Pediatric invasive long-term ventilation-A 10-year review

INTRODUCTION

The number of children with complex physical and developmental pathologies, including chronic respiratory insufficiency, surviving and growing beyond early childhood continues to rise. No study has examined the clinical pathway of children on invasive long-term mechanical ventilation (LTMV) in an Irish setting. Our data over a 10-year period were reviewed to see if our demographics and outcomes are in line with global trends.

METHODS

Children's Health Ireland (CHI) at Crumlin, Dublin is Ireland's largest tertiary pediatric hospital. A retrospective review analyzed data from children in our center commenced on LTMV via a tracheostomy over 10 years (2009-2018). This data was subdivided into two epochs for statistical analysis of longitudinal trends.

RESULTS

Forty-six children were commenced on LTMV from 2009 to 2018. Many had complex medical diagnoses with associated comorbidities. Far less children, 30.4% (n = 14) commenced LTMV in the latter half of the 10-year period, they also fared better in all aspects of their treatment course. Focusing solely on children who have needed LTMV over this timeframe we have been able to isolate trends specific to this cohort. Less patients commenced LTMV on a year-on-year basis, and for those that require tracheostomy and LTMV, their journey to decannulation tends to be shorter.

CONCLUSION

Over the period reviewed, less patients over time necessitated LTMV, and those patients are being weaned and decannulated with ever more success. This has implications in terms of predicting numbers transitioning to adult services and allocation of hospital and community care resources.

The role of rhinovirus infections in young children with cystic fibrosis

Rhinovirus (RV) is an important virus in children with chronic respiratory conditions such as asthma; however, little is known about its role in CF. Our aim was to examine the prevalence and clinical impact of different RV species in young children with CF. We collected clinical data and nasal swabs on patients at home and in the hospital setting. Parents filled out symptom diaries and collected nasal swabs when their children were symptomatic and asymptomatic. A novel RV typing PCR assay was used to determine the RV species present. We collected 55 nasal swab samples from ten preschool CF patients over a six month period. The quality of parent collected samples at home was sufficient for PCR analysis. RV was the most common virus detected in young children with CF. There was no difference in the frequency of RV species between symptomatic and asymptomatic subjects. However, parental home-sampling is an acceptable and feasible approach to monitoring young children with CF.

Caregiver Burden Due to Pulmonary Exacerbations in Patients with Cystic Fibrosis

OBJECTIVE

To describe the poorly understood burden of pulmonary exacerbations experienced by primary caregivers of children (aged 2-17 years) with cystic fibrosis (CF), who frequently require prolonged hospitalizations for treatment of pulmonary exacerbations with intravenous (IV) antibiotics.

STUDY DESIGN

In this prospective observational study, 88 caregivers in Germany, Ireland, the United Kingdom, and the US completed a survey during pulmonary exacerbation-related hospitalizations (T1) and after return to a "well state" of health (T2). The impact of pulmonary exacerbations on caregiver-reported productivity, mental/physical health, and social/family/emotional functioning was quantified.

RESULTS

Primary caregivers of children with CF reported significantly increased burden during pulmonary exacerbations, as measured by the 12-item Short-Form Health Survey mental health component and the Work Productivity and Activity Impairment: Specific Health Problem absenteeism, presenteeism, work productivity loss, and activity impairment component scores. Compared to the "well state," during pulmonary exacerbations-related hospitalization caregivers reported lower physical health scores on the Child Health Questionnaire-Parent Form 28. Quality-of-life scores on the Caregiver Quality of Life Cystic Fibrosis scale and total support score on the Multidimensional Scale of Perceived Social Support did not differ significantly between T1 and T2. More caregivers reported a negative impact on family/social/emotional functioning during pulmonary exacerbations than during the "well state."

CONCLUSIONS

Pulmonary exacerbations necessitating hospitalization impose a significant burden on primary caregivers of children with CF. Preventing pulmonary exacerbations may substantially reduce this burden.

The Prevalence of Pseudomonas Aeruginosa Infection Over a Ten-Year Period in Children with Cystic Fibrosis

Background Pseudomonas aeruginosa (PA) infection is associated with an increased morbidity and adverse prognosis in children with Cystic Fibrosis(CF). The aim of the study was to evaluate the prevalence and characteristics of PA over a ten year period at a single paediatric tertiary referral centre in Ireland. Methods This was a retrospective cross-sectional study. Patient’s case notes, microbiology laboratory results and CF Registry of Ireland(CFRI) data were used to collect the data. Results The overall chronic PA infection prevalence was 28.1%(45/160) in 2004 and 21.3%(35/164) in 2014. In 2004, 54/160(33.8%) patients were never infected with PA, 27/160(16.9%) were free for 12 months and 34/160(21.3%) were intermittently infected. In 2014; 80/164(49%) patients, 38/164(23.2%) and 11/164(6.7%) were never infected, free for 12 months and intermittently infected respectively. Conclusion There has been a decline in the overall prevalence of PA infection and a change in the pattern of prevalence over the last decade at our Centre.

A review of filamin A mutations and associated interstitial lung disease

The filamin A gene (FLNA) on Xq28 encodes the filamin A protein. Mutation in FLNA causes a wide spectrum of disease including skeletal dysplasia, neuronal migration abnormality, cardiovascular malformation, intellectual disability and intestinal obstruction. Recently, childhood-onset interstitial lung disease associated with a range of FLNA mutations has been recognised and reported. We document our personal experience of this emerging disorder and compile a comprehensive overview of clinical features and molecular changes in all identifiable published cases. Reviewing the emerging dataset, we underline this unanticipated phenotypic consequence of pathogenic FLNA mutation-associated pulmonary disease.Conclusion: From the emerging data, we suggest that while reviewing complex cases with a sustained oxygen requirement against a clincial background of cardiac concerns or intestinal obstruction to have a high index of suspicion for FLNA related pathology and to instigate early MRI brain scan and FLNA mutation analysis. What is Known: • FLNA gene on Xq28 encodes the filamin A protein and mutation therein is associated with variable phenotypes depending on its nature of mutation. • Loss-of-function mutation of filamin A is associated with X-linked inherited form of periventricular nodular heterotopia with or without epilepsy with most individuals affected being female. There is a recently recognised associated respiratory phenotype. What is New: • The respiratory phenotype in the form of childhood interstitial lung disease is a recently recognised clinical consequence of loss-of-function FLNA mutation. • Rare male patients with loss-of-function FLNA mutation-associated lung disease with residual protein function can survive into infancy with a severe form of the phenotype.

Pulmonary aspiration in preschool children with cystic fibrosis

Pulmonary aspiration of gastric refluxate (PAGR) has been demonstrated in association with pulmonary inflammation in school aged children with Cystic Fibrosis (CF). We sought to determine if similar findings were present in preschool children. Pepsin was measured in Broncho-alveolar lavage (BAL) fluid collected from clinically stable preschool children with CF and controls. Elevated pepsin levels were found in a subgroup of children with CF, but this was not found to be associated with pulmonary infection, pulmonary inflammation or respiratory or gastrointestinal symptoms.

Longitudinal assessment of airway responsiveness from 1 month to 18 years in the PIAF birth cohort

The Perth Infant Asthma Follow-up (PIAF) study involves a birth cohort of unselected subjects who have undergone longitudinal assessments of airway responsiveness at 1, 6 and 12 months and 6, 11 and 18 years of age. The aim of this study was to determine the relationship between increased airway responsiveness throughout childhood and asthma in early adult life.Airway responsiveness to histamine, assessed as a dose-response slope (DRS), and a respiratory questionnaire were completed at 1, 6 and 12 months and 6, 11 and 18 years of age.253 children were initially recruited and studied. Airway responsiveness was assessed in 203, 174, 147, 103, 176 and 137 children at the above-mentioned time points, respectively (39 participants being assessed on all test occasions). Asthma at 18 years was associated with increased airway responsiveness at 6, 12 and 18 years, but not during infancy (slope 0.24, 95% CI 0.06-0.42; p=0.01; slope 0.25, 95% CI 0.08-0.49; p=0.006; and slope 0.56, 95% CI 0.29-0.83; p<0.001, respectively).Increased airway responsiveness and its association with asthma at age 18 years is established between infancy and 6 years. We propose that airway responsiveness in early life reflects the initial airway geometry and airway responsiveness later in childhood increasingly reflects immunological responses to environmental influences.

Diagnosis and treatment of sleep related breathing disorders in children: 2007 to 2011

Sleep related breathing disorders (SRBD) have historically been under-recognised and under-treated. Obstructive sleep apnoea (OSA) affects approximately 3% of children. In line with the increased recognition of SRBD there has been an increase in demand for diagnostic services. We determined the awareness of SRBD amongst Irish paediatricians, examined the provision of sleep services to children throughout the country between 2007 and 2011 and audited diagnostic sleep services in a tertiary centre in 2011. Amongst respondents there was an awareness of SRBD but a poor understanding of diagnostic evaluation with 31/46 (67) referring to inappropriate services. There has been a sharp increase in both diagnostic sleep tests (433-1793 [414]) and in the use of non-invasive ventilation (NIV) (31-186 [627]) for treatment of SRBD between 2007 and 2011. Paediatric sleep services are organized in an ad-hoc manner nationally with significant service variation. The use of domiciliary overnight oximetry reduced the requirement for more formal polysomnography by 70%.

Rhinovirus and the developing lung

Human rhinovirus (HRV) infections are now widely accepted as the commonest cause of acute respiratory illnesses (ARIs) in children. Advanced PCR techniques have enabled HRV infections to be identified as causative agents in most common ARIs in childhood including bronchiolitis, acute asthma, pneumonia and croup. However, the long-term implications of rhinovirus infections are less clear. The aim of this review is to examine the relationship between rhinovirus infections and disorders of the lower airways in childhood.

Human rhinovirus species C infection in young children with acute wheeze is associated with increased acute respiratory hospital admissions

RATIONALE

Human rhinovirus species C (HRV-C) is the most common cause of acute wheezing exacerbations in young children presenting to hospital, but its impact on subsequent respiratory illnesses has not been defined.

OBJECTIVES

To determine whether acute wheezing exacerbations due to HRV-C are associated with increased hospital attendances due to acute respiratory illnesses (ARIs).

METHODS

Clinical information and nasal samples were collected prospectively from 197 children less than 5 years of age, presenting to hospital with an acute wheezing episode. Information on hospital attendances with an ARI before and after recruitment was subsequently obtained.

MEASUREMENTS AND MAIN RESULTS

HRV was the most common virus identified at recruitment (n = 135 [68.5%]). From the 120 (88.9%) samples that underwent typing, HRV-C was the most common HRV species identified, present in 81 (67.5%) samples. Children with an HRV-related wheezing illness had an increased risk of readmission with an ARI (relative risk, 3.44; 95% confidence interval, 1.17-10.17; P = 0.03) compared with those infected with any other virus. HRV-C, compared with any other virus, was associated with an increased risk of a respiratory hospital admission before (49.4% vs. 27.3%, respectively; P = 0.004) and within 12 months (34.6% vs. 17.0%; P = 0.01) of recruitment. Risk for subsequent ARI admissions was further increased in atopic subjects (relative risk, 6.82; 95% confidence interval, 2.16-21.55; P = 0.001). Admission risks were not increased for other HRV species.

CONCLUSIONS

HRV-C-related wheezing illnesses were associated with an increased risk of prior and subsequent hospital respiratory admissions. These associations are consistent with HRV-C causing recurrent severe wheezing illnesses in children who are more susceptible to ARIs.

The retinoblastoma tumor suppressor pathway modulates the invasiveness of ErbB2-positive breast cancer

The processes that control the progression of ductal carcinoma in situ (DCIS) to invasive breast cancer remain poorly understood. Epidermal growth factor receptor 2 (ErbB2) over expression is common in DCIS, as is disruption of the retinoblastoma tumor suppressor (RB) pathway. Here we examined the cooperative impact of ErbB2 and RB deregulation on facets of disease progression. Our studies demonstrate that RB deficiency altered the expression of key molecules needed for proper cellular organization and epithelial cell-cell adhesion as part of a program related to the epithelial to mesenchymal transition (EMT). An increase in the invasive potential of ErbB2 over expressing cells was observed upon RB depletion. Furthermore, stable knockdown of RB resulted in invasive lesions in orthotopic xenograft assays, compared to DCIS-like lesions developing from RB-proficient cells. Conversely, the invasive phenotype observed in ErbB2-positive cancer models was inhibited through CDK4/6 inhibition in an RB-dependent manner. Lastly, in a cohort of DCIS cases, we show that while elevated levels of ErbB2 are associated with increased risk of a subsequent DCIS recurrence, it is not associated with progression to invasive disease. In contrast, RB loss in ErbB2 positive DCIS cases was associated with increased risk for invasive breast cancer. Taken together, these data demonstrate a key role for the RB-pathway in invasion associated with breast tumor progression, and shed light on the key molecular events that promote the progression of DCIS to invasive disease.

Characterization of maximal respiratory pressures in healthy children

BACKGROUND

Measurements of maximal voluntary inspiratory (PI(max)) and expiratory (PE(max)) pressures are used in the management of respiratory muscle disease. There is little data on the appropriate reference range, success rates, or repeatability of PI(max) and PE(max) in children or on methodological factors affecting test outcomes.

OBJECTIVES

To determine PI(max) and PE(max) in healthy children and examine which published reference equations are best suited to a contemporary population. Secondary objectives were to assess within-test repeatability and the influence of lung volumes on PI(max) and PE(max).

METHODS

Healthy children were prospectively recruited from the community on a volunteer basis and underwent spirometry, static lung volumes, and PI(max) and PE(max) testing.

RESULTS

Acceptable and repeatable (to within 20%) PI(max) and PE(max) were obtained in 156 children, with 105 (67%) children performing both PI(max) and PE(max) measurements to within 10% repeatability. The reference equations of Wilson et al. [Thorax 1984;39:535-538] best matched our healthy Caucasian children. There was an inverse relationship between PI(max) and the percent of total lung capacity (TLC) at which the measurement was obtained (beta coefficient -0.96; 95% CI -1.52 to -0.39; p = 0.001), whereas at lung volumes of >80% TLC PE(max) was independent of lung volume (p = 0.26).

CONCLUSION

We demonstrated that the Wilson et al. [Thorax 1984;39:535-538] reference ranges are most suited for contemporary Caucasian Australasian children. However, robust multiethnic reference equations for maximal respiratory pressures are required. This study suggests that 10% within-test repeatability criteria are feasible in clinical practice, and that the use of lung volume measurements will improve the quality of maximal respiratory pressure measurements.

The impact of MRSA infection in the airways of children with cystic fibrosis; a case-control study

The prevalence of Methicillin Resistant Staphylococcus Aureus (MRSA) in patients with Cystic Fibrosis (CF) has risen dramatically over the past 10 years. The clinical significance of MRSA in CF patients remains undetermined. We conducted a review of patients with CF infected with MRSA over a 10 year period at Our Lady's Children's Hospital, Crumlin between 1999 and 2009. We collected data from 24 patients infected with MRSA and 24 control patients without MRSA There was a significant difference between the two groups in the rate of decline in percentage FEV1 two years after MRSA infection (Difference: -17.4, 95% CI: -30.48, -4.31, p = 0.01). A similar trend was seen for FVC% and FEF25-75% predicted. This study suggests that persistent MRSA infection in the airways of children with CF is associated with diminished lung function two years post acquisition, when compared to a matched control cohort without MRSA.

Association between human rhinovirus C and severity of acute asthma in children

A new and potentially more pathogenic group of human rhinovirus (HRV), group C (HRVC), has recently been discovered. We hypothesised that HRVC would be present in children with acute asthma and cause more severe attacks than other viruses or HRV groups. Children with acute asthma (n = 128; age 2-16 yrs) were recruited on presentation to an emergency department. Asthma exacerbation severity was assessed, and respiratory viruses and HRV strains were identified in a nasal aspirate. The majority of the children studied had moderate-to-severe asthma (85.2%) and 98.9% were admitted to hospital. HRV was detected in 87.5% and other respiratory viruses in 14.8% of children, most of whom also had HRV. HRVC was present in the majority of children with acute asthma (59.4%) and associated with more severe asthma. Children with HRVC (n = 76) had higher asthma severity scores than children whose HRV infection was HRVA or HRVB only (n = 34; p = 0.018), and all other children (n = 50; p = 0.016). Of the 19 children with a non-HRV virus, 13 had HRV co-infections, seven of these being HRVC. HRVC accounts for the majority of asthma attacks in children presenting to hospital and causes more severe attacks than previously known HRV groups and other viruses.

Recommendations for locus-specific databases and their curation

Expert curation and complete collection of mutations in genes that affect human health is essential for proper genetic healthcare and research. Expert curation is given by the curators of gene-specific mutation databases or locus-specific databases (LSDBs). While there are over 700 such databases, they vary in their content, completeness, time available for curation, and the expertise of the curator. Curation and LSDBs have been discussed, written about, and protocols have been provided for over 10 years, but there have been no formal recommendations for the ideal form of these entities. This work initiates a discussion on this topic to assist future efforts in human genetics. Further discussion is welcome.

A structured simple form for ordering genetic tests is needed to ensure coupling of clinical detail (phenotype) with DNA variants (genotype) to ensure utility in publication and databases

Researchers and clinicians ideally need instant access to all the variation in their gene/locus of interest to efficiently conduct their research and genetic healthcare to the highest standards. Currently much key data resides in the laboratory books or patient records around the world, as there are many impediments to submitting this data. It would be ideal therefore if a semiautomated pathway was available, with a minimum of effort, to make the deidentified data publicly available for others to use. The Human Variome Project (HVP) meeting listed 96 recommendations to work toward this situation. This article is planned to initiate a strategy to enhance the collection of phenotype and genotype data from the clinician/diagnostic laboratory nexus. Thus, the aim is to develop universally applicable forms that people can use when investigating patients for each inherited disease, to assist in satisfying many of the recommendations of the HVP Meeting [Cotton et al., 2007]. We call for comment and collaboration in this article.

Twenty-four novel mutations in Wilson disease patients of predominantly European ancestry

Wilson disease (WND), an autosomal recessive disorder of copper transport, shows wide genotypic and phenotypic variability, with hepatic and/or neurological symptoms. The WND gene, ATP7B, encodes a copper transporting ATPase that is involved in the transport of copper into the plasma protein ceruloplasmin, and in the excretion of copper from the liver. ATP7B mutations result in copper storage in liver and brain. From 247 WND patients worldwide whose DNA has been sequenced in our laboratory, we have identified 24 new mutations. The origins of the patients were European white (one deletion, one nonsense, one splice site, and 18 missense), Chinese (one deletion, one missense) and Bangladeshi (one missense). Most of these had strong support as disease causing mutations, based on conservation between species, structural changes, and absence in controls. One missense mutation in a Chinese patient was considered uncertain because of its conservative nature and position in the protein. We also identified 15 nucleotide substitutions (11 of them new) causing silent or intronic changes, none of which produce an additional splice site that could lead to disease. Characterization of mutations, both disease-causing and normal variants, is essential for accurate molecular diagnosis of this condition.

Genetic variation in the promoter and 5' UTR of the copper transporter, ATP7B, in patients with Wilson disease

ATP7B is a copper-transporting P-type ATPase defective in the copper transport disorder, Wilson disease (WND). We have sequenced the 5' UTR and promoter region of ATP7B in 37 unrelated WND patients in whom partial sequencing of the coding region and intron/exon boundaries of the gene had failed to identify one or both disease-causing mutations. Three patients were found to be heterozygous for a 15 bp deletion between nucleotides -424 and -441. This deletion had been previously identified as the most common mutation in Sardinian WND patients. Two novel single-nucleotide changes were also identified within the 5' UTR and promoter of ATP7B; however, these were found at a similar frequency in control chromosomes and are apparently normal variants. These results suggest that mutations in regulatory elements of ATP7B are uncommon in patients of European ancestry, except in Sardinia.

Disruption of the neuronal PAS3 gene in a family affected with schizophrenia

Schizophrenia and its subtypes are part of a complex brain disorder with multiple postulated aetiologies. There is evidence that this common disease is genetically heterogeneous, with many loci involved. In this report, we describe a mother and daughter affected with schizophrenia, who are carriers of a t(9;14)(q34;q13) chromosome. By mapping on flow sorted aberrant chromosomes isolated from lymphoblast cell lines, both subjects were found to have a translocation breakpoint junction between the markers D14S730 and D14S70, a 683 kb interval on chromosome 14q13. This interval was found to contain the neuronal PAS3 gene (NPAS3), by annotating the genomic sequence for ESTs and performing RACE and cDNA library screenings. The NPAS3 gene was characterised with respect to the genomic structure, human expression profile, and protein cellular localisation to gain insight into gene function. The translocation breakpoint junction lies within the third intron of NPAS3, resulting in the disruption of the coding potential. The fact that the bHLH and PAS domains are disrupted from the remaining parts of the encoded protein suggests that the DNA binding and dimerisation functions of this protein are destroyed. The daughter (proband), who is more severely affected, has an additional microdeletion in the second intron of NPAS3. On chromosome 9q34, the translocation breakpoint junction was defined between D9S752 and D9S972 and no genes were found to be disrupted. We propose that haploinsufficiency of NPAS3 contributes to the cause of mental illness in this family.

Current status of human chromosome 14

Over the past three decades, extensive genetic, physical, transcript, and sequence maps have assisted in the mapping of over 30 genetic diseases and in the identification of over 550 genes on human chromosome 14. Additional genetic disorders were assigned to chromosome 14 by studying either constitutional or acquired chromosome aberrations of affected subjects. Studies of benign and malignant tumours by karyotype analyses and by allelotyping with a panel of polymorphic genetic markers have further suggested the presence of several tumour suppressor loci on chromosome 14. The search for disease genes on human chromosome 14 has also been achieved by exploiting the human-mouse comparative maps. Research on uniparental disomy and on the search for imprinted genes has supported evidence of epigenetic inheritance as a result of imprinting on human chromosome 14. This review focuses on the current developments on human chromosome 14 with respect to genetic maps, physical maps, transcript maps, sequence maps, genes, diseases, mouse-human comparative maps, and imprinting.

Characterization and chromosomal localization of five canine ATOX1 pseudogenes

We have isolated six ATOX1 loci from the canine genome in BAC clones. Sequence analysis showed that five of these clones correspond to processed pseudogenes. Fluorescent in situ hybridization allowed us to map the genuine ATOX1 gene to CFA4q24-->q31 and the ATOX1 pseudogenes to CFA19q13.1, CFA4q24-->q31, CFA18q24-->q25, CFA9q22.1 -->q22.2 and CFA20q11-->q12.

Defining the breakpoints of proximal chromosome 14q rearrangements in nine patients using flow-sorted chromosomes

The breakpoints of deletions and translocations in the proximal chromosome 14q region were defined in nine patients, four of whom have not been reported previously. The aberrant chromosomes were isolated by flow cytometry and used to map the chromosome 14 deletion or translocation breakpoints. The parental origins of deletions were ascertained as paternal in five cases and maternal in one. With the draft genomic sequence for human chromosome 14 available, gene searches were performed on selected intervals of the 14q11.2-q21 region to identify candidate genes for the observed phenotype in some of those affected. Gain of function of the gene PAX9 on chromosome 14 is a possible candidate for a t(14;18) patient affected with mesomelic bone dysplasia. Furthermore, a compilation of other human chromosome 14q proximal deletion and translocation cases was obtained from a search on cytogenetic databases. These findings suggest a locus for myelofibrosis at chromosome 14q13. This study contributes to useful information for identifying disease genes in this region.

ATP6H, a subunit of vacuolar ATPase involved in metal transport: evaluation in canine copper toxicosis

Copper toxicosis (CT), resulting in liver disease, occurs commonly in Bedlington terriers. Canine CT is of particular interest because identification of the causative gene may lead to the discovery of another important gene in the copper transport pathway possibly related to human copper diseases not yet identified. Homologs of the copper transporting ATPase ATP7B, defective in Wilson disease, and the copper chaperone ATOX1 were potential candidates, but both have been excluded. The CT locus in Bedlington terriers has been mapped to canine chromosome region CFA10q26, which has a syntenic human chromosome region, HAS2p13-21. The gene ATP6H, for human vacuolar proton-ATPase subunit M9.2, is associated with copper and iron transport in yeast and has been mapped to HAS2p21 and suggested as a candidate gene for CT. We cloned canine ATP6H, which encodes a predicted protein with 99% amino acid sequence identity to the orthologous human protein. Canine ATP6H shows a conserved potential metal binding site, CSVCC, and a glycosylation site, NET. The canine ATP6H is organized into four exons, with a 246-bp open reading frame. Sequence analysis of the coding regions showed no mutations in ATP6H from genomic DNA of an affected dog. We have also identified two, apparently non-transcribed canine ATP6H pseudogenes. Mapping of the true ATP6H gene and a marker closely linked to the CT locus on a canine radiation hybrid panel indicted lack of close physical association. We have therefore excluded canine ATP6H as a candidate gene for canine copper toxicosis, indicating that some other unidentified gene is responsible for this copper storage disease.

Genotype-phenotype interactions in Wilson's disease: insight from an Icelandic mutation

Wilson's disease, an autosomal recessive disorder of copper transport, usually presents with symptoms from the liver or central nervous system. Rarely, the initial manifestation is fulminant hepatic failure. The abnormal gene (ATP7B) is located on chromosome 13q and encodes a copper-transporting ATPase. A large number of mutations have been reported. We describe a previously healthy 16-year-old girl who presented with fulminant hepatic failure. The girl died within 24 h of admission to a hospital from refractory shock. Autopsy revealed cirrhosis and widespread necrosis of the liver. The copper content of the liver was markedly increased (975 micrograms/g dry weight), strongly suggesting a diagnosis of Wilson's disease. Genetic studies revealed that the girl was homozygous for the mutation 2007 del7, which is the mutation found in all Wilson's disease patients previously identified in Iceland. This is the first known case of fulminant hepatic failure due to Wilson's disease in Iceland. Despite the same mutation, the clinical picture is vastly different from other Icelandic patients with Wilson's disease, who all presented with relatively late-onset neurological disease. This suggests that factors other than the specific mutation have significant impact on the phenotype of the disease.

Comparative mapping of human Chromosome 14q11.2-q13 genes with mouse homologous gene regions

An examination of the synteny blocks between mouse and human chromosomes aids in understanding the evolution of chromosome divergence between these two species. We comparatively mapped the human (HSA) Chromosome (Chr) 14q11.2-q13 cytogenetic region with the intervals of orthologous genes on mouse (MMU) chromosomes. A lack of conserved gene order was identified between the human cytogenetic region and the interval of orthologs on MMU 12. The evolutionary breakpoint junction was defined within 2.5 Mb, where the conserved synteny of genes on HSA 14 changes from MMU 12 to MMU 14. At the evolutionary breakpoint junction, a human EST (GI: 1114654) with identity to the human and mouse BCL2 interacting gene, BNIP3, was mapped to mouse Chr 3. New gene homologs of LAMB1, MEOX2, NRCAM, and NZTF1 were identified on HSA 7 and on the proximal cytogenetic region of HSA 14 by mapping mouse genes recently reported to be genetically linked within the relevant MMU 12 interval. This study contributes to the identification of homology relationships between the genes of HSA 14q11.2-q13 and mouse Chr 3, 12, and 14.

Severe hepatic Wilson's disease in preschool-aged children

A 3-year-old girl presented with hemolytic anemia, hepatosplenomegaly, ascites, and evidence of decompensated chronic liver disease. Genotypic DNA analysis revealed that the patient was homozygous for a splice site mutation now designated IVS4-1:G>C, expected to destroy completely the functional gene product of ATP7B, the gene responsible for Wilson's disease. We suggest that this severe mutation caused very early liver disease. Wilson's disease should be considered in the differential diagnosis of established liver disease in the preschool-aged child.

Copper-dependent trafficking of Wilson disease mutant ATP7B proteins

We have previously developed a functional assay in yeast for the copper transporter, ATP7B, defective in Wilson disease (WND). Analysis of WND variant ATP7B proteins revealed that several were able to completely, or nearly completely, complement a mutant yeast strain in which the ATP7B ortholog CCC2 was disrupted, indicating that these ATP7B proteins retained copper transport activity. We analyzed the intracellular localization of these active WND ATP7B variant proteins using transient transfection of Chinese hamster ovary cells and triple-label immunofluorescence microscopy, as a second possible aspect of defective function. Two ATP7B variants, Asp765Asn and Leu776Val, which have normal copper transport activity in yeast, retained partial normal Golgi network localization, but were predominantly mislocalized throughout the cell. Asp765Asn and Leu776Val proteins were capable of only partial copper-dependent redistribution. WND variant protein Arg778Leu, which has defective function in yeast, was extensively mislocalized, presumably to the endoplasmic reticulum. ATP7B variant proteins Gly943Ser, which has nearly normal function in yeast, and CysProCys/Ser (mutation of the conserved CysProCys motif to SerProSer), inactive in yeast, were localized normally but were unable to redistribute in response to copper. Localization data from this study, combined with functional data from our yeast studies, provide a biochemical mechanism that can explain in part the variable biochemical features of WND, in particular the normal holo-ceruloplasmin levels observed in some patients. Our data have direct implications for WND diagnosis, indicating that decreased serum ceruloplasmin concentration is not likely to be observed with certain genetic variants of WND.

Human microphthalmia associated with mutations in the retinal homeobox gene CHX10

Isolated human microphthalmia/anophthalmia, a cause of congenital blindness, is a clinically and genetically heterogeneous developmental disorder characterized by a small eye and other ocular abnormalities. Three microphthalmia/anophthalmia loci have been identified, and two others have been inferred by the co-segregation of translocations with the phenotype. We previously found that mice with ocular retardation (the or-J allele), a microphthalmia phenotype, have a null mutation in the retinal homeobox gene Chx10 (refs 7,8). We report here the mapping of a human microphthalmia locus on chromosome 14q24.3, the cloning of CHX10 at this locus and the identification of recessive CHX10 mutations in two families with non-syndromic microphthalmia (MIM 251600), cataracts and severe abnormalities of the iris. In affected individuals, a highly conserved arginine residue in the DNA-recognition helix of the homeodomain is replaced by glutamine or proline (R200Q and R200P, respectively). Identification of the CHX10 consensus DNA-binding sequence (TAATTAGC) allowed us to demonstrate that both mutations severely disrupt CHX10 function. Human CHX10 is expressed in progenitor cells of the developing neuroretina and in the inner nuclear layer of the mature retina. The strong conservation in vertebrates of the CHX10 sequence, pattern of expression and loss-of-function phenotypes demonstrates the evolutionary importance of the genetic network through which this gene regulates eye development.

Cloning and mapping of murine superoxide dismutase copper chaperone (Ccsd) and mapping of the human ortholog

Copper does not exist in a free state within cells but is found consistently bound to metalloproteins. Specific metallochaperones escort copper to numerous targets within the cell, providing protection from the toxic effects of intracellular free copper. Many metallochaperones have been characterized in yeast, mouse, and human. To further characterize mouse metallochaperones, we cloned murine Ccsd from an adult mouse cDNA brain library, including both the coding region and the 5' and 3' UTRs. We obtained a 1,174-bp cDNA with an 825-bp open reading frame, translating a 274 amino acid protein that is 86.9% identical to human CCS. Using a mouse x hamster radiation hybrid panel, we mapped Ccsd to a proximal position on mouse chromosome 19. We mapped human CCS to 11q13 (homologous with mouse chromosome 19), utilizing a human x hamster radiation hybrid panel. The human and mouse metallochaperones are ubiquitously expressed in the major tissues of the body but seem to have different transcription products.

Haplotype association and mutation analysis of the transglutaminase 1 gene for prenatal exclusion of lamellar ichthyosis

Lamellar ichthyosis (LI) is an autosomal recessive keratinization disorder of the skin. Genetic heterogeneity has been shown for the disease and there is evidence for the involvement of the transglutaminase 1 (TGM1) gene on chromosome 14q11. We have previously identified chromosome 14q11 haplotypes associated with ichthyosis in the Norwegian population. In this paper we describe antenatal exclusion of ichthyosis in two Norwegian families by chromosome 14q11 haplotype association and direct mutation analysis. In one pregnancy, the 11-week old fetus at risk for LI was found to share only one disease-associated haplotype. A subsequent mutation analysis of the TGM1 gene in fetal DNA revealed that the fetus carried a novel 3795A-->T transversion. The affected proband was compound heterozygous for the mutations 3795A-->T and 3239G-->C resulting in an Asp430Val and a Val379Leu, respectively. In another LI family, the 11-week old fetus was found to be heterozygous for the 14q11 haplotype associated with the disease. Subsequent mutation analysis revealed that the fetus was heterozygous for the 2526A-->G transition in the splice site of intron 5 whereas the proband was homozygous for the same mutation. Our results show that haplotyping can be a useful tool for prenatal diagnosis in diseases with genetic heterogeneity.

The copper chaperone Atox1 in canine copper toxicosis in Bedlington terriers

Copper toxicosis, resulting in liver disease, commonly occurs in Bedlington terriers. This recessively inherited disorder, similar in many respects to Wilson disease, is of particular interest because the canine Atp7b gene, homologous to ATP7B defective in Wilson disease, is not responsible for canine copper toxicosis as has been expected. Atox1, a copper chaperone delivering copper to Atp7b, therefore became a potential candidate. We cloned canine Atox1, which shows conserved motifs of the copper-binding domain (MTCXXC) and of the lysine-rich region (KTGK), and showed 88, 80, and 41% amino acid sequence identity with the orthologous mouse, human, and yeast proteins. No gross deletions of Atox1 could be identified in the affected Bedlington terriers by Southern blot analysis of genomic DNA. The canine Atox1 gene spans about 4 kb, with a 204-bp open reading frame cDNA contained within two exons. Sequence analysis of the coding regions, including intron/exon boundaries, showed no mutations in Atox1 from genomic DNA of an affected dog. We have also identified an apparently nontranscribed canine Atox1 pseudogene, with 12 sequence changes and no intron. Mapping of Atox1 and a marker closely linked to the canine copper toxicosis locus indicated lack of synteny. Atox1 is therefore excluded as a candidate gene for canine copper toxicosis, indicating that some other unidentified gene must be responsible for this copper storage disease in dogs and also suggesting the possibility of a similar gene responsible for a copper storage disease in humans.

Functional and antigenic concentrations of alpha-1-proteinase inhibitor after administration for the prevention of chronic lung disease of prematurity

OBJECTIVE AND METHODS

Alpha-1-proteinase inhibitor (A1PI) supplementation has been used in adults with inherited alpha-1-antitrypsin (A1AT) deficiency to impede the development of emphysema. A1PI supplementation may also be useful for protecting premature neonates who receive mechanical ventilation from the development of chronic lung disease (CLD). However, the pharmacokinetics of exogenous A1PI in this population are unknown. We attempted to determine the disposition of A1PI in premature infants with birth weight 600-1,250 g who received 60 mg/kg on days 0, 4, 7 and 14 in a randomized, placebo-controlled, double-blind trial. Functional and antigenic plasma concentrations of A1PI were measured at specified time points.

RESULTS

On both functional and antigenic assays, concentrations began in the normal adult range and rose from day 0 to 10 then fell slightly, but remained above initial values. The concentrations were not significantly different between the treatment and placebo groups.

CONCLUSIONS

The results of this study indicate that neonatal pharmacokinetics of A1PI differ markedly from those of the adult. Total plasma clearance of exogenous A1PI seems high in the ventilated premature neonate. Higher or more frequent doses may be necessary to maintain A1PI plasma concentrations above baseline.

Role of the copper-binding domain in the copper transport function of ATP7B, the P-type ATPase defective in Wilson disease

We have analyzed the functional effect of site-directed mutations and deletions in the copper-binding domain of ATP7B (the copper transporting P-type ATPase defective in Wilson disease) using a yeast complementation assay. We have shown that the sixth copper-binding motif alone is sufficient, but not essential, for normal ATP7B function. The N-terminal two or three copper-binding motifs alone are not sufficient for ATP7B function. The first two or three N-terminal motifs of the copper-binding domain are not equivalent to, and cannot replace, the C-terminal motifs when placed in the same sequence position with respect to the transmembrane channel. From our data, we propose that the copper-binding motifs closest to the channel are required for the copper-transport function of ATP7B. We propose that cooperative copper binding to the copper-binding domain of ATP7B is not critical for copper transport function, but that cooperative copper binding involving the N-terminal two or three copper-binding motifs may be involved in initiating copper-dependent intracellular trafficking. Our data also suggest a functional difference between the copper-binding domains of ATP7A and ATP7B.

Genetic mapping of the copper toxicosis locus in Bedlington terriers to dog chromosome 10, in a region syntenic to human chromosome region 2p13-p16

Abnormal hepatic copper accumulation is recognized as an inherited disorder in man, mouse, rat and dog. The major cause of hepatic copper accumulation in man is a dysfunctional ATP7B gene, causing Wilson disease (WD). Mutations in the ATP7B genes have also been demonstrated in mouse and rat. The ATP7B gene has been excluded in the much rarer human copper overload disease non-Indian childhood cirrhosis, indicating genetic heterogeneity. By investigating the common autosomal recessive copper toxicosis (CT) in Bedlington terriers, we have identified a new locus involved in progressive liver disease. We examined whether the WD gene ATP7B was also causative for CT by investigating the chromosomal co-localization of ATP7B and C04107, using fluorescence in situ hybridization (FISH). C04107 is an anonymous microsatellite marker closely linked to CT. However, BAC clones containing ATP7B and C04107 mapped to the canine chromosome regions CFA22q11 and CFA10q26, respectively, demonstrating that WD cannot be homologous to CT. The copper transport genes CTR1 and CTR2 were also excluded as candidate genes for CT since they both mapped to canine chromosome region CFA11q22. 2-22.5. A transcribed sequence identified from the C04107-containing BAC was found to be homologous to a gene expressed from human chromosome 2p13-p16, a region devoid of any positional candidate genes.

Disorders of copper transport

Copper is an essential component of a number of important enzymes. Efficient systems have developed for providing sufficient copper for essential functions, while eliminating excess to avoid tissue toxicity. Copper transport is disrupted in two human diseases: Wilson disease and Menkes disease. Both have defects in copper transporting membrane proteins. Many other proteins are involved in copper transport. Some of these proteins have been identified through a study of the similar copper pathway in yeast. This suggests other copper transport diseases are yet to be discovered. Molecular diagnosis holds promise for reliable diagnosis of patients. Testing of flanking markers is a reliable way to detect presymptomatic sibs of a definite patient.

Functional characterization of missense mutations in ATP7B: Wilson disease mutation or normal variant?

Wilson disease is an autosomal recessive disorder of copper transport that causes hepatic and/or neurological disease resulting from copper accumulation in the liver and brain. The protein defective in this disorder is a putative copper-transporting P-type ATPase, ATP7B. More than 100 mutations have been identified in the ATP7B gene of patients with Wilson disease. To determine the effect of Wilson disease missense mutations on ATP7B function, we have developed a yeast complementation assay based on the ability of ATP7B to complement the high-affinity iron-uptake deficiency of the yeast mutant ccc2. We characterized missense mutations found in the predicted membrane-spanning segments of ATP7B. Ten mutations have been made in the ATP7B cDNA by site-directed mutagenesis: five Wilson disease missense mutations, two mutations originally classified as possible disease-causing mutations, two putative ATP7B normal variants, and mutation of the cysteine-proline-cysteine (CPC) motif conserved in heavy-metal-transporting P-type ATPases. All seven putative Wilson disease mutants tested were able to at least partially complement ccc2 mutant yeast, indicating that they retain some ability to transport copper. One mutation was a temperature-sensitive mutation that was able to complement ccc2 mutant yeast at 30 degreesC but was unable to complement at 37 degreesC. Mutation of the CPC motif resulted in a nonfunctional protein, which demonstrates that this motif is essential for copper transport by ATP7B. Of the two putative ATP7B normal variants tested, one resulted in a nonfunctional protein, which suggests that it is a disease-causing mutation.

His1069Gln and six novel Wilson disease mutations: analysis of relevance for early diagnosis and phenotype

In the present study we examined 33 German and 10 Cuban unrelated Wilson disease (WND) index patients and their relatives. The common His1069Gln mutation accounted for 42% of all WND chromosomes in the German series and the haplotype C was found to be highly predictive for this mutation. Six WND gene mutations have not been described previously and involved a splice site at intron 18 (3903 + del1G), a termination codon in the copper-binding region of exon 2 (Cys271X), and missense mutations in transmembrane region 2 (Gly710Ala), in transmembrane region 3 (Tyr741Cys), in the DKTGT motif (Thr1031Ile) and in the ATP loop region (Gly1176Arg). In 15 German WND index patients and three sibs both WND mutations could be determined and a genotype-phenotype correlation was attempted. Patients homozygous for the His1069Gln mutation showed almost the complete range of clinical presentations, and thus in our study this mutation is not associated with a late, neurological presentation.

Elevated LDL triglyceride concentrations in subjects heterozygous for the hepatic lipase S267F variant

Although naturally occurring loss-of-function mutations in human hepatic lipase (HL) have been described, the biochemical phenotype of heterozygous HL deficiency remains ill defined. This may be due to the relatively small numbers of heterozygous adult carriers of HL mutations in index kindreds. We have identified several new heterozygotes for the catalytically inactive, nonsecreted HL variant S267F in the kindred that was originally ascertained because of hypertriglyceridemia due to the mutant, secreted, circulating apolipoprotein (apo) CII variant apo CII-T. Pairwise comparisons with family controls showed that only the plasma low density lipoprotein triglycerides (LDL TGs) were higher in 11 simple heterozygotes for HL S267F (P=0.002). In contrast, both plasma total TGs and LDL TGs were significantly higher in 12 simple heterozygotes for apo CII-T than in family-matched control subjects (P=0.005 and 0.009, respectively). These findings suggest that the TG content of LDL is increased by heterozygosity for 2 different mutations that affect different proteins involved in lipolysis. However, the mechanisms underlying this compositional change in LDL appear to be different for the 2 mutations, because the total TGs are also elevated in subjects heterozygous for apo CII-T but not in subjects heterozygous for HL S267F.

Wilson disease

Wilson disease is a recessively inherited disorder of copper transport. Clinical features are highly variable, with any combination of neurological, hepatic or psychiatric illness. The age of onset varies from 3 to 50 years of age. Diagnosis is challenging because no specific combination of clinical or biochemical features is necessarily definitive. The genetic defect is due to a variety of abnormalities in a copper-transporting membrane ATPase. Most of the more than 80 mutations are present at a low frequency, and mutations differ between ethnic groups. At least two mutations are sufficiently common to aid in rapid diagnosis, in European and Asian populations respectively. Molecular analysis can provide a definitive diagnosis for asymptomatic sibs. Treatment, using chelating agents or zinc, is most effective when started before permanent tissue damage occurs.

alpha1-Proteinase inhibitor therapy for the prevention of chronic lung disease of prematurity: a randomized, controlled trial

BACKGROUND

An imbalance between increased neutrophil elastase and a decreased antiprotease shield has been suggested as a factor contributing to the development of chronic lung disease (CLD). We hypothesized that administration of alpha1-proteinase inhibitor (A1PI), also known as alpha1-antitrypsin, to premature neonates would prevent CLD.

DESIGN

A randomized, placebo-controlled, prospective study of A1PI supplementation was performed. Neonates <24 hours of age with birth weights 600-1000 g on respiratory support, and 1001-1250 g with respiratory distress syndrome (RDS) were eligible. Intravenous A1PI (60 mg/kg) or placebo was infused on days 0, 4, 7, and 14. Primary outcome was CLD in survivors, defined as the need for supplemental oxygen on day 28.

RESULTS

A total of 106 patients were recruited. There were no significant differences between groups in birth weight or incidence of RDS. The incidence of CLD in survivors was lower in the treated group, but the difference did not reach statistical significance (relative risk [RR], 0.79; confidence interval [CI], 0.60-1.02). This beneficial trend persisted at 36 weeks corrected gestational age (RR, 0.48; CI, 0.23-1.00). The incidence of pulmonary hemorrhage was lower in the treated group (RR, 0.22; CI, 0.05-0.98). Other complications were not significantly different between groups.

CONCLUSIONS

In this, the first trial of a protease inhibitor for the prevention of CLD in premature infants, the infusions were well-tolerated. A1PI therapy may impede the development of CLD and appears to reduce the incidence of pulmonary hemorrhage in some neonates born prematurely.

Expression, purification, and metal binding properties of the N-terminal domain from the wilson disease putative copper-transporting ATPase (ATP7B)

The putative copper binding domain from the copper-transporting ATPase implicated in Wilson disease (ATP7B) has been expressed and purified as a fusion to glutathione S-transferase. Immobilized metal ion affinity chromatography revealed that the fusion protein is able to bind to columns charged with different transition metals with varying affinities as follows: Cu(II)>>Zn(II)>Ni(II)>Co(II). The fusion protein did not bind to columns charged with Fe(II) or Fe(III). 65Zinc(II) blotting analysis showed that the domain is able to bind Zn(II) over a range of pH values from 6.5 to 9.0. Competition 65Zn(II) blotting showed that Cd(II), Hg(II), Au(III), and Fe(III) can successfully compete with Zn(II), at comparable concentrations, for binding to the domain. In contrast, the domain had little or no affinity for Ca(II), Mg(II), Mn(II), and Ni(II) relative to copper. Neutron activation analysis of the copper bound to the domain showed a copper:protein ratio of 6.5-7.3:1. Both Cu(II) and Cu(I) were found to have a higher affinity for the domain relative to Zn(II). In addition, a sharp, reproducible transition was only observed in competition experiments with copper, which may suggest that copper binding has some degree of cooperativity.

Review: molecular approaches to inherited liver disease. Focus on Wilson disease

Although infectious agents account for a large proportion of liver disease, inherited forms of liver disease, often treatable, must not be overlooked. New approaches to the cloning of disease genes are allowing an increased understanding of the basic defect of human diseases. Identification of disease genes can have practical applications for diagnosis, can provide information on prognosis and can lead to new therapies. This review focuses on selected inherited liver diseases and the knowledge to be gained from molecular studies. Three genetic diseases affecting the liver, Wilson disease, haemochromatosis and alpha 1-antitrypsin deficiency, are selected as examples of current approaches to the study of genetic liver disease.

Physical and transcription map in the region 14q24.3: identification of six novel transcripts

The region of chromosome 14q24 has been of particular interest as it is known to contain one of the early-onset Alzheimer disease genes (AD3). Other genes of medical interest, such as arrhythmogenic right ventricular cardiomyopathy, have been mapped to this region by linkage analysis or chromosome rearrangements. We have focused on the region of a balanced translocation (2;14)(p25;q24). Members of a family with this translocation all have anterior polar cataracts, suggesting the presence of a gene involved in lens integrity at the vicinity of the breakpoint. The chromosome 14 breakpoint has been defined between the short tandem repeats D14S289 and D14S277, a region of overlap for yeast artificial chromosomes (YACs) 888b2 and 934d4. We have extended the study of the region to 2 Mb on chromosome 14 and present a physical map of this region, including several sequence-tagged sites. New probes were generated using several end clones and inter-Alu PCR fragments from YACs. cDNA selection was used to identify transcribed sequences. Mapping and alignment of 17 nonoverlapping cDNAs completed by sequence and expression pattern analysis suggested that a minimum of eight putative transcription units is present in this region: six of these units correspond to five new genes and one member of a new gene family.