Efficient nonparametric three-stage estimation of fixed effects varying coefficient panel data models

This paper is concerned with the estimation of a fixed effects panel data model that adopts a partially linear form, in which the coeffcients of some variables are restricted to be constant but the coeffcients of other variables are assumed to be varying, depending on some exogenous continuous variables. Moreover, we allow for the existence of endogeneity in the structural equation. Conditional moment restrictions on first differences are imposed to identify the structural equation. Based on these restrictions we propose a three stage estimation procedure. The asymptotic properties of these proposed estimators are established. Moreover, as a result of the first differences transformation, to estimate the unknown varying coeffcient functions, two alternative backfitting estimators are obtained. As a novelty, we propose a minimum distance estimator that, combining both estimators, is more effcient and achieves the optimal rate of convergence. The feasibility and possible gains of this new procedure are shown by estimating a Life-cycle hypothesis panel data model and a Monte Carlo study is implemented.The authors gratefully acknowledge financial support from the Programa Estatal de Fomentode la Investigación Científica y Técnica de Excelencia/Spanish Ministry of Economy and Competitiveness. Ref. ECO2016-76203-C2-1-P. In addition, this work is part of the Research Project APIE 1/2015-17: "New Methods for the empirical analysis of financial markets" of the Santander Financial Institute (SANFI) of UCEIF Foundation resolved by the University of Cantabria and funded with sponsorship from Banco Santander

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

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

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. 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. 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 (r 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 (r −0.85, p = 0.003) and IQ (r −0.94, p = 0.005) were found. Patients bearing p.E93A, p.C241S or p.R162W mutations presented a milder phenotype. 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 demonstrated

Mutation spectrum in RAB3GAP1, RAB3GAP2, and RAB18 and genotype-phenotype correlations in warburg micro syndrome and Martsolf syndrome

Warburg Micro syndrome and Martsolf syndrome (MS) are heterogeneous autosomal-recessive developmental disorders characterized by brain, eye, and endocrine abnormalities. Causative biallelic germline mutations have been identified in RAB3GAP1, RAB3GAP2, or RAB18, each of which encode proteins involved in membrane trafficking. This report provides an up to date overview of all known disease variants identified in 29 previously published families and 52 new families. One-hundred and forty-four Micro and nine Martsolf families were investigated, identifying mutations in RAB3GAP1 in 41% of cases, mutations in RAB3GAP2 in 7% of cases, and mutations in RAB18 in 5% of cases. These are listed in Leiden Open source Variation Databases, which was created by us for all three genes. Genotype-phenotype correlations for these genes have now established that the clinical phenotypes in Micro syndrome and MS represent a phenotypic continuum related to the nature and severity of the mutations present in the disease genes, with more deleterious mutations causing Micro syndrome and milder mutations causing MS. RAB18 has not yet been linked to the RAB3 pathways, but mutations in all three genes cause an indistinguishable phenotype, making it likely that there is some overlap. There is considerable genetic heterogeneity for these disorders and further gene identification will help delineate these pathway

Encephalopathies with intracranial calcification in children: Clinical and genetic characterization

none42noBackground: We present a group of patients affected by a paediatric onset genetic encephalopathy with cerebral calcification of unknown aetiology studied with Next Generation Sequencing (NGS) genetic analyses. Methods: We collected all clinical and radiological data. DNA samples were tested by means of a customized gene panel including fifty-nine genes associated with known genetic diseases with cerebral calcification. Results: We collected a series of fifty patients. All patients displayed complex and heterogeneous phenotypes mostly including developmental delay and pyramidal signs and less frequently movement disorder and epilepsy. Signs of cerebellar and peripheral nervous system involvement were occasionally present. The most frequent MRI abnormality, beside calcification, was the presence of white matter alterations; calcification was localized in basal ganglia and cerebral white matter in the majority of cases. Sixteen out of fifty patients tested positive for mutations in one of the fifty-nine genes analyzed. In fourteen cases the analyses led to a definite genetic diagnosis while results were controversial in the remaining two. Conclusions: Genetic encephalopathies with cerebral calcification are usually associated to complex phenotypes. In our series, a molecular diagnosis was achieved in 32% of cases, suggesting that the molecular bases of a large number of disorders are still to be elucidated. Our results confirm that cerebral calcification is a good criterion to collect homogeneous groups of patients to be studied by exome or whole genome sequencing; only a very close collaboration between clinicians, neuroradiologists and geneticists can provide better results from these new generation molecular techniques.noneTonduti D.; Panteghini C.; Pichiecchio A.; Decio A.; Carecchio M.; Reale C.; Moroni I.; Nardocci N.; Campistol J.; Garcia-Cazorla A.; Perez Duenas B.; Zorzi G.; Ardissone A.; Granata T.; Freri E.; Zibordi F.; Ragona F.; D'Arrigo S.; Saletti V.; Esposito S.; Pantaleoni C.; Riva D.; De Giorgis V.; Cereda C.; Valente M.L.; Sproviero D.; Poo Arguelles M.P.; Estupina C.F.; Sans Fito A.M.; Martorell Sampol L.; Del Mar O'Callaghan Gordo M.; Ortez Gonzalez C.I.; Gonzalez Alvarez V.; Garcia-Segarra N.; Fusco C.; Bertini E.; Diodato D.; Fazzi E.; Galli J.; Chiapparini L.; Garavaglia B.; Orcesi S.Tonduti, D.; Panteghini, C.; Pichiecchio, A.; Decio, A.; Carecchio, M.; Reale, C.; Moroni, I.; Nardocci, N.; Campistol, J.; Garcia-Cazorla, A.; Perez Duenas, B.; Zorzi, G.; Ardissone, A.; Granata, T.; Freri, E.; Zibordi, F.; Ragona, F.; D'Arrigo, S.; Saletti, V.; Esposito, S.; Pantaleoni, C.; Riva, D.; De Giorgis, V.; Cereda, C.; Valente, M. L.; Sproviero, D.; Poo Arguelles, M. P.; Estupina, C. F.; Sans Fito, A. M.; Martorell Sampol, L.; Del Mar O'Callaghan Gordo, M.; Ortez Gonzalez, C. I.; Gonzalez Alvarez, V.; Garcia-Segarra, N.; Fusco, C.; Bertini, E.; Diodato, D.; Fazzi, E.; Galli, J.; Chiapparini, L.; Garavaglia, B.; Orcesi, S