Analysis of exome data for 4293 trios suggests GPI-anchor biogenesis defects are a rare cause of developmental disorders.

Over 150 different proteins attach to the plasma membrane using glycosylphosphatidylinositol (GPI) anchors. Mutations in 18 genes that encode components of GPI-anchor biogenesis result in a phenotypic spectrum that includes learning disability, epilepsy, microcephaly, congenital malformations and mild dysmorphic features. To determine the incidence of GPI-anchor defects, we analysed the exome data from 4293 parent-child trios recruited to the Deciphering Developmental Disorders (DDD) study. All probands recruited had a neurodevelopmental disorder. We searched for variants in 31 genes linked to GPI-anchor biogenesis and detected rare biallelic variants in PGAP3, PIGN, PIGT (n=2), PIGO and PIGL, providing a likely diagnosis for six families. In five families, the variants were in a compound heterozygous configuration while in a consanguineous Afghani kindred, a homozygous c.709G>C; p.(E237Q) variant in PIGT was identified within 10-12 Mb of autozygosity. Validation and segregation analysis was performed using Sanger sequencing. Across the six families, five siblings were available for testing and in all cases variants co-segregated consistent with them being causative. In four families, abnormal alkaline phosphatase results were observed in the direction expected. FACS analysis of knockout HEK293 cells that had been transfected with wild-type or mutant cDNA constructs demonstrated that the variants in PIGN, PIGT and PIGO all led to reduced activity. Splicing assays, performed using leucocyte RNA, showed that a c.336-2A>G variant in PIGL resulted in exon skipping and p.D113fs*2. Our results strengthen recently reported disease associations, suggest that defective GPI-anchor biogenesis may explain ~0.15% of individuals with developmental disorders and highlight the benefits of data sharing

X-exome sequencing of 405 unresolved families identifies seven novel intellectual disability genes

X-linked intellectual disability (XLID) is a clinically and genetically heterogeneous disorder. During the past two decades in excess of 100 X-chromosome ID genes have been identified. Yet, a large number of families mapping to the X-chromosome remained unresolved suggesting that more XLID genes or loci are yet to be identified. Here, we have investigated 405 unresolved families with XLID. We employed massively parallel sequencing of all X-chromosome exons in the index males. The majority of these males were previously tested negative for copy number variations and for mutations in a subset of known XLID genes by Sanger sequencing. In total, 745 X-chromosomal genes were screened. After stringent filtering, a total of 1297 non-recurrent exonic variants remained for prioritization. Co-segregation analysis of potential clinically relevant changes revealed that 80 families (20%) carried pathogenic variants in established XLID genes. In 19 families, we detected likely causative protein truncating and missense variants in 7 novel and validated XLID genes (CLCN4, CNKSR2, FRMPD4, KLHL15, LAS1L, RLIM and USP27X) and potentially deleterious variants in 2 novel candidate XLID genes (CDK16 and TAF1). We show that the CLCN4 and CNKSR2 variants impair protein functions as indicated by electrophysiological studies and altered differentiation of cultured primary neurons from Clcn4−/− mice or after mRNA knock-down. The newly identified and candidate XLID proteins belong to pathways and networks with established roles in cognitive function and intellectual disability in particular. We suggest that systematic sequencing of all X-chromosomal genes in a cohort of patients with genetic evidence for X-chromosome locus involvement may resolve up to 58% of Fragile X-negative cases

Respiratory syncytial virus epidemiology in Turkey

PubMedID: 16363337Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in infants and young children worldwide. This study was conducted to determine the prevalence of RSV among high-risk children admitted with respiratory symptoms in a developing country. This is a multicenter study conducted among children less than 24 months of age and admitted to the hospital with respiratory symptoms. The inclusion criteria included: lower respiratory tract symptoms on admission, gestational age less than 35 weeks, and admission age less than six months, or children less than 24 months of age with a diagnosis of bronchopulmonary dysplasia requiring medical treatment or intervention during the last six months or with an uncorrected congenital heart disease (other than patent ductus arteriosus). Nasopharyngeal samples were obtained with one of the three standard methods: nasopharyngeal aspirate, nasopharyngeal wash or nasopharyngeal swab. RSV antigen was determined by enzyme immunoassay using Abbott TESTPACK RSV (No. 8100/2027-16). Statistical analysis was performed using Student's t-test and chi-square test. In this study, 332 children (135 females, 40.7%; 197 males, 59.3%) were included, and the nasopharyngeal specimens of 98 (29.5%) children were determined to be RSV-positive. There were no differences in sex, age of gestation, age of admission, family education, number of siblings and smoking at home for RSV-positive and -negative cases. Furthermore, underlying disease and duration of hospital and intensive care unit stay were similar among groups. Only otitis media was more common among RSV-positive cases. No fatality at hospital was recorded. Frozen samples revealed more negative results. Most cases presented during winter and the number of RSV-positive cases was higher in cold and economically poor areas. Premature children and children with underlying medical con dition acquire RSV irrespective of other sociodemographic risk factors, and most of them are hospitalized. Thus, an RSV vaccine seems the most effective mode of protection to decrease morbidity and mortality

Long COVID among Children: Persistence of Symptoms 12 Weeks and More in a Cohort Study from Turkey

BACKGROUND: COVID-19 usually cause a mild infection among children with a low fatality rate. On the other hand, increasing evidence suggests that children may have prolonged symptoms related to COVID-19. This study aims to describe the persistence of COVID-19 symptoms up to 12 or more weeks among children and to investigate associated factors including perceived socioeconomic status and parents’ education level. METHODS: The study group consisted of 759 cases aged <18 years detected as SARS-CoV-2 RT-PCR positive in DEU Hospital between March 2020, and May 2021. Interviews were conducted at 1st 3rd and 6th month of diagnosis. The ongoing self-reported symptoms 12 or more weeks after infection was the dependent variable. Multivariate logistic regression models were used to evaluate associated factors with long COVID, and robust clustering using links algorithm was used to assess long COVID symptoms clusters. RESULTS: Among 759 COVID-19 cases, 22 children were hospitalized, and 4 died. 9.6% of the children had at least one symptom related to COVID-19 after 12 weeks of the diagnosis, Symptom duration was minimum 84 days, maximum 344 days (mean±SD: 160±68 days). The most frequent symptoms were fatigue, muscle-joint pain, headache, and loss of smell and/or taste. In multivariate analysis, female gender (OR:2,3 95%CI:1.1-3.6) and symptomatic onset (OR:2,7 95%CI:1.7-20.9) were related to increased risk of long COVID. Age, long-term health conditions, socioeconomic status and mother's education level did not predict the risk of long COVID. No cluster of symptoms was found. CONCLUSIONS: About 10% of children suffer from symptoms related to COVID-19 for up to six months. Female gender and symptomatic onset of disease increased the risk of prolonged symptoms. Socioeconomic status and mother's education level was not associated with the risk of long COVID, but the evidence of the effect of social determinants of health on the outcomes of COVID-19 among children is still needed. KEY MESSAGES: • One out of ten children may suffer from long COVID represents symptoms such as fatigue, headache, and muscle and joint pain. Girls and children with symptomatic onset have a higher risk of long COVID. • The effects of social determinants on the susceptibility and outcomes of COVID-19, including death, were well studied among the adult population. There is a need for sound evidence for children

Early frameshift mutation in PIGA identified in a large XLID family without neonatal lethality

The phosphatidylinositol glycan class A (PIGA) protein is a member of the glycosylphosphatidylinositol anchor pathway. Germline mutations in PIGA located at Xp22.2 are thought to be lethal in males. However, a nonsense mutation in the last coding exon was recently described in two brothers with multiple congenital anomalies-hypotonia-seizures syndrome 2 (MCAHS2) who survived through birth likely because of the hypomorphic nature of the truncated protein, but died in their first weeks of life. Here, we report on a frameshift mutation early in the PIGA cDNA (c.76dupT; p.Y26Lfs*3) that cosegregates with the disease in a large family diagnosed with a severe syndromic form of X-linked intellectual disability. Unexpectedly, CD59 surface expression suggested the production of a shorter PIGA protein with residual functionality. We provide evidence that the second methionine at position 37 may be used for the translation of a 36 amino acids shorter PIGA. Complementation assays confirmed that this shorter PIGA cDNA was able to partially rescue the surface expression of CD59 in a PIGA-null cell line. Taken together, our data strongly suggest that the early frameshift mutation in PIGA produces a truncated hypomorph, which is sufficient to rescue the lethality in males but not the MCAHS2-like phenotype