the reassembly of nuclear membranes. To better define this process, we used long-term live cell imaging to observe micronucleation induced in mouse A9 cells by treating with the microtubule inhibitor colcemid. Our observations confirm that nuclear envelope formation occurs when mitotic-arrested cells shift to a pseudo G1 phase and adopt a tetraploid state, accompanied by chromosome decondensation. Unexpectedly, only a small number of cells containing large micronuclei were formed. We found that tetraploid micronucleated cells proceeded through an additional cell cycle, shifting to a pseudo G1 phase and forming octoploid micronucleated cells that were smaller and more numerous compared with the tetraploid micronucleated cells. Our data suggest that micronucleation occur when cells shift from mitotic arrest to a pseudo G1 phase, and demonstrate that, rather than being a single event, micronucleation is an inducible recurrent process that leads to the formation of progressively smaller and more numerous micronuclei.

Structural basis of pharmacological chaperoning for human ß-galactosidase.

GM1 gangliosidosis and Morquio B disease are autosomal recessive diseases caused by the defect in the lysosomal ß-galactosidase (ß-Gal), frequently related to misfolding and subsequent endoplasmic reticulum-associated degradation. Pharmacological chaperone (PC) therapy is a newly developed molecular therapeutic approach by using small molecule ligands of the mutant enzyme that are able to promote the correct folding and prevent endoplasmic reticulum-associated degradation and promote trafficking to the lysosome. In this report, we describe the enzymological properties of purified recombinant human ß-Gal(WT) and two representative mutations in GM1 gangliosidosis Japanese patients, ß-Gal(R201C) and ß-Gal(I51T). We have also evaluated the PC effect of two competitive inhibitors of ß-Gal. Moreover, we provide a detailed atomic view of the recognition mechanism of these compounds in comparison with two structurally related analogues. All compounds bind to the active site of ß-Gal with the sugar-mimicking moiety making hydrogen bonds to active site residues. Moreover, the binding affinity, the enzyme selectivity, and the PC potential are strongly affected by the mono- or bicyclic structure of the core as well as the orientation, nature, and length of the exocyclic substituent. These results provide understanding on the mechanism of action of ß-Gal selective chaperoning by newly developed PC compounds.

Chaperone therapy for Krabbe disease: potential for late-onset GALC mutations.

Krabbe disease is an autosomal recessive leukodystrophy caused by a deficiency of the galactocerebrosidase (GALC) enzyme. Hematopoietic stem cells transplantation is the only available treatment option for pre-symptomatic patients. We have previously reported the chaperone effect of N-octyl-4-epi-ß-valienamine (NOEV) on mutant GM1 ß-galactosidase proteins, and in a murine GM1-gangliosidosis model. In this study, we examined its chaperone effect on mutant GALC proteins. We found that NOEV strongly inhibited GALC activity in cell lysates of GALC-transfected COS1 cells. In vitro NOEV treatment stabilized GALC activity under heat denaturation conditions. We also examined the effect of NOEV on cultured COS1 cells expressing mutant GALC activity and human skin fibroblasts from Krabbe disease patients: NOEV significantly increased the enzyme activity of mutants of late-onset forms. Moreover, we confirmed that NOEV could enhance the maturation of GALC precursor to its mature active form. Model structural analysis showed NOEV binds to the active site of human GALC protein. These results, for the first time, provide clear evidence that NOEV is a chaperone with promising potential for patients with Krabbe disease resulting from the late-onset mutations.

Heterozygous nonsense mutations near the C-terminal region of IGF1R in two patients with small-for-gestational-age-related short stature.

OBJECTIVE: The type I insulin-like growth factor I receptor (IGF1R) plays an important role in growth. We aimed to evaluate the detailed mechanism underlying the effect of IGF1R on human growth. PATIENTS AND METHODS: We have performed sequence analysis of IGF1R in 55 patients with SGA short stature in Japan, since 2004, and identified novel heterozygous nonsense mutations in 2 patients: an 8-year-old Japanese boy (case 1), with a birthweight of 2228 g (-3·3 SDS) and height of 46 cm (-2·1 SDS), and a 3-year-old Japanese girl (case 2), with a birthweight of 2110 g (-3·0 SDS) and height of 44·3 cm (-2·8 SDS). Both patients had a short stature (-3·2 SDS, -3·1 SDS). We determined the protein expression of mutated IGF1R, assessed the effect of the endoplasmic reticulum-associated degradation (ERAD) pathway on mutated IGF1R, assessed the dominant-negative effect of IGF1R and performed quantitative RT-PCR analysis of IGF1R mRNA expression in whole blood cells. RESULTS: Two novel heterozygous nonsense mutations (case 1: p.Q1250X and case 2: p.W1249X) were identified. Although these mutations did not affect blood IGF1R mRNA levels, they significantly decreased the expression of IGF1R protein in transiently transfected cells. Treatment with the proteasome inhibitor MG132 showed significantly increased IGF1R protein. CONCLUSIONS: Heterozygous nonsense mutations affecting the C-terminal region (p.Q1250X, p.W1249X) of IGF1R decreased the expression of IGF1R through the ERAD pathway. Our study revealed the importance of the C-terminal region and the dosage of this receptor for growth.

Apoptosis induced by an uromodulin mutant C112Y and its suppression by topiroxostat.

BACKGROUND: Familial juvenile hyperuricemic nephropathy (FJHN) is an autosomal dominant disorder caused by mutations in UMOD that encodes uromodulin. Topiroxostat, a novel non-purine analog, selectively inhibits xanthine oxidase and reduces the serum uric acid levels and the urinary albuminuria. METHODS: Genomic DNA of a patient was extracted from peripheral white blood. Exons and flanking sequences of UMOD were amplified by PCR with primers. Mutation analysis was performed by direct sequencing of the PCR products. The wild-type and mutant uromodulin were expressed in HEK293 cells and analyzed by western blotting, immunoprecipitation, immunofluorescence, and flow cytometry. RESULTS: We identified an FJHN patient who carried a novel UMOD mutation G335A (C112Y). The levels of both cytosolic and secreted C112Y protein were significantly decreased compared with the wild-type, whereas the level of ubiquitination was higher in C112Y than that in the wild type. The half-life of C112Y was shortened and it was restored by a proteasome inhibitor MG132. Immunofluorescence revealed decreased levels of C112Y in the Golgi apparatus and on the plasma membrane. Expression of C112Y induced cellular apoptosis as revealed by flow cytometry. Apoptosis induced by C112Y was suppressed by topiroxostat. CONCLUSION: C112Y causes its protein instability resulting cellular apoptosis which could be suppressed with topiroxostat.

pH-Responsive Pharmacological Chaperones for Rescuing Mutant Glycosidases.

A general approach is reported for the design of small-molecule competitive inhibitors of lysosomal glycosidases programmed to 1) promote correct folding of mutant enzymes at the endoplasmic reticulum, 2) facilitate trafficking, and 3) undergo dissociation and self-inactivation at the lysosome. The strategy is based on the incorporation of an orthoester segment into iminosugar conjugates to switch the nature of the aglycone moiety from hydrophobic to hydrophilic in the pH 7 to pH 5 window, which has a dramatic effect on the enzyme binding affinity. As a proof of concept, new highly pH-responsive glycomimetics targeting human glucocerebrosidase or α-galactosidase with strong potential as pharmacological chaperones for Gaucher or Fabry disease, respectively, were developed.