Mutations in TRAPPC11 are associated with a congenital disorder of glycosylation.

Congenital disorders of glycosylation (CDG) are a heterogeneous and rapidly growing group of diseases caused by abnormal glycosylation of proteins and/or lipids. Mutations in genes involved in the homeostasis of the endoplasmic reticulum (ER), the Golgi apparatus (GA), and the vesicular trafficking from the ER to the ER-Golgi intermediate compartment (ERGIC) have been found to be associated with CDG. Here, we report a patient with defects in both N- and O-glycosylation combined with a delayed vesicular transport in the GA due to mutations in TRAPPC11, a subunit of the TRAPPIII complex. TRAPPIII is implicated in the anterograde transport from the ER to the ERGIC as well as in the vesicle export from the GA. This report expands the spectrum of genetic alterations associated with CDG, providing new insights for the diagnosis and the understanding of the physiopathological mechanisms underlying glycosylation disorders

Two novel variants of the ABCG5 gene cause xanthelasmas and macrothrombocytopenia: a brief review of hematologic abnormalities of sitosterolemia

[EN] Background: Sitosterolemia (STSL) is a recessive inherited disorder caused by pathogenic variants in the ABCG5 and ABCG8 genes. Increased levels of plasma plant sterols (PSs) usually result in xanthomas and premature coronary atherosclerosis, although hematologic abnormalities may occasionally be present. This clinical picture is unfamiliar to many physicians, and patients may be at high risk of misdiagnosis. Objectives: To report two novel ABCG5 variants causing STSL in a Spanish patient, and review the clinical and mutational landscape of STSL. Patient/Methods: A 46-year-old female was referred to us with lifelong macrothrombocytopenia. She showed familial hypercholesterolemia-related xanthomas. Molecular analysis was performed with high-throughput sequencing. Plasma PS levels were evaluated with gas–liquid chromatography. The STSL landscape was reviewed with respect to specific online databases and all reports published since 1974. Results: A blood smear revealed giant platelets and stomatocytes. Novel compound heterozygous variants were detected in exons 7 (c.914C>G) and 13 (c.1890delT) of ABCG5. The patient showed an increased plasma level of sitosterol. These findings support the diagnosis of STSL. In our review, we identified only 25 unrelated STLS patients who presented with hematologic abnormalities including macrothrombocytopenia

Phosphomannomutase deficiency (PMM2-CDG): Ataxia and cerebellar assessment

Background: Phosphomannomutase deficiency (PMM2-CDG) is the most frequent congenital disorder of glycosylation. The cerebellum is nearly always affected in PMM2-CDG patients, a cerebellar atrophy progression is observed, and cerebellar dysfunction is their main daily functional limitation. Different therapeutic agents are under development, and clinical evaluation of drug candidates will require a standardized score of cerebellar dysfunction. We aim to assess the validity of the International Cooperative Ataxia Rating Scale (ICARS) in children and adolescents with genetically confirmed PMM2-CDG deficiency. We compare ICARS results with the Nijmegen Pediatric CDG Rating Scale (NPCRS), neuroimaging, intelligence quotient (IQ) and molecular data. Methods: Our observational study included 13 PMM2-CDG patients and 21 control subjects. Ethical permissions and informed consents were obtained. Three independent child neurologists rated PMM2-CDG patients and control subjects using the ICARS. A single clinician administered the NPCRS. All patients underwent brain MRI, and the relative diameter of the midsagittal vermis was measured. Psychometric evaluations were available in six patients. The Mann-Whitney U test was used to compare ICARS between patients and controls. To evaluate inter-observer agreement in patients' ICARS ratings, intraclass correlation coefficients (ICC) were calculated. ICARS internal consistency was evaluated using Cronbach's alpha. Spearman's rank correlation coefficient test was used to correlate ICARS with NPCRS, midsagittal vermis relative diameter and IQ. Results: ICARS and ICARS subscores differed between patients and controls (p < 0.001). Interobserver agreement of ICARS was "almost perfect" (ICC = 0.99), with a "good" internal reliability (Cronbach's alpha = 0.72). ICARS was significantly correlated with the total NPCRS score (rs 0.90, p < 0.001). However, there was no agreement regarding categories of severity. Regarding neuroimaging, inverse correlations between ICARS and midsagittal vermis relative diameter (rs -0.85, p = 0.003) and IQ (rs -0.94, p = 0.005) were found. Patients bearing p.E93A, p.C241S or p.R162W mutations presented a milder phenotype. Conclusions: ICARS is a reliable instrument for assessment of PMM2-CDG patients, without significant inter-rater variability. Despite our limited sample size, the results show a good correlation between functional cerebellar assessment, IQ and neuroimagingFor the first a correlation between ICARS, neuroimaging and IQ in PMM2-CDG patients has been demonstratedThe work was supported by national grants PI14/00021, PI11/01096, PI11/01250, and PI10/00455 from the National Plan on I+D+I, cofinanced by ISC-III (Subdirección General de Evaluación y Fomento de la Investigación Sanitaria) and FEDER (Fondo Europeo de Desarrollo Regional) and IPT-2012- 0561-010000 from MINECO. Three research groups (U-746, U-737 and U703) from the Centre for Biomedical Research on Rare Diseases (CIBER-ER), Instituto de Salud Carlos III, Spain, have worked together for the present stud

Perlecan Maintains microvessel integrity in vivo and modulates their formation in vitro

Perlecan is a heparan sulfate proteoglycan assembled into the vascular basement membranes (BMs) during vasculogenesis. In the present study we have investigated vessel formation in mice, teratomas and embryoid bodies (EBs) in the absence of perlecan. We found that perlecan was dispensable for blood vessel formation and maturation until embryonic day (E) 12.5. At later stages of development 40% of mutant embryos showed dilated microvessels in brain and skin, which ruptured and led to severe bleedings. Surprisingly, teratomas derived from perlecan-null ES cells showed efficient contribution of perlecan-deficient endothelial cells to an apparently normal tumor vasculature. However, in perlecan-deficient EBs the area occupied by an endothelial network and the number of vessel branches were significantly diminished. Addition of FGF-2 but not VEGF165 rescued the in vitro deficiency of the mutant ES cells. Furthermore, in the absence of perlecan in the EB matrix lower levels of FGFs are bound, stored and available for cell surface presentation. Altogether these findings suggest that perlecan supports the maintenance of brain and skin subendothelial BMs and promotes vasculo- and angiogenesis by modulating FGF-2 function

α5β1 Integrin-Mediated Adhesion to Fibronectin Is Required for Axis Elongation and Somitogenesis in Mice

The arginine-glycine-aspartate (RGD) motif in fibronectin (FN) represents the major binding site for α5β1 and αvβ3 integrins. Mice lacking a functional RGD motif in FN (FNRGE/RGE) or α5 integrin develop identical phenotypes characterized by embryonic lethality and a severely shortened posterior trunk with kinked neural tubes. Here we show that the FNRGE/RGE embryos arrest both segmentation and axis elongation. The arrest is evident at about E9.0, corresponding to a stage when gastrulation ceases and the tail bud-derived presomitic mesoderm (PSM) induces α5 integrin expression and assumes axis elongation. At this stage cells of the posterior part of the PSM in wild type embryos are tightly coordinated, express somitic oscillator and cyclic genes required for segmentation, and form a tapered tail bud that extends caudally. In contrast, the posterior PSM cells in FNRGE/RGE embryos lost their tight associations, formed a blunt tail bud unable to extend the body axis, failed to induce the synchronised expression of Notch1 and cyclic genes and cease the formation of new somites. Mechanistically, the interaction of PSM cells with the RGD motif of FN is required for dynamic formation of lamellipodia allowing motility and cell-cell contact formation, as these processes fail when wild type PSM cells are seeded into a FN matrix derived from FNRGE/RGE fibroblasts. Thus, α5β1-mediated adhesion to FN in the PSM regulates the dynamics of membrane protrusions and cell-to-cell communication essential for elongation and segmentation of the body axis

Usefulness of cholestanol levels in the diagnosis and follow-up of patients with cerebrotendinous xanthomatosis

Introduction: Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive disease caused by a deficiency of mitochondrial enzyme sterol 27-hydrolylase. Such a deficiency results in a reduced production of chenodeoxycholic acid and in an increased formation of cholestanol. It is clinically characterized by cataracts, diarrhoea, xanthomas, premature arteriosclerosis and a number of progressive neurological symptoms. Although cholestanol levels are used for the diagnosis of CTX, their correlation with the clinical symptoms and their prognostic usefulness have not been assessed so far. Methods: We reviewed 14 CTX patients diagnosed between 1995 and 2008 in two reference centres for the genetic diagnosis of this disorder, whose cholestanol levels had been recorded. We studied the main demographic, clinical and therapeutical data and their correlation with plasma cholestanol levels. Results: The average cholestanol level at diagnosis was 105.8 μmol/l. These levels did not correlate with any neurological symptoms or with disability at diagnosis scored by the EDSS. After treatment, all patients achieved a significant reduction in plasma cholestanol levels (average reduction of 91 μmol/l in an average follow-up of 34 months), although only one patient remained clinically stable. Conclusions: High cholestanol levels are very useful for diagnosis of CTX but they do not have a prognostic value (they do not correlate with severity). Normalization of cholestanol levels is not always associated with clinical stabilization. However, follow-up of cholestanol levels can be useful for the dose adjustment. Resumen: Introducción: La xantomatosis cerebro-tendinosa (XCT) es una enfermedad autosómica recesiva producida por un déficit del enzima 27-hidroxilasa. Como consecuencia, existe una deficiencia de ácido quenodeoxicólico y una sobreproducción de colestanol que se deposita en los tejidos. Clínicamente cursa con cataratas, diarrea, xantomas y diferentes síntomas neurológicos. A pesar de que los niveles de colestanol se emplean en el diagnóstico de la XCT, se desconoce su correlación con la clínica y el pronóstico. Métodos: Se han revisado 14 pacientes de XCT, diagnosticados entre 1995 y 2008 en dos centros de referencia para el diagnóstico genético, en los que se había determinado el colestanol. Se han estudiado los principales datos demográficos, clínicos y terapéuticos y su posible relación con los niveles de colestanol. Resultados: La media de los niveles de colestanol al diagnóstico fue de 106 μmol/l. No se encontró ninguna relación entre el colestanol plasmático y los diferentes síntomas neurológicos, ni con el grado de discapacidad al diagnóstico medido mediante la EDSS. Tras la instauración del tratamiento se obtuvo una reducción significativa del colestanol plasmático en todos los casos (reducción media de 91 μmol/l en una media de 34 meses), a pesar de lo cual sólo un paciente se estabilizó clínicamente. Conclusiones: La presencia de niveles elevados de colestanol es muy útil para el diagnóstico de la XCT, pero no tiene valor pronóstico (no se correlaciona con la situación funcional). Su normalización no siempre se acompaña de una estabilización clínica, pero su monitorización puede ser útil para el ajuste del tratamiento. Keywords: Cerebrotendinous xanthomatosis, Cholestanol, Chenodeoxycholic acid, Palabras clave: Xantomatosis cerebro-tendinosa, Colestanol, Ácido quenodeoxicólic

Utilidad de los niveles de colestanol en el diagnóstico y seguimiento de los pacientes con xantomatosis cerebrotendinosa

Resumen: Introducción: la xantomatosis cerebro-tendinosa (XCT) es una enfermedad autosómica recesiva producida por un déficit de la enzima 27-hidroxilasa. Como consecuencia, existe una deficiencia de ácido quenodeoxicólico y una sobreproducción de colestanol que se deposita en los tejidos. Clínicamente cursa con cataratas, diarrea, xantomas y diferentes síntomas neurológicos. A pesar de que los niveles de colestanol se emplean en el diagnóstico de la XCT, se desconoce su correlación con la clínica y el pronóstico. Métodos: se han revisado 14 pacientes afectos de XCT, diagnosticados entre 1995 y 2008 en dos centros de referencia para el diagnóstico genético, en los que se había determinado el colestanol. Se han estudiado los principales datos demográficos, clínicos y terapéuticos y su posible relación con los niveles de colestanol. Resultados: la media de los niveles de colestanol al diagnóstico fue de 106 μmol/ l. No se encontró ninguna relación entre el colestanol plasmático y los diferentes síntomas neurológicos, ni con el grado de discapacidad al diagnóstico medido mediante la EDSS. Tras la instauración del tratamiento se obtuvo una reducción significativa del colestanol plasmático en todos los casos (reducción media de 91 μmol/ l en una media de 34 meses), a pesar de lo cual sólo un paciente se estabilizó clínicamente. Conclusiones: la presencia de niveles elevados de colestanol es muy útil para el diagnóstico de la XCT, pero no tiene valor pronóstico (no se correlaciona con la situación funcional). Su normalización no siempre se acompaña de una estabilización clínica, pero su monitorización puede ser útil para el ajuste del tratamiento. Abstract: Introduction: cerebrotendinous xanthomatosis (CTX) is an autosomal recessive disease caused by a deficiency of mitochondrial enzyme sterol 27-hydrolylase. Such a deficiency results in a reduced production of chenodeoxycholic acid and in an increased formation of cholestanol. It is clinically characterized by cataracts, diarrhoea, xanthomas, premature arteriosclerosis and a number of progressive neurological symptoms. Although cholestanol levels are used for the diagnosis of CTX, their correlation with the clinical symptoms and their prognostic usefulness have not been assessed so far. Methods: we reviewed 14 CTX patients diagnosed between 1995 and 2008 in two reference centres for the genetic diagnosis of this disorder, whose cholestanol levels had been recorded. We studied the main demographic, clinical and therapeutical data and their correlation with plasma cholestanol levels. Results: the average cholestanol level at diagnosis was 105.8 μmol/l. These levels did not correlate with any neurological symptoms or with disability at diagnosis scored by the EDSS. After treatment, all patients achieved a significant reduction in plasma cholestanol levels (average reduction of 91 μmol/l in an average follow-up of 34 months), although only one patient remained clinically stable. Conclusions: high cholestanol levels are very useful for diagnosis of CTX but they do not have a prognostic value (they do not correlate with severity). Normalisation of cholestanol levels is not always associated with clinical stabilisation. However, follow-up of cholestanol levels can be useful for the dose adjustment. Palabras clave: Xantomatosis cerebro-tendinosa, Colestanol, Ácido quenodeoxicólico, Keywords: Cerebrotendinous xanthomatosis, Cholestanol, Chenodeoxycholic aci

Two novel variants of the ABCG5 gene cause xanthelasmas and macrothrombocytopenia: a brief review of hematologic abnormalities of sitosterolemia

[Background]: Sitosterolemia (STSL) is a recessive inherited disorder caused by pathogenic variants in the ABCG5 and ABCG8 genes. Increased levels of plasma plant sterols (PSs) usually result in xanthomas and premature coronary atherosclerosis, although hematologic abnormalities may occasionally be present. This clinical picture is unfamiliar to many physicians, and patients may be at high risk of misdiagnosis. [Objectives]: To report two novel ABCG5 variants causing STSL in a Spanish patient, and review the clinical and mutational landscape of STSL. [Patient/Methods]: A 46-year-old female was referred to us with lifelong macrothrombocytopenia. She showed familial hypercholesterolemia-related xanthomas. Molecular analysis was performed with high-throughput sequencing. Plasma PS levels were evaluated with gas–liquid chromatography. The STSL landscape was reviewed with respect to specific online databases and all reports published since 1974. [Results]: A blood smear revealed giant platelets and stomatocytes. Novel compound heterozygous variants were detected in exons 7 (c.914C>G) and 13 (c.1890delT) of ABCG5. The patient showed an increased plasma level of sitosterol. These findings support the diagnosis of STSL. In our review, we identified only 25 unrelated STLS patients who presented with hematologic abnormalities including macrothrombocytopenia. It remains unknown why only some patients develop hematologic abnormalities. [Conclusions]: This is the first Spanish STSL patient to be reported and molecularly characterized. The early diagnosis of STLS is strongly supported by the presence of stomatocytes in blood smears. The definitive diagnosis of STSL by measurement of serum PS levels and molecular analyses prompted the use of ezetimibe therapy.This work was partially supported by grants from the Gerencia Regional de Salud (GRS 1370/A/16), ISCIII & Feder (PI14/01956), CIBERER CB15/00055, Fundacion Seneca (19873/GERM/15), and Sociedad Espanola de Trombosis y Hemostasia (SETH).Peer Reviewe